CA1073174A - Tape structures and methods of making same - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
The invention relates to a tape comprising two or more main filaments uniaxially oriented along their longitudinal axes and having a plurality of transverse tie filaments interconnecting said main filaments with portions of tie filaments protruding from the edges of said tape. The invention also relates to a method of making the tape and to material woven from the tape.

Description

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Our patent application Serial No. lgO,207, filed January 15, 1974, from which this application is divided, relates to new and improved network struc~ures and methods for making such network structures~ and particularly to network structures and methods for making them by embossing or forming ribs in both sides of a thermoplastic polymeric sheet in a par~icular manner so as to permit spon~aneous fibrillation or opening of the network structure upon drawing in one direction or in two preferably perplendicular directions ~;
and to provide a uniform open network structure having desirable strength characteristics. The present invention is concerned with making tapes and woven fabrics from network structures such as those which are the subject of application Serial No. 190,207.
In the manufacture of networks, it has previously been proposed to form continuous diagonal grooves in one direction in one side of a sheet of plastic material and continuous diagonal grooves in the opposite direction on khe other side of the sheet so that upon subjecting the sheet to biaxial ~
stretching the thin parts of the sheet, at the crossing points of the grooves, ~;
split and form perforations thereby opening the material into a network. For `
example, see United States Patent 3,488,415 to A. G. Patchell et al. The net works therein disclosed are formed in such a manner as to have thicker masses at the points where the ridges cross, which behave as discrete areas of rein~
forcement, since on biaxial stretching or drawing of the embossed sheet the thick areas where the ridges cross orien~ only to a limited extent if at all.
The tensile strength and tear characteristics of such a network are relatively poor because the presence of the unoriented thick areas weakens the tensile strength and tear resistance of the network so prepared, and such a network is not uniform in appearance. United States Patent 3,500,627 to Charles W.
Kim discloses making yarn by forming on one side of a ribbon of plastic material a plurality of parallel filament forming ribs and on the other side a plurality of fibril forming cross-ribs arranged at an acute angle to the filament forming ribs. The ribbon is then uniaxially oriented and mechani- -~

cally fibrillated by means of a toothed fibrillating device to break the fibril forming ribs and form a yarn having fibrils extending laterally there-from. Use of mechanical fibrillation makes reproducing uniform network struc-tures very difficult.
The invention of application Serial No. 190,2~7 relates to network structures and methods of making network structures comprising: forming a sheet having a plurality of parallel continuous main ribs extending in a first direction on one side thereof and a plurality of parallel continuous tie ribs on the other side thereof extending in a second direction other than said first direction; and drawing said sheet in at least one direction to separate the main ribs into continuously and uniformly oriented main filaments having a substantially uniform cross section and to separate the tie ribs into con-tinuous tie filaments interconnecting the main filaments thereby forming a ,~
network structure. The tie ribs are formed at any desired angle to the main ribs. The main ribs preferably have a cross-sectional area which is at least 1.5 times as great as the cross-sectional area of the tie ribs, and the main ribs have a height which is at least three times as great as the thickness of the webs between the main ribs. By forming the main ribs and tie ribs with a cross-sectional area ratio of at least 1.5:1 and a main rib height to web thickness ratio of at least 3:1, it is possible, among other things, to spon-taneously open or fibrillate the ribbed sheet into a network by drawing, and ~ ;
to orient the main ribs continuously and uni~ormly, thereby making the main ribs very strong. It is this feature which provides a network structure hav-ing high tensile strength in the direction parallel to the main ribs. Addi-tionally, by having continuous main ribs which are uniformly oriented, the tear strength in the direction across the main ribs is greatly enhanced.
After the main and tie ribs are formed in the plastic sheet the sheet is drawn in a direction to effect orientation of the main ribs continu-ously and uniformly, and may be drawn in two different, preferably perpendi-cular, directions to orient both the main and the tie ribs. For example, when ~ _ 3 _ .'~' ~ 74 the main ribs are formed in the machine direction and the tie ribs are formed in the cross-machine direction a network structure may be formed with only .
one draw, in this instance in the machine direction. Alternatively, a more open network structure can be formed by sequential or simul~aneous drawing in both the machine and - 3a -,~ .

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", cross-machine directions. In sequential drawing of a sheet hav-ing main ribs in the machine direction, the first draw is cus-tomarily in the cross-machine direction~ Upon drawing, the thinnest areas in the sheet namely the area~; where the webs be-tween the main ribs cross the webs between the tie ribs, become oriented and normally open up spontaneouslyy leaving a uniform pattern of holes or voids in the sheet. Uncler some conditions and levels of draw the web openings may not occur during the initial draw but may occur only during the subsequent perpendicular draw.
In any event, the web openings occur spontaneously and thus there is no need for mechanical fibrillation. This spontaneous fibril~
lation or opening of the webs converts or forms the tie ribs into tie filaments and the main ribs into main filaments~ Hereinafter, the term tie ribs shall be used to re~er to the tie ribs embossed on the sheet which are ordin~rily interconnected by webs. A~ter the webs split or open up, the tie ribs are separated and will be referred to as tie filaments. Likewise, the main ribs are re-ferred to as main ribs while interconnected by webs, but after the webs split or open, the main ribs are separated and will be referred to as main filaments. These main filaments are oontin-uous if in the machine direction, or if at an angle to the machine direction, are continuous from one edge of the sheet to the other~
It has been found that highly desirable strength char-acteristics are obtainable in a network structure having main filaments in one direction crossed by tie filaments in another direction wherein the main filaments are dominant in si~e so t~at all, or substantially all, of the orientation at the cross-over ; points of the main and tie filaments is applicable to the main filaments. The tie filaments are normally smaller and are usu ally oxiented to provide sufficient structural integrity for the network structure, tending to keep it flat and prevent folding, thus maintaining the main filaments in parallel and uniformly spaced relationO The single layer plastic network structures thus formed are dimensionally stable, self-supportiny, easy to .. . ... . ..

