US3485709A - Acrylic nonwoven fabric of high absorbency - Google Patents

Description

. 23, 1989 F. J. EVANS AGRYLIC NONWOVEN FABRIC OF HIGH ABSORBENGY 4 Sheets-Sheet 1 Filed May 16, 1966 HIGH PRESSURE WATER SUPPLY INVENTOR FRANKLIN JAMES EVANS MARTIN R. LEVY ATTORNEY L A S N A V E i F ACRYLIC NONWOVEN FABRIC OF HIGH ABSORBENCY 4 Sheets-Sheet 2 Filed May 16,. 1966 F I G.

ATTORNEY.

23, 1969 J, EVANS EFAL 3,485,709

ACRYLIC NONWOVEN FABRIC OF HIGH ABSORBENCY Filed May 16, 1966 4 Sheets-Sheet S INVENTORS FRANKLIN JAMES EVANS MART'IN R. LEVY ATTORNEY Dec. 23, 1969 F. .1. EVANS ETA!- ACRYLIC NONWOVEN FABRIC OF HIGH ABSORBENCY Filed May 16, 1966 4 Sheets-Sheet 4 FIG? ATTORNEY United States Patent 3,485,709 ACRYLIC NONWOVEN FABRIC OF HIGH ABSORBENCY Franklin James Evans and Martin R. Levy, Wilmington,

DeL, assignors to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed May 16, 1966, Ser. No. 550,253 Int. Cl. B32b 3/10, 5/02; D0411 l/OO US. Cl. 161-109 12 'Claims ABSTRACT OF THE DISCLOSURE This invention relates to nonwoven fabrics of textilelike properties and uses, and which can be prepared directly from loose fiber webs by treatment with highirnpact-pressure liquid streams. The invention is more particularly concerned with nonwoven textile-like fabrics containing a substantial proportion of acrylic fibers in an entangled structure which provides high absorbency and adequate durability to withstand repeat d laundering and reuse.

Nonwoven fabrics have previously been patented or described in printed publications which can be used as inexpensive substitutes for woven fabrics for some purposes. However, these nonwoven fabrics have not provided strength or durability in combination with t xti elike properties, particularly when absorbency for liquids is a requirement. Thus they have found limited use for such purposes as disposable diapers, where they are discarded after a single use since they are not suitable for laundering and reuse. While their strength or durability can be improved by application of binders or resins, these impair the softness and absorbency of the fabric to such an extent that it is no longer suitable for use as a diaper.

Reusable absorbent fabrics for such uses have had to be woven or knitted fabrics in order to obtain the necessary strength and durability for repeated use. In general, diapers have been wov n from cotton yarns, since cotton has been regarded as pr viding the desired combination of absorbency and aesthetic properties. Similar observations apply to other uses requiring a soft, absorbent fabric.

The present invention provides strong, absorbent nonwoven textile-like fabrics which are especiall useful for reusable diapers and for other purposes requiring absorbency, strength and durability in repeated use. The invention further provides nonwoven fabrics which are superior to the commonly employed woven cotton diapers in absorbency, durability and aesthetic properties. These and other advantages of the present invention will become apparent from the disclosure and claims.

3,485,709 Patented Dec. 23, 1969 In the accompanying illustrations,

FIGURE 1 is a schematic view of apparatus suitable for preparing the fabrics,

FIGURE 2 is a schematic isometric view of apparatus for high-speed, continuous production of the fabrics,

FIGURE 3 is a photograph showing in plan view, at substantially normal size, a portion of fabric prepared as described in Example I(A), Sample 1 of Table 1, and subjected to 25 wash-and-dry cycles,

FIGURE 4 is a photomicrograph at 60X magnification, showing the entangled fibers in a nub portion of the fabric shown in FIGURE 3, with linking bundles of fibers which bind the nub portion to other nubs,

FIGURE 5 is a photograph showing in plan view, at substantially normal size, a portion of fabric prepared as described in Example I(B), Sample 4 of Table 1, and subjected to 25 wash-and-dry cycles,

FIGURE 6 is a photomicrograph at 60X magnification of the fiber structure around an ap rture of the fabric shown in FIGURE 5 showing, between adjacent apertures, areas of entangled fibers which are intercon nected in one direction by fibers to form ridges and are interconnected in the other direction by bands of generally parallel fibers.

FIGURE 7 is a photograph showing in plan view, at substantially normal size, a portion of fabric prepared as described in Example I(C), Sample 2 of Table 1, and subjected to 25 wash-and-dry cycles,

FIGURE 8 is a photomicrograph at 60X magnification, showing entangled fibers in a band area of the fabric shown in FIGURE 7.

The products of the present invention are tangle-laced nonwoven fabrics composed of 50% to of acrylic fibers and up to 50% of other fibers. The term tanglelaced designates a unique structure of fiber entanglement which is defined in detail subsequently. In general, the fabric has a repeating pattern of fibers randomly entangled with each other in tanglelaced areas to form a strong fabric of high absorbency. The fabric structure imparts sufiicient durability to withstand repeated laundering and reuse, without the need for any bonding agents or resins.

Surprisingly, it has been found that tanglelaced fabrics prepared from a major proportion of acrylic fibers have unexpectedly high absorbency (liquid retention) in comparison with conventional woven diaper fabric, and a re duced tendency for liquid to spread (wick) to the edges of the fabric. Maximum absorbency is obtained by the use of 100% acrylic fibers, despite the fact that these fibers are hydrophobic. Moreover, the absorbency of these acrylic-fiber, tanglelaced fabrics is not only superior to that of a woven cotton fabric, or woven acrylic-fiber fabric, but is also superior to that of a patterned, tanglelaced fabric made of cotton fibers. The absorbency is determined by a wringer test described after Example V. Fabrics of the present invention also have other advantages over cotton fabrics, including faster drying properties, better durability, and a highly-desirable luxurious, soft hand.

Other fibers may be used in combination with the acrylic fibers in the fabrics of the present invention to enhance certain properties, but these additive fibers are used in minor amounts (up to about 50%), in order to retain the desirable features imparted by the acrylic fibers. A desirable fiber content is 50% to 75% of acrylic fibers with the remainder being one or more additive fibers. The addition of hydrophilic fibers (e.g., rayon) to the acrylic fibers provides improved resistance to the buildup of static charges, whereby the fabrics can be dried, folded and handled with little tendency to cling because of static build-up. Synthetic fibers which are normally hydrophobic can be especially modified to have hydrophilic antistatic properties for this purpose.

The fabrics of the present invention are suitably made from fibers which range from about 0.5 to denier per filament. In general, absorbency increases with decreasing fiber denier. Preferred products are made from 0.5 to 2 denier fibers. Advantageously, the products are made from a blend or mixture of long fibers and short fibers, wherein the long fibers have a length of 1 to 5 inches (2.5 to 12.5 cm.) and the short fibers range from 0.1 to 1 inch (0.25 to 2.5 cm.) in length. By the use of fibers of different lengths, products having improved surface stability are obtained. Mixtures of different deniers may also be desirable as illustrated in Table 1 of Example I.

A preferred embodiment of the present invention is a patterned tanglelaced nonwoven fabric comprising about 60 to 70% of 1 to 2-inch (2.5 to 5 cm.) long, 1 to 2 denier per filament, acrylic fibers and, correspondingly, to of 0.2 to 0.3-inch (0.5 to 0.8 cm.) long, 1 to 2 denier per filament, rayon fibers.

In the products of the present invention, fibers proceeding through the fabric are locked into place in tanglelaced areas by a fiber interaction which alone, without the need for binder or other supplementary treatment, imparts high strength to the fabric.

By locked into place is meant that individual fibers of the structure not only have no tendency to move from their respective positions in the patterned structure, but are actually physically restrained from such movement by interaction with themselves and/ or with other fibers of the structure. By interaction is meant that the fibers turn, wind, twist back-and-forth, and pass about one another in all dimensions of the structure, both individually and severally within the tanglelaced areas, in so intricate a fashion and with so great a frequency per fiber length that they cooperate with, act upon and interlock with one another when the fabric is subjected to stress, thereby providing coherency and strength to the fabric. For the purpose of the present invention, the various fiber gyrations, interentanglements, entwinings and the like, which result in the above described fiber-to-fiber interaction, will hereinafter be referred to simply as tanglelacing. Since the interaction is so complex and random, the special methods of characterizing the tanglelacing described near the end of the specification have been devised.

When preferred fabrics of this invention are evaluated by the methods described near the end of the specification, the fibers are found to be locked into place in tanglelaced areas by fiber entanglement at a density characterized by an impenetrability rating I of at least 0.5 and at an entanglement frequency f of at least 20 per inch with an entanglement completeness c of at least 0.5. The fabrics are evaluated in the bond-free state, i.e., in the absence of any substantial inter-fiber coherences, other than that induced by fiber entanglement. For example, these tests are run in the absence of chemical binder or interfiber fusion bonds.

