MXPA01001011A - Nonwoven webs having zoned migration of internal additives - Google Patents

Abstract

Nonwoven webs prepared from a blend of polymer and a migrating internal additive are heat treated only in selected regions to cause surface migration of the additive in those regions. The nonwoven webs have a desired property attributed to the additive in the selective regions. Regions surrounding the selected regions are not heat treated, and are either devoid of the desired property, or manifest the property to a lesser extent than in the heat treated regions.

Description

NON-WOVEN FABRICS THAT HAVE ZONED MIGRATION OF INTERNAL ADDITIVES FIELD OF THE INVENTION This invention is directed to non-woven fabrics having a zoned and selective migration of internal additives to create properties that affect only selected regions of the non-woven fabric.

BACKGROUND OF THE INVENTION Hot air blades have been employed to increase the integrity of non-woven fabrics such as yarn-linked filament fabrics. A hot air knife is useful for joining the individual polymer filaments together in several places, so that the fabric has increased strength and structural integrity. Hot air blades are also used to align meltblown fibers during the manufacture of melt blown fabrics, to cut non-woven fabrics, to trim waste and for a variety of other uses.

One use of the hot air blade is to improve the structural integrity of the non-woven fabrics before passing them through a standard filament bonding process. Air binding (" ") is a bonding process of a non-woven bicomponent fiber fabric in which the air is hot enough to melt one of the polymers in the fibers of the stressed fabric through the fabric. The air speed is between 100 and 500 feet per minute and the dwell time can be as long as 6 seconds.

The melting and resolidification of the polymer provides the bond.

A conventional hot air blade includes a mandrel with a groove that blows a jet of hot air over a nonwoven fabric surface. U.S. Patent No. 4,567,796 issued to Kloehn et al. Discloses a hot air blade which follows a programmed path to cut shapes necessary for particular purposes, such as leg holes in disposable diapers. U.S. Patent No. 5,707,468 issued to Arnold et al., Describes using a hot air blade to increase the integrity of a spunbonded web. United States of America patent application serial number 08 / 877,377 issued to Marmon et al., Filed on June 17, 1998, discloses a zoned hot air knife assembly used to heat discrete portions of a nonwoven fabric.

It is also known to use heat to facilitate the uniform migration of internal additives from non-woven fabrics. U.S. Patent Nos. 4,857,251, 4,920,168, 4,923,914 and 5,120,888, all issued to Nohr et al., Describe using heat to facilitate the migration of internal additives to the surfaces of non-woven fabrics.

SYNTHESIS OF THE INVENTION The present invention is directed to non-woven fabrics initially having an essentially homogeneous distribution of the internal additives. The internal additives are caused to migrate to the surface only in selected regions or "zones" of the non-woven fabric, making the non-woven fabric have desired or increased properties only in the selected areas. The selected migration of the internal additives may be in the X, Y and / or Z directions, and may cause the non-woven fabric to have differentiated properties in any direction. The invention also includes a method for making a non-woven fabric having differential properties in one or more directions, caused by a selected migration of the internal additives. . t BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a sectional view of a conventional hot air knife, used to supply hot air to a non-woven fabric.

Figure 2 is a perspective view of a process for causing a selected (regional) migration of additives in a nonwoven fabric, using a zoned hot air knife assembly.

DEFINITIONS As used herein, the term "nonwoven fabric or fabric" means a fabric having a structure of individual fibers or threads which are interleaved, but not in an identifiable manner as in a woven fabric. Fabrics or non-woven fabrics have been formed from many processes such as, for example, meltblowing processes, spinning processes, and carded and bonded weaving processes. The term also includes films that have been punched or otherwise treated to allow air to pass through them. The basis weight of non-woven fabrics is usually expressed in ounces of material per square yard (osy) or grams per square meter (gsm) and fiber diameters are usually expressed in microns. (Note that to convert from ounces per square yard to grams per square meter, multiply ounces by 33.91).

As used herein, the term "microfibers" means small diameter fibers having an average diameter no greater than about 75 microns, for example, having an average diameter of from about 0.5 microns to about 50 microns, more particularly , the microfibers can have an average diameter of from about 2 microns to about 40 microns.

As used herein, the term "spunbonded fibers" refers to fibers of small diameter which are formed by extruding the molten thermoplastic material as filaments of a plurality of usually circular and thin capillary vessels of a spinner with the diameter of the extruded filaments then being rapidly reduced as, for example, is indicated in United States of America patent No. 4,340,563 granted to Appel et al., in the United States of America patent No. 3,692,618 issued to Dorschner and others, in the patent to the United States of America No. 3,802,817 granted to Matsuki and others, in the patents of the United States of America Nos. 3,338,992 and 3,341,394 granted to Kinney, in the patent to the United States of America No. 3,502,763 granted to Hartman, in the patent to the United States of America No. 3,502,538 granted to Petersen and in the patent to the United States of America 3,542,615 granted a Dobo and others. The yarn bonded fibers are cooled and are generally not tacky on the surface when they enter the pulling unit, or when they are deposited on the collecting surface. Spunbonded fibers are generally continuous and have average diameters greater than 7 microns, often between about 10 and 20 microns.

As used herein, the term "spin-linked fabric" refers to a non-woven mat composed of yarn-bound yarns.

As used herein, the term "meltblown fibers" means fibers formed by extruding a molten thermoplastic material through a plurality of thin, usually circular, capillary vessels, such as strands or filaments fused into gas streams (eg. air) heated at high speed and converging which attenuate the filaments of the molten thermoplastic material to reduce its diameter, which can be to a microfiber diameter. Then, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a meltblown and randomly dispersed fiber fabric. Such process is described for example, in the patent to the United States of America No. 3,849,241 granted to Butin. Meltblown fibers are microfibers - ^ - -'- - which can be continuous or discontinuous, are generally smaller than 10 microns in diameter and are generally self-supporting when deposited on a collecting surface.

As used herein, the term "melt blown fabric" refers to a non-woven mat that is composed of blown fibers are melt.

As used herein, the term "polymers" generally includes but is not limited to homopolymers, copolymers, such as, for example, block, graft, random and alternating copolymers, terpolymers, etc., and mixtures and modifications thereof. In addition, unless specifically limited otherwise, the term "polymers" will include all possible geometric configurations of the material. These configurations include, but are not limited to, isotactic, syndiotactic and atactic symmetries.

As used herein, the term "machine direction" or MD means the length of a fabric in the direction in which it is produced. The term "cross machine direction" or CD means the width of a fabric, such as, for example, an address generally perpendicular to the machine direction.