:, 9L ~ , handle, and have high tensile strength in the direction o the main filaments and high tear resistance in the other direction.
Such nets are particularly useful for reinforcing paper products and nonwoven fabrics based on staple fibers and for covering absorbent pads.
Additionally, the network struotures so formed may be made into multi-layer fabrics by bonding together two or more layers of network struc~ures having the same or di~ferent config-urations so that the main filaments cross in various directions to provide a multi-layered product having certain desired strength characteristics. For example, orthogonal conskructions can be made wherein the main filaments of one layer cross at 90 to the main ~ilaments of another layer to simulate the appearance and physical properties of woven fabrics and to provide high ~trength and tear resistance in two directions. Diagonal constructions, wherein the main filaments of khe two layers cross preferably at about 90 to each other with the main filaments of both layers being at an angle to the machine direction of the fabric, possess stretch and recovery properties in the machine direction similar to those of knitted fabrics~ Fabrics made ~rom~three or more layers of networks each having the main filaments in different directions have excellent dimensional stability, high str~ngth and tear resistance in all directions and high burst strength.
For example, triaxial constructions, wherein a diagonal constxuc-tion is utilized having interposed between the two layers a net work having main filaments formed in the machine direction, pro-vide hish bursting strength with minimum weightO Isometric con-structions, wherein the main filaments of at least four layers are positioned at about 45 angles to each other, provide strength in all directions with dimensional stability heretofore unattain-able in woven, knit or other nonwoven fabric structures with equivalent unit weight.
Additionall~t the subject network structures which have main filaments in the machine dire~tion can be made into . . ,, ~ ~
.. , , ,.. , ,: , .. . . :"

~Q'~3~i~4 monofilaments, tapes or yarns by separating the network structl~re into strips which may be subsequently fi~rillated and twisted or bulked to entangle the main filaments of the strips. If desired, the strips may also be crimped or false ~wisted.
Hence, in one aspect the invention provides a tape comprising two or more main filaments uniaxially oriented along their longitudinal axes and having a plurality of continuous transverse tie filaments interconnecting said main filaments with portions of tie filam nts protruding from the edges o said tape.
In another aspect the invention provides a method of making a tape which comprises (1) forming a sheet having a plurality of parallel continu-ous main ribs extending in a first direction substantially parallel to the longitudinal axis of the sheet on one side thereof and a plurality of parallel continuous tie ribs on the other side thereof extending in a second direction different from the first direction, drawing the sheet in at least one direc-tion to separate the main ribs into continuously and uniformly oriented main ;
filaments having a substantially uniform cross-section and to separate the tie ribs into continuous tie filaments interconnecting the main filaments thereby forming a network structure; and (2~ breaking the tie filaments inter-connecting main filaments of the network structure to form a plurality of tapes composed of main filaments, each having portions of tie filaments pro-truding therefrom.
Other advantages of the present invention will be apparent from the following detailed description of the invention when considered in con-junction with the following detailed drawings, which drawings form a part of the specification. It is to be noted that the drawings illustrate only typi-cal embodiments of the invention and are therefore not to be considered limit-ing of its scope, for the invention may admit to other e~ually effective embodiments. Figures 1 to 20 illustrate the preparation of network structure in accordance with the parent application. Figures 21 to 26 particularly illustrate the invention claimed in this application.

Figure 1 is a perspective schematic view illustrating apparatus .,~.~ .,;, lO'~ q~ "
for embossing ribs on both sides of an advancing sheet o plastic material Figure 2 is an enlarged perspective view of a portion of the em-bossed sheet shown in Figure 1.
Figure 3 is an enlarged perspective view of a portion of an em-bossed sheet having main ribs which are spaced relatively far apart and have relatively deep grooves therebetween and tie ribs which are spaced close to-gether and have relatively shallow grooves therebetween. ;~
Figure 4 is an enlarged perspective view of a portion of another embossed sheet having ma m ribs which are spaced relatively close together and have shallow grooves therebetween and tie ribs which are spaced relatively far apart and have relatively deep grooves therebetween.
Figure 5 is an enlarged perspective view of a portion of the top of a network structure obtained after drawing and orienting the embossed sheet shown in Figure 2 in two directions.
Figure 6 is an enlarged perspective view of the bottom of the net-work structure shown in Figure 5.
Figure 7 is an enlarged perspective view of the tie ilament side of an embossed sheet illustrating the product made by a method wherein sub-stantially all of the polymer on the back side of the sheet directly opposite the main rib goes into forming the main rib as opposed to being in the tie rib so that the tie ribs are discontinuous.
Figure 8 is a schematic perspective view illustrating apparatus for embossing continuous longitudinal main ribs on one side of a sheet and discontinuous tie ribs on the other side of the sheet.
Figure 9 shows one side of a portion o the network structure made after stretching in two directions the sheet shown in either Figures 7 or 8.
Figure 10 shows the other side of a portion of the network struc-ture of Figure 9.
Figure 11 is a plan view illustrating a portion of a network struc-tute having main filaments in the machine direction and tie filaments in the cross-machine direction.

.. . . . . . . . .

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Figure 12 is a plan view illustrating a portion of a network structure having main filaments in the cross-machine direction and tie fila-ments in the machine direction.
Figure 13 is a plan view illustrating a portion of a network structure having main filaments formed at an angle to the machine direction with tie filaments formed in the machine direction.
Figure 14 is a plan view illustrating a portion of a network structure having main filaments formed at an angle to the machine direction with tie filaments formed perpendicular to the main filaments.
Figure 15 is a perspective schematic view illustrating apparatus for making multi-layer fabric structures.
Figure 16 is a perspecitve schematic view illustrating other appara-tus for making multi-layer fabric structures.
Figure 17 is a plan view illustrating a portion of a three-layer triaxial fabric with one layer having main filaments formed in the cross-machine direction and the other two layers having their main filaments formed at equal opposite angles to the cross-machine direction main filaments.
Figure 18 is a plan view illustrating a portion of two-layer diago-nal fabric formed by bonding together two network structures having their main filaments formed at equal opposite angles to the machine direction and desirably, but not necessarily, perpendicular to each other~
Figure 19 is a plan view illustrating a portion of a four-layer isometric fabric made by bonding together in any desired order the two layers shown in Figurç 15 and the two layers shown in Figure 18.
Figure 20 is a perspective view illustrating apparatus for rein-forcing paper, foil~ non-woven fabrics or films by utilizing a central net-work structure.
Figure 21 is a view illustrating apparatus fo~ making network structures into yarns.
Figure 22 is an enlarged view of the leasing rods of Figure 21 used to separate or tear the network structure into strips.

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Figure 23 is an enlarged plan view of a portion of a strip before fibrillation.
Figure 24 is an enlarged plan view of the strip of Figure 23 af~er fibrillation illustrating the broken tie filaments.
Figure 25 is a view of a portion of an air jet interlaced multi- `
filament yarn having protruding side fibers.
' Figure 26 is a view of a portion of a bulked entangled multi-filament yarn.
Referring now to Figures 1 and 2, there is shown an embossing roll ;
21 having a plurality of grooves 22 formed therein i` -~

