US 3708361 A
Descripción (El texto procesado por OCR puede contener errores)
Jan. 2, 1973 R. J. sTuMPF METHOD OF MAKING ELASTIC HIGH-LOFT NONWOVEN FABRIC WITH 4 Sheets-Sheet l IMPROVED CROSS DIRECTIONAL STRENGTH Filed Nov. 16, 1970 .mw .Illi
@mmm R. J. STUMPF Jan. 2, 1973 3,708,361 METHOD OF MAKING ELASTIC HIGH-LOFT NONWOVEN FABRIC WITH IMPROVED CROSS DIRECTIONAL STRENGTH 4 Sheets-Sheet 2 Filed Nov. 16, 1970 R. J. STUMPF Jan. 2, 1973 METHOD OF MAKINGELASTIC HIGH-LOFT NONNOVEN FABRIC WITH IMPROVED CROSS DIRECTIONAL STRENGTH 4 Sheets-Sheet 5 Filed Nov. 16, 1970 'Jan- 2 1973 R J. sTuMPF 3,708,361
METHOD OI" MAKING ELASTIC HIGH-LOFT NONWOVEN FABRIC WITH IMPROVED CROSS DIRECTIONAL STRENGTH vFiled Nov. 16, 1970 4 Sheets-Sheet 4 ,WJ v
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United States Patent O METHOD F MAKING ELASTIC HIGH-LOFT NGN- WOVEN FABRIC WITH IMPROVED CROSS DI- RECTIONAL STRENGTH Robert J. Stumpf, Appleton, Wis., assigner to Kimberly- Clark Corporation, Neenah, Wis. Filed Nov. 16, 1970, Ser. No. 89,860 Int. Cl. B321) 5/ 00 U.S. Cl. 156-72 14 Claims ABSTRACT 0F THE DISCLOSURE An elastic, high-loft, nonwoven fabric having improved cross-directional strength, such fabric including a discontinuous backing layer of adhesive and a multiplicity of heat-settable elements as well as filaments looped outwardly from the backing, and a method of making the fabric by embedding at least two webs in an open pattern of adhesive, with one web being comprised of a plurality of flexible elements extending longitudinally of the web and a second web being comprised of a plurality of unbonded randomly oriented continuous filaments. The ad hesive is then partially consolidated in a backing layer while the elements and filaments are looped outwardly from the backing and the elements are heat-set while minimizing bonding in the partially consolidated adhesive backing.
RELATED APPLICATIONS George H. Saunders, Robert C. Sokolowski and Robert J. Stumpf, Ser. No. 498,929 filed Oct. 20, 1965 now abandoned and replaced by Ser. No. 79,287 lfiled Oct. 8, 1970,
Ronald H. Wideman, Ser. No. 551,605, filed May 20, 1966 and now U.S. Pat. No. 3,553,064.
Robert I. Stumpf and William L. Mowers, Ser. No. 553,483 filed May 27, 1966 and now U.S. Pat. No. 3,553,065.
Robert I. Stumpf, Ser. No. 769,959, filed Oct. 23, 1968 now abandoned and replaced by Robert J. Stumpf, Ser. No. 31,225, led Apr. 23, 1970.
Robert I. Stumpf, Ser. No. 820,224, filed Apr. 29, 1969.
Paul B. Hanson and Leon B. Pennings, Ser. No. 15,034 filed Feb. 27, 1970 now abandoned.
BACKGROUND OF THE INVENTION This invention generally relates to a method of making an elastic, high-loft, nonwoven fabric and, more particularly, to a method of making a fabric that has improved cross directional strength, as well as the fabric formed by the method.
In recent years many different types of nonwoven materials have been produced both to replace the conventional woven fabrics and, also, to create new markets in which woven fabrics have not yet become established. This is particularly true in the case of materials for single-use in disposable products, such as santiary supplies, disposable diapers, hospital garments, disposable sheets, and the like. For these applications a nonwoven fabric is generally made in continuous sheet form with one or more layers of staple length fibers and/or a reinforcing scrim structure adhesively bonded together or laminated between plies of other material such as cellulosic wadding and plastic sheeting. The fibers may be natural, synthetic, or various blends thereof, and, of course, the particular composition of the nonwoven fabric is greatly influenced by its intended use.
Exemplary of such nonwoven fabrics are those disice closed in U.S. Pats. 2,902,395, 3,047,444, 3,072,511, 3,327,708, 3,484,330, 3,553,064 and 3,553,065, and the aforesaid copending application, Ser. No. 79,287 all of which are assigned to the same assignee as the present application. While the rproduct disclosed in the foregoing issued patents and copending applications have many different attributes and characteristics, they all have one thing in common-viz, the principal fibers are nearly all disposed substantially parallel to the surfaces of the nonwoven material. As a result, the material is either relatively thin and flat or, such substantial thickness and surface texture as are imparted to the fabric are lprovided by creping or embossing various layers of the material, or in some instances, the final nonwoven fabric.
In the aforesaid copending application, Ser. No. 769,- 959, assigned to the assignee of the present invention, there is disclosed a method for forming high-loft, nonwoven materials with a pleasing surface texture and appearance. That method obviates the need for employing creping, embossing or other texturizing operations to increase the bulk or thickness of the material or to improve its surface texture. The fabric is made by `first embedding a web of fibers in an open pattern of adhesive and, thereafter, at least partially consolidating the adhesive into a substantialy continuous backing layer while looping the fibers outwardly from the backing.
