WO1992016361A1 - Non-woven fabrics with fiber quantity gradients - Google Patents

Abstract

A process wherein the fibrous boundary junction (50, 52) of at least two fibrous layers (54, 56, 58) is accomplished by turbulent entanglement of the boundary fibers of adjacent gas-fiber streams or sprays of fibers (40, 42, 44) of at least two types during the travel of the fibers from their extrusion orifices to a collection surface. The resulting fabric (38) is also disclosed. This is achieved by simultaneously directing the heated expanding gas-fiber streams or sprays (40, 42, 44) onto the deposition surface (28) in a partially overlapped laydown pattern (46, 62) wherein predetermined portions of one stream of fibers are entangled with predetermined portions of a second stream of fibers to form a fiber quantity gradient of both streams of fibers across the depth of the boundary. The remaining portions of the two fiber streams form the stratified layers of the respective first and second fiber types.

Description

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NON-WOVEN FABRICS WITH FIBER QUANTITY GRADIENTS Background of the Invention

The present invention pertains to non-woven fabrics, and particularly to non-woven fabrics of the multilayered type having controlled intermingling of a portion of the fibers of each of the respective ad¬ joining or contacting fibrous layers in the formation of an intertwined coherent matrix of fibers.

There has been a need in the area of dispos- able non-woven fibrous fabrics for low cost stratified fabrics which can be inseparably joined from two or more types of fibrous layers or webs which are joined at their adjacent fibrous boundaries by an intermin¬ gling in the depth of the fibers comprising the re- spective layers or webs, and the process and apparatus for its formation.

The known composite non-woven fibrous fab¬ rics formed to date are fabrics which are formed by the deposition and formation of fibers onto a previ- ously formed web, which precludes any appreciable in depth penetration of the deposition fibers into the formed web. This severely limits the quality of the joining due solely to entanglement of the individual deposition fibers with the individual fibers of the previously formed web. - 2 -

The formation of these various fibrous webs are prepared and performed with the use of melt blow¬ ing techniques for forming fibers. These melt blowing techniques for forming from thermoplastic resins, elastomeric fibers and non-elastic but elongateable fibers can be prepared by known techniques as de¬ scribed in an article by Van A. Wente entitled "Super¬ fine Thermoplastic Fibers" appearing in Industrial and Engineering Chemistry, Vol. 48, No. 8, pp. 1342 to 1346. The fiber diameters may vary from 0.5 to 250 or more microns depending upon the combination of gas flow rates, polymer flow rate, die temperature and polymer molecular weight. Their lengths may vary from short fibers to substantially continuous length fila- ments depending upon the air temperature and velocity and the distance from the die to the collector. An¬ other publication dealing with melt blowing is Naval Research Laboratory Report 111437 dated April 15, 1954. The melt blowing process comprises heating a fiber forming resin to a molten state and extruding it through a plurality of fine orifices into a high ve¬ locity heated gas stream which attenuates the extrud- ate to form the melt blown fibers. This process is further described in U.S. Patent No. 3,849,241 to Butin et al., the disclosure of which is incorporated herein in its entirety by reference and relied upon.

Another reference describing this process in general is Morman, U.S. Patent No. 4,652,487, which discloses the separable joining of a fibrous non-woven gatherable web to an extended stretched non-woven elastic web by the entanglement of individual fibers of the fibrous non-woven gatherable web with the indi¬ vidual fibers of the fibrous non-woven elastic web. After gathering of the fibrous non-woven gatherable web has occurred due to the contraction of the compos- - 3 -

ite web upon the removal of the biasing force, the gathered fibrous non-woven web is separated from the non-woven elastic web and rolled up.

Morman '487 is an example of a method of fiber deposition onto an already formed fabric and is directed to the formation of a separably joined fi¬ brous non-woven gatherable web onto the surface of a non-woven elastic web while the non-woven elastic web is maintained at its extended stretched biased length. It is also there stated that the separable joining is achieved by the entanglement of the individual fibers of the fibrous non-woven gatherable web with the non- woven elastic web. It is further stated in Morman ^•487 that the separable joining of the fibrous non- woven gatherable web to the fibrous non-woven elastic web is achieved by entanglement of the individual fi¬ bers of the fibrous gatherable web with the individual fibers of the fibrous non-woven elastic web.

Morman, U.S. Patent No. 4,657,802, discloses several methods of joining a fibrous non-woven gather¬ able web to the non-woven elastic web. In that patent there is disclosed a method of heat bonding involving fusion, wherein the melt temperature of at least one of the materials is about 50* below at least one of the materials utilized to form at least one of the two webs, to about the melt temperature of at least one of the materials utilized to form at least one of the two webs. Morman '802 goes on to state that the heat bonding may also be performed under conventional pres- surized conditions. Morman '802 further states that conventional sonic bonding techniques may be substi¬ tuted for the heat bonding steps. In another embodi¬ ment disclosed in Morman '802, the joining of the two webs is achieved by forming the non-woven elastic web out of a tacky elastic material. In any of the em- - 4 _

bodiments of the process of joining the two webs there disclosed may be enhanced by applying pressure to the two webs after the gatherable web has been formed on the surface of the elastic web. Morman '802 also states that the joining of the two webs may be further improved by applying an adhesive material to the upper surface of the non-woven elastic web prior to forma¬ tion of the fibrous non-woven gatherable web thereon. This, of course, increases the stiffness of the fabric with a deleterious effect on the feel and hand.

Since this embodiment is identical to the embodiment disclosed in Morman '487, both of these patents have identical embodiments in that in both cases melt blown fibers are deposited on a previously formed, cooled and stretched elastic web, wherein the elastic fibers are bonded to each other and few if any of the elastic fibers are projecting from the surface of the web. Since the deposition of the melt blown fibers is onto an already formed, cooled and bonded web, the depositing fibers will form a web directly on the surface of this web with some of the depositing fibers lying in crevices and interstices of the elas¬ tic web, and other fibers entangled with any of the elastic fibers projecting from the surface. This type of joining is described in Morman '487 as separable joining.

In the two aforementioned patents, it should be noted that the melt blown elastic fibers are depos¬ ited on a foraminous collecting screen and as they are deposited upon the moving collecting screen, they en¬ tangle and cohere to form a cohesive fibrous non-woven elastic web while simultaneously being cooled by air movement through the collecting screen. The non-woven elastic web is subsequently stretched and followed by a direct deposition of melt blown fibers onto the - 5 -

stretched elastic web. This stretching of the flat web reduces the diameter of the elastic fibers which are lengthened by the stretching, which in turn reduc¬ es the size of or eliminates completely loops, curls and kinks which occur throughout their lengths, re¬ sulting in a thinner, more taut, non-woven web having few, if any, loose fiber ends or loops to become en¬ tangled with fibers of the subsequently deposited fi¬ brous non-woven web. This is demonstrated by the fact that the separably joined fibrous non-woven gatherable webs as taught in Morman '487 are easily separated and the joined fibrous non-woven gatherable webs compris¬ ing tacky webs as taught in Morman '802 are able to be separated without damaging or rupturing either web, but with more difficulty.

