Highly-drafted,sinusoidal patterned nonwoven fabric laminates and method of making same

Jan. 5, 1971 r. h. wideman 3,553,064

HIGHLY-DRAFTED SINUSOIDAL PATTERNED NONWOVEN FABRIC

LAMINATES AND METHOD OF MAKING SAME

Filed May 20. 1966 2 Sheets-Sheet 1

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Jan. 5, 1971 r. h. wideman 3,553,064

HIGHLY-DRAFTED SINUSOIDAL PATTERNED NONWOVEN FABRIC

LAMINATES AND METHOD OF MAKING SAME

Filed May 20, i960 2 Sheets-Sheet 2

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FIG.3. FIG.4.

United States Patent Office

3,553,064

Patented Jan. 5, 1971

3,553,064

HIGHLY-DRAFTED, SINUSOIDAL PATTERNED NONWOVEN FABRIC LAMINATES AND METHOD OF MAKING SAME

Ronald H. Wideman, Menasha, Wis., assignor to Kimberly-Clark Corporation, Neenah, Wis., a corporation of Delaware

Filed May 20,1966, Ser. No. 551,605

Int. CT. B32b 5/12, 7/14; D04h 1/74

U.S. Cl. 161—59 15 Claims

ABSTRACT OF THE DISCLOSURE

A nonwoven fabric comprising at least one layer of highly-drafted, staple length fibers extended to substantially their full length and arranged in a sinusoidal pattern with the fibers embedded in and bonded by a spaced patterned layer of flexible adhesive to at least one layer of lightweight cellulose wadding and the method of making same are disclosed. Also disclosed is the method and product resulting from laminating two such nonwoven fabrics together wtih the fiber layers facing one another and with the sinusoidal pattern of fibers in the opposing layers out of phase with one another.

This invention relates to an improved process for the manufacture of nonwoven webs and to products obtained thereby. More specifically it relates to a process for forming a bonded nonwoven web from a lamination of highly-drafted fibers and a carrier sheet.

It is known that individual textile fibers may be drawn out and substantially aligned to form a thin web-like layer by passing an array of juxtaposed slivers of staple length fibers through a multiple roll draw frame. The layer of fibers discharged from such a device is flimsy, film-like and gossamer in character, and, to be useful in web form while still retaining its highly-drafted alignment, must be immediately bonded to each other by some means, or supported by and bonded to as supplementary web. Highly-drafted fiber webs have approximately 80% to 95% of the fibers oriented substantially in the longitudinal direction. As disclosed in U.S. Pat. No. 3,327,708, such a high degree of fiber alignment is desirable in that it contributes substantially to improved longitudinal strength properties per unit weight when compared with prior art carded fiber webs in which only about 50% to 70% of the fibers are longitudinally aligned. However, while this high degree of fiber alignment improves the longitudinal strength, the transverse strength of the resulting web is lessened because of the relative paucity of crossing fibers, even though the bonding means may comprise transverse lines of strong adhesive or the like. Ordinarily this problem may be overcome by cross-laying and bonding two such webs together whereby the strength in each direction is equalized as disclosed in copending Saunders et al. application Ser. No. 498,929, filed Oct. 20, 1965 and assigned to the same assignee as the present application. However, known cross-laying methods usually entail either costly or low-speed equipment, adding considerable expense to the cost of the finished product.

The present invention overcomes the latter difficulties and provides a drawn-fiber nonwoven web of high transverse strength without cross-laying.

Accordingly, a primary object of the invention is to provide a process for fabricating a nonwoven web having improved cross-direction strength from a laminate of highly-drafted fibers and an integral carrier sheet.

Another object is to provide a laminated web in which at least one element is an array of highly-drafted and aligned fibers, and a second element comprises a carrier sheet to which the highly-drafted and aligned fibers are bonded in a regular sinusoidal pattern.

An additional object is to provide a laminated web comprised of multiple layers of highly-drafted substantially parallelized fibers arranged in a regular sinusoidal pattern combined with tissue carrier sheets.

Still another object is to provide a method for the economical, high-speed manufacture of webs of the character indicated.

Other objects and advantages will become apparent to persons skilled in the art upon examination of the following description and drawings.

In the drawings:

FIG. 1 is a diagrammatic view in persepective of a device suitable for carrying out one embodiment of the process of this invention.

FIG. 2 illustrates in side elevation a schematic arrangement for folding and further laminating the web produced by the device of FIG. 1.

FIG. 3 is a front elevation of the arrangement shown in FIG. 2.

FIG. 4 is a representation of the appearance of a laminated product fabricated as taught herein, when viewed by transmitted light.