Additionally, in the aforesaid copending application, Ser. No. 820,224, assigned to the assignee of the present invention, there is disclosed a method for forming a high-loft, nonwoven fabric having the pleasing structural and aesthetic properties thereinbefore described and which is further characterized by a high degree of stretchability and elasticity, particularly in the machine direction.
Although the fabrics produced by the methods disclosed in the last two above named applications have both desirable structural properties and pleasing aesthetic properties, a characteristic common to both of the fabrics is that the strength of the fabrics in the cross or transverse direction is considerably less than its strength in the machine direction. The lower cross-directional strength of such fabrics tends to preclude their use in certain products where they would otherwise find advantageous use.
Accordingly, it is a primary object of the present invention to provide an improved high-loft, nonwoven fabric of the foregoing type which is characterized by its improved cross-directional strength.
Another object of the invention is the provision of a method for making high-loft, nonwoven fabric having increased cross directional strength achieved during production of the fabric as opposed to being achieved by having to subsequently laminate additional layers of material to the fabric.
A still further object of the invention is the provision of a method for forming an elastic, high-loft, nonwoven fabric having increased cross-directional strength, which fabric is initially in a compact closed form and which may be subsequently opened or drawn when desired.
Other objects and advantages of the present invention will become more readily apparent upon reading the following detailed description and upon reference to the attached drawings, in which:
FIG. 1 is a schematic side elevation of one form of apparatus that may be employed to practice the method of the present invention;
FIG. 2a is a fragmentary plan view of an illustrative web of base material, somewhat simplified and exaggerated for the sake of clarity of illustration, and with portions broken away to expose the various layers, here illustrating the top web of flexible elements as having been applied in a generally sinusoidal pattern;
FIG. 2b is a fragmentary plan view of an illustrative web of base material, somewhat simplified and exaggerated for the sake of clarity of illustration, and with portions broken away to expose the various layers, here illustrating the top web of flexible elements as having been applied in a generally straight line pattern;
FIG. 3 is a fragmentary plan view of one embodiment of the product of the present invention;
FIGS. 4 and 5, respectively, are greatly enlarged, simplified and somewhat exaggerated sections taken substantially along longitudinal line 4-4 and transverse line 5-5 in FIG. 3; y
FIG. 6 is an enlarged schematic detail and side elevation of the forming drum and gathering blade of the apparatus shown in FIG. l;
FIG. 7 is a further enlarged schematic side elevation illustrating in somewhat idealized fashion the sequence of gathering and looping of individual elements;
FIG. 8 is an enlarged schematic fragmentary view taken substantially along the line 8 8 of FIG. 7, showing a fragment of the fiber web and adhesive pattern with illustrative fibers attached to the adhesive;
FIG. 9 is a simplified schematic view taken substantially along the line 9-9 of still another sequence as 'shown in FIG. 7;
FIG. 10 is an enlarged schematic bottom view showing the sequence of the partial consolidating or closing of the open adhesive pattern to form a discontinuous adhesive backing; and
FIGS. 11-14 illustrate in plan view exemplary alternative adhesive patterns that may be used for the base web in practicing the method of the present invention.
While the invention is susceptible of various modifications and alternative forms, a specific embodiment thereof has been shown by way of example in the drawings and will herein be describedin detail. It should be understood, however, that it is not intended to limit the invention to the particular form disclosed, but, on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the' invention as expressed in the appended claims.
THE ENVIRONMENT OF THE INVENTION In the manufacture of high-loft, nonwoven fabrics of the general type to which the present invention relates in its preferred form, a base web of fibers is first prepared and an open adhesive pattern is applied to one side of the web. Different procedures have been used in preparing the base web. For example, textile length fibers may be processed through conventional cotton card machinery to produce a carded web for the base web. In such a carded web 50% to 70% of the fibers may be oriented substantially parallel with the machine direction. It has been found, however, that the most uniform product has been obtained with the method of the present invention by using base webs having a higher percentage of the fibers aligned with the machine direction such, merely by way of example, as a highly drafted web in which, as a result of the drafting process, 80% to 95% of the fibers may be aligned with the machine direction. Such webs of bonded, highly drafted fibers, of course, have substantial utility in themselves and are the subject, for example, of the aforesaid copending application, Ser. No. 79,287 and U.S. Pat. No. 3,553,065. The present invention, however, goes far beyond the preparation of an adhesively bonded carded web or the products and methods disclosed in those two applications, and results in the formation of a high-loft, nonwoven fabric having significantly different characteristics than the nonwoven web utilized as the base material.
Broadly stated, the method of the present invention involves utilizing a base material of the type described hereinabove in conjunction with a web of unbonded randomly oriented, continuons filaments to form a composite base web and, thereafter, performing the subsequent steps of:
(l) reactivating the open pattern of adhesive in which the fibers are embedded; and (2) consolidating or partially consolidating the adhesive into a backing layer, while (3) simultaneously looping the portions of the fiber spanning the open spaces of the adhesive outwardly from the backing layer formed by the consolidated or partially consolidated adhesive. The resulting product is characterized by the high-loft or deep pile of the loops of fibers which extend outwardly from the adhesive backing and by its improved cross-directional strength. The particular depth of pile or degree of loft of the loops, of course, depends upon a combination of control parameters including, for example: the type and denier of the base fibers; the amount and spacing of the original adhesive pattern; the angle of the gathering blade; and the relative speeds of fiber delivery to and fabric discharge from the gathering blade; as will be discussed below and as is described in considerably more detail in the aforesaid copending applications, Ser. Nos. 769,959, 820,224 and 31,225, all of which are assigned to the assignee of the present invention.