The tanglelaced products illustrated in the examples have a regular pattern of discrete tangelaced areas, and the structural measure of fiber entanglement S in the regions of highest fiber entanglement and fiber cooperation is at least 0.1 when evalulated in the bond-free state by the method described near the end of the specification. It is desirable that the products have /90/135 numbers of at least 10, and those products having numbers of at least 20 have especially good surface stability in repeated use.

The unique tanglelaced structure of the products of the present invention is also evident from the launderability of these products. Thus, the highly tanglelaced, patterned fabrics of the present invention, in the absence of binder, can be repeatedly laundered in conventional, household washing machines and dried in conventional driers without loss of their utility as a fabric.

The products of this invention can be produced by treating a web or sheet of loose fibers with essentiallycolumnar, high velocity, high-impact-pressure liquid streams while supporting the web on a patterning plate or screen, as illustrated in the examples. Tanglelaced nonwoven fabrics can be produced in a variety of attractive patterns by critical selection of suitable patterning supports. The accompanying photographs show three of the many textile-like patterned tanglelaced products which can be produced.

FIGURES 3 and 4 are illustrative of types of fabrics in which fibers are periodically tanglelaced along their lengths in a repeating pattern of nubs bound to adjacent nubs by linking bundles of fibers, The linking bundles extend in different directions to define a mesh pattern. Each of the nubs ties together fibers which lie along a plurality of different paths through the pattern of nubs and linking bundles, and the fibers are locked into place in the nubs by tanglelacing to provide a strong unitary product.

FIGURES 5 and 6 are illustrative of a class of patterned fabrics, composed of fibers randomly entangled with each other in tanglelaced areas and joining tanglelaced areas, characterized by a fabric face layer of fiber groups in a regular pattern of ridges separated by grooves lying along generally parallel lines, which can be straight or otherwise. The ridge fiber groups are interconnected by bands of generally parallel fibers bridging under the ridge-separating grooves and locked into place in the tanglelaced areas. In the type of embodiment shown, the ridges and interconnecting bands define a repeating pattern of apertures spaced along the grooves. The particular embodiment illustrated is described in further detail in Example I(B).

FIGURES 7 and 8 illustrate an especially preferred type of patterned nonwoven fabric. It has a repeating pattern of fiber bands of substantially greater width than thickness which extend continuously along substantially straight parallel axes spaced regularly in one fabric direction. The bands alternate with rows of evenly-spaced apertures, the general appearance being like a woven or knit fabric. The bands have tanglelaced areas characterized by ridges, on at least one fabric face, which proceed continuously back and forth along each band in a zig-zag pattern, and interstitial arrays of generally parallelized fibers which extend lengthwise along each band between tanglelaced areas and are locked into place in the zig-zag tanglelaced areas. The bands are interconnected by bundles of generally parallelized fibers which extend laterally between corresponding elbows of tanglelaced areas in adjacent bands and are locked into place by the tanglelaced areas. The band-interconnecting fiber bundles extend regularly along the edges of the bands and define the rows of apertures therebetween. The apertures of adjacent rows are offset in a uniform direction oblique to the band axes, and the apertures are of oblong shape with the major axis aligned perpendicular to the band axes.

PROCESSING CONDITIONS Patterned, tanglelaced fabrics of this invention can be produced by a process in which nonwoven fibers or filaments are consolidated with streams of liquid to form a fabric on an apertured patterning member, such as a screen or plate having small openings and/or recesses arranged in a pattern corresponding to the location of tanglelaced areas desired in the fabric and of a size which provides a total open area in said pattern of 10% to 98%. A nonwoven batt or other initial fibrous layer is supported on the patterning member and is traversed with fine, essentially columnar streams of liquid, such as Water, until the fibers are rearranged in an ordered pattern, and are tanglelaced to lock the fibers into position in this pattern. In order to tanglelace the fibers, a stream must be impinged on the fibrous layer at high impact pressure. As illustrated in the examples, water pressures in pounds per square inch above atmospheric pressure (hereinafter abbreviated psi.) of 500 to 2000 p.s.i. (35 to 141 kg./ cm?) can be used for orifices 0.003 to 0.007-inch (0.0076 to 0.178 cm.) in diameter with orifice-to-fiber spacings ranging from substantially 0 to 4 inches (0 to 10.2 cm.), although greater pressures and spacings can be used. Lower water pressures can be used with closer spacing. Water at 0 to 100 C. is suitable.

The initial layer may consist of any web, matt, or batt of loose fibrous elements, disposed in random relationship with one another or in any degree of alignment, such as might be produced by carding and the like. The initial layer may be made by any desired technique, such as by carding, random laydown, air or slurry deposition, etc. It may consist of blends of fibers of different types and/ or sizes. If desired, this initial layer may be an assembly of loose fiber webs, such as, for example, crosslapped carded webs. The initial layer may include scrim, or other reinforcing material, which is incorporated into the final prodnot by the treatment. Particularly desirable products may be obtained by utilizing highly crimped fibers or fibers which have a latent ability to elongate, crimp, shrink or the like and then, after the formation of the patterned fabric, developing the latent properties of the fibers. The processibility of stiff fibers can be improved by plasticization with solvent or heat, e.g., by use of hot water.

The apertured backing member may consist of a perforated plate, sheet, woven screen, honeycomb or the like, made of any suitable material which is not susceptible to attack by the fluid used in the process. Suitably, a stainless-steel screen or perforated plate is used. This will usually be flat, but may be shaped in a three-dimensional contour when direct formation of shaped garments is desired. The apertures in the backing member may be of any desired shape and/ or size and may be arranged in any regular pattern, such as in parallel or staggered rows, providing that the open area of the apertured backing member and the size and spacing of the apertures are properly chosen so as to permit the fibers of the web being treated to move into a tanglelaced pattern. It is to be understood that these conditions may vary depending on the particular web to be patterned and tanglelaced. However, in general, the ease with which a given web can be patterned and tanglelaced on a planar patterning member, under a given set of process conditions, is diminished as the percent open area of the backing member is decreased. Processibility is improved with the use of nonplanar patterning members and with such members it improves with increasing depth or height of the recesses or protrusions, respectively. As illustrative of suitable apertured backing members are coarse, regular or fine-wire plain weave screens ranging from 3 mesh to 80 mesh (Wires per inch) (1.18 to 31.4 wires/cm.) having wire diameters ranging from 0.005 inch to 0.025 inch (0.0127 to 0.0635 cm.), and having from about to about 98% open area. Other examples are perforated metal plates having circular holes, ranging from 0.01 to 0.25 inch (0.025 to 0.635 cm.) in diameter, arranged in parallel or staggered rows and having from about 10% to 98% open area. Perforated plates having slots, triangles, and/or apertures of other geometrical shapes are also suitable. Moreover it is not necessary that all of the apertures in a given plate be of the same diameter or shape. Furthermore, an aperture can vary in cross-sectional area throughout the thickness of the plate, e.g., apertures may be of conical or other cross-section. Finally, they need not even extend completely through the thickness of the plate; thus, for example, patterned struc tures can be produced using a cross-grooved plate or a plate having pyramidal or other depressions and/or protrusions.

In operating the process as illustrated subsequently, water or other suitable liquid is forced under high pressure through small diameter orifices so as to emerge continuously or intermittently in the form of fine, essentially columnar, high-impact-pressure streams. The loose initial fibrous layer is placed on the selected apertured backing member, and the assembly is moved, layer side up, into the path of the high-impact-pressure streams. Either the web or the streams, or both, are moved to traverse the web.

When using a planar or substantial planar apertured patterning member, the high-impact-pressure streams impinge upon and physically cause the individual fibers to move in the general direction of the nearest aperture while simultaneously forcing segments of the individual fibers to move into and about other fibers and about themselves as they bridge the gap of the aperture, until a highly tanglelaced, dense, fibrous mass is produced within the aperture. During this impingement, segments of a given fiber may be caused to move toward one aperture while other segments of the same fiber are caused to move to one or more different apertures. As the impingement continues, that portion of the fiber which extends between adjacent apertures is reduced in length as the segments within the apertures are driven into tighter and tighter tanglelacing with themselves and other fibers. Thus, the fibers of the web are simultaneously realigned, tanglelaced, and locked into place in a pattern corresponding to the arrangement of holes in the apertured backing member. The resulting structure comprises fibers arranged in an ordered geometric pattern of intersecting bundles locked together at their intersections solely by fiber interaction. The ordered groups of fibers locked together in series in any given line form the structural elements of the patterned, tanglelaced fabric and are capable of withstanding stress as are the yarns of a conventional woven fabric. Unlike a conventional woven fabric, however, the structural elements of the patterned, tanglelaced fabric do not merely overlap one another but are locked with one another at each intersection, and the individual fibers migrate randomly from bundle to bundle via intersections.

