|Publication number||US3477103 A|
|Publication date||Nov 11, 1969|
|Filing date||Jul 7, 1967|
|Priority date||Jul 7, 1967|
|Also published as||DE1760812A1, DE1760812B2, DE1760812C3, US3460731|
|Publication number||US 3477103 A, US 3477103A, US-A-3477103, US3477103 A, US3477103A|
|Inventors||Henry Mccardell Troth Jr|
|Original Assignee||Du Pont|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (5), Referenced by (13), Classifications (6)|
|External Links: USPTO, USPTO Assignment, Espacenet|
N 11, 1969 H. MOCARDELL TROTH, JR 3,477,103
PREPARATION OF NONWOVEN WEB STRUCTURE Filed July 7, 1967 4 Sheets-Sheet 1 I FIG.I W
' I INVENTOR q HENRY MC CARDELL TROTH, JR,
ATTORNEY Now- 1969 H. M CARDELL TROTH, JR 3,477,103 FREPARATION OF NONWOVEN WEB STRUCTURE Filed July 7, 1967 4 Sheets-Sheet 2 22 HENRY MC CARDELL TROTH, JR.
INVENTOR Nov. 11, 1969 4 Sheets-Sheet 5 Filed July 7, 1967 FIG.4
INVENTOR HENRY MC CARDELL TROTH, JR.
' ATTORNEY M A H. o l W B 6 H H H 1523 M5: Q m 2233;
Nov. ll, 1969 HgM CARDELL T'ROTH, JR 3,477,103
r PREPARATIQN OF NQNWOVEN wma STRUCTURE Filed July 7, 1967 4 Sheets-Sheet 4 v INVENTOR HENRY MC CARVDELL TROTH, JR.
United States Patent 3,477,103 PREPARATION OF NONWOVEN WEB STRUCTURE Henry McCardell Troth, Jr., Hendersonville, Tenn., as-
signor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed July 7, 1967, Ser. No. 651,802 Int. Cl. DMh 11/00 US. Cl. 19163 8 Claims ABSTRACT OF THE DISCLOSURE Directional continuous filament nonwoven webs are prepared by depositing filaments from fluid streams each containing a plurality of continuous filaments, which streams have been deflected transverse to the initial fluid stream direction. Deflection is accomplished by periodically directing fluid streams at each fluid stream carrying the filaments to achieve specified transversal rates as the filaments transverse paths across the laydown receiver.
BACKGROUND OF THE INVENTION A recently developed process for preparing continuous filament nonwoven Webs in which filaments are well separated is described in British Patent 932,482. In this process an electrostatically charged multifilament strand of continuous filaments is forwarded under tension by means of a jet device toward a web laydown zone. As the tension on the filaments is released at the exit of the jet device, the filaments separate due to the repelling eflect of the charge on each of the filaments, and while thus separated, are collected as a nonwoven web. The nonwoven webs produced in the above described process contain well separated, randomly disposed filaments. These webs may be bonded by known methods to produce fabrics with properties which are independent of direction. The bonded nonwoven fabrics prepared as above are highly desirable for many uses.
SUMMARY OF THE INVENTION rected, they result in an undesirable change in tufting pattern as well as providing a tufted carpet of narrower width than is commercially acceptable.
This invention provides a process for preparing nonwoven webs of uniform basis weight in which the filaments are preferentially aligned in a given direction and yet also provide strength in the other directions. To accomplish this result, a primary fluid stream containing a plurality of electrostatically charged continuous filaments is directed toward a laydown zone on a receiver surface moving away from the laydown zone (Machine Direction, MD). A secondary fluid stream is periodically impinged on one side of said primary fluid stream thereby deflecting said primary fluid stream in a direction transverse to the original direction of the primary fluid stream. Preferably two secondary fluid streams are alternately impinged on opposite sides of said primary fluid stream thereby deflecting said primary fluid stream alternately ice in opposite directions transverse to the original direction of the primary fluid stream. The filaments of the primary stream are thereby laid down in swaths on the receiver, oriented in the direction of deflection. Adjacent swaths deflected in the cross machine direction, XD, are in contact, i.e., overlap or abut at the extreme of each swing where the direction is reversed. Adjacent swaths deflected in the machine direction abut or overlap along the sides of the swaths. The kinetic energy of each secondary fluid stream is varied cyclically in direct proportion to the deflection distance. By deflection distance is meant the distance from the point that the band of filaments or swath is laying down on the receiver to the point Where the undeflected band of filaments lay down. Thus the kinetic energy of each opposing pair of secondary fluid streams will increase substantially zero i.e., a kinetic energy having no deflecting effect, to a maximum at the swath reversal points. The deflection frequency and swath length are such as to provide a deflection speed that is at least equal to one third the filament speed at the jet exit.