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3~J4 for forming a plurality of transverse main ribs 23 on an advan-cing sheet of thermoplastic polymer material 24 with the ribs 23 being interconnected by webs 25 of reduced thickness. Another embossing roll 26 having a plurality of annular or helical grooves 27 formed therein is positioned opposite roll 21 for forming a plurality of longitudinal tie ribs 28 on the other side of the sheet 24 with the tie ribs being interconnected by webs 30 of reduced thickness. The embossing rolls 21 and 26 rotate in the direction shown by the arrowsO There are a variety of different ways to effect the double ernbossing des~ribed herein~
One method is to feed a molten plastic sheet, such as 24, coming directly from an extrusion die into the nip of two courlter-rotating er~ossing rolls, such as 21 and 26, which are urged toward each other by facilities which are not shownO The desired separation between.the rolls and ultimately the thickness of the ernbossed sheet is readily controlled by regulating thickness of the ex-truded sheet entering the embossing rolls and the pressure between the two er~ossing rollsO The roll temperatures typically are in-ternally controlled and serve to quench and solidify the molten plastic forming the desired embossed patterns on each sideO
Alternatively, a previously cast flat sheet.or film may be re-heated to its softening temperature and then advanced ~ .
through a.pair of ernbossing rolls, such as 21 and 26. Another method may utilize a polymer which is in powder ~orm and which is introduced into the nip between two heated rolls, not shown, to permit the heated rolls to melt and soften the polymer and form it into a.sheet which is then advanced between two emboss-ing rolls such as 21 and 26. An additional method is to pass a previously cast flat sheet or film between two ernbossing rolls pressed together under a sufficiently high pressure that the er~ossed patterns are pressed into the sheet without having to melt or soften the sheetO It is evident that many ernbossing techniques may be utilized to carry out the principles of this invention. Alternatively, instead of using embossing rolls to 9 -- .

, . . ..

'73~
form the desired ribbed configuration on both sides of a sheet, such a configuration may also be accomplished by using a pair of relatively movable concentric dies such as shown and described in the aforementioned U S 3,488,415.
It has been found that the most advantageous range of . the ratio of the cross-sectional area of the main ribs, to the cross-sectional area of the tie ribs is between 1.5~1 to 100:1 ;
with the ratio of the height of the main ribs to the thickness of the webs between the main ribs ~eing at least 3~1 or greater.
10 This relationship permits subsequent drawing and orientation .
steps to form.the.ribbed sheet into a.network.structure having .:
uniformly spaced main filaments oriented uniformly and continur ously along their lengths and being quite uni~orm in cross-sectionO With continuous.tie ribs and cross-sectional area ratios less than lo 5, uniform continuous orientation of the main filaments is not obtained, except with special polymers, or speGial embossing conditions or methods as described hereinater, because of a tendency for there to be thick areas where the main . filaments and tie filaments cross and for those areas to remain either:unoriented or only slightly oriented on drawingO As shown in FIGo 2, the cross-sectional area Al of the main ribs an~ the cross-sectional area A2 of the tie ribs each includes the web area adjacent to the base of each respective rib. Also iden- .
tified in FIG~ 2 is the height Tl of the main ribs and the thick~
ness T2 of the webs interconnecting the main ribs.
The cross-sectional shape of the ribs formed may vary.
They may be semi~circular, rectangular, triangular, truncated, or any other desired shape. Furthermore, the shapes of the main and tie ribs may be the same or different. Lik2wise, the shape and size of the grooves separating the main or tie ribs is not critical. The grooves may be narrow so that the ribs are close ' together, or wide so that the ribs are more.widely separated.
Furthermore, the tie ribs may be spaced farther apart than the main ribs or vice versa~ The size of the openings in t:he network ~.

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,, ' structure may be conkrolled to some degree by controlling the spacing of the main and tie ribsO
Referring to FIG. 3, there is shown a porti.on of an em-bossed sheet identified generally as 36 having a plurality o~ main ribs 37 ormed on one side of the sheet, and a plurality of tie ribs 38 formed on the other side of the sheet in a direction per-pendicular to the direction of the main rib~; 37O The main ribs 37 are spaced ~arther apart than tha tie ribs and have relatively wide webs 39 of reduced thickness therebetween. The tie ribs 38, however, have almost no web thereb~tween, but there is an area or line o~ reduced thickness at 40 between each pair of adjacent tie ribsO Note that the height 41 of the main rib 37, which is meas-ured.from the web 39 to the top of the main rib 37, is much greater than the height of the tie rib 38 which is measured from the bottom of 40 to the.top of tie rib 38~ However, referring now to FIGo 4 there is shown an embossed sheet generally desig-nated. as 43 having a plurality of closely spaced main ribs 44 formed in one direction on one side of the shaet~ and a plurality of spaced apart tie ribs 46 formed on the other side of the sheet in another directionO The web which is the line or area of re-.
duced thickness 4~ between the main ribs 44 is now very small, while.the web 48 between the tie ribs 46 is relatively larger.
Thus, it can be seen that the invention is relatively independent of the spacing between the ribs and the height of the ribs, Additionally~ the direction of'the main ribs is not . criticalO The main ribs may be formed in the machine direction ~- of the sheet, or transverse to the machine direction, i.eO, 90~ ;
thereto, or at any angle in between~ With the main ribs formed in either the machine direction or the transverse direction, orienting the main ribs along.their longitudinal axes is easily : accomplished by use of either a conventional linear differen-tial speed draw roll device or a conventional tenter. Li.kewiæe, if the embossed ribs are diagonal to the machine direction, ori-entation of the ribs and net formation may be achieved using the same type of equipment~ In oxienting main ribs which are formed at an angle to the machine direction along their longi-tudinal axes~ it is sometimes advantageous to utilize a long draw gap linear drawing unit so that upon drawing in the machine Airection the sheet is permitted to neck down and cause orienta~- .
tion of the main ribs principally along their longitudinal axes. . .
In drawing in such a manner~ it is usually desirable that the linear draw be preceded by a cross-machine direction orientation by passing the sheet through a tenterO
The direction of the tie ribs on the reverse side of the sheet should be a~ an angle to that of the main ribs, which in many cases is desirably 90, but can also be other angles.
Any angle between about 15 and 90 between the directions of the main ribs to the tie ribs is acceptableO
When the embossed sheet having a first pattern of con tinuous main ribs on one side and a second pattern of continuous tie ribs on the.other side is drawn, the thin areas.o~ the sheet, namely.the areas where webs 25 and;30 cross, spontaneously split~
forming openings~ After the second draw is completed, a network structure such as or similar to that shown in FIGS~ 5 and 6 is achievedO The main ribs 23 of the embossed sheet shown in FIGS.
1 and 2 have been separated into main filaments 53 which are oriented continuously and uniformly The tie ribs 28 have also been.separated and oriented into tie filaments 54 which inter-connect the main filaments 53 and keep them uniformly spaced apart. FIGo 6 shows the back side of the network shown in FIG
5 wherein it can be seen that the tie filaments 54 may extend.
continuously and without interruption across the main filaments Alternatively, the tie filaments 54 may be eliminated where they cross over the main filaments 53 by either controlled embossing to obtain a "cave-in" efect or by us.ing a discontin-uous tie rib embossing roll. Re~erring to FIGo 7, there is shown a portion of an embossed sheet having continuous main ribs 5 a and , r discontinuous tie ribs 5~ made under selected embossing condi- -tions. Note that on the tie rib side of the sheet there are cave-ins or discontinuities 60 in the tie ribs 59 where they cross the main ribs 58, thereby making the t:ie ribs 59 non-continuous~
In using grooved embossing rolls such as 21 and 26 shown in FIG 1, it is possible to control t:he distribution of polymer between the main rib and tie rib roJ.ls, among other things, by control of the melt temperature, the embossing roll temperatures, pressure between the rolls~ which roll the molten sheet contacts first, the time of contact of the emhossed sheet with one roll, and the thickness of the shee~ as it enters the nip between.the embossing rolls Shrinkage of the polymer as it cools may also be a factor contributing to the uni~ue results of thiS method~ Discontinuities in the tie rib embossing pattern may be obtained by using th~n sheets, relatively low melt tem-peratures and having the sheet contact the main rib embossing -roll before entering the nip ~etween the rollsO If the sheet is ~:
thin~ at the points where the. grooves 22 of the main rib emboss- -.
lng roll 21 cross the grooves! 27 of the tie rib embossing roll 26, there will be inadequate polymer. to fill both the relatively.
fine grooves 27 and.the relatlvely coarse grooves.22 because the ;~ available polymer will go into the larger grooves 22. This is because the polymer tends to flow in the path of least resistance, namely toward the larger grooves. Even with a thicker sheet with low pressure the same phenomenon will occur. At low emboss-ing temperatures, because of higher resistance of the polymer to flowj a greater tendency toward formation of a discontinuous tie rib pattern results. Accordingly, by such controls, coarse grooves 22 of embossing roll 21 will fill uniformly with polymer, but the fine grooves 27 of embossing roll 26 will not fill com-.
pletely, Thus, the embossed tie ribs are made discontinuous as shown in FIG 7, there being insufficient polymer flow to com-plete the kie ribs 59 in the areas 60 where they cross over the : . , . . . ~ . , . - . . . . " . .. - . . . . .