When using a nonplanar aperture patterning member, such as a screen woven of heavy wire and having a relatively coarse mesh or any other patterning member whose surface is characterized by the presence of channels or grooves, the high-impact-pressure streams force the fibers generally away from any protrusions and into and along the channels of the supporting surface of the patterning member. Preferably, there is used as a nonplanar patterning member a woven wire screen having a low open area and a relatively coarse mesh. Such screens are characterized by wires having a moderate degree of crimp amplitude in one axis and a greater degree of crimp amplitude in the transverse axis. Accordingly the surface of the screen is characterized by a series of slight protrusions, corresponding to the crimped portions of the wire, along one axis and a series of high protrusions along the transverse axis. The difference of the crimp amplitude in the two axes of the screen and the interweaving of the wires thereof impart to the screen a contoured surface characterized by the presence of regularly spaced channels or grooves, which may run along the screen at different levels and are separated from one another by the high points or protruding portions of the wire, in addition to the actual drainage apertures defined between the crossing wires. When a fibrous initial material is placed on such a screen and treated with high-impact-pressure liquid streams, the individual fibers and/or segments thereof are caused to move into the channels and to be consolidated with one another along the channels. In general, some fibers tend to move toward the lowest portion of the screen, i.e., into the deepest channels. As these channels become filled, fibers are caused to move into the other channels of lesser original depth. Accordingly, the ultimate fiber structure is of a layered or multilevel configuration. During their movement into the various levels of the screen, the fibers at certain localized regions are caused by the high-impactpressure streams to tanglelace with one another.

In contrast to the nonplanar screens described above, screens of very high open area, or screens of low open area and very fine mesh, are relatively flat and lack a channeled surface because the good conformability of the wires results in little difference in the crimp amplitude of the two axes. Thus, instead of multilevel structures, such screens yield products more closely resembling those produced with a perforated plate having apertures arranged in parallel in a square pattern.

The patterned tanglelaced fabrics prepared in accordance with the present invention may be dried while still on the apertured backing member or after removal from it. They are stable, coherent, strong and ready for textile use. If desired, they may be dyed, printed, heat-treated, or otherwise subjected to conventional fabric processing.

If the planar backing member has apertures aligned in parallel rows, the tanglelaced fabric will have a squaremesh pattern, simulating that of a plain weave fabric. If the apertures are arranged in staggered rows, the tanglelaced fabric will have a triangular-mesh pattern. Fancy patterns, such as a simulated herringbone weave or the like, may also be produced in the Web by proper choice of the backing member. If desired, one or more patterns may be superimposed on the web by treating it first on one backing member and then on another. Designs and/or lettering may also be produced in the web by blocking out selected portions of the backing member used in the production of the tanglelaced fabric. Different efiects can be achieved by the use of multicolored fibers and/or webs. For example, striped, tanglelaced fabrics may be made by the use of a starting web comprising parallel strips of fibers of different colors. Plaid, tanglelaced fab- .rics may be made by using two such webs, cross-laid with respect to one another, as the initial layer.

In the specific embodiments of the present invention wherein a patterned, tanglelaced fabric is produced and subsequently treated so as to crimp, elongate, shrink or otherwise change the dimensional properties of the individual fibers, it is to be understood that the gross pattern may be completely or partially obscured in the final product and/ or it may be drastically reduced in size. In general, such fabrics, on being stretched or pulled taut, will again reveal the gross pattern. Fabrics of this type are particularly desirable for use as apparel fabrics, since they provide a high degree of conformability, stretchability, drape and covering power in addition to the basic requisites of strength and the like.

EQUIPMENT A relatively simple form of equipment for treating fibrous webs with water at the required high pressure is illustrated in FIGURE 1. Water at normal city pressure of approximately 70 pounds per square inch (p.s.i.) (4.93 kg./cm. is supplied through valve 1 and pipe 2 to a high-pressure hydraulic pump 3. The pump may be a double-acting, single-plunger pump operated by air from line 4 (source not shown) through pressure-regulating valve 5. Air is exhausted from the pump through line 6. Water at the desired pressure is discharged from the pump through line 7. A hydraulic accumulator 8 is connected to the high-pressure water line 7. The accumulator serves to even out pulsations and fluctuations in pressure from the pump 3. The accumulator is separated into two chambers 9 and 10 by a flexible diaphragm 11. Chamber 10 is filled with nitrogen at a pressure of one-third to two-thirds of the desired operating water pressure and chamber 9 is then filled with water from pump 3. Nitrogen is supplied through pipe 12 and valve 13 from a nitrogen bottle 14 equipped with regulating valve 15. Nitrogen pressure can be released from system through valve 16. Water at the desired pressure is delivered through valve 17 and pipe 18 to manifold 19 supplying orifices 20. Fine, essentially columnar streams of water 21 emerge from orifices 20 and impinge on the loose fibrous web 22 supported on apertured patterning member 23.

The streams are traversed over the web, by moving the patterning member 23 and/ or the manifold 19, until all parts of the web to be treated are patterned and tanglelaced at high impact pressure. In general, it is pr ferred that the initial fibrous layer be treated by moving patterning layer 23 under a number of fine, essentially columnar streams, spaced apart across the width of the material being treated. Rows or banks of such spacedapart streams can be utilized for more rapid, continuous production of tangle-laced fabrics. Such banks may be at right-angles to the direction of travel of the web, or at other angles, and may be arranged to oscillate to provide more uniform treatment. Streams of progressively increasing impact pressure may be impinged on the web during travel under the banks. The streams may be made to rotate or oscillate during production of the patterned, tanglelaced fabrics, may be of steady or pulsating flow, and may be directed perpendicular to the plane of the Web or at other angles, provided that they impinge on the web at sutficiently high impact pressure.

Apparatus suitable for use in the continuous production of tanglelaced, patterned fabrics in accordance with the present invention is shown in FIGURE 2. A fibrous layer 29 on apertured patterning member 30 is supplied continuously to moving carrier belt 31 of flexible foraminous material such as a screen. The carrier belt is supported on two or more rolls 32 and 33 provided with suitable driving means (not shown) for moving the belt forward continuously. Six banks of orifice manifolds are supported above the belt to impinge liquid streams 34 on the fibrous layer at successive positions during its travel on the carrier belt. The fibrous layer passes first under orifice manifolds 35 and 36, which are adjustably mounted. Orifice manifolds 37, 38, 39 and 40 are adjustably mounted on frame 41. One end of the frame is supported for movement on a bearing 42, which is fixed in position. The opposite end of the frame i supported on oscillator means 43 for moving the frame back and forth across the fibrous layer to provide more uniform treatment.

High pressure liquid is supplied to the orifice manifolds through pipe 18, as in FIGURE 1. Each manifold is connected to pipe 18 through a separate line which includes flexible tubing 44, a needle valve 45 for adjusting the pressure, a pressure gage 46, and a filter 47 to protect the valve from foreign particles. As indicated on the gages in the drawing, the valves are adjusted to supply each successive orifice manifold at a higher pressure, so that the fibrous layer 29 is treated at increasingly higher impact pressure during travel under the liquid streams 34. However, the conditions are readily adjusted to provide the desired patterning and tanglelacing treatment of different initial fibrous layers.

The following examples illustrate preferred nonwoven fabrics of the present invention, and processes for preparing them, but are not intended to be limitative. Comparisons with other fabrics are included. The tests used for evaluating the fabrics are described after the last example.

EXAMPLE I This example illustrates the preparation from acrylic fibers of apertured, tanglelaced nonwoven fabrics in three different patterns, and compares them with other materials for use as diapers.

In each instance the initial layer is a web of randomlydisposed staple fibers prepared by an air'laying technique. The web is placed on a patterning member and, using apparatus of the type shown in FIGURES l and 2, is

treated with fine, essentially columnar streams of water at pressures up to 1500 p.s.i. (106 kg./sq. cm.) until a patterned tanglelaced fabric is obtained. The streams emerge from 0.005-inch (0.013 cm.) diameter holes spaced 40/inch (16/cm.) in a straight line along a manifold, the manifold being spaced 1 to 2 inches (2.5 to 5 cm.) from the web during treatment.