As used herein, the term "bicomponent" refers to fibers which have been formed from at least two extruded polymers of separate extruders but spun together to form a fiber. Bicomponent fibers are sometimes referred to as conjugated or multi-component fibers. The polymers are used differently from one another even when the bicomponent fibers can be made from fibers of the same polymer. The polymers are arranged in distinct zones placed essentially constant across the cross section of the bicomponent fibers and extend continuously along the length of the conjugate fibers. The configuration of such bicomponent fiber can be, for example, a pod / core arrangement where one polymer is surrounded by another or can be a side-by-side arrangement or an arrangement of "islands in the sea". The bicomponent fibers are taught in U.S. Patent Nos. 5,108,820 issued to Kaneko et al., In U.S. Patents Nos. 5,336,552 to Strack et al., 5,382,400 to Pike et al. For the two component fibers, the polymers may be present in proportions of 75/25, 50/50, 25/75 or any other desired proportions.

As used herein, the term "biconstituent fibers" refers to fibers which have been formed from at least two extruded polymers from the same extruder as a mixture. The term "mixture" is defined below. The biconstituent fibrass does not have the various polymer components arranged in different zones placed relatively constant across the cross-sectional area of the fib?-And the various polymers are usually non-continuous along the full length of the fiber; instead these usually form fibrils or protofibrils which start and end at random. Biconstituent fibers are sometimes referred to as ulticonstituent fibers. Fibers of this general type are discussed in, for example, patent.e to United States of America No. 5,108,827 issued to Gessner. Bicomponent and biconstituent fibers are also discussed in the textbook "Polymer Blends and Compounds" by John A. Manson and Leslie H. Sperling, copyright 1976 by Plenum Press, a division of Plenum Publishing Corporation of New York, IBSN 0-306-30831-2, pages 273 to 277.

As used herein, the term "mixture" means a combination of two or more polymers while the term "alloy" means a subclass of mixtures wherein the components are immiscible but have been compatibilized. The "immiscibility" and the "miscibility" are defined as mixtures that have positive and negative values, respectively, for the free energy of mixing. In addition, "compatibilization" is defined as the process to modify the interfacial properties of a mixture of immiscible polymer in order to make -_ -Mri ___ g _____ fc __- -_-- i ^ iiÉ__ta an alloy.

As used herein, the term "hot air blade" refers to a device through which air heated under pressure can be emitted and directed. With such a device, it is also possible to control the air flow of the resulting heated air jet. A conventional hot-air knife is described in United States of America patent No. 5,707,468 granted on January 13, 1998 and United States of America No. 4,567,796 issued on February 4, 1986, both of which are incorporated herein by reference. which are here incorporated by reference in their totalities. A zoned hot-air knife is described in United States of America patent application No. 08 / 877,377, the description of which is incorporated by reference.

As used herein, the phrase "non-woven fabric having zoned migration of internal additives" refers to a non-woven fabric initially prepared from an essentially homogeneous mixture of a polymer and an additive. The additives are made to selectively migrate to the regions or "zones" on the non-woven side surface, so as to impart unique or increased properties only to those regions. The selected migration of an additive can occur in spaced and spaced locations on a given surface or surfaces of the non-woven fabric, indicating zoning in the "X" and / or "Y" directions. Alternatively, the selected migration of an additive may occur on a surface of a non-woven fabric, and not on an opposite surface (or to a lesser extent on an opposite surface), indicating zoning in the "Z" direction. The additive may be any internally mixed, semi-solid liquid or solid additive which has a tendency to migrate to the surface of the polymer when sufficient heat is applied to the polymer.

DETAILED DESCRIPTION OF THE INCORPORATIONS CURRENTLY PREFERRED The starting material for the invention is a nonwoven fabric that includes a plurality of filaments made from a mixture of one or more polymers with an internal additive. The non-woven fabric can be a spunbonded fabric, a meltblown fabric, a bonded and bonded fabric, or another type of non-woven fabric, and can be present in a single layer or multi-layer composite including one or more layers of nonwoven fabric.

A wide variety of thermoplastic polymers can be used to build the non-woven fabric, including without limitation polyamides, polyesters, polyolefins, ethylene and propylene copolymers, ethylene or propylene copolymers with C4-C20 alpha-olefin , the terpolymers of ethylene with propylene and an alpha-olefin CfC ^, the copolymers of ethylene vinyl acetate, the copolymers of propylene vinyl acetate, the elastomers of styrene-poly (ethylene-alpha-olefin), the polyurethanes, the block copolymers AB wherein A is formed of poly (vinyl arene) moieties such as polystyrene and B is an elastomeric middle block such as a conjugated diene or a lower alkene, polyethers, polyether esters, polyacrylates, ethylene alkyl acrylates, polyisobutylene, polybutadiene, isobutylene-isoprene copolymers and combinations of any of the foregoing. Polyolefins are preferred. Polyethylene and polypropylene are most preferred. The fabrics may also be constructed of bicomponent or biconstituent filaments or fibers, as defined above. Non-woven fabrics can have a wide variety of basis weights preferably ranging from about 0.1 grams per square meter (gsm) to about 100 grams per square meter.

The internal additive is a compound which migrates from the inside of a polymer filament to the surface with the application of sufficient heat to at least soften or partially melt the polymer, followed by subsequent cooling. The additive can be a compound or a mixture capable of imparting any desirable property, including without limitation surfactants, repellents, stabilizers, colorants and combinations thereof. In an embodiment, the additive may have at least two halves, A and B in which: (A) Half A and half B act as a single molecular unit which is compatible with said polymer at melt extrusion temperatures but which is incompatible at temperatures below melt extrusion temperatures, but each half A and half B taken as separate molecular units is incompatible with said polymer at melt extrusion temperatures and at temperatures below melt extrusion temperatures; (B) Half B has a functional group which imparts to said polymeric material at least one desired characteristic.

Because the additive is compatible with the polymer at melt extrusion temperatures, the additive is miscible with the polymer and the polymer and additive form a metastable solution. The solution formed by the additive and the polymer at the temperature above the melt extrusion temperatures is mentioned herein as a metastable solution since the solution is not stable at temperatures below the melt extrusion temperatures. As the temperature of the newly formed fiber falls below the melt extrusion temperatures, the polymer begins to solidify; which contributes to the separation of additive from the polymer phase. At the same time, the additive becomes less compatible with the polymer. Both factors contribute to the migration or rapid segregation of the additive towards the newly formed fiber surface which occurs in a controllable manner.

The additive surface segregation is influenced by the molecular weight of the additive. More specifically, the lower the molecular weight of the additive, the faster the rate of segregation of the additive to the surface of the filament at any given temperature at which the filament is still in a sufficiently molten state. The additive can be monomeric, oligomeric or polymeric.

The molecular weight of additive should be in the range of about 400 to about 10 thousand. This scope covers the appropriate molecular weights of additive regardless of whether the additive to be used by itself or in a mixture of additives; The molecular weight range of the additive depends in part on whether the additive will be used or not by itself.