Turning now to the drawings, FIG. 1 schematically illustrates an exemplary apparatus for performing the method of the present invention. This apparatus includes a web forming section 12 and an adhesive compacting and fiber looping section 14. The web forming section 12 is generally similar to the apparatus disclosed in the af0resaid copending application7 Ser. No. 79,281, with certain modifications as disclosed in U.S. Pat. No. 3,553,065 but it is here shown in more complete and visible form than shown in either of those disclosures. It will be appreciated as the ensuing description proceeds, that fiber webs made in accordance with the method disclosed in the aforesaid copending application, Ser. No. 79,281, are also usable with the subsequent method steps of the present invention, as are carded web and web prepared by other processes.
As shown in FIG. l, multiple slivers 15 of textile fibers are drawn from their respective supply cans (not shown) into a draw frame, generally indicated at 16, which comprises a series of pairs of grooved rolls 18; the rolls of each pair being driven by appropriate gearing `(not shown, but well known in the art) at a peripheral rate of speed somewhat faster than the rate of operation of the preceding pair. Merely by way of example, the pairs of rolls 18 may be adjusted to provide an over-all increase in speed and, therefore, an extent of fiber draw on the order of 15:1 through the draw frame 16. As the juxtaposed slivers pass through draw frame 16, the individual fibers are drafted and spread out to form a fiat, striated web of substantially aligned fibers as shown at 19. Web 19 is maintained adjacent a supporting conveyor sheet 20 on the surface of which adhesive has been previously applied in a preselected pattern.
In this embodiment, the conveyor sheet 20 comprises an endless conveyor belt treated on at least its upper surface with a release agent. One example of such a belt comprises woven glass fiber with a surface coating of tetrafluoroethylene resin. Other examples of release coatings are well known, and comprise such materials as silicones, fatty acid metal complexes, certain acrylic polymers, and the like. Heat resistant films or thin metal sheets treated with release agents may also be used as the carrier sheet.
Prior tothe time the web 19 is picked up by the belt 20, the latter has imprinted on its release-treated surface a pattern of fiexible, thermoplastic adhesive such as is shown at 21 in FIGS. 2a and 2b. It will be understood that, as shown in FIG. 1, the adhesive is actually on the underside of belt 20 which becomes the upper surface after passing around roll 22, at which time the adhesive pattern 21, when making high-loft, nonwoven fabrics of the type disclosed in the aforesaid copending applications, Ser. Nos. 769,959 and 820,224, directly contacts the fiber web 19. The pattern is shown as being visible in FIGS. 2a and 2b only for illustrative purposes.
The belt 20 is fed around roll 22 at a speed slightly in excess of the delivery speed of the final pair of rolls 18 of draw frame 16 in order to maintain web 19 under slight tension, whereby the individual highly-drafted fibers are retained in their aligned and tensioned condition. Drive rolls 24, 25 are rotated (by suitable drive means, not shown) to drive belt 20 at a speed sufiicient to maintain the proper tension on the web 19.
In the method shown for applying adhesive, the belt 20 is fed through a nip formed between a printing roll 26 and a back-up roll 28 maintained in very light pressure engagement therewith. The surface of printing roll 26 is provided with an intaglio pattern to which adhesive may be supplied in various ways Well known to those skilled in the art. For example, in the aforesaid patent application, Ser. No. 769,959, a system is schematically disclosed wherein the lower portion of the printing roll 26 picks up adhesive directly from a dip pan, with excess adhesive being removed by a doctor blade, thus leaving only the intaglio patterned surface filled. However, in the practice of the present invention, it has been found that more satisfactory results are obtained by pumping or otherwise transferring adhesive 29 from supply pan 30 to a reservoir located immediately above an inclined doctor blade 31- the reservoir being defined in part by the upper surface of the inclined doctor blade and the adjacent portion of the rotating peripheral surface of the printing roll 26. Thus, as the printing roll 26 rotates (in a counter-clockwise direction as viewed in FIG. 1), the intaglio patterned surface thereof is filled with adhesive 29, excess adhesive is removed by the doctor blade 31, and a metered amount of adhesive is then transferred to the underside of release coated belt 20 in a preselected pattern. The pattern shown in FIGS. 2a and 2b is in the form of an open diamond pattern of adhesive.
The particular dimensions of the intaglio pattern employed and, indeed, the actual pattern itself, are not critical to the practice of the invention in its broadest aspects. Thus, it has been found that patterns other than the il lustrative diamond pattern hereinabove referred to can be utilized, and certain of such patterns will be subsequently described in connection with FIGS. ll-l4. For illustrative purposes, however, it is noted that excellent results have been achieved where a diamond pattern was employed in which adjacent lines of adhesive were spaced apart in both directions by 1A", and wherein the intaglio printing roll 20 had adhesive cells or lines 0.007 deep and 0.025" wide. In certain instances, however, it has been found that the dimensions of the adhesive cells or lines, together with their spacing, are critical and must differ from the foregoing exemplary dimensions.