(A) For preparing a typical pattern A, the web of fibers is supported on an apertured, stainless steel, patterning plate having 0.075-inch (0.191 cm.) diameter holes arranged on 0.1-inch (0.25 cm.) staggered centers. The plate has 112 holes/sq. in. (17 holes/sq. cm.) and 50% open area. The assembly of the web on the plate is passed under the streams of water at approximately yd./rnin. (9.2 m./min.). During the first four passes, water is supplied to the orifices at a pressure of 1500 p.s.i. (106 kg./sq. cm.) and another plate having 96 holes/ sq. in. holes/sq. cm.) and 50% open area is placed on top of the web. The top plate does not influence the final pattern; it merely helps to hold he web in place during the initial passes. The assembly is then passed, without any top plate, under the streams for two passes at each of the following pressures:

P- -t Kg./sq. cm. 500 35 750 53 1000 '70 1250 88 1500 106 The structure is then lifted from the plate, turned over, with no attempt to put the pattern in register with the pattern of the supporting plate, and subjected to two passes at each of the following pressures:

The assembly is turned 90 after each pass. The product obtained has tanglelaced areas or nubs (corresponding to the holes in the plate used during processing) and the nubs are connected with one another by bundles of generally parallel fibers. Top and bottom views of this type of product are as illustrated in FIGURE 3, and the fiber structure is shown greatly magnified in FIGURE 4. These are plan view photographs normal to a face of the fabric after subjecting it to wash-and-dry cycles, using conventional home washing and drying equipment.

(B) For preparing a typical pattern B, the web of fibers is supported on a plain weave, wire-patterning screen having 15 x 15 wires/inch and 15% open area; wire diameter is 0.041 inch. Processing is similar to that described in preparation of Pattern A except as follows. The assembly of web on screen is passed under streams of water at 1800 p.s.i. 20 times while the web is covered by a top plate having 462 holes/sq. in. and 50% open area. The top plate doesnt influence the final pattern; it merely helps hold the web in place during the initial passes. The top plate is then removed and the web-screen assembly is passed times under the streams at 1800 p.s.i. The structure is then turned over on the screen, with no attempt to put the pattern into register with the pattern of the supporting screen, and the web-screen assembly is subjected to 20 passes with top plate and 30 passes without top plate, at 1800 p.s.i.

The product obtained is illustrated in FIGURE 5, which shows the appearance of both faces of the fabric, after the fabric has been subjected to 25 wash-and-dry cycles, using a conventional home laundry machine and a tumble drier.

When viewed with suitable magnification, it will be seen that this type of nonwoven fabric is characterized by a regular pattern of ridges separated by evenly-spaced parallel grooves on at least one face of the fabric and by a repeating pattern of oblong-shaped apertures spaced at regular intervals along the grooves. The ridges wind between adjacent grooves and apertures along sinusoidal paths which are out of phase with respect to adjacent sinusoidal paths. Tanglelaced areas are located along the ridges between diagonally adjacent apertures; they correspond to the holes in the screen used during processing. Other fiber groups extend between the tanglelaced areas along the ridges so that the ridges are of substantially uniform height. In the direction generally transverse to the sinusoidal ridges, the tanglelaced areas are interconnected by ribbon-like groups of substantially parallel fibers. These ribbon-like groups may be seen at the base of the grooves between the ridges of the fabric. The fiber structure is shown at great magnification in FIGURE 6.

(C) For preparing a typical pattern C, the web of fibers is supported on a plain weave, wire patterning screen having heavier wires (8 per inch or 3 per cm.) in one screen direction and a greater number of finer Wires (30 per inch or 12 per cm.) in the other screen direction. Wire diameters are 0.032 and 0.018 inch (0.081 and 0.046 cm.). The screen has 34% open area and the holes in the screen are of oblong shape. Processing conditions are similar to those used for Pattern A except that 16 passes are used at 1500 p.s.i. (106 kg./sq. cm.) with the top plate. After removal of the top plate, treatment consists of 16 passes at each of the following pressures:

P.s.i.: Kg./ sq. cm. 500 35 1000 70 1500 106 This treatment is repeated again after the structure is turned over on the screen. The product obtained is shown after 25 wash-and-dry cycles (with conventional home equipment) in FIGURES 7 and 8, which are illustrative of normal and greatly magnified views of the nonwoven fabric.

This embodiment of nonwoven fabric has a striped appearance, wherein solid bands alternate with apertured rows. The solid bands are of substantially greater width than thickness and extend continuously along spaced parallel axes between rows of apertures in one fabric direction. Along each band a tanglelaced area proceeds obliquely back-and-forth in a zig-zag fashion. This is quite clearly seen as a darker area when the fabric is viewed by light transmitted through the fabric. Arrays of generally parallel fibers extend along each band between bends of the tanglelaced area. The apertured row is formed by spaced bundles of generally parallel fibers extending between adjacent solid bands and interconnecting with the bands at the elbows of the tanglelaced areas. The zig-zag tanglelaced areas correspond to zig-zag depressions extending along the surface of the patterning screen used as a support during processing.

In nonwoven fabrics A, B and C, the fibers are locked into place in the tanglelaced areas.

After removal from the patterning member, the patterned tanglelaced fabric is subjected to a boil-off (immersion in boiling water for a period of 5 minutes) and is then dried in a commercially available household dryer of the tumble-dry type. It is then tested for absorbency, using the procedure described after the examples.

Results for a commercially available cotton gauze diaper are included for comparison (sample 15). This diaper is woven from cotton yarns having a 36 singles cotton count and having a twist of 20 turns per inch. There are 88 warp yarns per inch and 69 filling yarns per inch. The basis weight is 3.2 oz./sq. yard as purchased but becomes 4.2/oz./ sq. yard after shrinkage due to wetting and drying.

Data for the products are given in Tables 1 and 2.

TABLE 1 Absorbency (g. water retained] g. fab.)

Diaper Composition Low High Weight, Pattern type pressure pressure oz./yd. Percent Inch D.p.f. Fiber Percent Inch D.p.f. Fiber Sample code:

1 A 6. 5 4. 3 2. 2 50 1. 5 1. 5 Acrylic 50 0.25 1 5 Acrylic 6. 9 4.3 2.1 50 1. 5 1. 5 do- 50 0.25 1 5 Do.

6. 2 3. 3 2. 9 100 1. 5 1. 5 5. 6 2. i) 2. 3 100 1. 5 1. 5 5. 3. 8 3.0 75 1. 1. 5 4.7 4.2 2.8 75 1.5 1.5 5.1 3.1 2.7 75 1.5 1.5 4. 6 3.1 4. 1 75 1. 5 1. 5 4. 5 4. 1 3. 2 75 1. 5 1. 5 4. 5 4. 1 3. 2 75 1. 5 l. 5 4.3 3.8 3.0 75 1.5 1.5 4. 6 4.0 3.0 75 1. 5 A 3. 1 1. 5 3. 5 100 l. 8 Knit fabric 2. 9 2.1 3.1 100 1. 5 1. 5 Woven fabric... 2.5 1.5 4.2 100 Cott-on 16 Woven fabric 2. 1 1. 5 3. 6 100 1 5 1. 5 Acrylic 1 Acrylic fiber comprising 93.6% acrylonitrile, (1% methyl acrylate, and 0.4% sodium styrene sulfonate. 2 Acrylic fiber of the same composition and having about 16% shrinkage on boil-ofi. 3 Bicomponent acrylic fiber substantially comprising as one component a copolymer of 96% acrylonitrile and 4% sodium styrene sulfonate and, is

the other component, polyaerylonitrile.

4 About 1. 5 The commercial diaper described previously.

TABLE 2 Absorbency (g. water/g. fabric) Diaper Composition Pattern Low High Weight,

type pressure pressure oz./ycl. Percent Inch D.p.f. Fiber Percent Inch D.p.f. Fiber 4. 7 3. 3 2. 4 50 1. 5 1. 5 Acrylic 50 1. 5 1. 5 Polyester 59 3.5 2.8 75 1.5 1.5 do. 1.5 0.5 Do? 5.8 3.2 2.8 75 1.5 1.5 .d0. 25 1.5 0.5 D0.-

1 Acrylic fiber comprising 93.6% acrylonitrile, 6% methyl acrylate, and 0.4% sodium styrene sulfonate.

2 Polyethylene terephthalate.

The marked superiority of the patterned tanglelaced nonwoven fabrics prepared from acrylic fibers is readily seen from a comparison of samples 112 of Table 1 with samples 1316 of Table 1. The tanglelaced fabrics of patterns A, B and C prepared from different types of acrylic fibers and including blends of different types, lengths and deniers (samples 112) have low pressure absorbencies ranging from 4.3 to 6.9 and high pressure absorbencies ranging from 2.9 to 4.3, depending on the particular diaper composition, when tested in the wringer test. By way of comparison, under the same wringer test conditions, the commercially available woven cotton diaper (sample 15) has lowand high-pressure values of 2.5 and 1.5, respectively. These results are even more surprising when it is observed that the improvement is not merely due to a difference between cotton and acrylic fibers. Thus, from samples 14 and 16, it is seen that woven or knit fabrics from acrylic fibers have approximately the same absorbencies as the Woven cotton fabric. Nor is the improvement in absorbency over that of a woven or knitted fabric due solely to the fabric structure since, from sample 13, it is seen that a patterned, tanglelaced fabric prepared from cotton fibers has roughly the same absorbencies as the woven cotton fabric (sample 15 or knitted acrylic fabric (sample 14).

