US 3747161 A
A method for producing, from a layer of fibrous material such as a fibrous web, nonwoven fabrics that contain apertures or holes or other areas of low fiber density and a pattern of groups of fiber segments defining such apertures, said fabric having improved cross strength. The method includes the steps of treating the fibrous layer by directing fluid rearranging forces against the layer while it is supported, stretching the treated layer in its transverse direction and treating the stretched layer with a plurality of fluid rearranging forces while the stretched layer is supported to produce a fabric having a pattern of fiber bundles defining a pattern of apertures or holes or other areas of low fiber density.
Claims available in
Description (OCR text may contain errors)
Kalwaites July 24, 1973 METHOD FOR PRODUCING A REARRANGED FABRIC HAVING IMPROVED CROSS-STRENGTH Frank Kalwaites, Gladstone, NJ.
Johnson & Johnson, New Brunswick, NJ.
Filed: Aug. 20, 1971 Appl. No.: 173,442
U.S. Cl. 19/161 P, 28/72 NW Int. Cl D04h 11/00 Field of Search 19/161 R, 161 P;
References Cited UNITED STATES PATENTS Primary Examiner-Dorsey Newton Attorney-Robert L. Minier  ABSTRACT A method for producing, from a layer of fibrous material such as a fibrous web, nonwoven fabrics that contain apertures or holes or other areas of low fiber density and a pattern of groups of fiber segments defining such apertures, said fabric having improved cross strength. The method includes the steps of treating the fibrous layer by directing fluid rearranging forces against the layer while it is supported, stretching the treated layer in its transverse direction and treating the stretched layer with a plurality of fluid rearranging forces while the stretched layer is supported to produce a fabric having a pattern of fiber bundles defining a pattern of apertures or holes or other areas of low fiber density.
3 Claims, 5 Drawing Figures pg imgwulzmzs SW 1 of 2 I ,7 7,151
INVENTOR A'ZWA A/rEs I ii I BY g/ ATTORNEY METHOD FOR PRODUCING A REARRANGEI) FABRIC HAVING IMPROVED CROSS-STRENGTH This invention relates to a method for the production of nonwoven fabrics and more particularly to a method for the production of nonwoven fabrics from a layer of fibrous material such as a fibrous web in which the individual fiber elements are capable of movement under the influence of applied fluid forces to form a fabric which contains apertures or holes or other areas of low fiber density defined by a pattern of fiber bundles with the resultant fabric having improved cross strength.
BACKGROUND OF THE INVENTION Various methods and apparatus for manufacturing apertured or rearranged nonwoven fabrics involving the rearrangement of fibers in a starting layer of fibrous material, have been known for a number of years. Some of the methods and apparatus for manufacturing such fabrics are shown and described in U.S. Pat. No. 2,862,251 which discloses the basic method and apparatus of which the present. invention is a specific form and in US. Pat. Nos. 3,081,500 and 3,025,585.
The nonwoven fabrics made by the method and apparatus disclosed in those patents contain apertures or holes or other areas of low fiber density often outlined by interconnected yarn-like bundles of closely associated substantially parallel fiber segments. (the term,
areas of low fiber density is used in this specification and claims to include both 1) areas in which relatively few fibers are found in comparison to the rest of the fabric, and (2) apertures (holes) that are substantially or entirely free of fibers); Such fabrics are sometimes referred to as bundled rearranged" nonwoven fabrics.
One of the specific methods for producing bundled rearranged" nonwoven fabrics is disclosed in US. Pat. No. 2,862,25] and is to support a loose fibrous web or layer between an apertured forming member and a permeable backing member, and direct streams of rearranging fluid through the apertures of the forming member in order to apply spaced sets of opposed fluid forces to the layer. The spaced streams of fluid pass through the fibrous layer over and through the backing member, to pack groups of fiber segments into closer proximity and substantial parallelism in interconnected yarn-like bundles of fiber segments that define holes or other areas of low fiber density corresponding to the pattern of the apertures of the apertured forming means.
In the method just described, the streams of rearranging fluid enter the fiber rearranging zone at spaced locations determined by the position of the apertures in the apertured forming means against which the fluid streams are first directed. Then, when the rearranging fluid leaves the rearranging zone, it does so through foramina uniformly dispersed throughout the permeable backing member. There are other specific methods for producing similar fabrics as described above; however, all of these methods, when used with a standard card web or oriented web as the starting material, produce a fabric that maintains the basic ratio of strength of the longitudinal direction of the starting material to the cross direction of the starting material.