The possibility of web separation problems occurring during use or when these fabrics are elon¬ gated and contracted as mentioned in Morman '802, or the separable joining of a fibrous non-woven gather- able web to an extended stretched non-woven elastic web as taught in Morman '487 is due in large part to the fact that the melt blown fibers which form the gatherable web are deposited on a stretched previously formed and cooled elastic web wherein there are a few if any fiber projections with which to intermingle. Moreover, since the stretched elastic web is cooled, there is very little chance of having fusion bonding between the newly deposited non-elastic fibers with the surface or surface fibers of a cooled, stretched and flattened elastic web to the extent that the two webs cannot be separated. It therefore appears that much of the entanglement of the individual fibers of the gatherable web is in the crevices and interstices of the elastic web. To date the known melt blown fibrous lami-

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nates have been formed by depositing two or more fi¬ brous layers onto each other to build up a multiple laminate, having relatively sharp lines of demarcation between the contacting surfaces of the layered fabric. 5 The bonding that takes place between layer surfaces consists mainly of the fibers of a subsequently depos¬ ited web being embedded in the crevices and interstic¬ es of the surface of a previously deposited fibrous web. This type of bonding or joining in the formation 10 of laminates is readily separated and the separated webs wound into rolls as taught in Morman '487. Any repetitive stretching and relaxing forces, if applied to this laminate, would have an adverse effect upon the fabric coherence and integrity such as the stress- 5 es applied to disposable garments. This is further discussed in Morman '802, wherein it is disclosed that this type of bonding may be further enhanced by the application of adhesive, heat bonding or the use of tacky melt blown fibers. 0 Certain of the prior art patents show fab¬ rics which are formed from two merging air-fiber streams under turbulent conditions to form an inte¬ grated air stream containing a thorough mixture of the two fibers. In this process, upon deposition onto a 5 collection surface, the two types of fibers are dis¬ tributed uniformly throughout the matrix of fibers to provide a homogenous material. A short description of these patents follows,

Hauser, U.S. Patent No. 4,118,531, discloses 0 a method wherein one air stream containing picked fi¬ bers is merged with a second air stream of melt blown microfibers where they become mixed and are subse¬ quently deposited on a collector surface. Once on that surface the fibers form a web or randomly and 5 thoroughly intermixed and intertangled fibers. - 7 -

Anderson et al., U.S. Patent No. 4,100,324, discloses a method wherein a first air stream contain¬ ing melt blown fibers is merged with a second stream containing wood pulp fibers under turbulent conditions to form an integrated air stream containing a thorough mixture of microfibers and wood pulp fibers. Upon deposition onto a collection surface, this mixture forms a fabric having a homogeneous distribution of both fibrous materials throughout the fabric. Perry, U.S. Patent No. 3,016,599, discloses a method whereby a first air stream containing staple fiber is merged with a second air stream containing freshly formed microfibers to cause a homogenous tur¬ bulent mixing of the two different types of fibers. Upon deposition onto a collecting surface, these mixed fibers form a bat of homogeneously mixed microfibers and staple fibers.

This invention relates to improvements to the fabrics and processes described above, and to so- lutions to some of the problems raised or not solved thereby. Summary of the Invention

It is the intent of this invention to pro¬ duce stratified layered fabrics having no sharp lines of demarcation which can be readily separated during use, but rather layered fabrics with surface bound¬ aries wherein the simultaneous surface fiber intermin¬ gling occurred between the emission nozzles and the collection surface. This one step process of joining stratified layers by the predetermined intermingling or intermix¬ ing of boundary fibers prior to their simultaneous deposition onto a collecting surface makes it possible to form two sided stratified fabrics having two or more fibrous webs or layers with different fiber types - 8 -

and inseparable joinings at their boundaries of inter- tangled and mingled fibers. The term "two sided fab¬ ric", is used herein to describe a fabric having out¬ side surfaces with different physical or other charac- teristics.

According to the invention the fiber quan¬ tity gradient across the depth of the fabric is easily changed by varying the amount of gas-fiber stream overlap. This gradient is shallow if the gas-fiber stream overlaps are small and can be of considerable depth if the gas-fiber stream overlaps are large. This increased depth of fiber quantity gradient may reach almost to the opposite side, yet the outside surfaces may have different characteristics which re- late to the respective fiber characteristics of the fibers contained in the gas-fiber streams.

In the instant invention the joining of two or more adjacent layers of non-woven fabric is ob¬ tained by the high velocity intermingling of fiber laden hot gas streams as they travel between the melt blown orifice and the deposition surface. The fiber bonding can range from fusion bonding of molten or heat softened bonds solely to intermingling or entan¬ gling to a predetermined depth of cooled, solidified fibers rather than the deposition of fibers onto an already formed and solidified web.

The quality and tenacity of the surface joining of directly deposited melt blown fibers onto a previously formed, cooled and stretched fibrous non- woven elastic layer or web is in sharp contrast to the superior quality and tenacity of the simultaneous sur¬ face or boundary joining of fibrous layers or webs wherein the fibrous stratified webs of the various fabrics are formed and joined simultaneously and wherein portions or depths of the fibers of each of - 9 -

the two joining boundaries or gas-fiber mixtures are intimately intermingled and intertwined prior to or at their deposition onto a collecting surface. This si¬ multaneous joining by intermingling in depth of two or more types of fibers and/or filaments between the extrudate orifices and the collection surfaces allow the intermingling to be accomplished in temperatures which range from molten to softened to solidified which in turn allows bonding of one or more types of fibers, to range between full fusion bonds, to stick bonds, to release bonds and finally, to the joining of solidified fibers or filaments by sole entanglement of two or more types of fibers. A more complete descrip¬ tion of these types of bonding is given in Sabee, U.S. Patent No. 4,910,064. If the fibers of at least one of the layers or webs are in a molten or heat softened state at the time of entanglement or intermingling, it would ensure a high degree of fusion bonding of the adjacent joined in predetermined boundary depth of fibrous layered or stratified composite materials.

The predetermined, boundary or gas-fiber mixture, depth joining of simultaneous depositions of two or more melt blown fiber and gas streams of like or dissimilar materials facilitates the homogeneous distribution of the two or more types of fibers, thereby forming an indepth boundary or gas-fiber mix¬ ture junction which is unseparable without damaging or rupturing the fabric. Extremely low basis weight webs of exceptional strength are obtained due to the inti- mate fiber indepth intermingling in the forming of the coalesced fabric.

The tenacity of the boundary or gas-fiber mixture "in-depth" joining by simultaneous fiberizing and mingling of various streams of air- or gas-borne fibers varies with the amounts or the size of the por- - lo ¬

tions of various fibrous streams which are mingled or entangled. The greater the portions of high velocity gas-fiber streams are, the greater will be the depth of the joining in the fibrous stratified fabric with a corresponding increase in the junction strength. This increase in the depth of the boundary or gas-fi¬ ber mixture junction of two or more fibrous layers or webs is obtained by increasing the portion of the heated gas-fiber deposition sprays which overlap and are turbulently intermingled upon their high velocity emission from the air and extrudate spinnerets or ori¬ fices in their travel from the spinnerets to the depo¬ sition surface.