main ribs 5S. After orientation~ this makes a strong and inex-j pensive network structure, among other reason~ because it causes a higher proportion of the polymer to be present ln the main ribs than under other operating conditions~ Additionally, the discontinuous tie ribs 59 are further advantageous in that they permit the main ribs 58 to be completely and uniformly oriented, since there is essentially no cross-over of the main xibs 58 and the tie ribs 59.
Discontinuities in the tie rib embossing pattern can also be obtained in an alternate way, such as by using a contin-- uous main rib embossing roll 61 and a discontinuous tie xib em-bossing rall 63 as shown~in FIGr 8. The main rib embossing roll 61 has a plurality of parallel annular grooves 62 formed therein for forming main ribs 67 in a sheet 700 The tie rib embossing roll 63 has a pluraliky of discontinuous grooves or recesses 64 formed therein parallel to the longitudinal axis of the roll for forming discontinuous tie ribs 68. In each row of grooves 64 across the embossing roll 63, each groove or recess 64 is blocked , from the adjoining recess by a blocking section 66 of the roll 63, Desirably, the width of the blocking section 66 is equal to or slightly less than the width of the groove 62 of the main rib embossing roll 610 It is to be noted that the tie ribs are not continuous across the embossed sheet~ but rather are continuous only from one main rib 67 to the adjoining main rib having a discontinuity at area 69 Because of the configuration of the - roll 63, little or no polymer is left cn the tie rib side of the sheet directly opposite the main rib 670 By embossing a sheet 70 in .this manner, and subsequently drawing in two directions, the main ribs can be highly oriented continuously and uniformly.
Using embossing roll 63 in this manner assures that little or no poly~er is formed across the main ribs 67. This allows for high orientation of the main ribs and optimi~es the polymer distribution. In view of the fact that there is little or no mass of polymer crossing over the main ribs when using either ~L~q~

the controlled embossing method described above to obtain the cave-in effect shown in FIG~ 7, or the discontinuous tie rib forming method as described above and shown in FIG. 8, the ratlo of cross-sectional areas of the main ribs to the tie ribs is not significant. Accordingly, a ratio of 1:1 will work satisfactorily.
However, to obtain low unit weights or finer network patterns, e~g., more square yards of net per ounce of polymex, it may be desirable to use a pattern having more and/or smaller tie ribs than main ribs. An advantage of the controlled embossing method -using two embossing rolls having continuous grooves such as shown in FIG~ 1, over the discontinuous tie rib forming method using a special roll such as 63 having discontin~ous grooves 64 as shown in FIGo 8 j is that there is no need in the former to precisely and accurately register and align the embossing rolls as is re- `
quired in using the FIG. 8 apparatus~
FIGS~ 9 and 10 show the top and bottom of a portion of a network structure formed after drawing the emboysed sheet shown . ~
in either! FIGo 7 or 8 in both the cross-machine and the machine directionsO Note that the main filaments 71 flatten out somewhat ~s`
after drawing, and that the tie filaments 72 uniformly space the main filaments 71 apart~ The tie ilaments 72 have their ends integrally joined to the main filaments 71~ and as shown in ~IGo 9 do not extend across the main filaments 71.
In drawing the embossed sheetJ the pre~erred amount o draw would depend on such factors as the polymer employed, the embossing pattern employed, and the degree of separation of the main filaments desired in the final network structure~ Custom-arily, the firsk drawing or orientation step involves drawing the embossed sheet in a direction generally transverse to the direction of the main ribs to cause orientation of the thinner areas of plastic material between the main ribsO Referring, for example, to the embossed sheet shown in FIG o 2, since the ~main ribs 23 are formed in the cross-machine direction, the first draw would normally be, but is not necessarily, in the .