SUMMARY OF INVENTION 1 have discovered a method for producing bundled rearranged nonwoven fabrics having improved cross strength; that is, the ratio of the long tocross strength of the resultant fabric is improved over the ratio of long to cross strength of the starting material. Furthermore, the resultant fabric will have a pattern of apertures or holes or other areas of low fiber density defined by interconnected bundles of fibers.
In the method of the present invention, the starting material is a layer of fibrous material whose individual fibers are in mechanical engagement with one another and are capable of movement under applied fluid forces. The layer of fibrous starting material is supported in a fiber rearranging zone. The layer is treated with a plurality of fiber rearranging forces longitudinally and transversely spaced over the layer to move fibers into areas of a lesser and greater fiber density. The treated layer is stretched in its transverse or crosswise direction at least percent and preferably -150 percent or more of its original width. The cross-stretched layer is then treated with a plurality of fiber rearranging forces to form a pattern of interconnected fiber bundles defining apertures or holes or other areas of low fiber density therebetween.
Surprisingly, it has been found that the above threestep method of applying fiber rearranging forces crossstretching, and again applying fiber rearranging forces, unexpectedly alters the ratio of the long strength to the cross strength to produce greater cross strength in the final product while the final product still unexpectedly has a pattern of fiber bundles defining holes or apertures or other areas of low fiber density.
The basic rearranging methods used in the method of the present invention are shown and described in the previously mentioned US. Patents. Full particulars of these rearranging'methods as disclosed in those patents are incorporated in this application by reference, although some of those particulars are repeated herein. In addition, the specific feature peculiar to the method of the present invention, which is the insertion of a cross-stretching step between two fiber rearranging steps, is described in detail in this application. Starting material.
The starting materials used with the method of this invention may be any of the standard fibrous webs such as oriented card webs, isowebs, air-laid webs, or webs formed by liquid deposition. The webs may be formed in a single layer or by laminating a plurality of the webs together. The fibers in the web may be arranged in a random manner or may be more or less oriented as in a card web. The individual fibers may be relatively straight or slightly bent. The fibers intersect at various angles to one another such that generally speaking, the adjacent fibers come into contact only at the points where they cross. The fibers are capable of movement under forces applied by mechanical means or by fluid means.
The method of this invention is probably most applicable to oriented webs such as card webs which have good long strength but poor cross strength in their original state. By treating such webs in accordance with the method of the present invention, the long strength may be somewhat reduced and the cross strength is greatly improved, and the resultant product is considerably more balanced in properties. Furthermore, the crossdirection modulus of the resultant product is unexpect edly greatly improved. It should be noted that if you desire to produce fabrics having even greater cross strengths than long strengths, this may be done by starting with an isoweb or a similar web having substantially the same cross and long strength in its original state.
To produce a fabric having the characteristic hand and drape of a textile fabric the layer of starting material used with the method of this invention may comprise natural fibers such as cotton, flax, etc.; mineral fibers such as glass; artificial fibers such as viscose rayon, cellulose acetate, etc., or synthetic fibers such as polyamides, the polyesters, the acrylics, the polyolefins, etc., alone or in combination with one another. The fibers used are those commonly considered textile fibers; that is generally having a length of from about A inch to about 2 to 2 k inches. Satisfactory products may be produced in accordance with this invention from starting webs weighing between 80 grains per square yard to 2,000 grains per square yard or higher. First rearranging step.
The initial rearranging treatment may be any of the known rearranging treatments well known in the art such as that disclosed and described in U.S. Pat. No. 2,862,251 wherein fluid mediums are used to rearrange the fibers into areas of lesser and greater fiber density. Also mechanical means may be used in this initial rearranging step to arrange the fibers into areas of lesser and greater fiber density such as mechanical methods and machines disclosed in U.S. Pat. Nos. 3,081,501 and 3,220,084. Other known methods may also be used so long as the fibers in the starting layer are moved into a pattern of areas of greater fiber density which define holes or apertures or other areas of lesser fiber density. Stretching step.