This simultaneous intermingling of two or more types of fibers and/or filaments between the extrudate orifices and the collecting surfaces allow the intermingling to be accomplished at fiber tempera¬ tures which range from molten to softened to solidi¬ fied in the various gas-fiber entangling streams. The temperature range of the intermingled fibers permits the bonding or joining of fibers ranging from full fusion to entangling of fibers having no bonding at their intersections. In addition to the excellent joining results obtained by indepth joining of inter- mingled cooled and solidified fibers in the formation of stratified fibrous fabrics, many types of fabric surface characteristics are obtained with the use of elastomeric materials in the forming of fabrics which contain at least some elastic fibers and some elon- gateable but non-elastic fibers. Suitable fibers for use in forming indepth joined stratified elasticized webs are elastomeric fibers of all kinds and types, self-adhering elastic fibers such as Fullastic self- adhering elastic materials from the H.B. Fuller Co. of St. Paul, Minnesota or pressure sensitive adhesive - 11 -

fibers of all types. It will be understood that this invention is not to be limited to the aforementioned adhesive fibers. On the contrary, it is intended that all fiberizable hot melt adhesives in addition to all types of fiberizable elastomeric adhesives and equiva¬ lents as may be included within the spirit and scope of the invention as defined by the appended claims.

The melt blowing of adhesive fibers is per¬ formed by the same technique as in the previously dis- cussed article by Van A. ente, and forms diameters ranging from less than 0.5 microns to more than about 250 microns. These adhesive fibers are made by ex¬ truding a molten thermoplastic adhesive material through a plurality of fine die capillaries as a mol- ten extrudate of filaments into a high velocity gas stream which attenuates the filaments of molten adhe¬ sive material to reduce their diameter to the above stated range in the formation of microfibers or fila¬ ments. Any fiberizable hot melt adhesive material is suitable in the formation of adhesive fibers to be used in the intermingling and the joining of strati¬ fied fibrous fabrics. Elastomeric adhesives, pressure sensitive adhesives, pressure sensitive hot melts, visco-elastic hot melts, self-adhering elastic materi- als and conventional hot melt adhesives are some of the adhesives suitable for forming adhesive fibers, but again it is to be understood that the present in¬ vention is not to be limited to these specific adhe¬ sives. As has been previously stated, the melt blown adhesive fibers do not stiffen the fibrous stratified fabrics as do the roller applied or coated adhesives. These latter adhesives fill crevices and interstices between the fibers of the fibrous layer or web, and after solidification can bind groups of fi- - 12 -

bers together. This effect stiffens the fibrous layer and has a deleterious effect on the hand and drape. The melt blown adhesive fibers on the other hand, act as do the fibers of the layered fibrous web, and not as sprays such as paint sprays, wherein small droplets of paint are emitted from the gun. The melt blown fibers, being flexible and of small diameter, are tur- bulently entangled with the fibrous web fibers and form bonds at their intersections with these fibers. These intersectional adhesive bonds behave similarly to fusion bonds with no noticeable stiffness of the composite fabric. They have the additional feature that the elastomeric adhesive fibers stretch or elon¬ gate under stress. The high velocity gas and fiber intermin¬ gling of two or more fiber types takes place in the overlapped portions of two or more deposition spray zones. Each of the spray zones is the shape of the intersection of two planes, with the apexes of the dihedral angles at the extrusion spinnerets, and the dihedral angle openings between the intersections of the planes being at the deposition surface. The smaller the overlap of the fiber deposition zones, the shallower will be the depth of the simultaneously in- termingled fibers of the overlapped deposition spray zones. That is, as the deposition zone overlap is reduced, the simultaneous intermingling depth becomes less. Finally as the overlap of the deposition zones is reduced to zero, any simultaneous intermingling of boundary fibers takes place on the deposition surface. If the deposition zones are separated completely, there is no simultaneous intermingling of the fibers in the deposition zone. The process then becomes one wherein the fibers of a first spray zone are deposited on a deposition surface, thereby forming a cooled fi- - 13 -

brous web, after which the fibers of a second spray zone are deposited onto the first fibrous web, forming a second cooled fibrous web. This resultant laminate is the result of two independent melt blown fiber de- positions rather than the simultaneous deposition of two types of fibers from two fiber laden high velocity gas streams wherein portions of each stream are entan¬ gled and intermingled during their passage to a depo- sition surface to form an indepth mingling of the two types of fibers having a quantity fiber gradient of both of these fibers throughout the depth of the re¬ sultant joined boundaries of both webs.

It is an object of this invention to form junctions between two fibrous stratified layers which are comprised of the controlled entanglement of the fibers of the two respective webs across the depth of the web and wherein the fibers of a first web have a decreasing first fiber quantity gradient across the web while the second web has an increasing second fi- ber quantity gradient across the web at the site of the joining of the two webs thereby eliminating need to use bonding or joining methods having sharp lines of demarcation with their associated web integrity and cohesion problems. Additionally, the present invention over¬ comes the delamination or web separation problem, with its accompanying loss of integrity upon application of a stretching force by providing a method or process for making low cost layered sandwiches, stratified fabrics or laminates wherein the various web or layer boundary fibers of one layer or web are intermingled to a predetermined depth with the adjacent boundary fibers of a second layer or web via turbulent mixing of the two sets of fibers in fiber laden gas streams. That is, a predetermined portion or depth of the - 14 -

boundary fibers and/or filaments of a first fibrous layer or web are intermingled or blended with a prede¬ termined portion or depth of the boundary fibers and/or filaments of a second layer or web. This tur- bulent mixing of the adjacent boundary fibers of two fibrous webs in a high temperature, high velocity gas stream prior to deposition onto a collection surface attains a homogeneous distribution of the two differ¬ ent surface or boundary fibers at the joining site, forming an intertwined, coherent high tenacity matrix of these two types of fibers to a predetermined depth.

The entangling of two types of fibers in two independent turbulent gas streams occurs after the emission of the extrudate and the high velocity fiberizing gas streams have left their respective spinnerette capillaries on their way to the deposition surface.

This intermingling and entangling begins at a distance from the die tip which is determined by the type of entangling and fiber joining desired. Fusion bonding of molten fibers occurs closer to the die tip than does the mechanical entanglement of solidified filaments.

It is at this initial stage of entanglement process that the velocities of gas and fibers are the highest and where the entangling process is the most efficient. As the gas-fiber mixture approaches the deposition surface which may consist of a foraminous belt or drum over a vacuum chamber, the fibers are cooled and solidified by aspirated air or gas above the foraminous belt and the ambient air which is drawn through the belt by the vacuum from the vacuum cham¬ ber.

