METHOD AND APPARATUS FOR DEPOSITING HIGHLY DRAFTED FIBER WEBS IN A SINUSOIDAL PATTERN
United States Patent 3616036
An improved method and apparatus for depositing a tenuous web of highly drafted fibers in a sinusoidal pattern on the adhesively printed surface of a carrier sheet are disclosed. The apparatus includes a rotating wave roll with axially spaced peripheral grooves which laterally oscillate the drafted web in a sinusoidal pattern as the roll rotates.
US Patent References:
Manufacture of alpha composite sheet
Collings - October 1932 - 1877270
Textile fabrics and methods of making the same
Barnard - November 1960 - 2958608
Cellulosic product
Bletzinger - November 1963 - 3110609
Method and apparatus for manufacturing compound non-woven textile structures
Romanin - April 1967 - 3314841
METHOD AND APPARATUS FOR PREPARING MULTICONDUCTOR CABLE WITH FLAT CONDUCTORS
Marcell - December 1969 - 3481802
Manufacture of alpha composite sheet
Collings - October 1932 - 1877270
Textile fabrics and methods of making the same
Barnard - November 1960 - 2958608
Cellulosic product
Bletzinger - November 1963 - 3110609
Method and apparatus for manufacturing compound non-woven textile structures
Romanin - April 1967 - 3314841
METHOD AND APPARATUS FOR PREPARING MULTICONDUCTOR CABLE WITH FLAT CONDUCTORS
Marcell - December 1969 - 3481802
Application Number:
04/816943
Publication Date:
10/26/1971
Filing Date:
04/17/1969
View Patent Images:
Export Citation:
Assignee:
Kimberly-Clark Corporation (Neenah, WI)
Primary Class:
Other Classes:
156/440, 156/77
International Classes:
D04H3/05; D04H3/02; B32B31/00; B65H54/06
Field of Search:
156/297,298,299,196,177,300,301,302,303,303.1,440,179 74/56-59 161/178,59
Primary Examiner:
Borchelt, Benjamin A.
Assistant Examiner:
Doramus V, J.
Claims:
I claim as my invention
1. A method for producing a nonwoven material including a web of highly drafted fibers disposed in a sinusoidal pattern comprising the steps of:
2. A method for producing a laminated nonwoven material including cellulose wadding and a web of highly drafted fibers disposed in a sinusoidal pattern comprising the steps of:
3. The method defined in claim 2 including the steps of:
4. An apparatus for forming a nonwoven material including a web of highly drafted fibers disposed in a sinusoidal pattern comprising, in combination:
5. An apparatus as defined in claim 4 wherein said carrier sheet is an endless release coated belt and including means for embedding said fibers in said adhesive and curing said adhesive prior to stripping said adhesive and embedded fiber web from said belt.
6. An apparatus as defined in claim 4 wherein said carrier sheet is a layer of cellulosic wadding and including means for embedding said fibers in said adhesive and curing said adhesive to bond said fiber web to said wadding layer.
7. An apparatus as defined in claim 6 including means for drawing a vacuum on the side of said wadding layer opposite said adhesively printed surface and in an area encompassing the intersection of said fiber web and wadding layer.
8. An apparatus as defined in claim 7 including a second draw frame disposed in vertical alignment with said first draw frame, a second wave roll disposed between said second draw frame and said wadding layer, and means for rotating said second wave roll out of phase with said first wave roll.
9. An apparatus as defined in claim 5 including a second draw frame disposed in vertical alignment with said first draw frame, a second wave roll disposed between said second draw frame and said belt, and means for rotating said second wave roll out of phase with said first wave roll.
10. The method defined in claim 1 including the steps of:
1. A method for producing a nonwoven material including a web of highly drafted fibers disposed in a sinusoidal pattern comprising the steps of:
2. A method for producing a laminated nonwoven material including cellulose wadding and a web of highly drafted fibers disposed in a sinusoidal pattern comprising the steps of:
3. The method defined in claim 2 including the steps of:
4. An apparatus for forming a nonwoven material including a web of highly drafted fibers disposed in a sinusoidal pattern comprising, in combination:
5. An apparatus as defined in claim 4 wherein said carrier sheet is an endless release coated belt and including means for embedding said fibers in said adhesive and curing said adhesive prior to stripping said adhesive and embedded fiber web from said belt.