Since the surface of belt 20 is treated with a release coating, the adhesive remains substantially on the surface with no penetration therein and is preferably in a somewhat tacky condition. The printed belt is drawn from the printing nip around roll 22 positioned below the draw frame 16, and from their around roll 32 positioned closely adjacent the output end of draw frame 16 and, as stated above, at a speed slightly in excess of delivery speed of the last two rolls in the draw frame. The web 19 emerging from the draw frame 16 is deposited on the tacky adhesive 21 on belt 20 and held in tensioned engagement therewith by the adhesive and the above-mentioned speed differential. This continuous tension prevents the fibers in the web from losing their high-drafted and aligned condition.
It is another aspect of the present invention that the fibers deposited on the web 14 from draw frame 16 need not be the same kind, size, color or quantity. Nor, for that matter, do the fibers of the slivers 15 need to be uniform in these respects as they are drawn into the draw frame 16. Thus, various blends of fiber sizes, kinds, colors and quantities can be deposited across the web 19 from the draw frame 16. Additional draw frames can also be employed if desired as more clearly disclosed in the aforesaid copending applications, Ser. Nos. 769,959 and 820,- 224.
Provision may also be made for imparting a patterned effect to the finished fabric. To this end, the fibers from the draw frame 16 pass under a bar 34 before being deposited on the belt 2f). The bar 34 may be oscillated in a direction generally transverse to the movement of the web 19 and, preferably, provision is also made for controlling the frequency and amplitude of the oscillation of the bar. Thus, as the bar is oscillated, the fibers deposited from the draw frame 16 take on a generally sinusoidal or saw-tooth wave pattern of controlled frequency and amplitude. A simple, but somewhat similar, oscillating bar arrangement is disclosed in the aforesaid U.S. Pat. No. 3,553,065.
.Examples of the web 19 formed on the illustrative apparatus 12 (FIG. 1) are shown in FIGS. 2a and 2b. As previously mentioned, a series of parallel and diagonally disposed lines of adhesive are printed in criss-cross fashion on the belt 20 to form a pattern 21 of adhesive having substantially open spaces in the configuration of diamonds. In depositing the fibers from the draw frame 16 in the web shown in FIG. 2b, the bar 34 was not, in this instance, oscillated. Thus, the fibers making up the component 1-9tb of the web 19 are substantially all aligned in the direction of web movement. The fibers making up the component 19a: of the web shown in FIG. 2a, however, Will be seen to be deposited in a generally wavy or saw-tooth pattern as a result of oscillation of the bar 34 associated with the draw frame 16, thus altering the appearance characteristics of the finished fabric.
Following deposit of web components 19a (FIG. 2a) or 191; (FIG. 2b) on the adhesive printed belt 20, the belt is drawn around a heated curing drum 35- where fusing and curing of the adhesive is substantially completed while the web 19 is maintained in firm contact therewith to bond the individual fibers. To insure effective heating and fusing of the adhesive, it is desirable that travel of the combined belt and web be around a substantial portion of the drum 35. In the illustrated embodiment, a fiy roll 36 is positioned to apply tension on the combined belt and web as they travel around the drum 35 to insure complete embedment of the fibers in the adhesive. The fibers of the web 19 are thus bonded together while retaining their highly-draft and substantially aligned condition in the particular pattern in which they were deposited on the open pattern of adhesive 21 printed on the belt 20.
After leaving the fly roll 36, the combined web 19 and belt 20 are preferably passed over the drive roll 24, which also serves as a cooling drum to set the adhesive. The bonded web 19 is stripped from the release-coated surface of the belt 20 by a guide roll 38 as the web leaves the cooling drum 24.
While various well-known adhesives may be employed in the foregoing process, advantages reside in the use of plastisols, which are colloidal dispersions of synthetic resins in a suitable organic ester plasticizer, and which, under the influence of heat, provide good binding power while remaining soft and flexible. While many adhesives of this type are known, those found particularly useful for incorporation in the product of this invention include vinyl chloride polymers, and copolymers of vinyl chloride with other vinyl resins, plasticized by organic phthalates, sebacates, or adipates. These provide a fast curing plastisol adhesive characterized by relatively low viscosity, low migration tendencies, and minimum volatility. Such adhesives remain soft and flexible after curing, :and can be reactivated by subsequent heating.
It has been found that other adhesives may be employed in the process-for example, organosols utilizing resins such as the vinyl chloride polymers and copolymers. Furthermore, still other adhesives may be employed provided that they satisfy specified characteristics in the base web produced in the web forming section 12, and in the finished fabric produced in the adhesive compacting and fiber looping section 14 (FIG. l). In general, such adhesives should be applied to the base web by procedures which will not disarrange the fibrous structure of the web; such adhesives should heat-set |at temperatures below the degradation temperature of the fibers in the base web 19 to secure bonding of the fibers to the adhesive; such adhesives should be reactivatable in the subsequent adhesive gathering and consolidation stage of the process; and such adhesives should form a :liexible backing layer for the finished fabric and should strongly bond the fiber loops in place. For example, emulsions of thermoplastic resins such as acrylics and rubber-like compounds, zillustratively ABS, have the requisite properties to serve as the bonding adhesive for the web 19.