Considering only the patterned tanglelaced fabrics of acrylic fibers, it is observed that absorbency is greater with lower denier fibers. This is also true when other fibers are blended with the acrylic fibers as may be seen in Table 2.

EXAMPLE II This example illustrates the effect of different proportions of long and short acrylic fibers on fabric properties. Six fabrics are made from various combinations of long acrylic fibers blended with short acrylic fibers as follows:

Sample:

A100% long fiber B75% long fiber/25% short fiber C% long fiber/50% short fiber D35% long fiber/% short fiber E25% long fiber/% short fiber F15% long fiber/% short fiber In all samples, the long fiber is 1.5-inch (3.8 cm.), 1.5 denier per filament (d.p.f.) acrylic fiber and the short fiber is 0.25-inch (0.64 cm.), 1.5 d.p.f. acrylic fiber. The acrylic fibers are prepared from the same polymer as sample 1 of Example I. For each of samples A-F, an initial Web of the fibers in random disposition is prepared by an air-laying technique.

The patterning screen used for all samples is a plain Weave wire screen having 14 x 14 wires/inch (5.5 X 5.5 wires/cm.) and 18% open area. Wire diameter is 0.041 inch (0.104 cm.).

The samples are prepared using apparatus of the type shown in FIGURE 2 with a belt speed of 2 yds./min. (1.8 m./min.) and a water delivery rate of 25 gal/min. 1./min.). Processing is done with the web/screen assembly spaced about 1 to 2 inches (2.5 to 5 cm.) from the orifices, which are 0.007 inch (0.018 cm.) in diameter and are spaced along the manifold in a line at a frequency of 20 orifices/inch (8/cm.). All samples are (1) passed once under the streams at 1500 p.s.i. (106 kg./cm. while a coarse mesh top screen covers the sample to help hold it in place, (2) removed from the patterning screen, turned over, replaced on the patterning screen, covered with a coarse mesh screen, and treated once again at 1500 p.s.i., and (3) treated twice at 1500 p.s.i. without a top screen. Total energy input for each of these samples is 3.12 horsepower-hours per pound of fabric produced (185x10 joules/gm.).

Each sample is removed from the patterning plate, subjected to a boil-off and then 25 cycles of washing and drying in a commercially available washer and dryer, and then tested. The products are similar to that shown in FIGURES 5 and 6. Properties are given in Table 3, where absorbency is in grams of water retained per gram of dry fabric when evaluated by the procedure described after the examples.

TABLE3 Fabric Composition A B C D E F Long acrylic fiber (percent) 100 75 50 35 25 15 Short acrylic fiber(percent). 25 50 65 75 85 Absorbency:

Low pressure 6.01 6.38 6.48 6.25 6.33 6.66

High pressure 3.58 4.05 4.21 3.88 3.93 4.12 Surface Stability Rating:

Topface 1.5 2.5 4.0 4.5 4.5 4.5

Bottomiace 1.5 2.5 4.2 4.5 4.5 4.5 Weight:

(Oz./yd. ),MD 2.9 3.2 3.1 3.3 3.2 2.8

(Centimeter),MD 1.8 1.8 1.7 1.7 1.5 1.7

(Centimeter),XD 1.8 1.6 1.7 1.9 1.6 1.5 Tongue Tear Strength:

(Lb./oz./yd.),MD 0.81 0.75 0.64 0.6 0.57 0.65

(Lb./oz./yd.),XD ".092 0.8 0.62 0.6 0.53 0.57 Strip Tensile Strength:

(Lb./in./oz./yd. ),MD 4.1 4.62 4.32 3.0 2.84 2.4

(Lb./in./oz./yd. ),XD 3.74 4.13 3.41 3.24 3.18 2.44 Pin Strength:

(Pounds),MD 86 8.6 6.1 6.0 5.2 5.3

(P0ll11ds),XD 87 8.7 7.5 6.6 4.6 5.7 Secant Modulus:

(Lbs./in./oz./yd.=),MD 0.48 0.47 0.36 0.29 0.27 0.30

(Lbs./in./oz./yd. ),XD 0.23 0.44 0.54 0.39 0.96 0.21 Elongation:

(Percent),MD 65.0 67.5 70.4 78.8 79.5 71.1

(Percent),XD 61.3 64.2 54.3 61.6 58.8 81.4

From Table 3 it is seen that all samples (A to F) have excellent absorbeucies at both low pressure (6.0 to 6.7 absorbency) and high pressure (3.6 to 4.2 absorbency) when compared with the commercial woven cotton diaper described in Example I, which has absorbeucies of 2.5 at low pressure and 1.5 at high pressure.

Surface stability increases with increasing amounts of short fiber present. It is determined by subjecting the sample to 25 cycles of washing and drying in a commercially available front-loading washing machine and tumble dryer of the home model type followed by visual inspection and rating of the sample from 1 to 5. A rating of 1 indicates failure of the sample due to objectionable surface fuzzing and a high degree of pilling. A rating of 5 indicates a perfect rating, i.e., essentially no surface fuzzing or pilling. A rating of 3 is considered the minimum required for acceptability; it permits presence of very few, very small pills and some fuzzing as long as the sample retains an unobjectionable appearance. From Table 3, it is seen that, for a blend of 1.5"

long fiber and 0.25 inch short fiber, the use of more than about 25% short fiber is preferred in order to achieve the desired surface stability. Preferably, no more than about short fiber is used in order to preserve optimum strength in the product.

EXAMPLE III Sample A Acrylic. B Rayon. C Polyethylene terephthalate. D Nylon. E Acrylic fiber made permanently antistatic by coat ing with a terpolyrner of glycidyl methacrylate, acrylic acid, and the acrylic ester of polyethylene oxide capped with nonyl phenol.

The patterning screen is a woven wire screen having 0.020-inch (0.05l-cm.) diameter wires arranged 20/inch (8/cm.) in each direction and having 36% open area. The screen forms the surface of a drum which is rotated at 5 yards/ min. (4.6 m./min.) to pass the web and screen assembly under 2 rows of high-impact-pressure-streams as follows:

Row 1.-Streams emerge from a manifold through 0.005-inch orifices arranged in a straight line at a spacing of 40/inch (16/cm.); water pressure is 500 p.s.i (35 kg./cm. the manifold is oscillated at 155, 320, 330, and 330 cycles/min. for samples A, B, C, D, and B, respectively; and the orifices are spaced 0.75 inch (1.9 cm.) from the web.

Row 2.--Streams emerge from another manifold through 0.007-inch (0.018 cm.) orifices arranged in a straight line at a spacing of 20/ inch (8/ cm.); water pressure is 900 p.s.i. (63 kg./cm. oscillation is as for Row 1; and the orifice to web spacing is 0.5 inch (1.3 cm.).

The web is then turned over on the screen and treated with 4 rows of streams, the first row streams being from orifices as in Row 1 above and the remaining 3 being from orifices as in Row 2 above, using different water pressures, oscillation rates, and drum speeds as follows:

During passage under the 4 rows of streams, drum speeds are 1.3, 2, 1.3, 1, and 1.6 yards/min. (1.2, 1.8, 1.2, 0.9 and 1.5 m./min.) for Samples A, B, C, D and E, respectively; manifold oscillations are 160 cycles/min. for

fibers E, greatly decreases the static propensity of the fabrics. Static propensity is determined by measuring the static charge decay rate using the Vykand Static Propensity Tester, manufactured by the Vykand Corporation. In this equipment, the fabric is used to form one plate or" Sample A, 300 cycles/min. for Samples B, C and D, and 320 cycles/min. for Sample E. The energy used in g g ig s ggs i g f z tf $633221: 1: 15:51 t i o t e making samples D and respectlvely 1S fabric then the sampli is rounded and :he time in secand horsepower'hours per Pound of onds re uired for leaka e $0 a lower volta e (char e de fabric and 213x104 jou1eS/gm')' The ca is re orted In e heral static ro er isit d c reases energy used is adjusted for the fibers used in order that 10 g .ncressin airnouits f Ta e ti mm: all samples have a minimum surface stability rating of or anltistafc fib o e y n er an s 3, when rated as described in Example 11. The patterned 1 tanglelaced fabric so obtained is then washed in 140 F. EXAMPLE IV 0 9 Wajter and tumble dned lismg hollsehold This example illustrates the use of acrylic fibers with chines, and is then tested. Propertles are In Table 4, 0 various amounts of rayon fibers n as Where absorbenqy 1s m grams of water retamed per The initial web is a web of randomly-disposed fibers gram of dry fabric when evaluated by the procedure demade by air laying Each Web has 50% of 1 finch i scnbedafter the examples. The fabrlc 1s similar to that dpi fiber and 50% of 0254mm dpi fibsr as shown 1n FIGURES 5 and 6. follows,

Sample A Sample B Sample C Sample D 50% long acrylic 50% long acrylic..." 50% long acrylic"... 50% long acrylic 50% short acryhc 35% short acryhm... short aGl'yllCL-.. 50% short rayon 15% short rayon... short rayon.--

TABLE 4 In each instance, the acrylic fiber is the same type as that of Example I, Sample 1. Fabn" Commsition The atterning screen used is the same as that in Exp I A B C D E am le III. Processing for each of the samples is also the Long fibe (65%) i 1 1 1 (1) 30 same: eXcept as follows: Short fibers 0) Absorbency:

Low pressure 6.8 5.2 6.7 5.4 6.9 High pressure--- 3.8 2.9 3.7 3.2 3.9 Surface Stability Rating:

Top face 3+ 3+ 3+ 3+ iottom face 3+ 3+ 3+ 3+ erg Water Web Manifold pressure speed oscillation g (P- -i.) (yds/min.) (cycles/min.)