6. An apparatus as defined in claim 4 wherein said carrier sheet is a layer of cellulosic wadding and including means for embedding said fibers in said adhesive and curing said adhesive to bond said fiber web to said wadding layer.
7. An apparatus as defined in claim 6 including means for drawing a vacuum on the side of said wadding layer opposite said adhesively printed surface and in an area encompassing the intersection of said fiber web and wadding layer.
8. An apparatus as defined in claim 7 including a second draw frame disposed in vertical alignment with said first draw frame, a second wave roll disposed between said second draw frame and said wadding layer, and means for rotating said second wave roll out of phase with said first wave roll.
9. An apparatus as defined in claim 5 including a second draw frame disposed in vertical alignment with said first draw frame, a second wave roll disposed between said second draw frame and said belt, and means for rotating said second wave roll out of phase with said first wave roll.
10. The method defined in claim 1 including the steps of:
Description:
BACKGROUND OF THE INVENTION
In copending application Ser. No. 551,605, now U.S. Pat. No. 3,553,064, filed May 20, l966, 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 pattern layer of adhesive to at least one layer of lightweight cellulose wadding and the method of making same are disclosed. In its preferred form, the method disclosed there involves laterally reciprocating the roll around which the wadding is guided just prior to the deposit of the highly drafted fiber web on the adhesively printed surface of the wadding. Alternatively, it is suggested that the entire draw frame can be laterally oscillated to produce the relative sinusoidal pattern between the drafted fiber web and the layer of cellulose wadding. In either case, however, the oscillating frequency and thus the operational speed of the apparatus are limited due to the weight and other forces imposed on the oscillating components.
SUMMARY OF THE INVENTION
Accordingly, it is the primary aim of the present invention to provide an improved method and apparatus for depositing a tenuous web of highly drafted fibers on the adhesively printed surface of a suitable carrier sheet.
It is a more particular object to provide such an improved method and apparatus which does not necessitate any laterally oscillating parts. Rather, it is a related specific object to oscillate the drafted web in a sinusoidal pattern by passing it partially around a rotating wave roll having a plurality of axially spaced, self-returning grooves in the periphery thereof which laterally shift the web back and forth as the wave roll rotates.
These and other objects and advantages of the invention will become more readily apparent upon reading the following detailed description and upon reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a schematic side elevation of the apparatus of the present invention;
FIG. 2 is an enlarged fragmentary front elevation view of the sinusoidal wave roll;
FIG. 3 is an enlarged fragmentary section taken substantially along line 3--3 in FIG. 2;
FIG. 4 is a projection of one of the grooves in the cylindrical surface of the wave roll shown in FIG. 2; and,
FIG. 5 is an enlarged and somewhat exaggerated plan view of one form of material made according to the method of the present invention with sections of individual layers broken away to show the details of its construction.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In the preferred embodiment of the invention, as shown in FIG. 1, multiple slivers 12 of staple length textile fibers are drawn in juxtaposed relationship into a draw frame 13 comprising a series of paired rolls 14 and 15. The rolls of each pair are driven by appropriate gearing, well known in the art, at a peripheral speed slightly faster than the speed of the preceding roll pair to draw out and align the individual fibers into substantially parallelized arrangement with the fibers extended to their full length. The drawn fibers are discharged from the draw frame 13 in the form of a flat, tenuous web 16.
As the web 16 is discharged from the draw frame 13 it is of such flimsy and gossamerlike character that it must be quickly deposited on a supporting carrier sheet 17 in order to maintain the substantially parallelized and fully extended condition of the fibers. In the particular embodiment here shown and described, the carrier sheet 17 comprises a continuous sheet of lightweight cellulose wadding which eventually becomes an integral part of the finished product. The 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 such stretching and ironing may not be necessary or even desirable.
The wadding sheet 17 is drawn from a supply roll 18 and over the surface of an adhesive printer indicated generally at 20. The adhesive printer includes an offset print roll 21 maintained in light pressure engagement with the wadding sheet 17. In this case, the surface of the offset roll 21 is provided with a spaced pattern of adhesive from an intaglio pattern on the surface of a print roll 22 which picks up adhesive from a dip pan 23. Excess adhesive is scraped off the print roll 22 by a doctor blade 24. The adhesive is preferably a low viscosity thermoplastic adhesive which remains substantially on the surface of the wadding sheet 17 in the form of a layer 25 of the spaced pattern selected. In the present instance the adhesive pattern is in the form of an open diamond configuration as is more readily apparent upon reference to FIG. 5. The printed sheet 17, bearing adhesive 25 on its surface, is then drawn around guide roll 26 and moves upwardly along a path which intersects the discharge path of the web 16 from the draw frame 13.