The angle of filament deflection i.e., the angle that the primary fluid stream is deflected from its original undeflected direction, is dependent on the kinetic energy of the deflecting fluid stream, which is in turn dependent on the deflection plenum pressure. The greater the kinetic energy of the deflecting fluid stream, the greater will be the deflection. Since it is desired that the continuous filaments be disposed in the nonwoven webs in a wellseparated condition, fiilament entanglement should be minimized by limiting the angle of filament deflection through use of a deflecting fluid stream of relatively low kinetic energy. The requirement of good filament separation limits the maximum angle of filament deflection to about Preferably this invention is used in conjunction with a process for the preparation of nonwoven webs as described in British Patent 932,482. A corona charging device as described in US. Patent 3,163,753, may be employed. A plurality of filament containing fluid streams are used to prepare wide continuous nonwoven webs of substantially uniform basis Weight.
Deflection of filament containing fluid streams with secondary fluid streams is shown in US. Patent 2,863,- 493. Australian Patent 242,895 concerns the preparation of continuous filament glass fiber mats by mechanical deflection of a fluid stream containing continuous glass fibers. These patents give no indication of filament directionality in the final product nor do they teach one skilled in the art the steps and conditions required in the instant process.
For the commercial production of nonwoven fabrics to be used for carpet backings a plurality of laterally aligned filament containing fluid streams can be employed. The deflected filaments loop back on themselves before beginning their traverse in the opposite direction, and provide nonwoven fabric strength in directions other than the direction of filament deflection. In order for one jet to lay down a swath with nearly constant unit weight and gradually tapering edges desirable for multiswath blending, the filament bundle should traverse the laydown receiver with a constant deflection speed, and should be well separated at the turn-arounds so that the edges taper gradually. Well separated filaments are achieved by electrostatic charging of the filaments before the jet, and constant rate of traverse may be achieved by regulation of the pressure cycle in the deflection plenums.
The directional Web prepared as above may be carried on the belt to a second laydown zone where a similar web oriented about to the orientation of the filaments in the first web is deposited thereon in a similar manner. If desired, the filaments of the second web may be randomly 3 oriented to yield a composite having predominant filament orientation in only a single direction. The webs may be laid down in varying order and number and the instant specification and claims are intended to cover such modifications.
Thus, a plurality of spaced moving streams each comprising an elastic fluid medium carrying and advancing a plurality of electrostatically charged continuous filaments at a velocity of at least 200 yards (183 m.) per minute is prepared and directed in parallel initial lines of direction into an elastic fluid atmosphere at a plurality of first positions. Each of said streams is then simultaneously laterally oscillated pneumatically from its initial line of direction in regular periodic laterally diverging patterns and the filaments of each moving stream are deposited as ribbons of filaments constituting the web in a laydown zone on a moving belt. The path of each ribbon of filaments as it is laid down traverses the receiver surface for a set distance and then reverses direction. Traverse occurs at a substantially uniform velocity of at least one third the filament velocity at the first positions and said traversal paths are in a direction substantially transverse to the stream direction at said first positions. Where a moving belt is used as a laydown receiver and filament deflection is in a direction parallel to the direction of belt movement, it may be desirable to deflect at dilferent speeds in the opposing directions to provide for constant traverse with respect to the belt. Adjacent swaths are overlapped or abutted to form a unitary directional web.