In order to convert the thus formed base web 19 to a finished high-loft, nonwoven fabric, the base material, made as heretofore described and comprising a web 19 of highly-drafted fibers embedded in an open adhesive pattern, is fed into the adhesive consolidating and fiber looping section 14 of the apparatus shown in FIG. 1. As shown here, the web 19 continues directly from the web forming section .12 to the consolidating and looping section 14. It should be appreciated, however, that the web 19 discharged from section 12 could be rolled up for storage or transport and then subsequently unrolled and fed into section 14. Also, as previously mentioned, other webs such, merely by way of example, as those made in accordance with the methods disclosed in the aforesaid copending application, Ser. No. 79,287 and U.S. Pat. No. 3,553,065, can be further processed in section 14 in keeping with the method of the present invention.
As illustrated in FIG. 1, the web 19, while still under tension, is fed around an idler roll 39 and onto the surface of a heated forming drum 40. In its preferred ernbodiment, the drum 40 is made of metal with a highly polished, chromium plated surface which is heated and maintained at a temperature of approximately `250 F. Also, the web 19 is arranged to travel a substantial distance around the drum 40 with the open pattern of adhesive 21 in contact with the heat drum surface. As the web 19 is fed onto the drum 40, the heat from the drum surface reactivates and softens the adhesive printed on the underside of the web, causing it to be tacky and to adhere slightly to the drum surface, thereby maintaining the web under constant tension. The drum temperature, which is heated sufficiently to maintain the web at about 250 F., is, however, maintained below lthe melting point of the adhesive to prevent dispersion of the adhesive into the bers of the web.
In order to form the finished fabric, the web 19 of fibers and softened adhesive is reformed by the cooperative action of the drum 40 and a gathering blade 41 having a fiat edge 42. The blade edge 42 operates to consolidate the open adhesive pattern 21 into a substantially continuous backing layer of adhesive, while simultaneously looping the fibers of the web outwardly from between the open spaces in the original adhesive pattern. The reformed and consolidated material 44 then leaves the blade edge 42 and moves onto a flat take-away surface 45 and a discharge conveyor 46.
Turning now to FIGS. 7-10, the method of making the high-loft, nonwoven fabric 44 described above will be explained in greater detail in connection with an illustrative sequence of the gathering and looping of a single fiber of the web 19 (FIGS. 7 through 9) and the partial consolidation of the illustrative diamond adhesive pattern 21 (FIG. l0). As seen in FIG. 8, the ber has a portion P which extends across the open space of the diamond pattern of adhesive 21 from point A to point B where it is embedded in the adhesive. Referring to FIG. 7, the series of views in this figure illustrates how the portion P of the fiber is formed into a loop; viz, when point A being carried around the heated drum 40 impinges against the gathering blade edge 42, its forward motion is halted and it is scraped along the surface of the drum,
while point B continues to advance with the drum surface since, due to its softened and tacky condition, it adheres to the smooth drum surface. As point B advances relative to point A, the portion P of the fiber between points A and B is cause to bow outwardly from the drum surface. Finally point B overtakes point A and these points of adhesive are brought close together without being consolidated as seen in FIG. 9. In the meantime, fiber portion P has been looped outwardly from the drum surface.
It will, of course, be understood that while looping of fiber portion P is occurring, additional adhesive points C-D, etc., traveling around the drum 40 impinge against the gathering blade edge 42 causing a consolidation of these adhesive points and looping of their intermediate fiber portion P1 as is also indicated in FIG. 9. This occurs simultaneously at all points across the web at the blade vedge angle, producing a backing layer of adhesive from which extends the multiplicity of loops formed by the fibers of the base web. The thus formed layer of adhesive is carried away from the blade edge 42 along the take-away surface 45 and provides backing layer for the outwardly looped fibers, thus producing the fabric 44.
Another important feature of the process herein described is that not only does each fiber portion P loop outwardly from the drum surface, but, also, as the loop is formed it turns, reaching a position in the fabric 44 generally perpendicular to the direction of the original alignment of fiber portion P. Thus, the ber loops arrange themselves so that the plane of each loop is substantially normal to the original liber alignment shown in FIG. 8. The reason for the loop twisting as it is formed may be explained by this observation. If two spaced points of a single fiber not in a web are brought together, it has observed that the ber will form a loop and, as the loop is formed, it twists towards a position of minimum internal stress, turning through an angle which tends to approach In carrying out the method herein described, because of the great number of fibers in the web and their proximity one to another, each fiber loop engages the neighboring fiber loops with the result that all the loops are blocked from turning beyond the plane substantially normal to the machine direction, and are constrained in that position by the interference between the loops. In practice, of course, the actual direction and degree of loop twist depend upon the characteristics of the fibers in the original web 19.
It is important to note, however, that throughout the fabric the heights of the fiber loops vary according to the spacing between the points of attachment of each liber to the open adhesive pattern in the base web. Referring to FIGS. 5, 8 and 9, it will be seen, for example, that the loop formed 'by the fiber portion P1 between the points of adhesive attachment C, D will have a lower height than the loop formed by the longer fiber portion P between the points A, B. On the other hand, however, successive loops in adjacent diamonds, when viewed in a; vertical section taken along the machine direction (FIG. 4), will have the same height since the fiber length P will remain the same between successive set of points A, B. This results in a dense fabric with the lower loops supporting and filling around the higher loops and the top surface of the fabric being formed by the tops of the higher loops.