In accordance with the present invention, the fiber web 16 passes partially around a rotatable wave roll 30 disposed between the draw frame 13 and the upwardly inclined sheet 17. As shown in greater detail in FIGS. 2 and 3 the wave roll 30 is provided with a plurality of axially spaced, self-returning grooves 31, each of which, in cylindrical projection, define a sinusoidal pattern (see FIG. 4). Suitable means (not shown) are also provided for rotating the wave roll and as it rotates, the grooves 31 impart a laterally oscillating sinusoidal movement to the web 16. To prevent wrap-up of the fibers on the wave roll and also to enhance the lateral force imparted to the web 16 by the grooves 31, the wave roll is preferably rotated with a differential surface speed relative to the discharge of the web 16 from the draw frame 13. Since the web 16 is the only thing that is shifted from side to side, it will be appreciated that the oscillating inertial forces are very low. Consequently, even very tenuous webs of highly drafted fibers can be rapidly oscillated in a sinusoidal pattern in order to achieve a very high operating speed.
From the wave roll 30, the web 16 is deposited directly upon the adhesively printed surface of the wadding sheet 17. As the web 16 is deposited on the sheet 17 it is important to maintain the fibers under tension at all times after drafting and during oscillation. The tension maintains frictional engagement between adjacent fibers so that the fibers are retained in their highly drafted and aligned form, whereby they remain substantially fully extended and parallel to each other.
In order to insure that tension is maintained in the drafted fiber web 16 during the transfer to the sheet 17, the sheet must, of course, travel at a speed slightly faster than the discharge speed of the web 16 from the draw frame 13. Also the rotating wave roll 30 serves not only to laterally oscillate the web 16, but also acts to hold the fibers in the web continuously under tension. As the drawn fiber web 16 is discharged from the draw frame 13 the fibers are aligned substantially in the direction of discharge. However, when the aligned fibers are deposited on the adhesive printed sheet 17, the oscillating motion imparted by the wave roll 30 causes the web to take the form of a sinusoidal pattern while the fibers still remain substantially parallel to one another.
The adhesive 25 has sufficient tack and viscosity to hold the fibers in alignment in spite of the oscillating movement of the web 16. As a result, the sinusoidal pattern comprises individual fibers in a substantially parallel wavelike arrangement. While the sinusoidal pattern is shown in FIG. 5 as parallel continuous lines, this showing is merely figurative. In reality, the web comprises a multiplicity of individual fibers aligned in side-by-side arrangement in the pattern illustrated by these continuous lines.
To facilitate the preliminary embedment of the fibers in the adhesive 25 printed on the wadding sheet 17, suction is drawn on the side of the sheet 17 opposite the adhesive 25. In the illustrated apparatus, the suction is drawn from a suction box 35 which is provided with a perforated surface 36 inclined upwardly and forwardly with respect to the discharge path of the web 16 from the draw frame 13 at an acute angle. It will be further noted that due to the relative movement of the wadding sheet 17 and fiber web 16 the effective angle of disposition of the web on the sheet is quite small. While the angular disposition of the web 16 to the sheet 17 is shown as 15° in the drawings, it will be understood that this angularity may be varied to suit the best running conditions of the apparatus.
From the suction box 35, the combined fiber web 16 and wadding sheet 17 are carried around guide rolls 38 and 39 and into prolonged contact with a heated drum 40. 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 40 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 41, which presses the fiber layer more firmly into the adhesive to assure permanent attachment. The laminated web is subsequently wound up in a takeup roll 42.
The laminated product 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 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 a second fiber web 16a is laminated to the sheet 17 to develop cross direction strength.