For the purpose of preparing a primary carpet backing with a highly desirable balance of physical properties, continuous filaments of isotactic polypropylene are employed. Nonwoven webs prepared according to this invention using isotactic polypropylene filaments comprising highly oriented and relatively unoriented zones spaced along the length of the filaments, which filaments are bonded in the manner described in Belgian Patent 668,406 provide a strong, dimensionally stable nonwoven fabric eminently suitable as a backing for tufted carpets.
DESCRIPTION OF THE DRAWINGS The process of this invention is best understood by reference to the following figures in which:
FIGURE 1 is an elevation view of the process and apparatus of this invention which for compactness illustrates only two deflection devices operating in each of the machine and cross-machine directions.
FIGURE 2 is a cross-sectional view of a modified slot jet suitable for use in this invention.
FIGURE 3 is a view of the exit end of the modified slot jet of FIGURE 2.
FIGURE 4 is a curve showing filament directionality obtained when the filament deflection speed in a single direction is about one half the filament speed.
FIGURE 5 is a curve showing filament directionality obtained when the filament deflection in a single direction is about equal to the spinning speed.
FIGURE 6 illustrates an apparatus which can be used to measure filament directionality in nonwoven webs.
In FIGURE 1, ribbons of electrostatically charged continuous filament fibers 1 are forwarded by means of slot jet devices 2, toward a flexible perivous belt 3, covering a suction means (not shown), as the tension on the filaments is released at the exit 4, of the slot jet device 2, the filaments are deflected alternately by opposed air streams issuing from filament deflection gaps 5, 6, suppled alternately by plenums 7, 8, 9 and 10. Plenums 7, 8, 9 and 10 are connected through manifolds and transfer lines (not shown) to compressed air supplies governed by rotary valves having variable speed drives (not shown), that alternately provide air to the opposing plenums.
In FIGURE 2, a ribbon of electrostatically charged continuous filaments is pulled into orifice 17 of slot jet 2, by flow of compressed air from a source (not shown) through entrance 19, and plenums 18, through entrance orifices 20, through elfuser throat 21, to slot jet exit 4.
Compressed air is supplied alternately through air inlets 22 and 23 to the plenums 7 and 8 and then through the respective deflection gaps 5 and 6 to impinge on the filament containing air stream emanating from exit 4, of slot jet 2.
In FIGURE 3 deflection gaps 5 and 6 are shown closely spaced and parallel to exit end 4 of slot jet 2.
In FIGURE 4 is shown a curve representing the filament directionality as obtained by the Randometer procedure, described hereinafter, for a bonded nonwoven web prepared by deflecting the filaments, in the machine direction (MD) only, at a filament deflection velocity equal to 55% of the filament velocity at the jet exit (535 y.p.m.). Improved filament directionality in the machine direction is noted. Flament deflection velocity is the speed at which the swath of filaments issuing from the exit of the jet traverses the receiver surface as it lays down.
In FIGURE 5 is shown a similar curve representing the filament directionality obtained in the same manner as for FIGURE 4 from a similar bonded nonwoven web prepared using a filament deflection velocity which is equal to the filament speed. Further improvement in filament directionality in the machine direction is noted.
In FIGURE 6 is shown a pictorial layout of an apparatus suitable for determining filament directionality in non-woven webs hereinafter referred to as a randometer.
DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred filaments for use in this invention comprise isotactie polypropylene filaments segmentally drawn along the length of the fibers by passage over three unheated rolls followed by passage over a steam heated roll such as that described in Edwards, US. 3,302,698. The latter is adapted with a radially slotted surface to heat 7 inch (17.8 cm.) segments of the filaments with one inch separations. The fibers are then passed over unheated draw rolls. The ribbon of continuous filaments thus formed is given a negative electrostatic charge by passing the ribbon of filaments across the target bar of a corona charging device such as that described in DiSabato and Owens, US. 3,163,753. Stripping of the ribbon of filaments from the draw roll is accomplished by the slot jet shown in FIGURE 2 which is similar to the slot jets described in Cope et al., UJS. 3,302,237, modified with a housing providing filament deflection gaps 5 and 6, which are supplied alternately with compressed air from the plenums 7 and 8.