FIG. 10 illustrates the partial consolidation that is desired when the open adhesive pattern is the exemplary diamond pattern. Thus, considering a single diamond S, each of the four corners T represents the crossing point of two intersecting lines of adhesive U and V. At every corner T then, as the adhesive is scraped along the surface of the drum 40, the crossing adhesive lines U and V are brought closer and closer together. The points closest to the corners T merge first because of the shorter distance of separation. Accordingly, point P on line U will merge with point P6 on line V before point P9 will meet point P10. Similarly, on the other side of the corner, the closer set of points (e.g., P7 and P8) will merge before points P11 and P12. It can be seen that, if the adhesive were allowed to scrape along the drum surface for a sufficient time period, the open pattern could be consolidated into a substantially continuous adhesive backing, as in the aforesaid copending application, Ser. No. 769,959.
However, in order to form a fabric 44 characterized by its elasticity (a process which as thus broadly defined, is dislosed in more detail in the aforesaid copending application, Ser. No. 820,224), the take-away speed is maintained at a rate so that the adhesive diamonds are not completely consolidated but, rather, are collapsed into fiat hexagonal shapes in which the crossing points of adhesive, as shown in FIG. l0, have been transformed by partial consolidation of the adhesive into lines that form the sides of the highly elongated hexagons. As may be seen in FIG. 3 which is a top plan view of a fabric made in accordance with the present invention with portions broken away, the transverse dimension of the elongated hexagons in the discontinuous adhesive backing is considerably longer than the machine direction.
If desired, the thus-formed elastic fabric could be rolled up and stored or transported elsewhere in this closed position or could be further processed to fabricate a variety of products. Alternatively, since the take-away surface is cooled, as best indicated at 48 (FIG. l) to render the adhesive non-tacky, only a certain part of the lines of adhesive that are in contact were allowed to establish bonds of any significant strength. Thus, where desired, the closed, compact form of the nonwoven fabric may be stretched apart to break the bonds of minimal strength (i.e., the bonds that will break before adhesive rupture or other degradation of the product). The fabric is then allowed to relax to come to an equilibrium state in its drawn or open position.
The drawing may be accomplished by hand and can be achieved by pulling the fabric apart (i.e., along the machine direction). Alternatively, shown in FIG. l, if it is desired to draw the fabric immediately after it has been formed, the fabric exit end of the conveyor 46 may be provided with a roll 49 to form a nip and a pair of rolls 50, 51 also forming a nip. Drawing is accomplished by driving the rollers 50, S1 at a higher speed.
THE MANUFACT URE OF HIGH-LOFT, NON- WOVEN FABRICS IN ACCORDANCE WITH THE PRESENT INVENTION Thus far, the environment of the invention has been described in connection with methods for making lhighloft, nonwoven fabrics by preparing a base web comprising an open pattern of adhesive and a plurality of fibers or similar fiexible elements extending generally longitudinally thereof and bonded thereto; and thereafter: (l) reactivating the open pattern of adhesive in which the fibers are embedded; and (2) consolidating or partially consolidating the adhesive into a backing layer, while (3) simultaneously looping the portions of the fibers spanning the open spaces of the adhesive pattern outwardly from the 'backing layer formed by the consolidated or partially consolidated adhesive. The resultant fabrics, while having numerous advantageous applications, are not characterized by significant cross-directional strength unless and Iuntil they are further processed-for example, until they are laminated to a reinforcing scrim material or the like.
In accordance with the present invention, provision is made for forming high-loft, nonwoven fabrics possessing many of the attributes and characteristics of the fabrics hereinabove described, yet which are, nonetheless, further characterized by their significantly improved strength characteristics as measured in the cross-direction of the 10 fabric. To this end, provision is made for modifying the base web formed in the web forming section 12 of the apparatus in such manner as to impart greater strength to the finished product without unduly interfering with the fiber looping and adhesive consolidating steps that occur `during later stages of the fabric forming process.
In carryng out this yaspect of the invention, a web 52 comprising a plurality of unbonded, randomly oriented, substantially continuous filaments of a synthetic polymer is unwound from a roll 54 (FIG. 1) and is preferably delivered to the adhesively coated carrier belt 20 in such a manner that the web 52 is interposed between the open adhesive pattern 21 on the ybelt 20 and the web 19 of fibers being fed to the belt through the draw frame 16. To accomplish this, the web 52 is fed through the last pair or pairs of rolls (for example, the pairs of rolls indicated at 55, 56 in FIG. 1) in a draw frame, generally indicated at 58, the output end of which is positioned closely adjacent the turning roll 22. Preferably the web of randomly oriented fibers emanating 'from the draw frame 58 passes under a bar 59 which may or may not be capable of oscillation in the manner previously described for bar 34 at the output end of draw frame 16. As was the case with draw frame 16, the successive pairs of rolls 55, 56 in draw frame 58 are driven at peripheral rates of speed which are slightly greater than the speed of the preceding pair. As a consequence of this construction, the web 52 of unbonded, randomly oriented fibers is drawn slightly and extended in the machine direction, although the bulk of the fibers retain their randomly oriented characteristics. The web 52, which is now slightly tensioned due to the drawings thereof in draw frame 58, is then deposited directly on the open pattern 21 of adhesive on belt 20 which, because it is traveling at a speed slightly in excess of the peripheral rate of speed of the pair of rolls 56, serves to maintain the web 52 in its tensioned state. Thereafter, the web 19 of drawn and substantially aligned fibers is deposited on top of the web 52 in the manner previously described, with the fibers in the web 19 contacting the adhesive in the open adhesive pattern 21 through the interstices in the web 52.