The molecular weight range for the additives which are to be used individually in the compositions for filament formation and not as part of a mixture of additives is typically from about 400 to about 3 thousand. Preferably, this range is from about 500 to about 2 thousand and more preferably from about 500 to 1,500. The most preferred range is from around 500 to about a thousand. , .iA When the additives are intended to be used in a mixture, however, higher molecular weights may be employed. Although the reasons for this are not clearly understood, admixture mixtures are often more compatible with the polymer at melt extrusion temperatures than individual admixtures. While the section of additive mixtures is somewhat empirical, in general such mixtures may use additives having molecular weights in the range of from about 4 mil to about 10 mil, and preferably from about 400 to about 8 one thousand.

It should be noted that the above molecular weight ranges are based on the presumption that the oligomeric or polymeric additives will preferably have wide polydispersities, for example in the order of about 1.2 and above. Even though narrow polydispersities are certainly achievable, usually at a higher cost, these are not necessary, even if relatively low molecular weight additives are to be employed. As a guideline, it can be noted that for a given additive, the average molecular weight of an additive having a narrower polydispersity usually must be slightly lower than the average molecular weight of an additive having a broad polydispersity. Even though this guidance line is not precise and is empirical in nature, an artisan will be able to properly select an additive of any polydispersity without undue experimentation.

The term "additive" is widely used herein to encompass the use of two or more additives in a given composition. Such two or more additives may have the same or similar halves B or different halves B having the same characteristic as, for example, wetting in water. On the other hand two or more additives can be used which have different characteristicswhose characteristics may be related or unrelated. Such two more additives may be present in similar or significantly different amounts. In addition, the additives may have the same or similar molecular weights in order to segregate in the filament to approximately the same region. Alternatively, different molecular weight additives may be employed in order to effectively layer the additives on the surface.

The use of different molecular or especially additive additives for some characteristics which reinforce each other with an example of which is the use of the first additive that has a B half which is an ultraviolet radiation absorber and a second additive which has a B half that inhibits degradation or light stabilization which works by deactivating excited oxygen molecules or strict free radicals. The first additive will usually have a lower molecular weight than the second. While both additives segregate to the surface, the first additive migrates primarily to the effective surface, while the second additive migrates primarily to the subsurface. Therefore, the actinic reaction which is not absorbed by the first additive is effectively nullified by the second additive, resulting in a complementary or synergistic effect.

The internal additive can be liquid or solid. In general, the weight ratio of the thermoplastic polymer to the internal additive is about 10 to one thousand. That is, the amount of additive in the composition used to make the non-woven fabric is about 0.1% by weight to about 10% by weight, preferably about 0.3-5% by weight, more preferably about 0.5-2.5. % by weight.

The thermoplastic composition can be prepared by any number of methods known to those having ordinary skill in the art. For example, the polymer powder, splinter or pellet and the powder additive, in the form of a splinter or pellet can be mechanically mixed. If desired, the additive can be dissolved in a suitable solvent, and can be coated on the polymer particles by mechanically mixing the two, even though the use of a solvent is not preferred. A liquid additive can also be coated on the polymer particles using the mixing process. The polymer and the additive mixture can then be added to the extruder supply hopper from which the filaments will emerge. Alternatively, the coated polymer may be charged to a heater mixer, such as a heated twin screw combiner, in order to disperse the additive through the volume of the polymer. The resulting thermoplastic composition is typically extruded as rods which are fed to a chipper. The resulting chips then serve as the supply for the extruder of the melt processing. In another method, the additive can be measured in the throat of the hopper which contains the polymer in the form of particles and which feeds the extruder. In yet another method, the additive can be dosed directly into the barrel of the extruder where it is mixed with the molten polymer as the resulting mixture moves into the matrix.

A wide variety of additive types that migrate internally can be employed in the zoned non-woven fabrics of the invention. Suitable types of additives include, without limitation, solvents, repellents, wetting agents and other surfactants, binders and adhesives, flame retardants, unsightly agents, -.:!_&*_ »stabilizers to ultraviolet radiation, heat stabilizers, dyes, inks and other compounds which migrate to the surface when exposed to heat.

Suitable migratory additives include fluorochemicals, which are thermally stable at melt extrusion temperatures of the polymer, and which can act as repellents and flame retardants. The fluorinated hydrocarbons are typically more dense and volatile than the corresponding hydrocarbons and have lower refractive, constant and electric lower indices, lower solubilities and lower surface tensions than the corresponding non-fluorinated hydrocarbons. The presence of fluoro atoms imparts this ability, non-flammability, hydrophobicity, and oleophobic characteristics to the underlying molecules. Perfluorinated molecules (C8F17--) are believed to be the most effective.

Suitable internal fluorochemicals include without limitation ZONYL * 8615 (a fluorinated molten additive available from E.l. DuPont DeNemours &Co.); FX-1801, a non-ionic fluorochemical resin available from 3M Company; TLF-8860, a fluorinated molten additive available from E.l. DuPont DeNemours & Co; and ZONYL * 9010, a fluorinated molten additive available from E.l. DuPont DeNemours & Co .. Other suitable internal fluorochemical additives are described and claimed in the United States of America patent 5,459,188 issued to Sargert et al .; in U.S. Patent No. 5,681,963 issued to Liss, and in U.S. Patent No. 5,025,052 issued to Crater et al., whose descriptions of which are incorporated herein by reference.

The internal silicone additives are also suitable as repellents and surfactants. Like fluorochemicals, silicones tend to be incompatible with polyolefins and certain other polymers, providing a driving force for additives to separate from matrix polymers in the presence of heat and migrate to the nearest surfaces. Suitable silicone-based additives are described and claimed in U.S. Patent No. 4,857,251 issued to Nohr et al., The disclosure of which is incorporated herein by reference. Preferred silicone-based additives include the siloxane-containing additives having halves A and B as previously described.

In some preferred embodiments, the A moiety comprises at least one tetrasubstituted disiloxanyl group, optionally associated with one or more groups selected from the group consisting of trisubstituted loxy and trisubstituted silyl groups, the substituents of all those groups being selected. independently of the group consisting of monovalent alkyl, cycloalkyl, aryl, and heterocyclic groups, each of which can be substituted or unsubstituted, and half B.

In still other preferred embodiments, the additives contain a plurality of groups selected from the group represented by the following general formulas. (1) Br-, (2) Br-O-, (3) R, - (4) Rr-Si =, (5) (R3) (R4) (R5) Si-, (6) (R6) ( R7) (R8) Si- -, (7) [-SMRg) (R10) -O-] a, and (8) [-Si (Rn) (B3) -0-] t; wherein each of R, and R 2 independently is a monovalent group selected from the group consisting of hydrogen, alkyl, cycloalkyl, aryl, and heterocyclic groups, each of which except hydrogen, can be substituted or unsubstituted; each of R3-s, inclusive, independently is a monovalent group selected from the group consisting of alkyl, cycloalkyl, aryl, and heterocyclic groups, each of which may be substituted or unsubstituted, and B4; each of R6-Rn, inclusive as independently is a monovalent group selected from the group consisting of alkyl, cycloalkyl, aryl, and heterocyclic groups, each of which may be substituted or unsubstituted; each of a and b independently represent an integer from zero to about 70 which indicates only the amount of the respective group present in the additive without indicating or requiring, in cases where an integer is greater than 1, than such a plurality of the group respective is connected to each other to form an oligomer or polymer or that all these groups have identical substituents; and each of B, -B4, inclusive, independently is a moiety which imparts to the additive at least one desired characteristic; with the proviso that such a plurality of groups results in at least one tetrasubstituted disiloxanylene group.