For maximum eflficiency the deflection gap should be arranged so that the deflecting streams impinge on the filament stream issuing from exit 4 of slot jet at an angle approaching The angle should be sufliciently less to avoid any coanda effect that might be caused by the plenum housing below the plane of the jet exit which would tend to hold the filaments in the fully deflected position. A useful compromise is to use a deflection gap angle 0 of 70. The deflection gap should be sized to achieve the desired deflection at a moderate plenum pressure and air flow rate. The configuration of the jet exit and deflection gaps also influence deflection efliciency. For example, notching the jet exit improves deflection efliciency. Design of this type of main jet-control jet interaction zone is known in the art, and has been published as in Department of Defense Report AD611189, Study of Incompressible Turbulent Bounded Jets by I. F. Foss and I. B. Jones.
For the preparation of wide nonwiven webs with filaments aligned in preferred directions, the output of many jets is blended to form a nonwoven web of uniform basis weight. The jets may be conveniently arranged in banks with the output of the jets in each bank being deflected in the same direction or the output of the jets in each bank can be deflected in different directions (interleaving) so long as the deflected air streams do not interfere one with the other. Several banks of jets may be used to prepare the nonwoven webs, e. g., two, three, four or more banks of jets may be used.
The manifolds and transfer lines connecting the compressed air supply with the plenums 7, 8, 9, and are sized so that the flow of compressed air is always at a subsonic velocity. In practice the manifolds split the main air pulse into individual pulses which simultaneously enter designated plenums so that all gaps providing air for deflection in a single direction receive pulses at the same instant and thus deflect in phase. Valves may be used to balance plenum pressures from jet to jet in a bank so that each jet deflects the threadline at the same angle.
Deflection air may be supplied to the plenums at a maximum pressure of from about 0.5 to about 50 p.s.i.g. (.036-3.52 kg./cm. but preferably not exceeding about 5 p.s.i.g. (.35 kg./cm. The filament forwarding jet 2 is normally operated with air at a pressure greater than p.s.i.g. (1.4 kg./cm. The deflection gaps 5 and -6 may vary from about .005 to about .080 inch (.0127 to .203 cm.) but are preferably .015 to .020 inch (.038 to .051 cm.). The deflection gaps 5 and -6 are preferably spaced from 0.1 to 0.2 inch (.25 to 150 cm.) from exit 4 of the slot jet 2 and extend the length of the exit 4. The slot jet exit 4, is spaced from 5 to 36 inches (12.7 to 91.5 cm.) preferably about 24 inches (61 cm.) above a suction laydown receiver.
Filament speeds employed in the process of this invention range from 200 to 1800 y.p.m. (183 to 1645 m./min.) or greater and the laydown receiver has a speed of from 6 to 150 y.p.m. (5.48 to 127 m./'min.). To achieve a maximum deflection distance of 3.5 to 28 inches (8.971.1 cm.) with a filament speed of 535 y.p.m. (489 m./min.) at the jet exit and a distance of 24 inches (61 cm.) between jet and receiver, it has been found that the process of this invention requires a minimum deflection frquency (twice the maximum distance between reversal points) of 1.9 to 15.3 cycles/second. At a deflection frequency greater than 6.7 cycles/second and a maximum deflection distance of 12 inches (30.5 cm.), the deflection speed is equal to the filament speed at the jet exit (535 y.p.m.) (489 m./min.). The deflection speed should be at least 2.5 the belt or laydown receiver speed. Further increases in the filament deflection frequency produce no further increase in filament deflection speed since this is now controlled by the filament speed at the jet exit. Under these conditions higher deflection frequencies produce shorter deflection distances. It is found that appreciable filament orientation in the direction of deflection is obtained when the deflection speed is at least one third of the filament speed.