Typical base webs embodying the features of the present invention are shown, by way of example, in FIGS. 2a and 2b. As here shown, it will be noted lthat such a base web includes at least three essential components-viz, (l) an open yadhesive pattern 21 which serves to bond both (2) a web 52 of randomly oriented fibers or filaments and (3) a web of drawn, highly oriented staple length fibers with the web 19 being disposed on top of web S2.
As previously stated, the web 52 is preferably comprised of a plurality of continuous filaments of a synthetic polymer such as polypropylene or polyester. The matter of an initial formation of the web 52 is not particularly important and a variety of well-known techniques can be used. In general, such techniques involve continuously extruding a polymer through a spinneret, drawing the spun filaments and depositing the filaments on a continuously moving surface in a substantially random fashion. Drawing serves to give the polymer filaments tenacity while the random deposition give the web desirable isotropic strength characteristics. U.S. Pats. Nos. 3,338,992, 3,341,394 and 3,276,944 and the aforesaid copending application, Ser. -No. 15,034, illustrate Nery useful techniques for initial web formation. It will be noted that the random web 52 is comprised of a multiplicity of swirled, looped and overlapping filaments, and is not bonded when fed through the drafting frame. The individual filaments within the web S2 are then bonded by the adhesive on the sheet 20 only where they contact the diamond patterned adhesive and are otherwise under no restriction, which facilitates the outward looping than occurs when the composite web 19 (FIG. 1) is fed through the gathering and looping section 14 previously described.
In accordance with an important aspect of the present invention, it has been found that significantly improved results in terms of the cross directional strength of the finished nonwoven fabric are Iattained as a result of the inclusion of the random web 52 which is incorporated into the composite web 60. Thus, it will be appreciated that in those instances where a random web 52 is not incorporated into the composite web 60, and where the bar 34 is not oscillated so that the fiber elements are in a substantially sinusoidal or saw-tooth wave form as shown at 19a in FIG. 2a, then the composite base web will be substantially devoid of fibers extending the cross direction and, as a result during the consolidation step the points A and B will be consolidated as shown in FIG. 7viz, substantially in the machine direction. This results in the cross directional strength of the fabric being defined susbtantially by the strength of only the adhesive, with none of the fibers extending across the web transverse to the machine direction.
Although limited cross directional strength is achieved by oscillating the bar 34 producing the sinusoidal p-attern of the fiber elements shown in FIG. 2a, so that many of the fiber elements do extend partially inthe cross direction, inclusion of the random web 52 having its substantial isotropic strength characteristics, has been found to impart considerable additional cross directional strength to the nished fabric 44 (PIG. 3) for the reason that the filaments of web 52 are randomly swirled, looped and overlapped in virtually all directions.
The vastly improved cross directional strength characteristics of high-loft, nonwoven fabrics made in accordance with the present invention will become more apparent upon consideration of the following data. A typical elastic, high-loft, nonwoven fabric was first made in accordance with the teachings in the aforesaid copending application, Ser. No. 820,224 from a base web of polyester staple length fibers and adhesive weighing 22 grams/yd?. The tensile strength of the web in the cross direction fabric was then measured and found to vary between 0.01 to 0.02 lb./in. A second elastic, high-loft, nonwoven fabric was then'made in accordance with the present invention utilizing a composite base web of substantially equal parts by weight of adhesive, polyester staple fibers, and randomly oriented, unbonded, polypropylene filaments, wherein the weight of the composite web was 21 grams/ yd. The tensile strength of the composite web in the cross direction of the fabric was then measured and found to be 1.47 lbs./in.-viz, in increase in cross directional strength by a factor of approximately 100.
Of course, those skilled in the art will appreciate that the adhesive could be applied in patterns other than the open diamond pattern shown by way of example in FIG. 2. For example, the adhesive could be applied in the form of criss crossed sine waves `80 as shown in FIG. 11, or in the form of evenly spaced diagonal lines 82 as shown in FIG. 12; or in the form of parallel sine waves 84 as shown in FIG. 13; or in the form of a brick like pattern 86 as shown in PIG. 14; or, for that matter, in numerous other types of patterns. The applicability of patterns such as those shown in FIGS. 1l through 14 is described in greater detail in the aforesaid copending application, Ser. No. 820,224.
I claim as my invention:
1. A method for producing a high-loft nonwoven fabric with improved cross directional strength, comprising:
preparing a first web comprised of a plurality of exible elements extending substantially longitudinally of the web;
preparing an unbonded, nonwoven second web comprised of a plurality of continuous filaments, with the filaments being randomly oriented and overlapping therein;
bonding the first and second webs in an open pattern of adhesive which becomes tacky at elevated temperatures;
softening the adhesive to a tacky state;
consolidating the open pattern of tacky adhesive at a consolidating station (i) to form an at least partially consolidated adhesive backing layer (ii) while looping the element and filament portions located in the open spaces of the adhesive pattern outwardly from the backing layer; and conveying the adhesive and outwardly looped elements and filments away from the consolidating station while allowing the outwardly looped elements and filaments to cool.