machine direction ~his draw could be effected by using conven-tional linear differential speed draw rolls. This orientation, which is usually 1~5X or greater, generally results in incipient or actual voids or openings being ormed between the main ribs with the formation of small tie filaments spanning the openings between the main, as yet unoriented, ribs or filaments. Drawing to an extent greater than five times its ori.ginal length ~5X) at tXis stage is usually undesirable since cross-orientation of the . polymer at the cross over points of the main ribs and tie ribs may occur~ This may interfere with the desired uniform orienta-tion of the main filaments in the subsequent drawing steps.
As an alternative; it may be desirable to carry out an initial draw such as~ for example, up to 2X, in the direction of the main ribs prior to the.drawlng.step transverse to this direc-tion. This initially orients and strengthens the main ribs and tends to prevent any possible distortion or development of cross orientation of the polymer in the.cross-over areas during the.
transverse orientationO.
The second orientation step is normally carried out in a direction generally parallel to the main ribs Thus, refer-ring again to the embossed sheet shown in FIGo 2, the second.
orientation would be in the cross-machine direction. This trans- -verse drawing step, could be carried out on a conventional tenter The transverse draw causes.orientation of the main ribs along their.longitudinal axes and separation of the smallj connecting tie filamentsO The amount of draw will determine the strength . and size of the resulting main filaments. It can vary from as low as 1.5X to lOX or greater.. The maximum draw will depend on the orientation characteristics of the polymer employed, among.
other thingsO Temperatures for drawing will vary depending upon the polymer employed but generally will be sllghtly lower than those employed for orienting flat sheets of the same polymer.
While reference has been made to first and second sequential drawing steps 7 both draws may be carried out simulataneously, if .
desiredO
The network structures produced by the foregoing methods contain as desired longitudinal, transversa or oblique oriented main filaments interconnected by normally lower denier, oriented tie filaments, with tne main filaments having orientation contin-uously over ~heir lengths~ Examples of the different configur~-tions of network structures that can be made are shown in FIGS.
11 7 12~ 13 and 14. In FIGo 11, a network structure is shown hav- -ing main filaments 73 extending in the machine directiont the direction of the arrow, and tie filaments 74 being formed in the cross-machine direction 90 to the machine direction n In FIG. .
12, the main filaments 75 are formed t~ansverse to the machine : ~
direction, indicated.by the arrow, and the tie filaments 76 are :
formed par~l].el to the machine direckionO In FIGo 13/ the main filaments 77 are formed at an angle to the machine direction, ...
shown.by the arrow~ and the tie filaments 78 are fQrmed parallel to the machine direction Alternatively, the tie ilaments 78 may be formed in the cross-machine direction or so they axe per- :~
20 pendicular to the main filaments such as shown in FIGo 14. Nhen :
the main filaments ~7 are formed at an angle of 75 or less to the machine direction, in order to orient such filaments, it is sometimes desirable to draw in the machine direction while per-mitting necking down o~ the network structure~ Ordinarily, in making this configuration, the cross-machine draw in a tenter, if desired~ comes first, followed by the machine direction draw allowing neck-down It is apparent that many other configura-tions of network.structures may be made in accordance with the principles of this invention~ having the main filaments at any desired angle wherein maximum tensile strength is desired and the tie filaments formed at an angle relative to the main filaments~
The network structures descxibed herein have good.

tensile strength in the direction of the main filaments which ~ O~J3'~ r --reflects the degree and uniformity of orientation along the length of these filaments~ Thls strength is lower in the opposite di-rection because of the smaller size of the interconnecting tie filamentsO The tear s~rength is high in the direction transverse to the main filaments because of the strength of the main fil~ :`
mentsa. It is to be noted that the networX structures such as shown in FIGSo 5~ 6, 9 and 10 have tie filaments which either are continuous and cross over the main filaments or are discontinuous and integrally join the main filaments~ without in either case there.being notches at the junctures as is charactexistic of many network,structures prepared by previous.methodsO Such notches at the junctions.or cross-overs enable a network.to tear easily in either direction, The subject network structures, while useful as single layer netwo,rk structures, may also be employed to prepare very useful multi-layer fabric structuresO Referring to FIGo 151 there is shown one ne~work structure, generally designated as 81, having main filam~nts 82 formed in the machine direction and tie filaments~ not shown~ formed in the cross-machine direction being laminated or bonded to a second network structure, gener-ally designated as 83, having main filaments 84 formed in the cross machine direction~ Tie filaments are not shown.in any of the network structures shown in FIGSo 15-20 to facilitate il- ~, lustration and description of the fabric structures. Neverthe~
less, the tie filaments are present in each network and may be assumed to be as shown in FIGS. 11-14 or as previously described.
One way of bonding the two network structures 81 and 83 together ~ , is to pass them through rolls 79 and 80 into a preheater 84 to heat the networks under tension without adversely affecting the ,~
orlentation thereof and then advance them into the nip o~ two heated calender rolls 86 and 87 to bond the plastic materials to each other. Rolls 79 and 80 rotate very slightly slower than rolls 86 and 87 to maintain the networks 81 and 8~ under tension during heating to avoid.loss of orientat:ion. Likewise, ! - 18 -", ~ 3~
.
it may be desirable to use a tenter, a series of closely spaced ~, rolls or other means to prevent lateral shrinkage of the net-works in this areaD This bonding or lamination process orms a ~ ' two-layer fabric which has the appearance and physica]. proper- ' ties o a woven fabric having high strength and go~d tear re- ~' sistance in both the machine and cross-machine directions. Such a fabric has substantially no stretch in the machine and cross-machine directions, but does stretch on the bias.
-Three or more layer fahrics can also be prapared with 1~ the main filaments.of each.being formed in ~ifferent diractions :
~' to pro~ide.fabrics having excellent dimensional stability, high ,, str ngth in all directions and.hi~h.burst strengthc As shown in FIG. 16, a first layer or network structure, generally designated.
as 88~ has main filaments 89 formed at an angle to the machlne ~irection which is indicated by the arrowD A second,central layer or network structure 91 has main filaments 92 formed in the : machine diraction~ A third layer or network structure 93 has.main filaments 9~ formed at an acute an~le.to the machine direction ~pposite that of the angle,of layer 88D The three--layers pass, ~:
thxough the.nip.of rolls 85 and,90,.into a preheater 95 and ~, through the nip of two heated calendar rolls 96 and 97 which, bonds the three layers together at their cross-over.points. The bonded,fabric may then pass through an annaaling unit 98 and is , taken up on take-up spool 19D If desi~ed,.a conventional tentex or other means could be used to maintain tension in the cross, machine.direction during heati'ng and bondin~O Such three or m~re layer.fabrics provide strength in all dir~ctions and dimen- -sional stability unobtainable in woven~ knitted or other non-woven fabric structures with aquivalent weight. Such fabrics.
provide good.stretchability in the cxoss-machine direction.
Referring to FIG. 17, there is shown a similax three : layer fabric, except that it has a central layer havirlg its main filaments 100 in tho cross-machine direction. Such a fabric has good stretchability in the machine direction. .
.:

~ 3~
`' `

If the central network layer 91 shown in FIG 16 i9 eliminated, a two-layer fabric such as shown in FIGo 18 i9 pro-vided havlng the main filaments 89 on one layer 88 extending at an angle~ such as 45 to the machine direction, and tha second :~
layer 93 having main filamen~s 94 extending oppositely at an equal angle to the machine direction. If the main filaments 89 and 94 are formed 45 to the machine direction then main filaments 94 will be perpendicular to the main filamen~s 89 Such a netwoxk structure with the central layer 91 eliminated has stretch and re-covery properties in ~he machine and cross-machine directi.ons sim-ilar to those of a knitted fabricO That is, the fabric wi.ll stretch both in the machine and cross-machine direction~
If desired, the three-layer structure of FIGo 16 could be made into a four-layer isometri~ fabric structure by bonding.ox laminating as a top layer, a network structure such as 83 shown in FIG~ 15 which has main filaments 84 extending in the cross~
machine direction Such a four.layer isometric fabric is shown in FIG~ l9 o For the most uniform properties in such a fabric, it is preferred that the main filaments 89 and 94 be formed at 45 :~
angles to the machine directionO This fabric is dimensionally stable and has substantially no stretch in any direction. -:.
Referring to FIGD 20p a single layer plastic network structure, generally designated at 101, having its main filaments 102 formed in the cross--machine direction is bonded between two layers 103 and 104 of paper~ film, foil or nonwo~en web such as carded, garnetted or air laid fiber webs, or any combinations thereof by first.passing the network structure 101 and the layer 104 through an adhesive applicator 1060 Then layer 103 is bonded to the other two layers by curing the adhesive as by passing them through a heated zone such as calender rolls 107 and 108, after which the reinforced paper, nonwoven fiber webs, film or foil structure is taken up on take-up spool lO9o It can be appreciated that many different multi-layer fabrics can be prepared in accordance with the principles of `:

this invention by taking one network structure having main fila-ments in one direction and bonding -thereto one or more other net~orks havlng main filaments in different directions. Then the layers may be bonded toyether into a fabric in many ways in-cluding applying or spraying an adhesive between the layers and passing them through an oven and calender rolls to bond the layers together, or by passing the layers only through a pair o~ heated calender rolls to heat bond them together, or by using ultrasonic bonding, or spot bonding or any other known conventional bonding ;~
techni~ue.
Among the many uses of the subject network structures, either as single or multi-layer fabrics, are sanitary napkins, diapers, continence pads, tampons, surgical dressings, surgical sponges, burn dressings, and reinforcing material for paper and paper products, films and other nonwovens and woven fabrics, For example, a network may be used to reinforce masking tape or wallpaper, thereby contributing increased tensile strength and tear resistance propertiesO In the case of paper and staple fiber nonwovens, the network structures of the type shown in FIG.
20 having main filaments in the cross-machine direction are par-ticularly advantageous. This is because in preparing or making paper or staple fiber nonwovens the fibers therein customarily become oriented in the machine direction and increased strength in the cross-machine direction a~ well as increased tear re-sistance in the machine direction is needed. Additionally, the thermoplastic networks can be used as an adhesive in bonaing other materials together under heat and pressure. The networks are also usable for fusible inner-liners in shirts and the like, and can be used in place of cheesecloth for the manufacture and processing of cheeses.
The multi-layer ~abrics described above are useful for applications similar to those described for the single layer network structures, and particularly useful for those applica-tions in which balanced and high strength and tear resistant ~ ~0~3~

propertles are desiredO Multi-layer products are particularly useful, for example, for the preparation of high impact resis-tant plastic bags, primary and secondary tufted carpet backings, plastic coated fabrics, and for other indust:rial fabric appli-cations. Many other uses are evident for these networks and fabrics which have such properties as not being absorbent, not sticking to wounds or other materials, readily passing liquids therethrough because of the openings in the network structures, and relatively light weight and high strength~
While emph;~sis has been placed on the high tensile strength and high tear resistance of the subject networks, it is of course appaxent that network structures may be made in accor-dance with the principles of this invention without necessarily drawing the main filaments to a high degree so that network s~ruc-tures may have less strength and tear resistance for applications where those characteristics are not important. In certain appli-cations, texture and smoothness may be more significant than strength~ An example of such an application is the use of net-work structures as a covering in a sanitary napkin wherein it is highly desirable that the network have a so~t and smooth texture in order to prevent irritation and also have high permeability to permit fluids to pass and be absorbed by the absorbent inner-material of the napkin.
The subject network structures are very smoo~h since they do not have any reinforced bosses or thick masses at the cross-over points of the main filaments and tie filaments. Such smoothness gives the network a soft hand or feel to make it de sirable for many uses wherein irritation of the user or wearer may be an important factor. Additionally, the network structures can be drawn in such a manner as to provide relatively flat structures, that is, a structure having a relatively uniform thickness as measured in the plane perpendicular to the plane of the network. This may be significant for its use as an ad-hesive where it may be desired to bond two materials together ~ 3~
:

to provide a laminated or bonded fabric having a uniform thickness.
It is also possible to make novel monofilaments or ~arns from certain of the network structures described above Referring to FIGo 21~ there is shown a network structure generally desig-nated as 110 having main filaments 111 extending in the longitu~
dinal or machine direction and tie filaments 112 extending in the cross-machine direction, 90 to the main filaments 111 Any net-work structure having its main filaments formed in the machine direction and its tie filaments formed at an angle to the machine direction may be utilized in making monofilaments or yarns. The network 110 is advanced by nip rolls 115 through a plurality of lease rods generally designated as 114 to split the network struc- -tures into individual filaments or relatively narrow tapes or strips llOa, llOb, llOc~ llOd, etc~ consisting of a number of main filaments interconnected by tie filamentsO The network 110 can easily be split into monofilaments or tapes of any desired widthD
This is accomplished by initially cutting or tearing the leading end of the network 110 into strips of the desired width and feed~ ;
ing adjacent strips differently through the lease rods 114 so that upon advancement the lease rods tear or split the network as desiredO For example~ as shown in FIGS ~ 21 and 22, strip llOa is fed over lease rod 114a~ under lease rod 114b~ and over lease rod 114co The ad~acent strip llOb is fed or passes under lease rod 114a~ over lease rod 114b~ and under lease rod 114co Thus, as strips llOa and llOb advance~ the lease rods break the tie fila-ments interconnecting the adjacent strips~ Because of the relative sizes of the main filaments to the tie filaments, the tie filaments break easlly upon passing through the lease rods as shown, without need for any cutting or slitting elements. If desired~ the strips can then be fibrillated to completely or partially sever the tie filaments such as by passing the strip over a beater bar 116 sim-ilar to that described in UOSO Patent 3~495~752O FIGo 23 shows a portion of strip llOa as it looks prior to fibrillation. Com-plete fibrillation of the network breaks substantially all of the - 23 ~