A measurement of filament directionality can be obtained by determining the total length of the filament segments that are oriented at the various directions throughout the sheet. This measurement has the advantage that it is universally applicable to straight, curved, or crimped fibers. In a random sheet, the total length of filament segments at any one orientation is the same as at any other orientation.
It has been found that the measurement of the length of filament segments at the various orientations can be made rapidly and accurately by an optical method. The method is based on the principle that only the incident light rays which are perpendicular to the fiber axis of a round fiber are reflected as light rays which are perpendicular to the fiber axis and has been named the randometer method. Hence, by focusing a beam of parallel light rays on a nonwoven sheet at an incident angle less than 90, e.g., 60, the light which is emitted perpendicular to the plane of the sheet comes only from filaments having an orientation within the plane of the sheet which is perpendicular to the incident light rays. By collecting and measuring photoelectrically the intensity of the light, the total length of the filament segments perpendicular to the light rays, therefore, parallel to each other, can be determined. By rotating the sheet, the parallel filament segments for any given direction can be measured and from this measurement, an analysis of filament directionality can be made.
An apparatus suitable for this measurement is shown schematically in FIGURE 6 and will hereinafter be re-- ferred to as a randometer. A detailed description of the components, the method of operation, and the method for standardizing the characterizations are given below.
As shown in FIGURE 6, the apparatus has a revolving stage 46 on which the sample 47 to be examined is placed. Stage 46 is modifiedby gear 48 which has half the teeth removed so that when driven by synchronous motor 49, it rotates only 180. Stage 46 rotates at r.p.m., thus the time for rotation of the sample through 180 is 2 minutes. Lamp 50 is located directly over the sample and in line with magnifying lens system 51. Lamp 50 is a 6-volt lamp and its intensity is controlled through 6-volt transformer 52 and variable-voltage transformer 53. The light from 50 is focused by lens 51 onto the bottom of the sample, and when projected through objective lens 54, eyepiece 55 and reflected from mirror 56, gives a shadow of the sample on ground-glass screen 57 at a magnification of 36X. Screen 57 is circular and has a diameter of 6.9 inches (17.5 cm.).
A second lamp 58 is mountned in a housing with projection lens 59 to focus the light on the sample at an angle of 60. Lamp 58 is a 25-watt, concentrated arc lamp receiving its power from power supply 61 which is modilied to eliminate the A.C. ripple. The filaments or segments or filaments which are perpendicular to the light from lamp 58 reflect the light into the magnifying lens and mirror system to screen 57 for measurement. Optical slit 62 is located between the objective lens 54 and stage 46 and serves to control the limits of the light reflected from the sample. The slit is A in. x in. (.159 cm. x .954 cm.) and is mounted with its long axis parallel to an imaginary line which is perpendicular to the light from lamp 58 and within the plane of the sample.
The light from the screen is focused by Fresnel lens 63 onto photomultiplier tube 64 (RCA type IP21) having a 2500 volt DC. power supply 65. The screen, Fresnel lens, and photomultiplier tube are contained in a single lighttight unit, which can, however, be opened for visual observation of the screen. The output from the photomultiplier tube is fed into a microampere recorder 66 having a chart speed of 8 in./min. (20.3 cm./min.) and a chart 9.5 in. wide (24.2 cm.). The chart records the light reflected from the parallel filaments at each direction as the sample is rotated through 180. The sensitivity of recorder 66 should be adjusted so that a current of 6 microamperes gives pen deflection.
A two-way switch 67 is in the line from the photomultiplier tube to the recorder so that the signal can be measured on a sensitive microampere meter 68, if desired. This meter can also be used in conjunction with a 6-volt lamp of fixed intensity to measure the fiber density of the sample so that, if desirable, all samples can be compared on the same basis.
Samples of the nonwoven sheet to be examined should permit clear viewing on the randometer of all the filaments through the thickness of the samples. Samples in excess of 1.9 oz./yd. (64.2 g./m. should be delaminated to fall within the range stated below, but care should be exercised to avoid disturbing the directionality during delamination.