In one embodiment of the invention, as shown in FIG. 1, multiple slivers of textile fibers 11 are drawn from their respective supply cans over a guide comb 13 in juxtaposed relationship into a draw frame 15 comprising a series of paired grooved rolls 14 and 14α. The rolls of each pair are driven by appropriate gearing, well known in the art, at a peripheral speed slightly faster than the rate of operation of the preceding pair to draw out and align the individual fibers from the slivers into substantially parallelized arrangement with the fibers extended to their full length. The drawn fibers are discharged from draw frame 15 in the form of a flat web 16 in substantially aligned arrangement. Web 16 is of such flimsy and gossamer-like character that it must be quickly deposited on a supporting carrier sheet 17 immediately after discharge from draw frame 15 in order to maintain its form. While other types of carrier sheets may be employed for this purpose, in the particular embodiment here shown and described, the carrier sheet 17 comprises a single ply of lightweight cellulose wadding which eventually becomes an integral part of the finished product. Wadding sheet 17 preferably has been stretched and ironed to facial tissue softness by known means to provide a like softness and hand to the finished product. However, for certain products stretching and ironing may not be desirable.

The wadding sheet 17 is drawn from supply roll 21 into a nip formed by a printing roll 22 and a back-up roll 24 maintained in very light pressure engagement with sheet 17. In this case, the surface of printing roll 22 is provided with an intaglio pattern 23 which picks up adhesive 25 from dip pan 26. Excess adhesive is scraped off by doctor blade 27. The adhesive preferably is a low viscosity thermoplastic adhesive which remains substantially on the surface of the wadding in the form of the pattern selected.

The pattern shown on the drawing comprises parallel, discontinuous transverse lines in a brick-like design as shown at 18 merely for illustrative purposes, it being un3,553,064 derstood that the adhesive actually is on the underside of sheet 17 at this point. The printed sheet 17, bearing adhesive 18 on its undersurface, is then drawn around roll 19 positioned adjacent the discharge end of draw frame 15 at which point the adhesive is on the upper surface and the drawn fiber web 16 is deposited thereon. Roll 19, in addition to rotating in the direction shown, is also simultaneously oscillated transversely as indicated by double arrow 12, by known means, such as by a mechanized Scotch yoke or similar device. Because wadding sheet 17 is flexible, the oscillating roll 19 can move the sheet back and forth transversely without tearing the sheet. The drawn fiber web 16 is discharged from the draw frame with the fibers aligned substantially in the direction of discharge. However, when the aligned fibers are deposited on the adhesive printed sheet 17α, the oscillating motion causes the web to take the form of a sinusoidal pattern shown at 10 while the fibers still remain substantially parallel to one another. The adhesive 18 has sufficient tack and viscosity to hold the fibers in alignment in spite of the oscillating movement. As a result, the sinusoidal pattern comprises individual fibers in a substantially parallel wave-like arrangement. While the sinusoidal pattern 10 is shown as parallel continuous lines, this showing is merely figurative. In reality, the web at this stage comprises a multiplicity of individual fibers aligned in side-by-side arrangement in the pattern illustrated by these continuous lines.

The combined sheet 17 and patterned fiber lay 10 is carried around guide roll 28 into prolonged contact with heated drum 20. The heat fuses and cures the adhesive to a substantially nontacky condition while the fibers are in firm contact with the drum surface. To provide this curing effect, travel around a substantial portion of drum 20 as in the manner shown is desirable. The laminated web with the fibers partially embedded in the adhesive then passes under a pressure roll, or calender roll .30, which presses the fiber layer more firmly into the adhesive to assure permanent attachment. The laminated web is subsequently wound up in a roll 29.

The laminated product in roll 29 which comprises a drawn fiber web with the fibers arranged in an aligned sinusoidal pattern and adhesively bonded and laminated to a lightweight cellulose wadding sheet, has a limited number of uses without further processing, especially for uses where cross-direction strength is unimportant. However, a larger number of potential uses are obtained when the resulting sheet is further laminated to develop crossdirection strength.

One means of accomplishing this is shown in FIGS. 2 and 3. As shown in these figures, the laminated sinusoidal pattern material produced in the above-described manner is fed from supply roll 29α around guide roll 31, over a conventional V-shaped folding board or frame 32, between the nip of heated calender rolls 33, bringing the fiber side of the material together in face-to-face contact to form laminated web 34 which is wound up into finished roll 35. The heat and pressure from the calender rolls activates the adhesive causing portions, causing adhesive in one layer to intrude between the fibers in that layer to join the adhesive from the opposing layer whereby the laminated material is bonded together into a unitary web. Selvage edge 36 subsequently may be trimmed off.

While the preferred embodiment of the folded laminated material has the fiber surfaces disposed face-to-face, the material may also have the wadding surfaces face-toface before calendering. However, the resulting product has less transverse strength than the preferred embodiment, probably because less adhesive migrates between layers to form bonds between sheets.