tie filaments, leaving the main filaments intact thereby forming each strip into a yarn consisting of a plurality of individual main filaments which are not interconnected and have protruding portions of tie filaments extending perpendicularly therefrom, or at some other angle if the tie filaments are initially formed at some other angle. FIGo 24 shows a portion of strip llOa after fibrillation with the tie filaments broken. The main filaments are pulled through another set of nip rolls 117 and then may pass over a yarn guide 118 for further processingO The fibrillation by use of a beater bar 116~ or by any other means, converts the strips:llOa~ llOb, etcO either partially or completely into a series of multi-filaments each with.protruding normally smaller side filaments attached. If desired, bulking may be effected by ~ :.
known cri.mping or false twist methodsO Also, bulking may be e~fected.by heat relaxation if the main filaments have been pre-: pared from bicomponent polymer sheetsO For example, referring - again to FIGo 21, the fibrillated strips llOa may be passed from ; the yarn guide 118 into a heater ll9 to provide bulkingO If de~
sired~ a false twist-may be put into.the yarns by use of false ~ .
twisting head 120 after which the yarns are wo-md on a take-up spool.l21, Alternativelyt i zero twist yarns are desired~ the unfibrillated or fibrillated strip llOb may be wound directly onto a take-up apool 122 as shown in FIGo 210 Alternatively, if desired, a fibrillated strip llOc may be passed through an air-jet interlacer 123 and then wound on a take-up spool 124 If ::
further desired, the fibrillated strip llOa may pass through a conventional down twister 126 and then be wound on a take-up spoolO Conventional air-jet entangling may be employed to convert the yarns to a.form which can be wound and unwound from a package 30 readilyO FIGo 25 illustrates an air-jet entangled or interlaced .~ yarn l280 FIG. 26 illustrates a bulked yaxn 129 which is subse-quently air-jet entangled. Twister take-up packages may also be used.to form compact, readily handleable yarnsO Of couxse, many combinations of these steps such as fibrillation followed by heat relaxation and twisting may be employed The unfibrillated strips or tape networks are also use- ~ -ful in untwisted form in weaving or knitting operations where max-imum coverage in a light weight but strong fabric is desired.
Such weaving or knitting operations can be ca:rried out in line with the strip or tape forming operation.
The yarn prepared in accordance with these techni~ues are unique in that the main filaments have protruding tie fila~
ments which contribute bulk~ cover and a desirable appearance.
These yarns are useful for knitting~ weaving, tufting and contin-uous filament nonwoven applications in general. The presence of the side tie filament portions provide improved adhesion of plas-tic, rubber or other coatings when fabrics prepared ~rom these yarns are subsequently coatedO Furthexmore, because of the pro-truding side tie filament portions, the yarns and the fabrics have good abrasion and pilling resistance.
The strips 110 or individual filaments of this invention ~ :
containing spaced side fibrils may also be cut into staple length fibers. Such staple fibe~rs are of particular advantage for con-version into spun yarns, prepared for example by conventional cot-ton, wool or worsted spinning processes, 4r into nonwoven fabrics, prepared for example by conventional cording or air-laying methods~
Because of the protruding tie filaments on the staple fibers or on the yarns either made from staple fibers or continuous filaments as described above the nonwoven fabrics~ or woven, knit or tufted fabrics prepared from such fibers or yarns are pleasing in appear .ance~ h ve high thermal insulating value, high moisture absorptionp and provide good adhesion to othex materials used to bind or coat the fabrics~
In the preceding discussion of the embossing methods, customarily one embossing roll drives the other embossing roll through the melt or sheet with each roll rotating at t:he same speed~ However, when using polymers that are relatively difficult to split spontaneously, such as for example, polyesters, polyamides ~ 3~

and vinyl polymers, differential speed embossing rolls can be used to effect incipient ~plit-ting of these polymers at the em bossing stageO By differential speed, it is meant that the sur-face speed of the main rib embossing roll is different, from a slight difference up to about a 50~ difference, either faster or slower, than the surface speed of the tie rib embossing roll. By using differential speed, of the main and tie rib embossing rolls it is possible to bring about splitting of the thin web areas of the embossed sheet at the embossing stage~ This facilitates sub-sequent splitting or opening up into a uni~orm network structureupon drawing.
", The materials that the above network structures, fab-rics and yarns can be formed from include any thermoplastic fiber-forming polymers. Among these are polyethylene, polypropylene homopolymer, random copolymers of propylene containing up to 10 percent of another olefin, block copolymers of propylene contain- ;
ing up to 25 percent of another olefin, nylon-6, nylon-66, poly-ethylene terephthalate, other-high molecular weight thermoplastic ~polyesters, and vinyl polymers such as polyvinyl chloride. Con-jugate or bicomponent plastic sheets in which two or more differ-ent polymexs are extruded together to form sheets containing layers of separate polymers are also possibleO For example, two layers or network structures, each having a portion thereof made of a relatively high melting point polymer with the remaining portion being made of a lower melting point polymer, may be bonded together by placing the lower melting point polymers of each layer together and heating. Alternatively, a network struc-ture made of a higher melting point polymer may be bonded to a network structure made of a lower melting point polymerO Fur-thermore, a network structure having a portion thereof made ofa relatively high melting point polymer with the remaining por-tion being made of a lower melting point polymer, may be honded to another network structure being made only of a higher melt~
ing point polymer~ Particularly desirable are conjugate plastic ~ 3~7~ ~

in which a higher melting point component, such as nylon or poly-ester, is used to form the main portion of the main fibers. This permits lamination without adhesive of two layers by bonding with heat and pressure or self bulking by heating -the network struc-tures or yarns prepared from such structures, Alloys or mixtures of polymers may also be employed.
The principles of this invention are exemplified by the following examples, which are given to illustrate the inven-tion, and are not to be considered limiting in any way.
E ~
Propylene homopolymer with a melt flow index of 7~5 and a randon copolymer of propylene with ethylene containing 2 D 5~
ethylene with the same melt index were coextruded through a slit die at 465F~ to form a conjugate sheet in which the homopolymer comprised 75% of the thickness of the sheet. The slit die was 12 inches long with an opening 15 mils wide. The molten sheet was passed into the nip of two chrome-plated steel embossing rolls, one 4 inches in diameter, the other 3 inches in diameter, each being 13 inches longO The 4 inch roll had an embossed pattern consisting of a plurality of grooves extending circumferentially around the roll with a spacing of 48 grooves per inchu This roll was internally cooled to maintain its temperature at 70Co The other 3 inch roll had a pattern of straight grooves extending parallel to its longitudinal axis having a uniform spacing of 111 grooves per inch, This 3 inch roll was not cooled and assumed a temperature of about 60Co The molten sheet was passed between the two rolls at a rate of 15 feet per minute and went around the 48 grooves per inch roll wi~h 180 contactO The homopolymer side of the conjugate sheet was in contact with the 48 grooves pex inch roll. The embossed sheet contained 48 main ribs per inch in the longitudinal direction on one side with the ribs being sep-arated by grooves 10 mils wideO On the other side of the sh~et the continuous tie ribs were formed with 111 tie ribs per inch with each paix of tie ribs being separated by grooves 5 mils wide.