The delaminated samples are placed between two microscope slides which are then taped together. The slide is placed on the revolving stage so that the light from lamp 58 shows on the sample. The background lamp 50 is then turned on and the filaments are focused as sharply as possible by moving revolving stage 46 up or down, while they are viewed on the screen. Lamp 50 is then turned oif. Stage 46, lamp 58 and projection lens 59 are enclosed in a lighttight unit. The voltage of power supply 65 is adjusted so that the pen will remain on scale in the directions of maximum filament alignment and the intensity of the reflected light is recorded on the microampere recorder chart as the sample is rotated through 180.
The heights of the intensity-orientation curve so obtained are measured in inches from the zero line of the chart at 80 equally spaced orientations and the arithmetic mean of these heights is determined. To standardize the randometer characterization, each of the 80 readings is multiplied by the factor arithmetic mean to shift the curve to a standard mean (5 in. pen deflection). When obtaining measurements on nonwoven webs with preferentially oriented filaments, the samples are delaminated into layers having fabric weights between 0.75 and 1.9 o: :./yd. (25.4-64.2 g./m. and measurements are taken on each layer. To improve the precision several measurements may be made on each layer. For each layer, the standardized readings at each angle are averaged to obtain a curve for that layer. Then a curve for the entire sample is reconstructed by averaging the readings at each angle for the different layers in proportion to the fabric weight of these layers.
This method was used to obtain the data plotted in FIGURES 4 and 5. A measure of the directionality of the filaments of a nonwoven web aligned in a given direction can be expressed as the percentage of the area under a curve, corresponding to the curves of FIGURES 4 and 5, and within i9 of the given direction, to the total area under the curve.
When the filaments are aligned preferentially in the machine and cross machine directions the direction corresponding to the peak pen deflection is taken as the machine direction (MD) or cross machine direction (XD) and should correspond within of the true machine direction (length of nonwoven fabric) and cross machine direction (width of nonwoven fabric), respectively.
EXAMPLE I A nonwoven web is produced using an arrangement similar to that illustrated in FIGURE 1 except that a first bank of 14 slot jets (12% inches apart, center to center) are used for machine direction deflection and a second bank (about 7 ft. from the first bank) of 14 slot jets (12% inches aaprt, center to center) are used for cross machine direction deflection. Each jet has a 6 inch wide inlet and a 9.31 inch wide diffuser. Polypropylene fibers (500 filaments at each position) are spun and segmentally drawn along the length of the filaments by passage successively over three unheated feed rolls operating at peripheral speeds of 187, 195 and 207 y.p.m. (171, 178 and 189 m./min.) and then over a heated roll of the type disclosed in Edwards, US. 3,302,698 operating at a mripheral speed of 216 y.p.m. (197 m./min.) and heated at 130 C. but adapted with an axially slotted surface to heat seven inch (17.8 cm.) segments of the filaments with one inch (2.54 cm.) separations and then passed over two draw rolls operating at 653 y.p.m. (596 m./min.). The ribbons of continuous filaments thus formed are given a negative electrostatic charge by passage across the target bars of corona charging devices such as those described in DiSabato et al. US. 3,163,753. Stripping of the ribbons of continuous filaments from the draw rolls is accomplished by slot jets of the type shown in FIGURE 2 using a jet plenum pressure of 24 p.s.i.g. (1689 g./cm. in the jets aligned for machine direction deflection and a jet plenum pressure of p.s.i.g. (1407 g./cm. in the jets aligned for deflection in the cross machine direction. The output of the first bank of jets is deflected a total distance of 20 inches (50.8 cm.) at a deflection frequency of 4.5 cycles/sec. using a peak deflection plenum pressure of 1 p.s.i.g. (70.3 g./cm. The output of the second bank of jets is laterally deflected a total distance of 26 inches (66 cm.) at a deflection frequency of 4.5 cycles/ sec. using a peak deflection plenum pressure of 2 p.s.i.g. (140.6 g./cm. The nonwoven web is collected on a suction laydown receiver moving at 14.9 y.p.m. (13.6 m./min.) and bonded in saturated steam at p.s.i.a. (6.3 kg./cm. A nonwoven fabric with a basis weight of 3.5 oz;/yd. (128.5 g./m. is obtained.