The appearance of the finished web 34, when viewed by transmitted light, is shown in FIG. 4. The arrangement as illustrated might be defined as the overlapping of several parallelly-aligned vibrating strings in which the nodes 37 intersect and are bonded to each other, and the segments 38 and 39 overlie and cross each other at multiple points to form additional bonds. These multiple bonds form a diamond-like arrangement of fibers and adhesive and when force is exerted in a transverse direction provide flexible restraint and resilient cross-direction strength.

While the above-described process provides bonding between the sinusoidal array of drawn fibers and the underlying carrier sheet by means of a thermoplastic adhesive previously applied to the carrier sheet, another means of bonding may be used without materially disturbing the fiber alignment. In the latter case, a number of the slivers introduced into the draw frame may comprise thermoplastic fibers, or preferably, thermoplastic fibers may be mixed into each sliver. A large variety of such man-made fibers are now available including polyethylene, polypropylene, polyesters, polyacrylonitrile, polyvinyls, etc.

In one specific example, slivers were prepared containing 20% polypropylene fibers and 80% rayon fibers. These mixed slivers were run through the draw frame as shown in FIG. 1 and described above. Roll 19 was oscillated as before causing the highly-drafted fiber web emerging from the draw frame to be deposited on the carrier sheet in a uniform sinusoidal pattern of parallellyaligned fibers. No adhesive was applied to the tissue carrier sheet. The fibers, nevertheless, retain the aligned sinusoidal pattern. It is not known why the fibers remain aligned in the wave pattern shown, but apparently, sufficient electrostatic or frictional attraction exists between the carrier sheet and the drawn web to keep the pattern undisturbed. Upon hot calendering, a self-sustaining laminate was obtained. This product was in turn folded and further laminated to provide a nonwoven web with improved cross-directional strength, and having an appearance similar to that shown in FIG. 4. The bonding strength in this instance coming from the thermoplastic nature of some of the fibers.

While a folding arrangement is shown in FIGS. 2 and 3 as the means employed to obtain the laminated product of FIG. 4, it will readily be seen that a similar product may be obtained by taking two rolls of the product obtained from the first stage of the process, and by running the webs together in face-to-face arrangement between rolls of a heated calender stack for bonding purposes. To be effective with respect to cross-direction strength, however, the sinusoidal patterns of the webs before lamination should be arranged with respect to one another so that the sinusoidal pattern in one web is out of phase from the sinusoidal pattern in the other web, to overlap and intersect the aligned fibers of the other web in the manner shown in FIG. 4.

While various well-known adhesives may be employed in the process, advantages reside in the use of plastisols, which, as is well known, comprise 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, adipates, or phosphates. 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, can be reactivated by the application of heat and pressure, such as by hot-calendering for the aforesaid lamination purposes, and insure that the resultant product retains a desirable softness and proper hand and feel.

While plastisols are preferred, polyvinyl resins per se, plasticized or unplasticized may also be used. Other flexible adhesives, which may be employed, although generally less desirable, include materials such as acrylic res3,553;

ins like the alkyl acrylates and butadiene resins such as buna-S and buna-N.

The adhesive pattern shown in the illustrations comprises a spaced brick-like arrangement. Other well-known patterns may be employed, such as spaced continuous _gparallel lines, spaced circles, dots, V’s, herringbones, etc. It is preferred that the pattern be substantially open with large adhesive free areas. If flexibility is desired, it is preferred that the total area occupied by the adhesive comprise not more than 25% of the total area of the original fiber-wadding laminate. No matter what adhesive arrangement is chosen, care should be taken to assure that the adhesive-free area between adjoining adhesive patterns be less in the longitudinal direction of the fibers than the average length of the individual fibers, in order that the in- 15 tegrity of the web is maintained.

The fibers used in the process may comprise most of the staple length fibers employed in textiles. These include both natural and synthetic fibers such as cotton, viscose or acetate rayon, nylon, polyesters, acrylonitriles, 20 polyolefins, and the like. When synthetic fibers are used, a denier range of 0.5 to 3 is preferred. However, coarser denier may be used. It is also preferred that the fibers be of staple length, or in the range of to about 3 inches or longer, with the majority of fibers being at least 25 one inch in length. For most purposes, the drafted web should be as light weight as possible commensurate with handleability on the drawing frame. Suitable webs in the weight range of 3 to 20 grams per square yard have been successfully drafted and bonded at speeds of from 20 30 feet per minute to well over 500 feet per minute. Webs of a higher weight may also be successfully made by this process.

While in the illustrated process, sheet 17 is oscillated transversely by means of oscillating roll 19, it will readily 35 be seen that a sinusoidal pattern may also be obtained by oscillating the entire draw frame 15.

It will be apparent to those skilled in the art that many variations from the examples given may be employed without departing from the spirit of this invention. For 40 example, the weight of the starting slivers may be varied to provide a-drawn web of varying thickness throughout its width. Similarly, various mixtures of thermoplastic and nonthermoplastic fibers may be used.