In still other preferred embodiments, the additive is a compound having the following general formula B $ - (Hsi-0) -c-B6 R13 wherein each of R12 and 33 independently is a monovalent group selected from the group consisting of hydrogen, alkyl, cycloalkyl, aryl and heterocyclic groups. Each of which except for hydrogen can be substituted c not substituted; and each of B5 and B6 independently is a monovalent group having the desired characteristics; and c represents an integer from 2 to about 70.

In still other preferred embodiments, the additive is a compound having the following general formula: ^ 15 ^ 17 ^ 1 ^ 20 Rl4-S Í-O S i-O) S i-OKS i-R21 R16 R18 B7 R22 wherein each of RM-R22 inclusive, independently, is a monovalent group selected from the group consisting of hydrogen, alkyl, cycloalkyl, aryl, and heterocyclic groups, each of which, except for hydrogen, may or may not be substituted replaced; B7 is a monovalent group that has a desired characteristic; d represents an integer from zero about 70; and e represents an integer from 1 around 70.

In still other preferred embodiments, the additive is a compound having the following general formula R • .24 R23-YES [(- O-Si- / B8] 3 R ^ 2.5 in each of 23-25 inclusive, independently is a monovalent group selected from the group consisting of hydrogen, alkyl, cycloalkyl, aryl, and heterocyclic groups, each of which, except for hydrogen, may be substituted or unsubstituted; B8 is a monovalent group having a desired characteristic; and f represents an integer from 1 to 5 around 70.

According to the invention, the polymeric nonwoven fabric containing the migrant additive is selectively heated in zones, to be a selective migration of the additive. internal to the surface, resulting in the desired surface properties that occur in the zones. The additive can be made to migrate to the surface only in one or more selected spaced and separated zones. Alternatively, the additive can be made to migrate to the surface to an extent in the selected area and to a lesser extent in a region not in the selected area. The selected area and the region not in the selected area can be the same or opposite sides of the non-woven fabric or they can both be on both sides. A preferred way to cause heating is selective through the use of a zoned hot air knife described in United States of America patent application No. 08 / 877,377, granted to Marmon et al., Filed on June 17, 1998, the description of which is Incorporated here by reference. 25 Figure 1 shows a hot air blade - --- - iÉb »ÉWiÉliaBj ^ B _-_____ example ifi-l in cross section. Hot air supplied from a plenum through a slot 2 over a telephone; gone (not shown). In a zoned hot air knife array which includes a plurality of spaced apart hot air blades, the length of each slot 2 (e.g. in a direction perpendicular to the paper) will be almost as large as each of the spaced zones and corresponding separations that are being treated.

Figure 2 illustrates a hot air knife assembly 10, including a head 12 which is supplied with hot air through the inlet channels 14 and 16. The head 12 is shaped like an elongated hollow cylinder having the ends 18 and 20 and a main body 22. The hot air supply channels 14 and 16 supply air inside the ends 18 and 20 of the head 12 as shown by the arrows.

The hot air supplied to the headboard 12 may have a temperature of about 150-500 ° F, more generally around 200-450 ° F, more commonly around 250-350 ° F. The optimum temperature will vary according to the type of polymer, the basis weight and the speed of the non-woven fabric line 40 traveling under the hot air knife assembly 10. For a non-woven polypropylene fabric having a base weight of about 0.5-1.5 ounces per square yard.

-A ** »* -..-.» »- traveling at a line speed of about 1000-1500 feet per minute, a hot air temperature of about 250-325 ° F is desirable. Generally, the hot air temperature should be or should be (for example slightly below) the melting temperature of the non-woven fabric.

The preferred volumetric flow of the hot air being supplied to each hot air blade from the head 12 generally depends on the composition and weight of the fabric, the line speed, and the degree of migration of additive required. The air flow rate can be controlled by controlling the pressure inside the head 12. The air pressure inside the head 12 is preferably within about 1-12 inches of water (2-22 millimeters Hg), more preferably of between about 4-10 inches of water (8-18 mm Hg). Of course, the volume of hot air required to effect the desired level of additive migration can be reduced by increasing the temperature of the hot air. Operating parameters such as line speed, hot air volume, and hot air temperature can be determined and adjusted using techniques known and / or available to persons of ordinary skill in the art.

In the embodiment shown in Figure 2 the head 12 is cylindrical, but this may be rectangular or otherwise. Numerous sizes and shapes can be employed for the head 12, with the preferred size depending mostly on the width of the non-woven fabric and the degree of joining required. The headboard 12 can be constructed of aluminum, stainless steel, or other suitable material.

Extending from the head 12 are six spaced and spaced hot air passages 24, 26, 28, 30, 32, and 34. The passages may be rigid or flexible, but are preferably made of a flexible material so as to allow adjustment and / or the movement. The conduits are each connected at one end to the head 12 and are connected at their other ends to six plenums 36, 38, 40, 42, 44, and 46. Each plenum engages a hot air knife slot, with the slots being labeled 48, 50, 52, 54, 56 and 58. The plenums and slots shown in Figure 2 may each have a cross section similar to that shown in Figure 1 and described above.

The hot air from the head 12 is preferably supplied to approximately equal volume and equal velocities to each of the conduits 24, 26, 28, 30, 32 and 34. This equal division of flow can be achieved in a simple manner, by the ensure that the ducts are of equal dimensions and sizes and that the air pressure is uniform at the duct entrances. On the other hand, if a particular application requires the supply of more or less air inside one of the ducts than others, different flow rates can be achieved by placing valves individually in the ducts, by designing them with different sizes, or by the valves to the plenums as indicated below.

The plenums 36, 38, 40, 42, 44 and 46 are mounted on a sliding support bar 60. The plenums are mounted so that the lower tips of the air knife slots 48, 50, 52, 54, 56, and 58 are at a predetermined distance above the non-woven fabric 40. The distance between the air knife slots and the non-woven fabric should be from about 0.25 to about 10 inches, preferably from about 0.75 to about 3.0. inches, more preferably from about 1.0 to about 2.0 inches. Preferably, the plenums are adjustably mounted to the support bar 60 so that the distance between the knife slots and the fabric can be varied according to the needs of the application.