The rearranged fabric is stretched in the transverse direction; that is, in the direction of its width. The fabric may be stretched anywhere from about 50 percent of its original width to 150 percent of its original width or more. It is preferred the fabric be stretched from about I to 150 percent of its original width. If the fabric is not stretched enough, the fibers which have been rearranged so that fiber portions now lie in a more cross-wise direction than they did in the original web, will not be further aligned in the cross-wise direction in the second rearranging step. If the fabric is stretched too much in the cross-wise direction, the fibers tend to slip by one another and holes or weak points appear in the web. The apparatus used for cross-stretching the web may be any of the known cross-stretching devices such as, bow spreaders, tenter frames or similar mechanisms. As the web comprises very light fibers with the fibers having little coherence for adjacent fibers due to the frictional entanglement between fibers, it is preferred that the mechanism used stretch the web uniformly across its width, as this is easier to control and makes the web easier to handle.
During the transverse stretching step the web is allowed to retract in the longitudinal direction. The amount of retraction will depend on many factors such as the speed of processing, type of fibers, amount of transverse stretching and so forth. Retractions of up to about 35 percent in the longitudinal direction have been found satisfactory.
Final rearranging step.
The final rearranging step should be accomplished by fluid forces; that is, by applying fluid forces longitudinally and transversely spaced over the fabric to move fibers out of areas to produce holes or apertures or other areas of lesser fiber density defined by groups of fiber segments which lie in close proximity and increased parallelism to form yarn-like fiber bundles which define the holes. Such rearranging methods are more fully described in U.S. Pat. No. 2,862,251. The rearranging fluid for use with this method of the invention is preferably water or similar liquids, or may be other fluids such as gas, steam, etc.
In accordance with the present invention a plurality of transverse stretching steps may be used provided a rearranging step is always interposed between two transverse stretching steps.
BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fully described in connection with the accompanying drawings in which:
FIG. 1 is a view in perspective of one set of apparatus that may be employed to carry out the method of the present invention with the set of apparatus comprising a rearranging unit, a spreading unit, and a second rearranging unit;
FIG. 2 is a diagrammatic plan view of one type of backing means and forming means with the web sandwiched therebetween which may be used in the rearranging units of the present invention;
FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2.
FIG. 4 is an enlarged sectional view of another set of apparatus which may be used to carry out the method of the present invention with this apparatus comprising a mechanical rearranging means, another type of stretching means and yet another type of rearranging means.
FIG. 5 is a top view of the stretching means depicted in FIG. 4 taken from line 55 of FIG. 4.
DETAILED DESCRIPTION OF THE SPECIFIC FORMS OF THE INVENTION FIG. 1 of the drawings shows one form of apparatus for carrying out the method of the present invention. The apparatus may be divided into three groups for carrying out the three basic steps of the present process. The first unit (A) is the first rearranging unit, the second unit (B) is the cross-stretching unit, and the third unit (C) is the second rearranging unit. With regard to the first rearranging unit, this apparatus is shown ane described in detail in U.S. Pat. No. 2,862,251. This apparatus comprises a foraminous forming member in the form of a perforated drum 10. A backing member in the form of a continuous screer; belt 1 1 passes about the greater portion of the periphery of the drum as shown. Spray nozzles 12 are located inside the drum for projecting streams of fluid, preferably liquid, such as water, through the perforations in the drum and out through the screen belt. A layer of starting material 13 suitably formed of laminated webs of carded cotton fibers; for example, may be sandwiched between the drum and the belt for processing by the fluid being projected through the drum to be formed into a rearranged fabric.
The screen belt 11 passes around a major segment of the drum l0 and is held in position thereon by positioning rollers 14 and 15 located above the drum close to its surface. The first positioning roller 14 appears at the left and the second positioning roller 15 appears at the right. These rollers are fixed to shafts (not shown) which are free to rotate. The belt also passes around guide rollers 16 and 17 mounted below the drum.
This rearranged fabric 20, after passing around the drum, turns around the second positioning roller then around and through the nip between a pair of squeeze rollers 21 and 22. Preferably the bottom roller is driven through a power source not shown, through conventional means such as a belt, chain, or chain of gears also not shown. The pressure at the nip between the rollers may be controlled by any suitable means.