Upon deposition onto the deposition surface, the excess air is removed from the air or gas-fiber - 15 -

mixture leaving a compacted fibrous stratified fabric on the foraminous belt. This fabric is comprised of 100% fibers of a first material at one outer surface of the fabric and 100% fibers of a second material at the second outer surface of the web with the central portion of the fibrous fabric comprised of an entan¬ gled mixture of fibers from the first and second mate¬ rials having fiber quantity gradients across its depth at the joining site. The resultant fabric is a strat- ified two fibrous layered fabric of different fibrous materials having no sharp line of demarcation at the joining site of the two layers but rather having a fiber quantity gradient across the depth of the join¬ ing site. It should be understood that it is almost impossible to turbulently intermingle portions of two or more sets of fibers and deposit them in clear cut or sharp lines of deposition. Rather, it is generally a feathered out entanglement which is preferred. It is the main objective of the present in¬ vention to provide a process wherein the fibrous boundary junction, of at least two fibrous layers, is accomplished by turbulent entanglement of the boundary fibers of at least two adjacent gas-fiber streams or sprays during their travel from the extrusion orifices to the collection surface. This is achieved by simul¬ taneously directing the heated expanding gas-fiber streams or sprays onto the deposition surface in a partially overlapped laydown pattern wherein predeter- mined portions of one type of fiber are entangled with predetermined portions of a second type of fiber to form a fiber quantity gradient of both types of fibers across their depth and wherein the remaining portions of the two fiber types form the stratified layers of the respective first and second fiber types. - 16 -

It is another object of the present inven¬ tion to provide a process and method of varying the depth of boundary fiber intermingling to form layered laminated fabrics having no sharp lines of demarcation between adjacent fibrous layers thereby eliminating the need for adhesive coatings and other types of bonding of the individual fibrous layers to each other to form fibrous fabrics having many various properties and uses. In a preferred embodiment elasticized fab¬ rics are formed wherein the elastomeric or elastic fibers are intertwined with the non-elastic fibers throughout the fabric in a predetermined manner which is suitable for extremely light weight, low basis weight elasticized fabrics.

An important object of the present invention is to provide a low cost, light weight, stratified fabric comprising two or more fibrous webs wherein the joining of various fibrous webs or layers is accom- plished by an indepth intermingling and entangling of the fibers of the joining surfaces to a predetermined depth while the fibers are at temperatures wherein they vary from the molten to the cooled solidified states and wherein the junction ranges from fusion bonding of entangled fibers to only the physical tur¬ bulent entanglement of the solidified fibers. The range of bonding includes release or stick bonds which are more fully described in Sabee '064.

It is another object of the present inven- tion to provide a process and apparatus for forming stratified fibrous fabrics wherein two or more fibrous layers or webs are joined with a predetermined indepth penetration and intermingling of the boundary fibers of the joined layers or webs. It is another feature of the present inven- - 17 -

tion to provide a fabric comprising three stratified fibrous layers or webs wherein at least a portion of the fibers of all three layers or webs are entangled and intermingled with each other. It is yet another object of the present in¬ vention to provide a stratified fabric wherein at least the surface fibers of adjacent fibrous webs are joined to each other by fiber entanglement and wherein the fiber entanglement of adjacent webs with each oth- er occurred prior to deposition onto a collection sur¬ face.

It is another feature of the present inven¬ tion to provide a stratified fibrous fabric formed by turbulently entangling about 100% of the fibers of a first gas-fiber spray with a portion or portions of the fibers of a second gas-fiber spray to form, upon deposition onto a collection surface, a two sided fab¬ ric, each side having different physical properties and characteristics. Yet another general object of the present invention is to provide a stratified fabric comprising fibrous layers in which at least one of the fibrous layers consists of adhesive fibers and in which prede¬ termined portions of the adhesive fibers are entangled and intermingled with predetermined portions of fibers of at least one adjacent layer or web boundary to form a predetermined fiber quantity gradient of the adhe¬ sive fibers in the depth direction of the adjacent layer or web. It is another object of this invention to produce a process and apparatus for producing a strat¬ ified fibrous elasticized fabric wherein a predeter¬ mined amount of boundary fibers of an elastomeric fi¬ brous layer are intermingled and entangled with a pre- determined portion of non-elastic but elongateable - 18 -

boundary fibers of a non-elastic but elongateable fi¬ brous layer or web to form boundary junctions compris¬ ing fiber quantity gradients across their depths. These non-woven elasticized fabrics may vary from ex- tremely light weight webs of about 10 grams or less per square meter to heavy weight webs of more than 300 grams per square meter and may comprise one or more layers of elastomeric fibrous webs alternating between layers of elongateable but non-elastic fibrous webs. It is also a primary object of this inven¬ tion to form an elasticized fabric which does not have coherency problems wherein the elongateable but non- elastic fibrous layer is not sufficiently cohered to the elastomeric fibrous layer to prevent web separa- tion and loss of integrity of the formed fabric upon the application of a stretching force.

It is also a primary object of the present invention to provide a non-woven elasticized fabric having one or more elongateable but non-elastic fi- brous webs sandwiched or combined with one or more elastomeric fibrous webs and wherein at least a prede¬ termined portion of the elongateable but non-elastic fibers are intermingled and fusion bonded or stick bonded to a predetermined portion of the elastomeric fibers.

Another object of the present invention is to provide a process which does not require heat, ad¬ hesives or sonic bonding in the forming of non-woven elasticized webs. Another object is to provide a process not requiring the necessity of having a relaxing and cool¬ ing step as used in the stretch bonded process.

It is also a primary object of this inven¬ tion to have predetermined amounts of the surface fi- bers of a first web intermingled or entangled with - 19 -

predetermined amounts of the surface fibers of a sec¬ ond web thereby forming a quantity gradient of the fibers of the first and second webs throughout the depth of the boundary layer of the fabric. It is another object of this invention to provide a non-woven stratified fabric in which the intermingled fibers of the various webs or layers are joined while in a physical state ranging from molten to heat softened to full solidified or in any interme- diate state.

It is also an object of this invention to have the intermingled fibers of a first layer or web be in a molten or heat softened state while the inter¬ mingled fibers of a second layer or web are in a so- lidified state at the time when entanglement takes place.

It is also an object to have intermingling of layer boundary fibers take place between the emis¬ sion nozzles and the collection surface. It is also an object to provide joined multilayer fabrics wherein stratified portions of said joined layers or webs comprise mainly one type of en¬ tangled fibers which lie between boundary layers com¬ prising at least two types of entangled fibers. Other objects and advantages of the inven¬ tion will become apparent hereinafter. Description of the Drawing

Fig. l is an isometric view of an apparatus constructed to practice one embodiment of the method of the invention, and to produce one embodiment of the product of the invention.

Fig. 2 is a bottom view, looking up, of a number of extrusion heads for a melt blowing device as employed in the practice of the invention. Fig. 3 is a side view of the apparatus shown - 20 -

in Fig. 1.

Fig. 4 is a side view of an apparatus con¬ structed to practice an alternative embodiment of the invention incorporating a creping function. Fig. 5 is a side view of an apparatus con¬ structed to practice the invention by use of a drum- type collector.

Fig. 6 is a side view of an apparatus con¬ structed to practice an alternative to that shown in Fig. 5.

Fig. 7 is a side view of an apparatus con¬ structed to practice another alternative to that shown in Fig. 5.

Fig. 8 is a side view of an apparatus con- structed to practice an embodiment which is a slight modification from that shown in Fig. 6.

Fig. 9 is a side view of a number of extru¬ sion heads for a melt blowing device as employed in the practice of the invention, including orifice ex- trusion tips which are specially angled and posi¬ tioned. Description of the Preferred Embodiments

The term "boundary joining" as used herein pertains to the joining of the broad surfaces, not the ends or sides, of the various fibrous layers or webs being joined, and to the turbulent intermingling or intertangling of the two respective surface fibers with each other prior to or at their simultaneous de¬ position onto a collecting surface. This intermin- gling of the respective layer surface fibers of two fibrous layers prior to or at their simultaneous depo¬ sition onto a collection surface, forms a far superior joining than does the joining obtained by the deposi¬ tion of fibers onto a previously deposited solidified fibrous web, wherein the newly deposited fibers lie - 21 -

mainly on top of the previously deposited layers, with some of the fibers lying onto or in crevices and in¬ terstices of the previously formed layer, rather than being turbulently intermingled with another boundary fiber.