(Centimeter),MD 1.3 2.0 1.8 1.7 (Centimeter),XD 1.5 1.9 1.8 1.8 1.8 f 900 5 Tongue Tear Strength: Row 2 500 5 375 (Lb./0z./yd. ),MD 0.84 0.59 0.71 0.82 0.58 sampleA side? (Lb./oz./yd. ),XD 0.88 0.61 0.58 0.74 ROW i 600 1 75 m Strip Tensile Strength: Row 2 1 300 75 -/yd."),1\1D --2.25 3.31 3.57 3.72 3.79 Rows" 2,000 (Lb./ir1./oz./yd. ),XD 2.66 3.30 2.96 3.0 2'000 5 Pin Strength: Sample B 'side 1: W

(P011HdS),MD 5.6 7' R i 500 5 340 (P0t1ndS),XD 6.0 6.5 6-5 ROW2 900 5 B40 5% Secant Modulus: sample B Side (Lbs./in./oz./yd. ),MD 0.66 1. 03 1.86 1.78 Bowl 500 1 6 325 E1 (Lbs./in./oz./yd. ),XD 1.08 1.02 0.95 1 84 j "jjjjjjj 1 200 1,5 ongation: I}-

(Percent),MD 58.1 51.6 59.0 55.6 53. g$2-;; (Percent), XD--- '3.6 71.6 87-1 sample 0 s H Grab Tensile Strength. R0 500 5 W40 (Pounds),MD. 27.7 28.8 23.7 25.6 24.5 ROWZ 900 5 1: (Pounds),XD 22.8 25.8 20.9 s c 431E621 Charge Decay-.. 500 1.6 325 1 Row 2 1, 200 1. 6 825 a Row 3 2, 000 1. 6 1125 ay n. Row 4 2, 000 1. 6 525 3 Polyester. Sample D t y g Row 1---. 600 5 220 Antistatic acryhc. R g 800 5 320 6 2% in 3,600 sec. Sample D Side 2: 50% in 225 sec. R0 1' 500 2 50 1 10% in 1,550 sec. 1 200 2 1150 9 0.5% in 3,600 S80. 2' 000 2 350 w 50% in 1,538 sec. 21000 2 050 From Table 4 it can be seen that all of the patterned, tanglelaced fabrics have exceptional absorbencies when compared with the standard values for the commercial woven cotton diaper described in Example I, which has absorbencies of 2.5 for low pressure and 1.5 for high Energy expended for A, B, C and D, respectively, is pressure. The maximum absorbency is obtained with the 4.4, 4.8, 4.8 and 3.9 horsepower-hours per pound of acrylic diaper (A and E). All have satisfactory fabric obtained. Each fabric is washed in F. Water surface stability and pin strength for use as diapers. From and tumble-dried in household machines, and is then the char e deca values reported it is seen that the additested. Properties are in Table 5. The sam les have the g y u l p tion of rayon fibers B, or of antistatic-coated acrylic 75 same appearance as those of Example III.

TABLE 5 Fabric Composition Short acrylic fibers, percent- Short rayon fibers, percent 0 Absorbency:

Low pressure (g./g. fabric) 6. 9 High pressure (gJg. fabric) 3 9 Surface Stability Rating:

Top face 4. 6 4

Bottom face Weight:

(Oz./yd. XD Drapetlex:

Centimeter, MD

Centimeter, XD Tongue Tear Strength:

(Lb./oz./yd.=), MD 0.

(Lb./oz./yd. XD 1. Strip Tensile Strength:

(Lb./in./oz./yd. MD 3. 4

(Lb./in./oz./yd. XD. Pin Strength:

Pounds, MD

Pounds, XD- Secant Modulus:

(Lbs./in./cz./yd. MD 1. 2

(Lbs./in./oz./yd. XD 0. Elongation:

Percent, MD

Percent, XD Grab Tensile Strength:

Pounds, MD

Pounds, XD

new

EXAMPLE V This example illustrates preparation of prefold diapers from 3 different fiber blends.

The initial web is a web of randomly-disposed fibers made by air-laying and containing 50% of 1.5-inch, 1.5 d.p.f. fibers and 50% of 0.25-inch, 1.5 d.p.f. fibers as follows:

(A) 50% long acrylic; 50% short acrylic. (B) 50% long acrylic; 50% short rayon. (C) 50% long polyester; 50% short rayon.

The patterning support is a 14 x 14 wires/inch screen, Woven from 0.041-inch diameter wires and having 18% open area. The screen forms the face of a drum on which the web is treated by passage under 4 rows of streams. The streams of each row emerge from 0.007-inch orifices arranged in a straight line in a manifold at a frequency of 20 orifices/inch. For rows 1 and 3, the orifices are spaced 0.25 inch from the web during treatment. For rows 2 and 4, the spacing is 0.375 inch. For samples A and B, web speed is 2 yards/min, water pressures for rows 1, 2, 3 and 4, respectively, are 500, 1000, 2000 and 1900 p.s.i., and the manifolds are oscillated at a frequency of 275 cycles/min. For sample C, web speed is 3 yards/ min., water pressures are 300, 600, 1950, and 1950 for the 4 rows, and manifold oscillation is at 320 cycles/min. Energy used in preparing Samples A, B and C, respectively, is 3.5, 4.2 and 4.5 horsepower hours/lb. of fabric. The fabric is washed at 140 F. in household washer, dried in a. tumble dryer, and tested. Properties are in Table 6. Again, the superior absorbency of the acrylic fiber, tanglelaced product is evident from a comparison of A and B with C.

The fabric is converted into a prefold diaper having an over-all size of 14 x 18 inches and containing 3 layers of fabric sewed together. The 2 outer layers of the diaper are 14 x 18 inches. The inner layer is about 6.5 x 18 inches and is centered with respect to the 14-inch overall width of the diaper. Tests of the fabrics as diapers confirm the superiority of the all acrylic and of the acrylic/ rayon products over the commercial woven cotton diaper described in Example I, in softness, absorbency and quickdrying capability.

Another series of samples are subjected to durability tests together with 5 of the commercial Woven cotton diapers. After 200 cycles of washing (with amounts of detergent and bleach in accordance with manufacturers directions) in a front-loading, tumble-type washer, followed by tumble drying, the patterned, tanglelaced diapers are still completely intact whereas the woven cotton diapers each has one ply completely worn away so that they are no longer suitable for use as diapers.

TABLE 6 Fabric Composition A B 0 Long fibers (50%) Short fibers (50%) Absorbency:

Low pressure (g./g. fabric). 5. 9 4. 0 3. 2 High pressure (g./g.fab1ic) 4.2 2. 7 2. 1 Weight (on/yd?) 2. 9 3.3 3. 1 Strip Tensile Strength (lbs./in./oz./yd. 2. 9 2.9 4.3 Elongation, percent 43 37 49 5% Secant Modulus (lb./in./oz./yd. m 1.10 0.7 1.4 Tongue Tear Strength (lb./0z./yd. 0. 72 0. 6 0.85 Pin Strength, lbs 5. 0 5. 8 8. 4 Grab Tensile Strength, lbs 21. l 22. 4 35. 6

1 Acrylic. 2 Polyester. 3 Rayon.

TESTS 'FOR EVALUATING PHYSICAL PROPERTIES In the above examples, the tensile properties are measured on an Instron tester at F. and 65% relative humidity. Strip tensile strength is determined for a sample 0.5-inch wide, using a 2-inch gauge length and elongating at 50% per minute. Grab tensile strength is measured on a sample 4-inches wide, using a 3-inch gauge length, and elongating at 400% per minute. Initial modulus is determined by measuring the initial slope of the stress-strain curve. The 5% secant modulus is determined by A.S.T.M. Standards E6-6l, part 10, page 1836. Drape flex or bending length is determined by using a sample 1- inch wide and 6-inches long and moving it slowly in a direction parallel to its long dimension so that its end projects from the edge of a horizontal surface. The length of the overhand is measured when the tip of the sample is depressed under its own weight to the point where the line joining the tip to the edge of the platform makes an angle of 41.5 with the horizontal. One-half of this length is the bending length of the specimen, reported in centimeters. Thickness is measured with A'mes thickness gauges. Tongue tear strength is measured in accordance with ASTM D-39 except that a sample 2.25 inches by 2 inches and having a 1-inch slit is used and a constant cross-head speed of 10 inches per minute is used. Pin strength is determined by inserting a piece of a 0.0415- inch (0.105 cm.) diameter spring wire one inch (2.54 cm.) from the upper edge and in the center of a 2 inch by 4 inch (5 cm. x 10 cm.) strip of the test sample. This wire size is about equivalent to that found in diaper-size safety pins. The wire is held in the upper clamp of an Instron tester and the lower inch of the test strip is clamped in the Instron (providing about a 2-inch sample length for testing). The maximum force to tear the sample at a cross-head speed of 1 inch/min. (2.54 cm./ min.) is reported in lbs. (or in kg). In performance tests on diapers, values of about 5 lbs. (2.3 kg.) have been found to be satisfactory.