A control panel 62 is provided on one side of the hot air blade assembly 10 incorporating the individual flow controls for the hot air entering the plenums. As shown, the plenums are provided with individual flow control valves 66, 64, 68, 70, 72, and 74 which can be used to individually adjust the air flow to each plenum. The flow control valves can be electronically linked to individual controls in the control panel 62 using conventional techniques available to those skilled in the art., as explained above, it is often desirable to have an air flow oximately equal to each of the plenums. The valves can be used to fine-tune and fine-tune the air flows to the plenums or to differentiate between them if different flows are desired.

The non-woven fabric 40 is carried on an endless belt conveyor including a carrier grid 77 driven by the rollers (one of these at point 76) at a predetermined line speed. The nonwoven fabric 40 moves in the machine direction (indicated by the arrow 78) under the hot air knife assembly 10, at a rate of generally about 100-3000 feet per minute, more commonly around 500-2500 feet per minute, desirably at about 1000-2000 feet per minute, the hot air blade slots 48, 50, 52, 54, 56 and 58 apply the hot air jets to the nonwoven fabric, causing that an emigration of localized additive occurs in spaced and separated places. The spaced apart areas of the additive migration increased by hot air blades are represented by the areas 80, 82, 84, 86, 88 and 90. In the embodiment shown, the additive migration zones are linear. In another embodiment the support bar 60 is in communication with an oscillator (not shown) which causes the support bar 60 to move back and forth in the transverse direction (eg, perpendicular to the machine direction) to the the non-woven fabric 40 is brought forward in the direction of the machine. By using an oscillator, the increased additive migration zones 80, 82, 84, 86, 88 and 90 can be formed in a wave type pattern including without limitation sinusoidal waves, triangular waves, square waves, trapezoidal waves or waves irregular.

The thickness of zones 80, 82, 84, 86, 88 and 90 corresponds to the lengths of the air knife slots 48, 50, 52, 54, 56 and 58. Zones can be as wide or narrow as necessary, to minimize energy requirements while providing adequate regions; of increased properties. The air knife slots may each have lengths of less than about 1.0 inches, preferably less than about 0.5 inches, more preferably about 0.10-0.25 inches. The length of the air knife slots correspond essentially to the width of the additive migration regions in the fabric 40. The lengths of the air knife slots (for example perpendicular to the movement of the fabric) can be determined based on the percentage of the emigration area. of desired additive.

The width of the openings in the hot air knife slots 48, 50, 52, 54, 56 and 58 (for example the width of the opening as shown in Figure 1) must be configured to give the desired speed of blades of air sticking on the surface of the fabric 40. The actual velocity of the air jets is determined by the air pressure inside the head 12. The total number of air knife grooves, the lengths of the air knife grooves , and the widths of the hot air knife slots. The desired air blast velocity of the air knife slots is any speed that is required to cause migration of suitable additive to the surfaces of the nonwoven fabric filaments. Generally, the width of each air knife slot opening (eg, parallel to the direction of tissue movement) should be about 0.5 inches or less.

The number of air knife slots and spacings spaced apart may vary according to the width of the nonwoven fabric being treated, and the lengths of the individual air knife slots. The larger the number of plenums and slots is, the greater the maximum width of the tissue that can be effectively treated. Generally, the hot air blade assembly 10 should include at least two air knife slots and spacings spaced apart, when the nonwoven fabric 40 has a width of about 14-16 inches. Non-woven fabrics may fear widths of up to 140 inches or greater, and the desired number and / or the size of the air knife plenums may increase with the width of the nonwoven fabric. As explained above, the air knife assembly 10 shown in Figure 2 includes six air knife slots and spacings spaced apart. The air knife plenums may be spaced apart from about 1-24 inches apart, but are preferably spaced from about 4-20 inches apart, more preferably from about 10-15 inches apart. . Alternatively, the same effect can be created by providing a single slot opening extending across the width of the head 12, and blocking the portions of the slot opening to create one or more individual slot openings between the regions. blocked.

The hot air knife assembly 10 of the invention makes it possible to produce non-woven fabrics with limited additive migration from the filaments, and correspondingly less overall surface migration than the non-woven fabrics which are treated in their entirety. The hot air knife assembly 10 is especially useful for effecting limited migration of the additives from the meltblown fabrics as shown in Figure 2.

Selective migration of additives is effected on the non-woven fabric 40 (Figure 2) moving under the hot air knife and contacted with one or more hot air jets, preferably within about 15 ° of perpendicular to the fabric. As a consequence of the thermal energy imparted by the combination of temperature, pressure and cups of turbulent flow of one or more of the air jets, the filaments of non-woven fabric are heated in the regions or zones below the hot air blades , to cause an emigration of selective additive and desired properties to regions 80, 82, 84, 86, 88 and 90 shown in Figure 2.

Other methods and devices may also be employed to create selected regions or zones of additive migration in a non-woven fabric. For example, the tissue may be selectively heated and treated using infrared radiation, induction heat or other methods. Also, the techniques of the invention can be employed to cause zoned migration of additives in the "Z" direction, as well as in the "X" and "Y" directions as described above. To achieve zoned migration in the "Z" direction, a heat source can be directed to a surface of a non-woven fabric in such a way that the one surface is heated to an extension much greater than the opposite surface. For example, a heat source, such as a hot air jet, may be directed to a surface of the non-woven fabric at a low angle which is almost parallel to a surface. This will cause most convective heat transfer and additive migration to occur on one surface in opposition to the other.

Examples (Fabrics 1-9) The meltblown non-woven fabrics having internal fluorocarbon additives were prepared from essentially homogeneous polymer blends and internal additives. The resulting tissues were selectively heat treated to cause zoned migration of the additives, and tested for alcohol repellency. The polymer component of each fabric contained about 90% by weight of polypropylene mixed with 10% by weight of polybutylene. The following polymers and additives were used in the non-woven fabric samples: Internal Fluorochemical (IFC): a) 3M FX-1801, a non-ionic fluorochemical resin, b) DuPont Z0NYL * 8615, a fluorinated molten additive, c) DuPont TLF-8860, a fluorinaid molten additive, d) DuPont ZONYL * 9010, a fluorinated molten additive.

Polypropylene (PP): a) Exxon 3746G, a resin of 800 MFR or b) Montell PF-015, a resin of 400 MFR.

Polybutylene (PB): Shell DP-8911, a 5.5% ethylene, 94.5% of: .- butene copolymer.

The repellency of finished non-woven fabrics to isopropyl alcohol (IPA) was tested by placing drops of water / isopropyl alcohol solutions on the surface of the fabric. The solutions contained from 20-100% by volume of isopropyl alcohol in water, varied increments of 10%. When the level of isopropyl alcohol in the solution was increased, the surface tensions of the solution decreased. Therefore, solutions with high levels of isopropyl alcohol are more difficult to repel. As a benchmark, 100% isopropyl alcohol has a surface tension of about 22 dynes per centimeter.