Preferably, the nozzles 12 for supplying liquid in streams to the inside wall of the perforated drum are mounted at the ends of tubes 23 arranged in banks along the length of the pressure cylinder 24.
Fluid under pressure may be applied to the interior of the cylinder 24 from any suitable force not shown. There may be one line or bank of nozzles positioned partly or entirely across the perforated wall of the drum, but it is preferred that at least two banks of nozzles be employed. Three, four, or maybe more banks of nozzles may be advantageous under certain conditions, since they tend to increase the range of speed of the V machine. Various conventional forms of nozzles may be employed although solid cone nozzles are preferred.
In operation, the layer of starting material which may be a web of carded cotton fibers, may be passed over the first positioning roller and into contact with the continuous screen. The screen carrying the web may be passed around the portion of the drum in the way of liquid being projected through perforations of the drum, then around the drum over the second positioning roller and thence through the nip formed by the squeeze rollers. The web of material is formed into a rearranged fabric as it passes through the way of the liquid being projected through the perforations in the drum.
A portion of the sandwich formed by the drum 10, web 13 and screen 11, is shown in FIGS. 2 and 3. The perforations 26 in the drum are round and arranged in a regular spaced square pattern or other desired regular pattern. In general, it is preferred that the dimension of the foramina or openings in the foraminous screen be substantially less than the dimension of the openings in the drum, and for best results, it is preferred that the openings in the screen be considerably smaller than the openings in the drum. For example, with the drum having uniform openings in the order of about l/32 of an inch in diameter, good results may be obtained where openings in the foraminous screen may vary about 900 openings per square inch to about 50,000 openings per square inch, preferably from about 10,000 openings to about 40,000 openings per square inch.
From the first rearranging unit (A) the fabric passes to the spreading unit (B) which spreads the fabric preferably from about 50 to 100 percent of the original width. The spreader. unit is formed by a plurality of extensible coil springs 30 circumferentially arrangedto constitute the peripheral wall of the spreader. Each spring is secured adjacent the periphery of end discs 31 and 32. Each of the end discs is operatively connected to means whereby each disc can be angularly disposed relative to the other at the desired spreading angle. As shown in FIG. 1, the rearranged fabric is placed on a conveyor 33. The fabric passes under rollers 34 and 35 and is fed to the web spreader at the position where the peripheral portion of the end discs are close together. The springs and end discs rotate with the rearranged fabric thereon to the point where the peripheral portion of the end discs are substantially further apart,
thus spreading the fabric being carried by the springs.
The mechanism described spreads the fabric uniformly across its width. The fabric 38 is removed from the spreading means to pass through a pair of nip rolls 40 and 41 and to a second rearranging means (C).
The second rearranging means is the same as the first rearranging means and the description f0 this means is the same as the first and hence, like numerals have been used in both rearranging means. The only difference between the second rearranging means is that it is wider than the first rearranging means and is as wide as is required dependent upon the degree to which the fabric is spread by the web spreading means. The stretched fabric 38, after passing through the second rearranging means, is rearranged into a fabric 43 having fiber bundles comprising groups of fiber segments in close proximity and in increased parallelism to one another which are interconnected to define holes or apertures or other areas of low fiber density with the pattern of openings or holes or areas of low fiber density corresponding to the holes in the perforated drum, and with the resultant fabric having improved cross strength. The fabric is removed from the rearranging means and may be either further processed by normal nonwoven processes or may be wound up for use in various products.
In FIG. 4, there is shown another type of apparatus for carrying out the method of the present invention. In this form, the first rearranging means (D) is a mechanical rearranging means followed by a stretching means (E), followed by another rearranging means (F) different from any other of the rearranging means described previously. The feed end of the mechanical rearranging means is at the left of the drawing and the layer 50 of irregularly arranged fibers is fed to this end of the machine. Wet-out rolls 51 and 52 entend transversely of the machine and are rotatably mounted in vertical alignment at the feed end of the machine. The lower wet-out roll 52 is partially immersed in a water pan 53. The pair of wet-out rolls cooperate to control the moisture content of the layer of fibers which is preferably controlled between and 200 percent moisture as it leaves the wet-out rolls.