One means of accomplishing this and as is shown in FIG. 1, is to employ a second draw frame 13a, the operation of which is similar to that of the first draw frame 13. After discharge from draw frame 13a, a second highly drafted fiber web 16a passes under a wave roll 30a and is deposited on the wadding sheet 17. The second draw frame 13a is located directly above and slightly forward of the first draw frame 13 and the arrangement of the second draw frame 13a with respect to the sheet 17 and vacuum box 35 is similar to the arrangement of the first draw frame 13. In adjusting the apparatus care should be taken to see that the wave roll 30a cooperating with the upper draw frame 13a is disposed sufficiently high above the previously deposited drawn web 16 so that it does not touch the previously deposited web 16 or interfere with its fiber alignment.
To provide additional cross-directional strength to the laminated material, the second fiber web 16a is preferably oscillated in a sinusoidal pattern by wave roll 30a out of phase with the sinusoidal oscillation of web 16 by wave roll 30. This causes the fibers of the second web 16a to be deposited on top of the fibers of the first web 16 with the fibers of the respective webs crossing one another. After lamination, this is the product shown in FIG. 5 and it will be appreciated that the crossing sinusoidal patterns of fibers in the webs 16 and 16a impart added cross-directional strength to the resulting material.
If desired a top sheet 17a of cellulose wadding can also be brought in over the drawn webs 16 and 16a. For this purpose a second supply roll 18a is provided. The underside of the second wadding sheet 17a may also be printed with a spaced pattern of adhesive with an adhesive printer 20a similar to the adhesive printer 20 for the carrier sheet 17.
In the foregoing description the adhesively printed carrier sheet 17 becomes part of the final laminated web. However, this may not always be necessary or desirable. Thus, the sheet 17 could be replaced with a release coated carrier belt. When such a belt is treated with a release agent and used merely as a carrier for the adhesive, the bonded fiber web is subsequently stripped from the belt and the finished web comprises only the adhesive binder and fibers. It is to be understood, of course, that prior to passing around roll 16 the belt has printed on its release coated surface a pattern of adhesive to which the fibers of the webs 16 and 16a adhere as they are deposited in their respective sinusoidal patterns.
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.
Although 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 resins like the alkyl acrylates and butadiene resins such as buna-S and buna-N.
The adhesive pattern shown in the illustrations comprises an open diamond arrangement. Other well-known patterns may be employed, such as spaced continuous parallel lines, spaced circles, dots, V's, herringbones, etc. It is preferred, however, 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 percent of the total area of the original fiber-wadding laminate. No matter what adhesive arrangement is chosen, care should be taken to assure that that 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 integrity of the web is maintained.
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 silver. A large variety of such man-made fibers are now available including polyethylene, polypropylene, polyesters, polyacrylonitrile, polyvinyls, etc.
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, 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 one-half to about 3 inches or longer, with the majority of fibers being at least 1 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 feet per minute to well over 500 feet per minute. Webs of a higher weight may also be successfully made by this process.
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 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. Other suitable changes, modifications, and variations may also be made without departing from the scope of the invention.
In copending application Ser. No. 551,605, now U.S. Pat. No. 3,553,064, filed May 20, l966, 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 pattern layer of adhesive to at least one layer of lightweight cellulose wadding and the method of making same are disclosed. In its preferred form, the method disclosed there involves laterally reciprocating the roll around which the wadding is guided just prior to the deposit of the highly drafted fiber web on the adhesively printed surface of the wadding. Alternatively, it is suggested that the entire draw frame can be laterally oscillated to produce the relative sinusoidal pattern between the drafted fiber web and the layer of cellulose wadding. In either case, however, the oscillating frequency and thus the operational speed of the apparatus are limited due to the weight and other forces imposed on the oscillating components.
SUMMARY OF THE INVENTION
Accordingly, it is the primary aim of the present invention to provide an improved method and apparatus for depositing a tenuous web of highly drafted fibers on the adhesively printed surface of a suitable carrier sheet.
It is a more particular object to provide such an improved method and apparatus which does not necessitate any laterally oscillating parts. Rather, it is a related specific object to oscillate the drafted web in a sinusoidal pattern by passing it partially around a rotating wave roll having a plurality of axially spaced, self-returning grooves in the periphery thereof which laterally shift the web back and forth as the wave roll rotates.