To carry out the test, 8 drops of each of the water / isopropyl alcohol solution was placed along the cross-machine direction of the meltblown fabric being tested. After 5 minutes, a repellency rating was given. The repellency rating was the solution with the highest percentage of isopropyl alcohol that did not wet the surface of the fabric. The back of each fabric was observed to determine if the fabric was wetted by the isopropyl alcohol solution. If one or more of the eight drops of the isopropyl alcohol solution moistened the fabric, then the fabric was considered to have failed at that level.

In some cases, a rating between increases of 10% isopropyl alcohol was given. For example, a rating of 85% isopropyl alcohol indicates that; the fabric easily repelled 80% isopropyl alcohol, only a drop or two of 90% isopropyl alcohol only slightly moistened the fabric. For control purposes it was determined that the meltblown web without the IFC treatment passed only 20% isopropyl alcohol.

The compositions and fabrics were prepared as follows: * * ... ......

Fabric No. 1 2. 75 pounds of SCC-4983 (one master load composed of 15% FX-1801 IFC / 85% of 3746 GPP), 4 pounds of DP-8911 PB, 34 pounds of 3746G PP, and 0.75 pounds of SCC-IIIL? A blue pigment was dried in a mixer for at least 30 minutes, and then added to the extruder and processed into a meltblown web having a basis weight of 0.5 ounces per square yard. This composition gives an objective level of 1.0% FX-1801 IFC, 9.6% PB, 87.6% PP, and 1.8% pigment in the meltblown web.

Fabric No. 2 0. 41 pounds of TLF-8860, 4 pounds of DP-8911 PB, 36 pounds of 3746G PP, and 0.8 pounds of SCC-11115 blue pigment were agitated in a mixer for at least 30 minutes, and then added to the melt blown extruder and blown to a cloth having a basis weight of 0.5 ounces per square yard. This composition gives a target level of 1.0% TLF-8860 IFC, 9.7% PB, 87.4% PP and 1.9% pigment.

Fabric No. 3 0. 44 pounds of Z0NYL * 8615, 4 pounds of DP-8911 PB, 36 pounds of 3746G PP, and 0.8 pounds of SCC-11115 of blue pigment were dried with agitation in a mixer for at least 30 minutes and then added to the extruder of blowing with melting and blowing on a cloth having a basis weight of 0.5 ounces per square yard. This composition gave a target level of 1.1% of ZONYL®8615 IFC, 9.7% PB, 87.3% PP and 1.9 * of pigment.

Fabric No. 4 0. 41 pounds of ZONYL * 8615, 4 pounds of DP-8911 PB, 36 pounds of 3746G PP, and 0.75 pounds of SCC-11115 of blue pigment were dried with agitation in a mixer for at least 30 minutes and then added to the extruder of blowing with melting and blowing on a cloth having a basis weight of 0.5 ounces per square yard. This composition gave a target level of 1.0% ZONYL®8615 IFC, 9.7% PB, 87.5% PP and 1.8% pigment.

Fabric No. 5 0. 54 pounds of ZONYL * 8615, 4 pounds of DP-8911 PB, 36 pounds of 3746G PP, and 0.75 pounds of SCC-11115 of blue pigrrento were dried with stirring in a mixer by pulling them for 30 minutes, and then they were added to the melt blown extruder and blown onto a cloth having a basis weight 0.5 oz. per square yard. This composition gave a target level of 1.3% of ZONYL®8615 IFC, 9.7% PB, 87.2% PP and 1.8% pigment.

Fabric No. 6 0. 41 pounds of ZONYL * 9011, 4 pounds of DP-8911 PB, 36 pounds of 3746G PP, and 0.75 pounds of SCC-11115 blue pigment were dried with agitation in a mixer for at least 30 minutes, and then added to the mixer. melt blown extruder and blown into a cloth having a basis weight of 0.5 ounces per square yard. This composition gave a target level of 1.0% ZONYL®9010 IFC, 9.7% PB, 87.5% PP and 1.8% pigment.

Fabrics Nos. 7-9 0. 83 pounds of ZONYL * 8615, 8 pounds of DP-8911 PB, 72 pounds of 3746G PP, and 1.5 pounds of SCC-11115 blue pigment were dried with agitation in a mixer for at least 30 minutes, and then added to the mixer. melt blown extruder and blown into a cloth having a basis weight of 0.5 ounces per square yard. This composition gave a target level of 1.0% ZONYL®8615 IFC, 9.7% PB, 87.5% PP and 1.8% pigment. Three rolls of cloth were made with this composition.

Each of fabrics 1-9 had a width of about 18-20 inches to create a zoned effect, each fabric was treated using a single hot air knife, centered approximately through the fabric, having a long dimension about 12 inches perpendicular to the direction of the fabric machine. This created a central zone of heat treated fabric selectively, and two side areas of untreated fabric.

The following Table 1 shows the process conditions and the effect of the hot air knife (HAK) on the repellency of the No. 1 fabric. The hot air knife was mounted outside the melting blower case, 25 inches from the center of the roll winder, and one inch above the fabric. The repellency ratings were taken in the area treated with the hot air blade for the treated sample and compared with the repellent effect of the hot air blade against any hot air blade.

Table 1: Repellency Ratings for Fabric No. 1 ¿^^^^^ a * í ^ _í.¿u ___? _? ____________.

The following table 2 compares the effect of different process conditions and the effect of the hot air knife on the No. 2 fabric. This time, the hot a.ire blade was mounted inside the forming box, to about 2 inches of the curtain of blown fibers with fusion. The UWV was increased to remove the extra air from the hot blade. For the sample treated with a hot air knife, the repellency was measured in the region treated with a hot air knife unless otherwise noted.

Table 2: Repellency Ratings for Fabric No. 2 Table 3 below compares the effect of different process conditions and HAK on No. 3 fabric. The HAK was mounted in the melt blower box, about 2 inches from the curtain of blown fibers with melting. Again, the UWV had to be increased to remove the extra HAK air. For the HAK sample treated, repellency was measured in the region exposed to HAK unless noted otherwise.

Table 3: Repellency Ratings for Fabric No. 3 The following Table 4 compares the effect of different levels of additive and HAK using fabrics Nos. 4 and 5. The HAK was mounted outside the melt blow box, 25 inches from the center of the roll winder, and around 1 inch above the fabric. Again, the repellency was measured in the region treated with HAK when the HAK was in place.

Table 4: Repellency ratings for Fabrics Nos. 4 and 5 The following Table 5 compares the effect of different process and HAK conditions on fabric No. 6.

The HAK was mounted outside the melt blow box, 25 inches from the center of the roll winder, and about 1 inch above the fabric. Again, the repellency was measured in the region treated with HAK when the HAK was in place.