The terms "simultaneous intermingling in¬ depth", "predetermined surface depth joining", "prede¬ termined surface depth junction", "joined indepth", "indepth intermingling", "indepth surface joining", "indepth fiber entanglement", "indepth bonding", "indepth joining" and "indepth junction" are herein used interchangeably and are intended to mean the type of entangling of fibers that is obtained when a por¬ tion of one gas-fiber stream is entangled with a por- tion of one or more other gas-fiber streams in their travel between a die orifice and a collection surface.

There term "indepth boundary fibers", is herein meant to be the joining fibers of two or more fibrous layers which have been intermingled in the distance between the extrusion fiberizing die and the collection surface, and may consist of thermoplastic fiberized materials, pulp fibers or any of the staple fibers.

The terms "gas-fiber spray", "gas or air- ^• fiber spray", "gas-fiber stream", "gas-fiber mixture", "fiber", "gaseous stream" and "deposition spray zone" are herein used interchangeably and are intended to mean a high velocity stream or spray comprised of in¬ termingled fibers turbulently mixed in air or substan- tially inert gases such as carbon dioxide or nitrogen.

As has been previously stated, the melt blown adhesive fibers do not stiffen the fibrous stratified fabrics as do the roller applied or coated adhesives. These latter adhesives often fill crevices and interstices between the fibers of the fibrous lay- - 22 -

er or web and, after solidification, bind groups of fibers together, which stiffens the fibrous layer and has a deleterious effect on the hand and drape. The melt blown adhesive fibers on the other hand act as do the fibers of the layered fibrous web and not as sprays such as paint sprays, wherein small droplets of paint are emitted from a gun. The melt blown fibers, being flexible and of small diameter, are turbulently entangled with the fibrous web fibers and form bonds at their intersections with these fibers. These in- tersectional adhesive bonds behave similarly to fusion bonds with no noticeable stiffness of the composite fabric. They also provide the additional feature that the elastomeric adhesive fibers stretch or elongate under stress.

Some of the materials for use in forming indepth, joined, stratified webs such as those dis¬ closed here are polyolefins such as polypropylene, polyethylene, polybutane, polymethyldentene, ethylene- propylene co-polymers; polyamides such as polyhexa- methylene adipamide, poly-(oσ-caproa ide) , polyhexa- methylene sebacamide, polyvinyls such as polystyrene, thermoplastic elastomers such as polyurethanes, other thermoplastic polymers such as polytrifluorochloroeth- ylene and mixtures thereof; as well as mixtures of these thermoplastic polymers and co-polymers; ethylene vinyl acetate polymers, synthetic polymers comprising 40% or more of polyurethane; polyetheresters; poly- etherurethane; polyamide elastomeric materials; and polyester elastomeric materials S-EB-S Kraton "G" Block co-polymers and Kraton GX 1657 Block co-polymers as furnished by Shell Chemical Company; polyester elastomeric materials under the trade name "Hytrel" from the Dupont Company; polyurethane elastomeric ma- terials under the trade name "Estane" from B. F. Good- - 23 -

rich and Company and polya ide elastoceric material under the trade name "Pebax" from Rilsam Company, in¬ cluding co-polymers, blends or various formulations thereof with other materials. Also included are viscoelastic hot melt pressure sensitive adhesives such as "Fullastic" supplied by H.B. Fuller and Compa¬ ny and other hot melt adhesives including pressure sensitive adhesives. Any of the fiber forming thermo¬ plastic polymers including fiber forming hot melt ad- hesives, pressure sensitive adhesives, and viscoelas¬ tic hot melt pressure sensitive adhesives can be used for stabilizing the web or bonding the stabilized web to one or more cellulose webs, wood pulp webs, melt blown fibrous mats, or for laminating and bonding two or more stabilized webs to from laminates. The in¬ stant invention is not limited by the above polymers, for any thermoplastic polymer, co-polymer or mixture thereof capable of being melt blown into fibers or filaments is suitable. Any of the thermoplastic elas- tomers which are capable of being melt blown or melt spun are suitable for the manufacture of stretchable fabrics.

It will be understood that this invention is not to be limited to the aforementioned materials. On the contrary, it is intended that, unless the context requires otherwise, all fiberizable thermoplastic polymers, co-polymers and blends thereof, in addition to wood pulp or cellulose fibers and including staple fibers and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims are to be included.

Referring now to Figure 1, there is shown fabric forming apparatus 10 for forming stratified fi¬ brous melt-blown fabrics having boundary joinings or junctions of fiber-to-fiber quantity gradients across - 24 -

their depths. The apparatus 10 includes a number of extruders 12a, 12b and 12c, each having a respective die head 14, 16 and 18.

Four die heads 14, 16, 18, 19 are shown in Fig. 2, as an example and to indicate that various numbers of die heads may be employed within the spirit of the invention. As shown in Fig. 2, each die head 14, 16, 18, 19 includes a plurality of orifice extru¬ sion tips 20, 22 and 24, preferably arranged in one or more rows, wherein the longitudinal and lateral spac- ings and the angles or directions of extrudate emis¬ sion as shown in Fig. 2 are varied to obtain various indepth entanglements or various fiber quantity gradi¬ ents across the depth of the joined fabric at the site of the junction. According to the invention, the amount of gas-fiber spray overlap onto the adjacent gas-fiber spray determines the depth of the fiber quantity gradient of the two or more entangled fibers. The individual extrusion tips 20, 22, 24 may be spaced and positioned at angles such that fibrous emissions from extrusion tips 24 in the last row of melt blown die 16 are directed between the fibrous emissions from extrusion tips 20 in the first row of melt blown die 18, and so on. This allows the intermeshing of fi- brous emissions from extrusion tips 24 of melt blown die 16 and the fibrous emissions from extrusion tips 20 of melt blown die 18. This intermeshing of the various fiber streams with one another facilitates deeper penetration of two or more types of entangling fibers.