A main drive shaft 55 mounted in suitable framing (not shown) carries a cylinder 56 which rotates with the drive shaft. The cylinder is provided with a plurality of needles 57 or similar sharp, tapered implements, projecting angularly from its peripheral surface. The needles are secured to the surface of the cylinder by any suitable manner and are arranged in accordance with any desired pattern. During operation of the machine, the drive shaft rotates the needle bearing cylinder continuously. From the nip between the wet-out rolls, the layer of irregularly arranged fibers is moved into contact with the sharp ends of the needles projecting regularly from the peripheral surface of the cylinder. The layer of fibers is pulled into contact with the sharp pointed ends of the needles in an area of the peripheral surface of the cylinder in which pressure means such as an embedding brush 60 is adapted to impale the layer of fibers on the needles. The embedding brush extends longitudinally of the needle bearing cylinder and covers substantially the entire width of the cylinder. The working surface of the embedding brush formed by the ends of the brush bristles 61, is substantially flat but is curved slightly in its transverse direction to allow it to conform to the circumference of the curvature of the needle bearing cylinder. The brush comprises a plurality of soft bristles 61 secured to a backing 62 which is pivotally secured to a plate 63 at the lower end of a reciprocating rod 64. The embedding brush is reciprocally driven so as to continually press the layer of fibers down around the pins. The fibrous web on the pins is moved along with the needles as the cylinder rotates. About the circumference of the cylinder there is mounted a series of rotary brushes 65, 66, 67 and 68. The bristles of each of the rotary brushes are very soft so that they may rearrange the fibers of the layer without destroying the integrity of the layer. As seen in FlG. 4 some of the britles are long enough that except as they are prevented from doing so by the presence of the fibrous web being rearranged they extend between the spaced needles below the free end of the needles. The web 69 after it is brushed and rearranged, is removed from the needle bearing cylinder and passes between a pair of nip rolls 70 and 71 and to the cross stretching unit (E).
in this embodiment, the cross stretching or transverse stretching unit is a tenter frame. For for sake of clarity, a top view of this tenter frame is shown in FIG. 5. The rearranged layer 69 is fed to a pair of divergent conveyors 72 and 73. The conveyors have gripping means 74 which grip the edges of the fabric. As the conveyors diverge, the fabric is stretched in the transverse direction and the fibers reoriented in accordance with the present invention. At the wide end of the diverging conveyors the gripping means release the fabric 75 and the fabric is carried forwardly through the nip of a pair of rolls 76 and 77 into the second rearranging unit (F).
in the second rearranging unit, horizontal frame members 80 are supported by legs 81 and 82. At the feed end of the machine (in the left-hand side of the FIGURE) a pair of vertical frame members 83 extend upwardly above horizontal frame members to carry the pair of nip rolls 76 and 77 rotatably mounted between them.
The stretched fibrous layer 75 moves from the nip of the rolls 76 and 77 to the second fiber rearranging zone to effect the rearrangement of fibers in the stretched layer and produce the rearranged fabric of the present invention. The stretched layer of fibers is supported on a backing member 85 in the form of an endless belt which extends around a pair of parallel rolls 86 and 87 rotatably mounted adjacent opposite ends of the frame.
A water pipe 88 mounted in a suitable manner supports a pair of headers 89 and 90 above the upper reach of the endless belt. Each header extends transversely of the belt and has row of jet nozzles 91 to provide water sprays across the width of the belt.
These nozzles may be fine orifice-like jets directly above the belt or they may be the spray type nozzles described in conjunction with the rearranging means of FIG. I.
A pair of suction boxes 92 and 93 are mounted beneath the endless belt with one of the boxes located directly beneath each row of nozzles. Each suction box is closed on all sides except for an opening 94 to which a vacuum line is connected. The top wall of each suction box is positioned adjacent the underside of the upper reach of the endless belt.
The endless belt or backing means is foraminous. Preferably, the backing belt is a heavy wire screen; that is, it has substantially straight wires in one direction and highly crimped wires in the other direction. The projections formed by these crimped wires causefibers to align in a pattern in accordance with the high points of the wire. If desired, the backing member may be substantially planar such as, a perforated plate or a fine wire screen. During the rearrangement, some fibers or segments of fibers are moved by the jet streams into interentangled relationship in the apertures or perforations in the patterning member while other fibers or segments of fibers form groups of fiber bundles which link or interconnect the entangled fiber areas. Virtually any type of backing member can be used with any pattern of apertures or non-planer areas depending on the desired pattern of apertures and fiber bundles desired in the final product.