These and other objects and advantages of the invention will become more readily apparent upon reading the following detailed description and upon reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a schematic side elevation of the apparatus of the present invention;
FIG. 2 is an enlarged fragmentary front elevation view of the sinusoidal wave roll;
FIG. 3 is an enlarged fragmentary section taken substantially along line 3--3 in FIG. 2;
FIG. 4 is a projection of one of the grooves in the cylindrical surface of the wave roll shown in FIG. 2; and,
FIG. 5 is an enlarged and somewhat exaggerated plan view of one form of material made according to the method of the present invention with sections of individual layers broken away to show the details of its construction.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In the preferred embodiment of the invention, as shown in FIG. 1, multiple slivers 12 of staple length textile fibers are drawn in juxtaposed relationship into a draw frame 13 comprising a series of paired rolls 14 and 15. The rolls of each pair are driven by appropriate gearing, well known in the art, at a peripheral speed slightly faster than the speed of the preceding roll pair to draw out and align the individual fibers into substantially parallelized arrangement with the fibers extended to their full length. The drawn fibers are discharged from the draw frame 13 in the form of a flat, tenuous web 16.
As the web 16 is discharged from the draw frame 13 it is of such flimsy and gossamerlike character that it must be quickly deposited on a supporting carrier sheet 17 in order to maintain the substantially parallelized and fully extended condition of the fibers. In the particular embodiment here shown and described, the carrier sheet 17 comprises a continuous sheet of lightweight cellulose wadding which eventually becomes an integral part of the finished product. The 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 such stretching and ironing may not be necessary or even desirable.
The wadding sheet 17 is drawn from a supply roll 18 and over the surface of an adhesive printer indicated generally at 20. The adhesive printer includes an offset print roll 21 maintained in light pressure engagement with the wadding sheet 17. In this case, the surface of the offset roll 21 is provided with a spaced pattern of adhesive from an intaglio pattern on the surface of a print roll 22 which picks up adhesive from a dip pan 23. Excess adhesive is scraped off the print roll 22 by a doctor blade 24. The adhesive is preferably a low viscosity thermoplastic adhesive which remains substantially on the surface of the wadding sheet 17 in the form of a layer 25 of the spaced pattern selected. In the present instance the adhesive pattern is in the form of an open diamond configuration as is more readily apparent upon reference to FIG. 5. The printed sheet 17, bearing adhesive 25 on its surface, is then drawn around guide roll 26 and moves upwardly along a path which intersects the discharge path of the web 16 from the draw frame 13.
In accordance with the present invention, the fiber web 16 passes partially around a rotatable wave roll 30 disposed between the draw frame 13 and the upwardly inclined sheet 17. As shown in greater detail in FIGS. 2 and 3 the wave roll 30 is provided with a plurality of axially spaced, self-returning grooves 31, each of which, in cylindrical projection, define a sinusoidal pattern (see FIG. 4). Suitable means (not shown) are also provided for rotating the wave roll and as it rotates, the grooves 31 impart a laterally oscillating sinusoidal movement to the web 16. To prevent wrap-up of the fibers on the wave roll and also to enhance the lateral force imparted to the web 16 by the grooves 31, the wave roll is preferably rotated with a differential surface speed relative to the discharge of the web 16 from the draw frame 13. Since the web 16 is the only thing that is shifted from side to side, it will be appreciated that the oscillating inertial forces are very low. Consequently, even very tenuous webs of highly drafted fibers can be rapidly oscillated in a sinusoidal pattern in order to achieve a very high operating speed.
From the wave roll 30, the web 16 is deposited directly upon the adhesively printed surface of the wadding sheet 17. As the web 16 is deposited on the sheet 17 it is important to maintain the fibers under tension at all times after drafting and during oscillation. The tension maintains frictional engagement between adjacent fibers so that the fibers are retained in their highly drafted and aligned form, whereby they remain substantially fully extended and parallel to each other.
In order to insure that tension is maintained in the drafted fiber web 16 during the transfer to the sheet 17, the sheet must, of course, travel at a speed slightly faster than the discharge speed of the web 16 from the draw frame 13. Also the rotating wave roll 30 serves not only to laterally oscillate the web 16, but also acts to hold the fibers in the web continuously under tension. As the drawn fiber web 16 is discharged from the draw frame 13 the fibers are aligned substantially in the direction of discharge. However, when the aligned fibers are deposited on the adhesive printed sheet 17, the oscillating motion imparted by the wave roll 30 causes the web to take the form of a sinusoidal pattern while the fibers still remain substantially parallel to one another.