Table 5: Repellency Ratings for Fabric No. 6 For fabrics Nos. 7-9, the temperature of the fabric was monitored. The No. 8 fabric was run without the HAK. Fabric No. 8 was run with the HAK, resulting in a higher fabric temperature. The No. 9 fabric was run with the HAK being vented to remove some of the additional heat. To ventilate the HAK, the pipe that feeds the HAK was vented up and out of the meltblown die tip.

The HAK was mounted 25 inches from the roll winder and placed 1.5 inches above the forming wire. This caused a curtain of air to stick on the fabric just before the furler. When the HAK was ventilated, the HAK increased the ambient air temperature without causing a curtain of air to hit the fabric. .-fr-v tS &7 Table 6: Repellency Ratings for Fabrics Nos. 7-9 Examples (Fabrics 10-14) The melt blown nonwoven fabrics similar to fabrics 1-9 were prepared, except that the internal wetting agents were used instead of the repellents. Two internal humidifying treatments were evaluated: a) SF-19, a polysiloxane polyether from PPG Industries, introduced as a 12% master filler in polypropylene; Y b) Atmer 8041, a surfactant from ICI Surfactamts of Delaware, identified only as "20% Super Concentrate".

The following fabrics 10-14 were produced and tested for wetting using the static water droplets.

Fabric No. 10 1. 67 pounds of the 12% SF-19 masterbatch was dried with agitation with 38.5 pounds of PF-0.5% PP for at least 30 minutes. The mixture was then placed in the extruder and a 0.5 ounce fabric was made per square yard of meltblowing. The objective comtion of the fabric was therefore 0.5% SF-19 and 99.5% PP. Process conditions were melt temperature = 520 ° F, PAT = 505 ° F, PAFS = 5.5, low wire vacuum = 30.2%, extruder pressure = 1000 pounds per square inch, and yield = 2 pounds per inch per hour ( PIH). The treated fabric was not wettable with static water droplets.

A roll of fabric with the comtion was exd to the hot air knife (HAK). The other process conditions were the same as described for the aforementioned fabric. The hot air blade was mounted to about 25 inches from the roll winder and was placed about 1-1.5 inches above the forming wire. The conditions of the hot air blade were 290 ° F and 20 pounds per square inch. This cloth was also not wettable with static water droplets.

Fabric No. 11 1. 67 pounds of the 12% SF-19 masterbatch were agitated with drying with 4 pounds of DP-8911 PB and 34.5 pounds of PF-015 PP for at least 30 minutes. The mixture was , B ^ < - * J - - - "- '- then put into the extruder and 0.5 ounces per square yard of the meltblown fabric was made.The target comtion of the fabric was therefore 0.5% SF-19, 10.8 % PB and 89.5% PP The process conditions were melting temperature = 520 ° F, PAT = 505 ° F, PAFS = 5.5, low wire vacuum = 30.2%, extruder pressure = 1000 pounds per square inch, and production = 2 pounds per inch per hour.The treated fabric was not wettable with static water droplets.

A roll of fabric with the above mentioned comtion was then exd to the hot air knife (HAK) The process conditions were the same as those described for the aforementioned fabric. The hot air blade was mounted at about 25 inches from the roll winder and was placed about 1-1.5 inches above the forming wire. The conditions of the hot air blade were 290 ° F and 20 pounds per square inch. The fabric was also not wettable with static water droplets.

Fabric No. 12 pounds of the 12% SF-19 masterbatch were agitated with 37 pounds of PF-015 PP for at least 30 minutes. The mixture was then placed in the extruder and 0.5 ounces per square yard of the meltblown fabric was made. The objective comtion of the fabric was therefore 1.4% of SF-19 and 98.6% of PP. The process conditions were melting temperature = 520 ° F, PAT = 515 ° F, PAFS = 5.1, low wire vacuum = 30.2%, extruder pressure = 1000 pounds per square inch, and yield = 2 pounds per inch per hour. The treated fabric was not wettable with static water droplets.

A roll of fabric with the comtion mentioned above was then exd to a hot air knife (HAK). The process conditions were melting temperature = 520 ° F, PAT = 510 ° F, PFS = 5.0, low wire vacuum = 30.2%, extrusion pressure = 1000 pounds per square inch, and yield = 2 pounds per inch per hour. The hot air blade was mounted at about 25 inches from the roll winder and was placed about 1-1.5 inches above the forming wire. The conditions of the hot ctire blade were 340 ° F and 20 pounds per square inch. This cloth was slightly humid to static water droplets. The wetting was described as slow and not uniform, but the fabric did not transmit the water vertically.

Fabric No. 13 2 pounds of 20% of Atmer's super concentrate 8041 were dried with agitation with 39.25 pounds of PF-015 PP * ^^ .... * -.._ for at least 30 minutes. The mixture was then put in: the extruder and 0.5 ounces per square yard of meltblown fabric were made. The objective comtion of the fabric was therefore 1.0% Atmer and 99.0% PP. The process conditions were melting temperature = 520 ° F, PAT = 505 ° F, PAFS = 5.0, low wire vacuum = 30.2%, extruder pressure = 1000 pounds per square inch, and yield = 2 pounds per inch per hour. The treated fabric was not wettable with static water droplets.

A roll of fabric with the composition mentioned above was then exposed to a hot air knife (HAK). The process conditions were melting temperature = 520 ° F, PAT = 505 ° F, PFS = 5.0, low wire vacuum = 30.2%, extrusion pressure = 1000 pounds per square inch, and yield = 2 pounds per inch per hour. The hot air blade was mounted at about 25 inches from the roll winder and was placed about 1-1.5 inches above the forming wire. The conditions of the hot air blade were 290 ° F and 20 pounds per square inch. This cloth was also not wettable with static water droplets.

Fabric No. 14 2 pounds of 20% super concentrated Atmer 8041 were shaken with drying with 4 pounds of DP-8911 PB and 35.25 pounds of PF-015 PP for at least 30 minutes. The mixture was then placed in the extruder and 0.5 ounces per square yard of the melt blown fabric were made. The objective composition of the fabric was therefore 1.0% Atmer, 9.7% PB and 89.3% PP. Process conditions were melting temperature = 520 ° F, PAT = 505 ° F, PAFS = 5.1, low wire vacuum = 30.2%, extruder pressure = 1000 pounds per square inch, and yield = 2 pounds per inch per hour . The treated fabric was not wettable with static water droplets.

A roll of fabric with the aforementioned composition was exposed to a hot air knife (HAK). The other conditions of the process were the same as described for the aforementioned fabric. The hot air blade was mounted at about 25 inches from the roll winder and was placed about 1-1.5 inches above the forming wire. The conditions of the hot air blade were 290 ° F and 20 pounds per square inch. The fabric was also not wettable with the static water droplets.