Turning back to Fig. 1, beneath the die heads 14, 16 and 18 is positioned a collection or de¬ position surface 26 comprising a foraminous belt 28 moving over a vacuum chamber 30 equipped for indepen- dent vacuum pressures under each die head. The neces- - 25 -

sary hoppers, drives, temperature controls, and vari¬ ous air or gas pressure and vacuum supplies are well known and are not shown. Each die head 14, 16, 18 may extrude one or more fiberizable materials and be posi- tioned at various angles to each other as determined by the angles of polymer emission at which the orifice extrusion tips 20, 22, 24 are to be set. As the extrudate is emitted from the extrusion tips 20, 22 and 24 into high velocity gas streams, they form fiberized turbulent gas-fiber mixtures or fibrous sprays 32, 34 and 36 in their travel from the orifices to the deposition surface 26 to form a .layered or stratified fibrous non-woven fabric 38 by being drawn onto the deposition belt 28 with vacuum from chamber 26. The various melt blown gas-fiber sprays 32, 34, 36 are deposited simultaneously onto the foraminous belt 28 in partially overlapping orientations of their respective portions, subsequent to turbulent intermin¬ gling and entangling before reaching the foraminous belt. The overlapping of the gas-fiber sprays 32, 34, 36 is variable and is accomplished by varying the dis¬ tance between the die heads 14, 16 and 18 and the foraminous belt 28 and the distances between each of the die heads themselves. Referring now to Figs. 1 and 3, the gas-fi¬ ber mixture 32 and the gas-fiber mixture 34 are com¬ bined to form the gaseous mixture of fibers 40 and 42 at joining site 46, while simultaneously combining the gas-fiber mixture 34 and the gas-fiber mixture 36 to form the gaseous mixture of fibers 42 and 44 at join¬ ing site 48. Upon deposition onto foraminous belt 28, the air or gas is withdrawn from the gaseous mixture, thereby compacting all the fibers and mixtures of fi¬ bers into the stratified fibrous fabric 38. As can be seen at Fig. 3, the fabric 38 contains the indepth - 26 -

boundary 50 comprising intermingled fibers 40 and 42 and also the indepth boundary 52 comprising intermin¬ gled fibers 42 and 44. That is, the stratified fi¬ brous fabric 38 contains the indepth intermingled fi- brous boundary 50 comprising fibrous layers or webs 54 and 56 and the indepth intermingled fibrous boundary 52 of fibrous layers or webs 56 and 58. This indepth intermingling processing of fibers 40 and 42 forms this fiber quantity gradient 50 at joining site 46 and deposited onto collecting site 60. Both the die spac- ings and the distances between the die orifices and the deposition surfaces are adjustable to facilitate the setting of predetermined fiber gradient depths and surface characteristics. In particular, the process of forming strat¬ ified fibrous fabrics having predetermined fiber in¬ depth entanglements of the various layer boundaries with one another during fabric formation includes the following steps. The polymeric material, after pas- sage through the heated extruder 12, die heads 14, 16, 18 and extrusion tips 20, 22, 24, is emitted from the extrusion tips as molten extrudate in the form of fil¬ aments or fibers 40, 42, 44 and injected into a high velocity heated gas stream. The gas stream may be air, nitrogen or some other inert gas which attenuates the molten filaments 40, 42, 44 at fiberizing veloci¬ ties to form gas-fiber sprays 32, 34, and 36 respec¬ tively. A first portion of the fibers 40 of gas-fiber spray 32 are deposited directly onto foraminous belt 28. A second portion of the fibers 40 of gas-fiber spray 32 are then intermingled with a first portion of the fibers 42 of gas-fiber spray 34 and deposited onto the previously deposited fibers 40. This is followed by a deposition of a second portion of fibers 42 of gas-fiber spray 34 onto the previously deposited in- - 27 -

ter ingled fibers 42 and 403. The third remaining portion of fibers 42 of gas-fiber spray 34 are then intermingled with a first portion of fibers 44 of gas- fiber spray 36 and deposited onto the previously de- posited second portion of fibers 42 of gas-fiber spray 34. Lastly, the second and remaining portion of fiber 44 of gas-fiber spray 36 is deposited onto the previ¬ ously deposited intermingled fibers 40 and 42, thereby completing the forming and emergence of a three layer stratified fibrous fabric 38 having two boundary junc¬ tions of fiber to fiber quantity gradients 50 and 52 across their depths. The first fiber quantity gradi¬ ent 50 occurs at site 46 with an intermediate of fi¬ bers 40 and 42, the second fiber quantity gradient 52 occurring at site 48 with an intermingling of fibers 42 and 44. The lower surface of the stratified fi¬ brous fabric 38 adjoining the foraminous belt 28 is comprised of fibers 40, with the upper surface 58 be¬ ing comprised of fibers 44 and the central layer or web 56 comprising fibers 42.

By use of the invention, the complete fabri¬ cation of a composite non-woven elasticized fabric having relatively inseparable junctions at the bound¬ ary sites of intermingled fibers of different types, such as intermingled elastomeric fibers and elongate¬ able but non-elastic fibers, is now possible. In par¬ ticular, as shown in Fig. 4, such a fabric is formed by the simultaneous deposition of two or more gas-fi¬ ber overlapping sprays, one of which comprises elasto- meric fibers which upon deposition onto a collecting surface forms boundary junctions of fiber-to-fiber quantity gradients across their depths. Elastic fi¬ bers are simultaneously extruded and melt blown through three melt blown dies 14, 16 and 18. The cen- ter die 16 forms elastomeric fibers 42, while the out- - 28 -

er dies 14 and 18 form elongateable but non-elastic fibers 40 and 44. Portions of each type of fiber are intermingled before deposition onto collection surface 26 wherein the collected fibers form a three layer stratified elastomeric fibrous fabric 38 with boundary junctions having fiber quantity gradients across their depths.

The elasticized fabric 38 may be subsequent¬ ly passed through squeeze rolls 64, stretch-and-draw rolls 66 and/or corrugated crimp rolls 68 to stretch the inner elastomeric fibrous layer 56 and elongate and molecularly orient the two outer elongateable but non-elastic fibrous layers 54 and 58. Upon completion of stretching and molecular orientation, the fabric 38 may be relaxed, whereupon gathers are formed in the two outer non-elastic layers 54 and 58 by the inner elastomeric layer 56. The relaxed elasticized fabric 38 may then be wound into a roll 70 conventionally on a two drum winder 72. The incremental stretching pro- cess is further described in Sabee '064, Sabee '664; and in application Docket No. 1344 entitled "Elasti¬ cized Fabric with Continuous Filaments", the disclo¬ sures of which are incorporated herein by reference and relied upon. As previously mentioned, many types of fab¬ ric surface characteristics are obtained with the use of various types of fibers which may be mingled in varying degrees with other fibers to form non-slip surfaces, pressure sensitive adhesive surfaces, elas- tomeric fibrous surfaces and many others. Varying degrees of adhesive properties are obtained by varying the predetermined depth of joining of simultaneous overlapping depositions of two or more melt blown gas- fiber streams, at least one of them being adhesive fibers. Elastomeric fibers having low to high elastic - 29 -

recovery after stretching and relaxation are suitable for tailoring the surface characteristics of fibrous melt blown fabrics. In addition elongateable but non- elastic fibers do not necessarily require high perma- nent elongation to effectively vary surface character¬ istics of fibrous webs having fibrous quantity gradi¬ ents across their depths. This allows the use of low cost materials in the forming of fibrous fabrics hav¬ ing unique surface characteristics. The predetermined intermingling of at least two types of polymeric fi¬ bers can take place in a narrow portion of the fabric depth wherein one side of said fabric is comprised of substantially all of a first type of fiber with the opposite side of the said fabric being comprised of substantially all of a second type of fiber. Alterna¬ tively the predetermined entanglement of at least two types of polymeric fibers may take place throughout a major portion of the fabric wherein one side of the said fabric may be comprised of an intermingled ix- ture of a large portion of a first type of fiber and a small portion of a second type of fiber with the opposite side comprising a large portion of a second type of fiber intermingled with a small portion of a first type of fiber. It is to be understood that it is not intended to limit the fibrous materials to those disclosed herein, because any polymeric fiberiz¬ able material will suffice. This includes all fiber¬ izable polymeric thermoplastic materials ranging from elastomeric to non-elastic materials including adhe- sive materials ranging from elastomeric pressure sen¬ sitive adhesives to hot melt polymeric adhesives.