2. A method for producing anl elastic high-loft nonwoven fabric with improved cross directional strength, comprising:
preparing first and second webs comprised of a plurality of flexible heat-settable elements extending substantially longitudinally of the webs;
preparing an unbonded, nonwoven web comprised of a plurality of continuous filaments, with the filaments being randomly oriented and overlapping therein; bonding the webs in an open pattern of adhesive which becomes tacky at temperatures within the range in which the elements are heat-settable, with the random web being intermediate of the first and second webs; softening the adhesive to a tacky state;
consolidating the open pattern of tacky adhesive at a consolidating station (i) to form a partially consolidated backing layer (ii) while looping the element and filament portions located in the open spaces of the adhesive pattern outwardly from the backing layer; and conveying the adhesive and outwardly looped elements and filaments away from the consolidating station at a rate suiiicient to minimize bonding of the adhesive backing, while allowing the outwardly looped elements and filaments to cool.
3. The method of claim 1 wherein the adhesive backing and outwardly looped elements and filaments being conveyed away from the consolidating station are conditioned to provide heat setting conditions for the outwardly looped elements while rendering the adhesive backing non-tacky to minimize bonding of adjacent portions of the partially consolidated backing layer to each other.
4. The method of claim 1 wherein the open pattern of adhesive is au interconnecting diamond pattern.
5. The method of claim 1 wherein the flexible heat settable elements are iibers of staple lengths.
6. The method of claim 1 wherein the filaments are a thermoplastic polymer.
7. The method of claim 6 wherein the thermoplastic polymer is polypropylene.
8. The method of claim 1 wherein the loops formed by the outwardly looped element portions twist to lie in generally transverse planes.
9. The method of claim 1 wherein the adhesive is applied to a moving sheet prior to receiving the webs thereon, and the sheet is separated from the adhesive and webs subsequent to the webs being bonded in the adhesive.
10. The method of claim 1 wherein the elements of one of the first and second webs are applied to the adhesive pattern in a generally sinusoidal manner.
11. The method of claim 1 wherein the bonded webs are carried to a movable heated surface with the adhesive in contact with the surface such that the adhesive is softened to a tacky state, and consolidation of the open pattern of adhesive is achieved by carrying the webs on the surface to the edge of a gathering blade and impinging ledelements, filaments and adhesive against the gathering 12. The method of claim 1 wherein the second web is interposed between the open adhesive pattern and the iirst web.
13. A method for producing an elastic high-loft, nonwoven fabric having improved cross directional strength, comprrslng:
introducing an unbonded, nonwoven web comprising a plurality of continuous filaments, with the filaments being randomly oriented and overlapping therein;
introducing a web comprising a plurality of iiexible elements extending substantially longitudinally of the web;
bonding the said webs in an open pattern of adhesive which becomes tacky at elevated temperatures, the web of flexible elements being positioned on top of the web of continuous filaments,
feeding said webs onto a smooth movable surface with said adhesive in contact with said surface, softening said adhesive to a tacky state so it adheres to said surface,
longitudinally carrying said webs on said surface to the edge of a gathering blade and impinging said elements, filaments and softened adhesive against the edge of said gathering blade (i) to loop the portions of said elements and the longitudinally extending portions of the continuous filaments spanning the open portions of said adhesive pattern outwardly from said web,
. (ii) while gathering said open adhesive pattern in the machine direction into an adhesive backing layer,
the transversely extending portions of the continuous filaments providing increased cross direction strength,
conveying said adhesive backing layer, outwardly looped elements and filaments away from said surface and said gathering blade at a rate sufficient to minimize the bonding together of adjacent portions of the gathered open pattern of adhesive to form a partially consolidated backing layer and setting said adhesive backing layer to form the fabric.
14. A method for producing a stretchable high-loft,
nonwoven fabric having improved cross directional strength, comprising the steps of introducing a tirst web and comprising a plurality of flexible elements extending substantially longitudinally of the web;
introducing an unbonded, nonwoven second web comprising a plurality of continuous, heat-settable filaments, with the filaments being randomly oriented and overlapping therein;
bonding the webs in an open pattern of adhesive with the randomly oriented filament overlying the web of flexible elements;
longitudinally carrying the webs onto a heated, smooth surface which heats the adhesive to a tacky state causing it to adhere to the surface,
gathering the open pattern of tacky adhesive by impinging the elements, filaments and tacky adhesive adhered to the surface against the edge of a relatively moving gathering blade to loop the portion of the elements and the longitudinally extending filaments spanning the open spaces of said adhesive pattern outwardly from said webs and to form a partially consolidated backing layer, the transversely extending filament portions contributing to the increased cross-directional strength of the fabric,
conveying said adhesive backing layer and outwardly looped elements and filaments away from said surface and said gathering blade at a rate sufficient to minimize bonding of adjacent portions of the consolidated adhesive backing to each other and heatsetting said filaments.
References Cited UNITED STATES PATENTS 2,550,686 5/1951 Goldman 156-471 2,639,250 5/1953 Reinhardt 161-65 3,214,323 10/1965 Russell et al. 161-148 3,220,056 11/1965 Walton 18--19 3,236,718 2/1966 Cohn et al. 161-128 WILLIAM A. POWELL, Primary Examiner J. J. BELL, Assistant Examiner U.S. Cl. X.R.