Filament alignment of this bonded nonwoven fabric obtained by the randometer method showed 15.0% of the total filament length is aligned in the machine direction and 9.9% of the total filament length is aligned in the cross machine direction.
The bonded nonwoven fabric is submerged in a 4% aqueous dispersion of a polysiloxane which contains 0.4% of a surface active agent (sodium alkylarylsulfonate). The fabric is then squeezed between two rolls with a nip pressure of 50 p.s.i.g. (3.5 kg./cm. at a speed of 1.5 yd./min. (1.4 m./min.) and dried in a circulating air oven at 93 C. for 45 minutes. About 2% by weight polysiloxane is added by this treatment. The fabric is tufted under the following conditions:
Gauge (distance between needles): 0.188 in. (0.48 cm.).
Speed: 400 tufts/min, 7 tufts/in. (2.8 tufts/cm) Pile Yarn (nylon carpet yarn): 3700 denier (410 tex) continuous filament.
Tuft Height: 0.438 in. (1.11 cm.).
Type Pile: loop.
After tufting, the nonwoven fabric has a machine direction tongue tear strength of 29 lbs. (13.2 kg.) and a cross machine direction grab tensile strength of 78 lbs. (35.4 kg.). On loading 3.3 lbs. per inch (0.589 kg./cm.) in the machine direction the nonwoven fabric decreases in width 1.1%.
EXAMPLE II An interleaved nonwoven web is produced using an arrangement similar to that of FIGURE 1 except one jet deflecting in the machine direction and two jets deflecting in the cross machine direction are used. The jets are arranged with the cross machine direction deflecting jets spaced seven inches (17.8 cm.) on each side of the center of the narrow wall and eight inches (20.3 cm.) on each side of the center of the wide wall of the machine direction deflecting jet. Polypropylene filaments are spun and segmentally drawn along the length of the filaments by passage successively over unheated feed rolls operated at peripheral speeds of 169, 186 and 195 y.p.m. (154, 170 and 178 m./min.) and then over a heated roll of the type described in Edwards US. 3,302,698 operating at a peripheral speed of 209 y.p.m. (191 m./min.) and heated at C. but adapted with an axially slotted surface to heat seven inch (17.8 cm.) segments of the filaments with one inch (2.54 cm.) separations and then passed over two draw rolls operating at 593 y.p.m. (542 m./min.). The ribbon of continuous filaments thus formed are given a negative electrostatic charge by passage across the target bars of corona charging devices such as those described in DiSa-bato et al. US. 3,163,753. Stripping of the ribbons of continuous filaments from the draw rolls is accomplished with slot jets of the type shown in FIGURE 2 using 30 p.s.i.g. (2110 g./cm. jet air for all jets. The output of each jet is deflected a total distance of 28 inches (71 cm.) at a deflection frequency of 4 cycles/sec. (deflection speed=0.7 spinning speed) using a peak deflection plenum pressure of 5 p.s.i.g. (351 g./crn. Direction of deflection is controlled so that the jets do not interfere one with another. The edges of the web not covered by the machine direction deflection are discarded. Basis weight is 4.8 oz./yd. (135.6 g./m. The web is bonded in saturated steam at 84 p.s.i.a.
After tufting, the nonwoven fabric had a machine direction tongue tear strength of 75.0 lbs. (24.0 kg.), a cross machine direction tensile strength of 142 lbs. (64.2
9 kg.) and a neckdown of 1.4% when subjected to a longitudinal stress of 3.3 lbs/in. (0.589 kg./cm.).