Fig. 5 illustrates one application of this concept. A stratified elastomeric fibrous fabric 78 having fiber quantity gradients across the depth of the fabric is formed on a drum-type collector 74 hav- - 30 -

ing a patterned or smooth surfaced foraminous rotating drum 76. In this embodiment, a first extrusion die 80 is positioned above the clockwise-rotating deposition drum 76. A first gaseous stream 82, containing elas- tomeric fibers 84, is emitted, the fibers being depos¬ ited onto drum 76. Adjacent to and downstream from first die 80 is a second die 86 from which a second gaseous stream 88 containing non-elastic polymeric fibers 90 is emitted. The second die 86 is positioned with respect to the first die 80 so that the fibers 90 are deposited onto drum 76 in a partially overlapped and intermingling mixture with a portion of the elas¬ tomeric fibers 84. The unlapped portion of fibers 90 is deposited and joined indepth to the previously de- posited mixture of fibers 84 and 90 to form fibrous layer or web 92.

The surface of the formed fabric 78 adjacent to the drum 76 is comprised of elastomeric fibers 84 with a rubbery feel and a high degree of slip resis- tance. This is because first gas-fiber stream 82 con¬ taining elastomeric fibers 84 is deposited onto the drum 76 prior to the deposition of the intermingled elastomeric and non-elastic polymeric fibers, that is, prior to the fibrous quantity gradient deposition area 94 at the joining site 96. The fiber quantity gradi¬ ent 98 comprising elastomeric fibers 84 and non-elas¬ tic polymeric fibers 90 lies between the elastomeric fibrous layer 100 and the non-elastic polymeric layer 102 comprising the outer layer on the drum 76. The outer surface of layer 102 will have characteristics related to the fibrous material forming layer 102. As the gas-fiber stream 88 is increased in size so as to overlap a greater area or portion of the gas-fiber stream 82, the less rubbery and less slip resistant will be the outer surface of layer 100. - 31 -

Reversing the rotation of collecting drum 76 of Fig. 5 will form a fabric having the surface adja¬ cent to the drum 76 comprised of non-elastic polymeric fibers 90 and an outer surface comprising elastomeric fibers 84.

Fig. 6 illustrates a case wherein the melt blown fiber dies 80 and 86 are positioned so that the second gas-fiber stream 88 containing non-elastic but elongateable polymeric fibers 90 completely envelopes the first gas-fiber stream 82 containing elastomeric fibers 84. The result of this arrangement is that the surface of the fabric 78 adjacent to collecting drum 76 comprises an intermingled mixture of elastomeric fibers 84 and non-elastic polymeric fibers 90. Hence that surface of the fabric 78 has a decreased rubbery feel and a lower slip resistance level. This lower slip resistance can be reduced further by reducing the throughput of the melt blown elastomeric fiber 84. This reduction can be accomplished by merely reducing the extruder screw velocity, adjusting the polymer temperatures, changing the fiberizing air pressures and temperatures, or some combination of these adjust¬ ments.

Again, reversing the rotation of collecting drum 76 of Fig. 6 will form a fabric having a surface adjacent to the drum 76 comprised of intermingled elastomeric fibers 84 and non-elastic polymeric fibers 90, and an outer surface of non-elastic polymeric fi¬ bers 90. The non-slip resistance can be varied by increasing or decreasing the extruder screw velocity which in turn varies the throughput of extruders 80 and 86.

Fig. 7 illustrates a drum type collector 104. The rotating deposition drum 106 of the collec- tor 104 may be foraminous and include a fixed vacuum chamber 108, and may have a surface ranging from smooth to patterned, on which to collect fibers which, in combination with various fiber materials, will form various surface characteristics of a formed non-woven stratified fibrous fabric 110. In the embodiment shown in Fig. 7, there are deposited three stratified fibrous layers or webs 112, 114 and 116 wherein at least a portion of the fibers of all three fibrous layers or webs are entangled and intermingled with each other at their respective boundaries. In a pro¬ cess the same as described above with respect to the other embodiments of the present invention, the gas- fiber sprays 118, 120 and 122 are extruded and emitted from dies 124, 126 and 128, respectively. The fibers 130, 132 and 134 of these sprays are turbulently en¬ tangled with each other to form the gaseous mixture of the fibers at site 136. Upon deposition onto the for¬ aminous drum 106, then, the stratified fibrous fabric 110 is formed, containing fiber quantity gradient 138 across the depth of the web is formed. Fabric 110 is thus comprised of fibrous layers or webs 112, 114 and 116 having a common fiber quantity gradient 138 of fi¬ bers 130, 132 and 134 at joining site 136.

An alternative embodiment is shown in Fig. 8, in which is illustrated the same structure as Fig. 6, but with certain additional structure. As shown in Fig. 8, an added extrusion die 140 may be used to form elastomeric filaments for the elasticizing of the fab¬ ric 78 by extruding elastomeric filaments 142 through extrusion die 140, cooling and solidifying the molten filaments 142 on temperature controlled chill roll 144 and depositing the solidified filaments on foraminous deposition drum 76. In this embodiment the drum 76 is traveling at a higher surface velocity than the sur- face velocity of chill roll 144. This difference in - 33 -

velocity stretches and elongates the elastic filaments 142 prior to the deposition of elastomeric adhesive fibers 146 onto drum 76 and subsequent depositions of a turbulent mixture of adhesive fibers 146 and non- elastic polymeric fibers 90 and the final deposition of only non-elastic polymeric fibers 90, thereby form¬ ing the stretched elasticized fabric 148. Upon exit¬ ing the drum 76 and consequent relaxation, the stretched elasticized fabric 148 contracts and forms gathers in the non-elastic fibrous layer 102. Another alternative is to extrude non-elastic filaments rather than elastic filaments 142 which upon being stretched between roll 144 and the deposition drum 76 are molec- ularly oriented, thereby increasing the strength of the final fabric. Another alternative is to deposit another web 150 from parent roll 152 onto drum 76 pri¬ or to the deposition of adhesive fibers 146. This again is followed by a turbulent mixture of adhesive fibers 146 and fibers 90 and the final deposition of only fibers 90, thereby forming a high strength lami¬ nated fabric comprising web 150, fibers 146 and fibers 90. The web 150 from parent roll 152 may be any suit¬ able prefabricated web including but not limited to dry or wet laid webs, spun bonded webs, melt blown webs, air laid webs, hydroentangled webs, film, spun laced webs, fibrillated films, needle punched webs, high loft fabrics, and stabilized, non-random laid, continuous filament webs as described in Sabee '064.