Absorbency (liquid retention) is determined by means of a wringer test, since this test has been found to provide the best correlation with data obtained in use tests of diapers on babies. No significant difference was found between wringer-test measurements made using urine or water. Therefore, for convenience, wringer tests are conducted with water. The wringer test consists of passing 4 thicknesses of a thoroughly wet (dripping wet) diaper fabric between rubber wringer rolls (such as those commonly employed in household washing machines) running at a surface speed of ft./min. (46 m./min.). The weight of the fabric (to the nearest tenth of a gram) is a4sa709 determined after wringing at high pressure and again, separately, at low pressure. In each instance, the weight after wringing is compared with the dry weight of the fabric and the amount of water retained is reported in terms of grams of water retained per gram of fabric. Using the cotton fabric specified below for control purposes, pressure on the wringer rolls is adjusted to yield a retention of 2.5 grams of water per gram of the cotton fabric as the standard low pressure condition and a value of 1.5 grams of water per gram of the cotton fabric as the standard high pressure condition. The cotton fabric used as a control is a commercially available gauze diaper woven from cotton yarns having a 36 singles cotton count and having a twist of 20 turns per inch. This cotton diaper has 88 warp yarns per inch and 69 filling yarns per inch, and weighs 2.1 oz.

EVALUATION OF TAN GLELACING The impenetrability rating I is determined by testing the impenetrability to a needle of entangled areas of fibers in a bond-free state. The fibers must not be adhered with binder or inter-fiber fusion bonds, The needle has a shank about 0.015 inch (0.038 cm.) in diameter with a conical point having sides making an angle of about 26 with the axis. The needle is held by an L. S. Starrett C pin vise, the total weight of the assembly being about 24 grams. This is used in conjunction with a support plate, inch (0.078 cm.) in thickness, having a series of holes of difierent diameters drilled in it. These holes are suitably marked for diameter-identification.

To obtain an impenetrability rating I, a section of the fabric is marked so as to delineate a region containing 25 circular entangled areas. The average diameter of the entangled areas is estimated with a hand comparator and the specimen is placed on the above-mentioned plate, so that for hydraulically processed fabric the fabric face upstream to the fluid stream during processing is adjacent the plate and the selected entangled area is placed over a plate-hole having a diameter approximately 75% of the diameter in the entangled area being tested. For other fabrics, either face may be used. For testing entangled areas which are smaller in diameter than about 133x the needle-shank diameter, the entangled area may be placed over a plate-hole having a diameter slightly larger than that of the needle shank. A light source under the plate-hole and suitable optical magnification are used to assist in achieving the correct placement over the hole. The needle is placed vertically above the entangled area in a central position. The weight of the needle assembly is then allowed to rest on the entangled area by lightly supporting the assembly with the hand to keep the needle vertical. Record is kept of whether it is penetrated or not, using 25 tests as the standard sample. The impenetrability rating I is the ratio of the number of entangled areas not penetrated to the total number tested. This test allows for the variation in entanglement in the various areas in a given sample and provides the average fraction of representative entangled areas which will not be penetrated. The highly entangled areas in the products of the present invention have an impenetrability rating of at least 0.5.

ENTANGLEMENT FREQUENCY AND COMPLETENESS TESTS In preferred tests, nonwoven fabrics are characterized according to the frequency f and the completeness c of the fiber entanglement in non-bonded fabric, as determined from strip tensile breaking data using an Instron tester.

Entanglement frequency f is a measure of the extent of fiber entanglement along individual lengths of fiber in the nonwoven fabric. The higher the value of f the greater is the surface stability of the fabric, i.e., the resistance of 20 the fabric to the development of pilling and fuzzing upon repeated laundering.

Entanglement completeness c is the proportion of fibers that break (rather than slip out) when a long and wide strip is tested. It is related to the development of fabric strength. A completeness 0 rating of 1 means that all of the fibers are being utilized in the development of fabric strength.

The products of the present invention have an entanglement frequency f of at least 20 per inch and an entanglement completeness c of at least 0.5

Entanglement frequency f and completeness c are calculated from strip tensile breaking data, using strips of the following sizes:

For patterned fabrics, strips are cut in two directions: (a) in the direction of pattern ridges or lines of highest basis weight (i.e., weight per unit area), and (b) in the direction at to the direction specified in (a). In unpatterned fabrics any two directions at 90 will suffice.

In cutting the strips from fabrics having a repeating pattern of ridges or lines of high and low basis weight, integral numbers of repeating units are included in the strip width, always cutting through the low basis weight portion and attempting in each case to approximate the desired widths (W W W2) closely. Ten or more specimens are tested at each strip width, using an Instron tester with standard jaw faces and the gauge lengths and elongation rates listed above. Average tensile breaking forces for each width (W W and W2) are correspondingly reported as T T and T It is observed that:

u a e 1 2 we It is postulated that the above inequalities occur because:

(1) There is a border zone of width D at the cut edges of the long gauge length specimens, which zone is ineffective in carrying stress; and

(2) With zero gauge length, fibers are clamped jaw-tojaw and all fibers carry stress up to the breaking point, while with long gauge length, some poorly entangled fibers slip out without breaking. The proportion of stresscarrying fibers is called entanglement completeness 0.

Provided that D is less than /2 W then:

From testing various specimens, it is observed that when 0 is greater than 0.5, the value D/ vol/1.5 where d is the effective fiber denier, is a measure of the average distance required for fibers in the fabric to become completely entangled so that they cannot be separated without breaking. This value is practically independent of fiber length. The reciprocal of the value is the entanglement frequency f per inch, i.e.,

f=(1/D) Id/1.5 If the fabric contains fibers of more than one denier, the effective denier d is taken as the weighted average of the deniers.

Both 0 and f are determined in both major directions 21 as defined above, and the geometric means are reported as the proper values. In any determination of f, if turns out to be negative this is equivalent to a very high entanglement frequency and f=l per inch is taken as the value to be used. When 0 is less than 0.5, it has been found that D and hence 1 may be influenced by factors other than entanglement. Accordingly, when 0 is less than 0.5, calculation of f as described above is not meaningful.

STRUCTURAL MEASURE OF ENTANGLEMENT The structural measure S for patterned fabrics requires three types of determinations. structurally, the extent of fiber interentanglement is related to the concentration of fibers in the interentangled area C and the density of the interentangled mass d. The product of those two factors provides a measure of the frictional engagement and interaction of the fibers in the interentangled area serving to lock the fibers in place in the fabric to thereby permit maximum utilization of fiber strength when the fabric is subjected to stress. Also, influencing maximum utilization of fiber strength is the cooperation-under-stress exhibited by the group of fibers which extends between any two entangled areas, which cooperation is inversely related to the average-free-length factor of the individual fibers in the group F. The structural measure of entanglement and cooperation S is defined as the value for nonbonded fabric given by the equation:

SZCd/F The fiber concentration factor C is the ratio of the length of fiber actually in the entangled area to the length which would be there if there were no patterning and/ or entanglement of the fibers, i.e., if the fibers of the fabric were uniformly distributed in the plane of the fabric. Since there is a direct relation between fiber length and fiber weight, the fiber concentration factor C may also be described as the ratio of the weight per unit area of the entangled portion W to the Weight per unit area of the entire fabric W i.e.:

W and W are determined from the fabric sample by direct measurement. For W an average of ten values is used and each value is determined by cutting the entangled mass or representative portion thereof from the fabric with a suitable die. The area of the mass then corresponds to the area of the die. All ten specimens are weighed at one time on a suitable microbalance.