1. A process for preparing an elongated wide unitary coherent directional nonwoven web structure comprising forming a plurality of spaced moving streams each comprising an elastic fluid medium carrying and advancing a plurality of electrostatically charged dispersed continuous filaments at a velocity of at least 200 yards per minute, directing said streams in parallel initial lines of direction into an elastic fluid atmosphere at a plgrality of fist positions, simultaneously at each of said first positions pneumatically oscillating each of said streams laterally from their initial lines of direction in regular periodic patterns and depositing the filaments of each moving stream in swaths or ribbons constituting a web, in a laydown zone on a receiver surface that continuously moves the web from the laydown zone, said swaths or ribbon, as they lay down, traversing a path for a set distance on the receiver surface and reversing direction, at a substantially uniform velocity of at least one third the filament velocity at the first positions.
2. The process of claim 1 wherein the swaths are laid down on the receiver surface transverse to the direction of movement thereof and adjacent swaths are contacted at reversal points.
3. The process of claim 1 wherein the swaths are laid down on the receiver surface in the direction of movement thereof.
4. The process of claim 1 wherein said web structure is deposited on a nonwoven web structure in the laydown zone.
5. A process for preparing an elongated wide unitary coherent directional nonwoven web structure comprising forming a plurality of spaced moving streams each comprising an elastic fluid medium carrying and advancing a plurality of electrostatically charged dispersed continuous filaments at a velocity of between 200 and 1800 yards per minute, directing a first group of said streams in laterally aligned relationship in parallel initial lines of direction into an elastic fluid atmosphere at a plurality of first positions, simultaneously at each of said first positions pneumatically oscillating each of said first group of streams laterally from their initial lines of direction in regular periodic laterally aligned patterns and depositing the filaments of each first group of moving streams in contacting swaths constituting a first web in a first laydown zone on a receiver surface that continuously moves the web from the first laydown zone, said swaths, as they lay down, traversing a path for a set distance across the receiver surface and reversing direction, at a substantially uniform velocity of at least one third the filament velocity at the first positions; continuously moving said first web from said first laydown zone to a second laydown zone; directing a second group of said streams in laterally aligned relationship in parallel initial lines of direction into an elastic fluid atmosphere at a plurality of second positions, simultaneously at each of said second positions pneumatically oscillating each of said second group of streams laterally from their initial lines of direction in regular periodic laterally aligned patterns and depositing on the first web in said second laydown zone the filaments of each second group of moving streams as swaths constituting a web, said swaths traversing a path for a set distance across the first Web and reversing direction at a substantially uniform velocity of at least one third the filament velocity at the second positions, said traversal paths being in a direction substantially perpendicular to the swath traversal paths of said first web and continuously moving said resultant composite web from said second laydown zone.
6. The process of claim 5 wherein the swaths of both webs are laid down on the receiver surface in the direction of and transverse to the direction of movement there of respectively.
7. A process for preparing an elongated wide unitary coherent directional nonwoven web structure comprising forming a plurality of spaced moving streams each comprising an elastic fluid medium carrying and advancing a plurality of electrostatically charged dispersed continuous filaments at a velocity of between 200 and 1800 yards per minute, and (1) directing a first group of said streams in laterally aligned relationship in parallel initial lines of direction into an elastic fluid atmosphere at a plurality of first positions, simultaneously at each of Said first positions pneumatically oscillating each of said first group of streams laterally from their initial lines of direction in regular periodic laterally aligned patterns and depositing the filaments of each first group of moving streams in contacting swaths constituting a first Web in a first laydown zone on a receiver surface that continuously moves the web from the first layadown zone, said swaths as they lay down traversing a path for a set distance on the receiver surface and reversing direction, at a substantially uniform velocity of at least one third the filament velocity at the first positions; cotninuously moving said first web from said first laydown zone to a second laydown zone; and (2) directing a second group of said streams in laterally aligned relationship in parallel initial lines of direction into an elastic fluid atmosphere at a plurality of second positions and depositing the filaments of each second group of moving streams without pneumatic oscillation on the first web in said second laydown zone as a random web and continuously moving said resulting composite web from said second laydown zone.
8. The process of claim 7 wherein the random web is deposited first.
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|U.S. Classification||19/163, 264/DIG.750|
|Cooperative Classification||Y10S264/75, D04H3/02|