Fig. 9 shows three die heads 154, 156, 158 in end view, and corresponding rows of extrusion tips, in an arrangement modified from that shown in Fig. 2. As shown in Fig. 9, each die head 154, 156, 158 in¬ cludes a plurality of rows of orifice extrusion tips 160, 162 and 164. Tips 160 are straight, tips 162 are angled to one side and tips 164 are angled in the op- - 34 -

posite direction. As can be seen in Fig. 9, the lat¬ eral spacings and the angles or directions of extrud¬ ate emission are arranged so that the angled tips 162, 164 actually extrude fibers closer to the adjacent head than to the head to which the respective tip is attached. This embodiment further assures the turbu¬ lent intermixing of the fibers from the different die heads to obtain indepth entanglements and fiber quan¬ tity gradients across the depth of the joined fabric at the site of the junction, and facilitates deeper penetration of two or more types of entangling fibers.

In another embodiment, referring again to

Figs. 1, 2 and 3, fibers 40, 42 and 44 of lengths varying from about li inches to substantially continu- ous, are cooled to solidification between the orifice extrusion tips 20, 22, 24, and the deposition surface 26, and in so doing these fibers are frozen and set in spiraled, convoluted, twisted and bent shapes of all sizes. When portions of two or more gas fiber streams 32, 34, 36 of these wiry, twisted shaped filaments 40, 42, 44 are intermingled, the resultant web 38 consists of these turbulently entangled, springy, bulky, resil¬ ient and thick high loft fibers and/or filaments. Un¬ der compression, this fabric 38 resists matting or packing down, and upon the relaxation of the compres- sive force it expands and tends to return to substan¬ tially its original precompressed height. Applicant has found that the greater the overlap of the gas-fi¬ ber streams 32, 34, 36, the greater will be the in depth intermingling of the entangled boundary surface fibers and the greater will be the strength of the joined webs at their boundary.

While the apparatus hereinbefore described is effectively adapted to fulfill the aforesaid ob- jects, it is to be understood that the invention is not intended to be limited to the specific preferred embodiment of non-woven fabrics with fiber quantity gradients, and methods of preparing these fabrics, set forth above. Rather, it is to be taken as including all reasonable equivalents within the scope of the following claims.

Claims

- 36 -I claim:

1. A process for producing a fibrous strat¬ ified fabric, said process comprising: providing a moving deposition surface; extruding a first type of melt blown fibers into a first fibrous spray wherein said fibers are turbulently mixed with a gas; depositing said first type of fibers onto said deposition surface to create a fibrous layer en¬ tirely of said first type of fibers; extruding a second type of melt blown fibers into a second fibrous spray wherein said fibers are turbulently mixed with a gas; at least partially overlapping said second fibrous spray onto said first fibrous spray, such that said first type of fibers are at least partially in¬ termingled with said second type of fibers such that a mix of turbulently entangled fibers is formed; depositing said mix of turbulently entangled fibers onto said deposition surface to create an in- termingled fibrous layer of both types of fibers; depositing said second type of fibers not intermingled with said first type of fibers onto said deposition surface to create a fibrous layer entirely of said second type of fibers.

2. A process for producing an elasticized fibrous stratified fabric, said process comprising: extruding melt blown elastomeric fibers into a fibrous spray wherein said elastomeric fibers are turbulently mixed with a substantially inert gas; depositing said fibrous spray of elastomeric fibers onto a deposition surface; extruding melt blown elongatable but sub¬ stantially non-elastic fibers into a fibrous spray wherein said fibers are turbulently mixed with a gas, - 37 -

said fibrous spray of non-elastic fibers at least par¬ tially overlapping said fibrous spray of elastomeric fibers, such that said elastomeric fibers are at least partially intermingled with said non-elastic fibers to create an intermingled mix of turbulently entangled fibers; depositing said intermingled mix of fibers onto said deposition surface to create an intermingled fibrous boundary; drawing said first type of fibers onto a deposition surface by means of vacuum to form a first fibrous layer; depositing said non-elastic fibers not in¬ termingled with said elastomeric fibers onto said de- position surface to create a fibrous layer entirely of said non-elastic fibers.

3. A process for producing a fibrous strat¬ ified fabric, said process comprising: extruding a first type of melt blown fibers into a first fibrous spray; extruding a second type of melt blown fibers into a second fibrous spray wherein said fibers are turbulently mixed with a gas; positioning said said second fibrous spray so that said first fibrous spray is completely over- lapped by said second fibrous spray, such that all of said first type of fibers are intermingled with some but not all said second type of fibers, forming a mix of entangled fibers of both types; depositing said mix of entangled fibers onto a deposition surface to create an intermingled fibrous layer of both types of fibers; depositing said second type of fibers not intermingled with said first type of fibers onto said deposition surface to create a fibrous layer entirely - 38 -

of said second type of fibers.

4. A nonwoven fabric comprising at least two melt blown fiber depositions wherein portions of each said deposition is intermingled with each other and have an indepth fiber quantity gradient across the boundary depth of the web.

5. A nonwoven fabric comprising at least three melt blown fiber depositions wherein portions of each of said fiber depositions is intermingled with portions of its adjacent fiber depositions, the inter- mediate of said fiber depositions having both of its boundary portions intermingled with boundary portions of its adjacent fiber depositions, and having an in¬ depth fiber quantity gradient across the boundary depth of the web.

6. A nonwoven fabric comprising two or more melt blown fiber depositions wherein at least one of said fiber depositions is substantially completely intermingled with another fiber depostion and has an indepth fiber quantity gradient across its boundary depth.

7. A nonwoven fabric comprising three or more melt blown fiber depositions wherein portions of at least two fiber depositions are intermingled with each other portions and wherein at least one of said fiber depositions is substantially completely inter¬ mingled with portions of at least two other deposi¬ tions, and has one or more fiber gradients comprising said fibers of at least three of said fiber deposi¬ tions across its boundary depth.

8. A nonwoven fabric comprising two or more melt blown fiber depositions with at least a portion of a first melt blown fiber deposition intermingled with at least a portion of a second melt blown fiber deposition having fiber quantity gradients across its - 39 -

boundary depth, and joined to stretched and elongated, continuous, molecularly oriented, substantially non- elastic but elongatable, polymeric filaments.

9. A nonwoven fabric as recited in claim 5 wherein said stretched continuous filaments are at least somewhat elastomeric.

10. A nonwoven fabric as recited in claim 5 wherein said stretched continuous filaments are a stabilized continuous filamentary curtain.

11. A nonwoven fabric as recited in claim 10 wherein said stabilized continuous filamentary cur¬ tain is at least somewhat elastomeric.

12. A nonwoven fabric as recited in claim 10 or claim 11 wherein said stabilized continuous fil¬ amentary curtain contains transverse continuous fila¬ ments.

13. A non-woven fabric as recited in any one of claims 4, 5, 6 or 7 further comprising a pre¬ fabricated web joined to melt blown depositions.

14. A nonwoven fabric according to claim 13 wherein said prefabricated web is chosen from the group consisting of: fibrillated film, high loft fab¬ ric, dry laid web, wet laid web, film, spun bonded web, air laid web, melt blown web, spun laced web, hy- droentangled web, needle punched web or stabilized continuous filament non-random laid web.

15. A nonwoven fabric comprising two or more melt blown fiber depositions, wherein the fiber lengths vary from about lj inches to substantially continuous lengths, and wherein the fibers are solidi¬ fied into random shapes and wherein portions of each said deposition are intermingled with each other and have an in depth fiber quantity gradient across the boundary depth with a springy, resilient, bulky char¬ acteristic.