The selectively zoned nonwoven fabrics of the invention have a wide variety of potential uses. In one application, the edges of the diaper cover can become more water repellent than the center, thereby directing the fluid towards the center (and inside the absorbent core) and out from the edges which make contact with the user. . Other applications of non-woven fabric could also benefit from controlled fluid flow, in which fluid is directed out of certain places and into other places. The bottom of the fabric may become more wettable than the top, or vice versa, thereby urging the fluid which contacts the fabric to one side of the fabric and out the other side.

Although the embodiments of the invention described herein are currently considered to be preferred, various modifications and improvements can be made without departing from the spirit and scope of the invention. The scope of the invention is indicated by the appended claims and all changes that fall within the meaning and range of equivalences are intended to be encompassed therein.

Claims (32)

R E I V I N D I C A C I O N S

1. A non-woven fabric having at least one selectively zoned region of additives on an outer surface and at least one area not in the selectively zoned region, comprising: a plurality of nonwoven filaments made of a mixture that includes one or more polymers and an internal migrant additive; where the internal additive has migrated to the surface to a greater extent in the region selectively zoned than in the area not in the region selectively zoned.

2. The non-woven fabric as claimed in clause 1, characterized in that the internal additive is present on the surface only in the selectively zoned region.

3. The non-woven fabric as claimed in clause 1, characterized in that the internal additive is present on the surface to a greater extent in the selectively zoned region, and to a lesser extent in the area not in the selectively zoned region. . _, _.._ «- .- _.

4. The non-woven fabric as claimed in clause 1, characterized in that the region selectively zoned, and the area not in the selectively zoned region, are on one side of the non-woven fabric.

5. The non-woven fabric as claimed in clause 1, characterized in that the selectively zoned region, and the area not in the selectively zoned region, are on opposite sides of the non-woven fabric.

6. The non-woven fabric as claimed in clause 1, characterized in that the region selectively zoned, and the area not in the selectively zoned region, are both present on two sides of the non-woven fabric.

7. The non-woven fabric as claimed in clause 1, characterized in that it comprises a fabric linked with yarn.

8. The non-woven fabric as claimed in clause 1, characterized in that it comprises a fabric blown with fusion.

9. The non-woven fabric as claimed in clause 1, characterized in that it comprises a carded and bonded fabric.

10. The non-woven fabric as claimed in clause 1, characterized in that the polymer in the non-woven filaments comprises a material selected from polyolefins, polyamides, polyesters, copolymers of ethylene and propylene, copolymers of ethylene or propylene with an alpha-olefin C4-C20, terpolymers of ethylene with propylene and an alpha-olefin CI-CJO, copolymers of ethylene vinyl acetate, copolymers of propylene vinyl acetate, elastomers of styrene-poly (ethylene-alpha-olefin), polyurethanes, block copolymers AB in where A is formed of poly (vinyl arene) halves such as polystyrene and B is an elastomeric middle block such as a conjugated diene or a lower alkene, polyethers, polyether esters, polyacrylates, ethylene alkyl acrylates, polybutylene, polybutadiene , isobutylene-isoprene copolymers and combinations thereof.

11. The non-woven fabric as claimed in clause 10, characterized in that the polymer comprises a polyolefin.

12. The non-woven fabric as claimed in clause 11, characterized in that the polyolefin comprises a polyethylene.

13. The non-woven fabric as claimed in clause 11, characterized in that the polyolefin comprises polypropylene.

14. The non-woven fabric as claimed in clause 13, characterized in that it also comprises polybutylene.

15. The non-woven fabric as claimed in clause 1, characterized in that the migrant additive comprises a material selected from repellents, wetting agents, binders, adhesives, flame retardants, antistatic agents, stabilizers, colorants, inks, and combinations of same.

16. The non-woven fabric as claimed in clause 1, characterized in that the migrant additive comprises a fluorochemical.

17. The non-woven fabric as claimed in clause 16, characterized in that the fluorochemical comprises a material selected from non-ionic fluorochemical resins, fluorinated melt additives and combinations thereof.

18. The non-woven fabric as claimed in clause 1, characterized in that the migrant additive comprises a silicone compound.

19. A nonwoven fabric prepared from an essentially homogeneous mixture that includes a polymer and an internal additive that has a tendency to migrate to a surface of the non-woven fabric when exposed to heat, the non-woven fabric comprises: a plurality of nonwoven filaments made of an essentially uniform mixture of polymer and internal additive; one or more areas of the non-woven fabric selectively exposed to heat to cause a selective migration of the internal additive to the surface; Y one or more areas of the non-woven fabric that have less internal additive on the surface than in one or more zones selectively opposed to heat.

20. The non-woven fabric as claimed in clause 19, characterized in that the essentially homogeneous mixture comprises about 0.1-10% by weight of the internal additive.

21. The non-woven fabric as claimed in clause 19, characterized in that the essentially homogeneous mixture comprises about 0.3-5% by weight of the internal additive.

22. The non-woven fabric as claimed in clause 19, characterized in that the essentially homogeneous mixture comprises about 0.5-2.5% by weight of the internal additive.

23. The non-woven fabric as claimed in clause 19, characterized in that the polymer comprises a polyolefin.

24. The non-woven fabric as claimed in clause 19, characterized in that the polymer comprises a mixture of polypropylene and polybutylene.

25. The non-woven fabric as claimed in clause 19, characterized in that the internal additive comprises a fluorochemical.

26. The non-woven fabric as claimed in clause 23, characterized in that the internal additive comprises a fluorochemical.

27. The non-woven fabric as claimed in clause 19, characterized in that the internal additive comprises a silicone compound.

28. The non-woven fabric as claimed in clause 23, characterized in that the internal additive comprises a silicone compound.

29. A process for preparing a non-flowing fabric having one or more selected properties in one or more selected areas on a surface thereof, comprising the steps of: forming a non-woven fabric of an essentially homogeneous mixture including a polymer and an internal additive which has a tendency to migrate to a surface of the non-woven fabric when exposed to heat; Y applying heat to the non-woven fabric only in one or more selected areas to cause a selective migration of the additive to the surface in one or more selected areas of the non-woven fabric; thus imparting the one or more selected properties in the one or more selected zones but not in the surrounding regions in the nonwoven fabric.

30. The process as claimed in clause 29, characterized in that the heat is applied using a hot air knife.

31. The process as claimed in clause 30, characterized in that the hot air knife comprises a zoned hot air knife.

32. The process as claimed in clause 29, characterized in that the heat is applied in a central area of the non-woven fabric and not in the surrounding end regions of the fabric. SUMMARY Nonwoven fabrics prepared from a mixture of polymer and an internal migrant additive are heat treated only in selected regions to cause surface migration of the additive in those regions. The non-woven fabrics have a desired property attributed to the additive in the selected regions. The regions surrounding the selected regions are not treated with heat, and are devoid of the desired property, or manifest property to a lesser extent than in heat-treated regions. «W .._.-_ aa_to -..-, J__. _.... .'..._ ..