The rearranged web or fabric produced by the practice of this invention may be treated with an adhesive dye or other impregnating, printing, or coating material in a conventional manner. For example, to strengthen the rearranged fabric, any suitable adhesive bonding materials or binders may be included in an aqueous or non-aqueous medium employed as the rearranging fluid in the second rearranging step. Adhesive binder may, if desired, be printed on the rearranged fabric to provide greater fabric strength. Thermoplastic binders may, if desired, be applied to the rearranged web in powder form before, during, or after rearranging and then fused to bond the fibers.
The optimum binder content for a given fabric according to this invention depends upon of factors number ofactors including the nature of the binder material, the size and shape of the binder areas, and their arrangement in the fabric, the nature and length of the fibers, total fiber weight and the like. In some instances because of the strength of the fibers used and the tightness of their interentanglement in the rearranged fabric or both factors, no binder at all need be employed to provide a usable fabric.
The following is an illustrative Example of the use of the method and apparatus of this invention to produce a rearranged fabric.
EXAMPLE Using the second rearranging unit as illustrated in FIG. 4, a web of loosely assembled fibers such as may be obtained by carding, is fed onto a foraminous conveyor. The web weight is about 500 grains per square yard and its fiber orientation ratio approximately seven to one in the direction of travel. lts long strength is seven to 10 times greater than its cross strength. The web contains 95 percent polyester fibers approximately 1 k inch long and l k denier and 5 percent rayon fibers approximately 1 9/16 inch long and l b denier. The backing belt is a woven screen about 15 X 15 with about 35 percent open area.
Above the belt and directed against the upper reach of the belt are two water jet manifolds. Each manifold consists of two rows of orifices. The orifices are staggered in adjacent rows and each orifice has a diameter of about 0.0l2 inch. Water, at pounds pressure, is directed through orifices on to the web while the web is supported by the foraminous backing means. The water is removed by the vacuum boxes beneath the upper reach of the backing means. The vacuum applies about 2 inches of mercury. The web, as it passes under the water jets, is rearranged into a pattern of fiber bundles with entangled junctures connecting the fiber bundles.
The treated fabric is passed to a cross-stretching unit similar to that depicted in FIG. 1. The web is stretched in its transverse direction 100 percent of its original width and then folded lengthwise to maintain its approximate original weight of 520 grains per square yard.
The cross-stretched web is passed through the same rearranging unit as described above with the exception that the water pressure is increased to 160 pounds per square inch and it is passed through the rearranging unit three times.
The resultant rearranged fabric is tested inboth the cross direction and the machine direction for tensile strength, elongation, and tenacity. The tensile strength in the machine direction of the web is 8.98 pounds and the tensile strength in the cross direction of the web is 3.80 pounds, so that the ratio of strength in the machine direction and the cross direction has been improved from the original seven to to one to only about 2 A to l. The tenacity has also been improved in a similar manner in that the tenacity of the web in the machine direction is 1.74 while the tenacity in the cross-direction is 0.730 and the elongation of the rearranged fabric in the machine direction is 38 percent while the elongation in the cross direction is 57 percent.
The above detailed description has been given for clearness of understanding only. No unnecessary limitations should be understood therefrom, as modifications will be obvious to those skilled in the art.
What is claimed is:
1. A method of manufacturing a rearranged nonwoven fabric having improved cross strength comprising: (a) treating a layer of fibers with a plurality of rearranging forces to move fibers into areas of lesser fiber density and areas of greater fiber density, (b) stretching the rearranged layer of fibers in its transverse direction, and (c) treating the stretched layer with a plurality of rearranging forces to form a plurality of interconnected bundles of fiber segments defining a pattern of areas of lesser fiber density.
2. A method according to claim 1 wherein the rearranged layer of fibers is stretched in the transverse direction uniformly across its width in an amount of from about 50 to 150 percent of its original width.
3 A rnethod according to claim 1 wherein the layer of fibers is treated with a plurality of longitudinally and transversely spaced streams of water, the rearranged layer of fibers is stretched in a transverse direction uniformly across its width in an amount of about from 50 to 150 percent of its original width, and the stretched layer is treated with a plurality of longitudinally and transversely spaced streams of water.