~ 3~

The maximum thickness of the sheets was 15 mil. The ratio of the cross-sections of the main ribs to the tie ribs was about 2:1 and the ratio of the height of the main ribs to the thickness of the webs between the main ribs was 8:1. The embossed sheet was fed into a tenter heated with circulatiny air to' 110C. at a speed of 20 feet per minute and it was stretched to tw:ice its width. In this operationJ it opened in-to a uniforrn network structure, the grooves between the main ribs becoming openin~s or voids crossed ~ -by oriented tie filaments with the main ribs now beinq separated by about 30 milsO The sheet was then drawn in ~he linear direc-tion by passing it in frictional contact with a series of :Ll steel rolls heated to 120~Co and moving at progressively increasiny speeds. The sheet was fed in at 15 feet per minute and exited at 105 feet per minute and accordingly was drawn seven times its length in the machine direction~ The resulting network structure had a weight of 0,32 ounce per square yard~ The uniformly ori-ented main filaments were about 45 denier in size. This ne~work structure had a tensile strength of 11 pounds per inch and an elongation of 12 percent in the machine direction. The strength in the cro~s-mAchine direction was about 1.9 pounds per inch and the elongation 12 percentO The net was very resistant to tearing in the cross-machine direction, giving a value of 30 pounds when tested by the Finch edge tear method, ASTM D-827.
Example 2 Propylene homopolymer with a melt flow index of 7 was extruded at 400Fo through the slit die described above in Ex-ample 1. The molten sheet was embossed between two rolls, one being the same as used in Example 1 and containing 111 grooves per inch extendiny parallel to the rolls longitudinal axis. The other roll had 36 annular grooves per inch extencling in the cir-cumferential directionO The ratio of the cross-sectional areas of the main ribs to the tie ribs formed on both sides of the re-sulting embos~ed plastic sheet was about 13:1 and the ratio of the height of the main ribs to the thickness of the webs between 31~4 the main ribs was 5O1. The embossed sheet was then stretched totwice its width in a tenter at 80Co during which operation reg-ular voids or openings were formed between the main filaments.
The sheet was then drawn linearly 9.2 times its length by passing it over a series of differential speed rolls heated to 120C.
The weight of the network structure so formed was 0.45 ounce per square yard~ The uniformly oriented main filaments were about 160 denier in size. This network structure had a tensile strength of 22 pounds per inch in the machine direction and an elongation of 12 percent. The strength in the cross~machine direction was 0O8 pound per inch and the elongation was 22 percent~ It had ex-cellent tear resistance in the cross-machine direction having a `~
value of 50 pounds when tested by the Finch edge tear methodO
E ~
A cross-laid fabric was prepared by bonding the network.
structure of Example l to a similar network structure having-the main filaments in the cross-machine direction by pressing the two networks between steel platens in a compression press at a temper-ature of 270Fo A pressure of 15 p~ s o i o was applied for 15 sec-2d onds. The fabric so prepared had a weight o 0O7 ounce per.squareyard and a strength of lO pounds per inch in one direction and lO
pounds per inch in the opposite direction, the elongation being 12 percent in each caseO The fabric had excellent tear resistance in both.directions, giving a value of 25 pounds in the machine direction and 25 pounds in the cross-machine direction when tested by the Finch edge tear.method Its Mullen burst strength was 35 p.s.i.
E ~
High density polyethylene with a melt ind~x of lO was extruded at 450F~ through a slit die 18 inches long and with an opening 15 mils wide. The molten sheet was passed int.o the nip of two chrome-plated steel embossing rolls, one 4 inches in di-ameter, the other 6 inches in diameter, each being 15 inches and 20 inches long respectively~ The 4 inch roll had an embossed 3~7~pattern consisting of a plurality of grooves around the roll with a spacing of 75 grooves per inch, with the grooves on the roll being at an angle of 45 to the longitudinal axis of the roll.
The 6 inch roll had an embossed pattern consisting of a plurality of grooves around the roll with a spacing of 250 grooves per inch, with the grooves on the roll being also at an angle of 45 to the longitudinal axis of the rollO The temperature of these rolls was internally controlled to maintain around 150Fo The molten sheet was then passed between the two rolls at a rate of 20 feet per minute and had a thickness of 5 milsO A sheet was em-bossed containing 75 main ribs per inch in the oblique direction on one side with the ribs being separated by grooves 5 mils wide.
On the other side of the sheet the tie ribs were formed with 250 tie ribs per inch with each pair of ribs being separated by grooves l mil wide~ The ratio of the cross~section of the main ribs to the tie ribs was about 13 and the ratio of the height of the main ribs to the thickness of the webs between the main ribs was 3.5:1 The embossed sheet was fed into a linear draw roll which was heated to 120Co at a speed of 50 feet per minute and it was stretched to three times its length. The sheet was then fed into a tenter heated with circulating air to 110Co at a speed of 150 feet per minute and it was stretched to 3~0 times its width~ In this operation, it opened into a uniform network structure~ the grooves between the main ribs becoming openings or voids crossed by oriented tie fil aments-with the main filaments now separated by abou~ 15 mils. The ! ~, sheet was then drawn in the linear direction once more by passing it in frictional contact with a series of 11 steel rolls heated to 120Co and moving at progressively increasing speeds The sheet was fed in at 115 feet per minute and exited at 150 feet per rnin-ute and accordingly was drawn 1~3 times in its length in the machine directionO The resulting network structure had a weight o~ 0O35 ounce per square yard~ The uniformly oriented main fil-aments were about 90 denier in siæe.

31q~ ~
It is to be understood ~hat the above described embod iments are merely illustrative of applications of the principles of this invention and that numerous other arrangements and mod-.
ifications may be made within the spirit and scope of the invention, ::
' . . ' . - 31 -

Claims (7)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A tape comprising two or more main filaments uniaxially oriented along their longitudinal axes and having a plurality of continuous transverse tie filaments interconnecting said main filaments with portions of tie fila-ments protruding from the edges of said tape.

2. A method of making a tape which comprises (1) forming a sheet hav-ing a plurality of parallel continuous main ribs extending in a first direc-tion substantially parallel to the longitudinal axis of the sheet on one side thereof and a plurality of parallel continuous tie ribs on the other side thereof extending in a second direction different from the first direction;
drawing the sheet in at least one direction to separate the main ribs into continuously and uniformly oriented main filaments having a substantially uniform cross-section and to separate the tie ribs into continuous tie fila-ments interconnecting the main filaments thereby forming a network structure;
and (2) breaking the tie filaments interconnecting main filaments of the net-work structure to form a plurality of tapes composed of main filaments, each having portions of tie filaments protruding therefrom.

3. A method according to claim 2 wherein the said second direction is perpendicular to the longitudinal axis of the sheet.

4. A method according to claim 2 wherein the network structure is separated into a plurality of longitudinal tapes each having two or more main filaments therein interconnected by tie filaments.

5. A method according to claim 2 wherein the said second direction is perpendicular to the longitudinal axis of the sheet and wherein the network structure is separated into a plurality of longitudinal tapes each having two or more main filaments therein interconnected by tie filaments.

6. A method of making a woven fabric comprising weaving tapes made by a method according to claim 2, 3 or 4.

7. A woven fabric comprising a plurality of tapes, each tape having two or more uniaxially oriented main filaments interconnected in a predeter-mined uniform spaced relationship by a plurality of continuous transverse tie filaments, and each tape having portions of tie filaments protruding from the edges thereof, said tapes being woven together to provide a woven fabric hav-ing a predetermined porosity.