The density d of the entangled mass can be measured by calculating the volumes of the cut-out specimens mentioned above. To do this, the specimens are mounted axially on broaches and are photographed at X to provide a cross-sectional view. The cross-section thus photographed may be irregular in shape. If so, the shape is approximated with rectangles and/or triangles. The shapes are then measured and, using the appropriate geometric formulas, the corresponding volumes are calculated. The total weight of the ten specimens is then divided by the sum of the ten volumes to give the average density d in grams/cu. centimeter of the entangled area.

The average free-length factor F of the fibers in the group extending between any two entangled areas is estimated by direct observation (under a microscope) of the fibers in the group and comparison to a set of standards. The fiber group is observed both in plan view and in cross-sectional view, the latter being from a specimen cut along the group and viewed edge-on. The five ratings used as standards and the corresponding curvatures and free lengths are shown below.

22 CHART FOR ESTIMATING FREE LENGTH Approx.

Free Rating h/hl Length F Appearance w hl F- o.5o 15% 3 h I: Q

If, for example, the fibers in the group on the average are visually estimated to have a curvature such that the ratio of the deviation from straightness h to the halflength in the group observed hl is about 0.5, then a rating of 3 is assigned. Such estimates are made three times independently, and averaged both in the plane of the fabric and normal to or out of the plane (cross-section). The two estimates are then combined geometrically by taking the square root of half the sum of the squares of the two ratings. If F is the estimated in-plane rating and F is the estimated out-of-plane rating, the average free-length factor F is:

In practice, it is observed that structures made from straight (i.e., non-crimped or non-curled) fibers do not have ratings of one (corresponding to no curvature). Instead, there is always some free length and an appropriate class rating which may be used for structures made from straight fibers is 1 1.4. Similarly, it is observed that the rating for samples made from conventional staple fibers or low crimp continuous filaments ranges from 1.8 to 2.5. For such fibers, an average class rating of F =2.1 may be used. For highly crimped fibers, the estimated values of F should be used.

The tanglelaced products of the present invention illustrated in the examples, where the entangled regions are discrete areas, have values of at least 0.1 for the structural measure of fiber entanglement S in the regions of highest fiber entanglement and fiber cooperation in the structure.

MEASUREMENT OF FIBER ORIENTATION The relative total fiber length oriented at angles 45, and to the plane of the fabric is a measure of fiber transversity in tanglelaced structures. First, a sample of fabric is embedded in a clear plastic of index of refraction at 6328 A. differing by at least 0.01 from the index of refraction of the fibers in the fabric. An axis is fixed arbitrarily on the fabric face and a second axis 90 to the first is then drawn. Sixty consecutive cross-sections are then cut along each axis. The sections are 30 microns thick, 4 mm. wide and 10 mm. long. Every other section is discarded and those sixty remaining are each mounted between two glass slides held apart by glass spacers. The same plastic in which the samples are embedded is used for mounting.

The scanning apparatus consists of:

(l) A source of a collimated beam of 6328 A. wave length light which is used to illuminate a 1 mm. diameter area of sample section. A typical source is a heliumneon laser operating in the TEM mode, equipped with a quarter-wave plate. The more uniform the light intensity over the 1 mm. diameter area, the more accurately the relative length can be measured.

(2) A lens.

(3) A thin opaque plate with a narrow slit which is partially blocked by a relatively wide opaque strip perpendicular to the slit.

(4) A second lens similar to the first.

(5) A photocell with a 1 mm. diameter aperture.

(6) A recorder to pick up the signal from the photocell.

(7) A projection lens.

The focal length of the lenses and the slit size are in proper proportion such that the photocell signal from a straight fiber segment goes for maximum to /2 value when the fiber is rotated 913 from the angle at which maximum signal occurs.

To effect the measurement, the cross-section is placed one focal length from one of the lenses. One focal length on the other side of that lens is placed the thin plate with the slit. That location is also one focal length from the second lens which is located on the other side of the slit. On the other side of the second lens and one focal length from it is placed the (removable) photocell. The projection lens is placed behind the photocell position.

The light beam is thus directed through the crosssection, first lens, on the strip over the slit (and an equal distance from the edges of the slit), through the second lens and to the photocell or projection lens.

A section is scanned by orienting the slit parallel to the length of the section. The section image formed after the slit is projected on a screen with the projection lens and the section is moved along its length until the region is located where the greatest concentration of fibers is seen (regions near the edges of the section are avoided). The angular orientation at that region is obtained by rotating the slit through 180 and recording the signal from the photocell as a function of the angle the slit makes with the width of the cross-section. The area under the curve of the recorded signal vs. angle is a function of the angular position of the fibers in the region measured. The greater the area within any angular range, the more fiber length is aligned within that angular range. The angles are determined with an accuracy of :6 and a precision of if. The relative light intensity is determined with an accuracy of il0% and a precision of i2%.

In the region of greatest fiber transversity in each section, the total fiber length at 90il2 with respect to the fabric plane is compared to the total fiber length in that region at 45il2 and l35:l2. The number of sections wherein the value for the 90 measurement is greater than the values found for both the 45 and 135 measurements is designated the 45/ 90/ 135 number. This test is applicable to structures of homogeneous fibers.

Since many different embodiments of the invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited by the specific illustrations except to the extent defined in the following claims.

We claim:

1. A tanglelaced nonwoven fabric composed of 50% to 100% of acrylic fibers and up to 50% of other fibers the fabric having a repeating pattern of fibers randomly entangled with each other in tanglelaced areas and joining tanglelaced areas to form a strong fabric characterized by a high absorbency for water in comparison with the absorbency of woven fabric of the same fiber composition and with woven cotton fabric of similar basis weight, where the absorbency is determined by measuring the water retained after the thorougly wet fabric has been passed through a conventional wringer and then dividing the weight of retained water by the weight of the completely dry fabric, the fibers of the fabric being locked into place by a three-dimensional fiber entanglement characterized by a fiber entanglement frequency of at least 20 per inch with a fiber entanglement completeness of at least 0.5 when evaluated in a bond-free state, and wherein fibers in said tanglelaced areas turn, wind. twist back-and-forth and pass about one another in all three dimensions of the structure in so intricate a fashion that fibers interlock with one another when the fabric is subjected to stress to thereby provide coherency and strength to the fabric.

2. The fabric defined in claim 1 wherein the fibers are periodicaly tanglelaced along their lengths in a repeating pattern of nubs bound to adjacent nubs by linking bundles of fibers.

3. The fabric defined in claim 1 characterized by a fabric face layer of fiber groups in a regular pattern of ridges separated by grooves lying along generally parallel lines, the ridge fiber groups being interconnected by bands of generally parallel fibers bridging under the ridge-separating grooves and locked into place in tanglelaced areas.

4. The fabric defined in claim 3 wherein the ridges and interconnecting bands define a repeating pattern of apertures spaced along the grooves.

5. The fabric defined in claim 4 wherein the ridges windbetween adjacent grooves and apertures along sinusoidal paths having parallel axes and 180 out of phase with respect to adjacent sinusoidal ridge paths; the fabric structure comprising tanglelaced ridge fiber groups located between diagonally adjacent apertures, ridge fiber groups interconnecting the tanglelaced groups in ridges of substantially uniform height, and parallel fiber groups interconnecting the tanglelaced groups along straight paths between the apertures at right angles to the ridge-separating grooves.

6. The fabric defined in claim 1 characterized by a repeating pattern of fiber bands of substantially greater width than thickness which extend continuously along substantially straight parallel axes spaced regularly in one fabric direction and which comprise tanglelaced fiber areas that form ridges on at least one fabric face; said bands being interconnected by generally parallelized fibers which extend laterally between tanglelaced areas in adjacent bands and are locked into place by the tanglelaced areas; the band-interconnecting fibers being spaced apart along the edges of the bands and defining rows of apertures there-between.

7. The fabric defined in claim 6 composed of 50% to 75% of 0.5 to 2 denier, acrylic fibers and 50% to 25% of 0.5 to 2 denier, hydrophilic fibers.

8. The fabric defined in claim 1 wherein 5 0% to of the fibers are a mixture of different acrylic fibers.

9. The fabric defined in claim 1 wherein the fibers are of 0.5 to 5 denier per filament.

10. The fabric defined in claim 1 wherein 50% to 75% of the fibers are acrylic fibers and the remainder are hydrophilic fibers.

11. The fabric defined in claim 1 wherein the fibers are of 1 to 2 denier, 60% to 70% of the fibers are acrylic fibers and the remainder comprises rayon fibers.

12. The fabric defined in claim 1 having a regular pattern of discrete tanglelaced areas joined by ordered fiber groups to provide a fabric having an appearance similar to that of a conventional woven fabric.

References Cited UNITED STATES PATENTS 2,862,251 12/1958 Kalwaites 19l61 ROBERT F. BURNETT, Primary Examiner R. L. MAY, Assistant Examiner U.S. Cl. X.R.

19l6l; 281, 76; 16l169; 162-1l5, 204

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