The adhesive 25 has sufficient tack and viscosity to hold the fibers in alignment in spite of the oscillating movement of the web 16. As a result, the sinusoidal pattern comprises individual fibers in a substantially parallel wavelike arrangement. While the sinusoidal pattern is shown in FIG. 5 as parallel continuous lines, this showing is merely figurative. In reality, the web comprises a multiplicity of individual fibers aligned in side-by-side arrangement in the pattern illustrated by these continuous lines.
To facilitate the preliminary embedment of the fibers in the adhesive 25 printed on the wadding sheet 17, suction is drawn on the side of the sheet 17 opposite the adhesive 25. In the illustrated apparatus, the suction is drawn from a suction box 35 which is provided with a perforated surface 36 inclined upwardly and forwardly with respect to the discharge path of the web 16 from the draw frame 13 at an acute angle. It will be further noted that due to the relative movement of the wadding sheet 17 and fiber web 16 the effective angle of disposition of the web on the sheet is quite small. While the angular disposition of the web 16 to the sheet 17 is shown as 15° in the drawings, it will be understood that this angularity may be varied to suit the best running conditions of the apparatus.
From the suction box 35, the combined fiber web 16 and wadding sheet 17 are carried around guide rolls 38 and 39 and into prolonged contact with a heated drum 40. 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 40 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 41, which presses the fiber layer more firmly into the adhesive to assure permanent attachment. The laminated web is subsequently wound up in a takeup roll 42.
The laminated product 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 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 a second fiber web 16a is laminated to the sheet 17 to develop cross direction strength.
One means of accomplishing this and as is shown in FIG. 1, is to employ a second draw frame 13a, the operation of which is similar to that of the first draw frame 13. After discharge from draw frame 13a, a second highly drafted fiber web 16a passes under a wave roll 30a and is deposited on the wadding sheet 17. The second draw frame 13a is located directly above and slightly forward of the first draw frame 13 and the arrangement of the second draw frame 13a with respect to the sheet 17 and vacuum box 35 is similar to the arrangement of the first draw frame 13. In adjusting the apparatus care should be taken to see that the wave roll 30a cooperating with the upper draw frame 13a is disposed sufficiently high above the previously deposited drawn web 16 so that it does not touch the previously deposited web 16 or interfere with its fiber alignment.
To provide additional cross-directional strength to the laminated material, the second fiber web 16a is preferably oscillated in a sinusoidal pattern by wave roll 30a out of phase with the sinusoidal oscillation of web 16 by wave roll 30. This causes the fibers of the second web 16a to be deposited on top of the fibers of the first web 16 with the fibers of the respective webs crossing one another. After lamination, this is the product shown in FIG. 5 and it will be appreciated that the crossing sinusoidal patterns of fibers in the webs 16 and 16a impart added cross-directional strength to the resulting material.
If desired a top sheet 17a of cellulose wadding can also be brought in over the drawn webs 16 and 16a. For this purpose a second supply roll 18a is provided. The underside of the second wadding sheet 17a may also be printed with a spaced pattern of adhesive with an adhesive printer 20a similar to the adhesive printer 20 for the carrier sheet 17.
In the foregoing description the adhesively printed carrier sheet 17 becomes part of the final laminated web. However, this may not always be necessary or desirable. Thus, the sheet 17 could be replaced with a release coated carrier belt. When such a belt is treated with a release agent and used merely as a carrier for the adhesive, the bonded fiber web is subsequently stripped from the belt and the finished web comprises only the adhesive binder and fibers. It is to be understood, of course, that prior to passing around roll 16 the belt has printed on its release coated surface a pattern of adhesive to which the fibers of the webs 16 and 16a adhere as they are deposited in their respective sinusoidal patterns.
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.
Although 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 resins like the alkyl acrylates and butadiene resins such as buna-S and buna-N.
The adhesive pattern shown in the illustrations comprises an open diamond arrangement. Other well-known patterns may be employed, such as spaced continuous parallel lines, spaced circles, dots, V's, herringbones, etc. It is preferred, however, 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 percent of the total area of the original fiber-wadding laminate. No matter what adhesive arrangement is chosen, care should be taken to assure that that 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 integrity of the web is maintained.
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 silver. A large variety of such man-made fibers are now available including polyethylene, polypropylene, polyesters, polyacrylonitrile, polyvinyls, etc.
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, 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 one-half to about 3 inches or longer, with the majority of fibers being at least 1 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 feet per minute to well over 500 feet per minute. Webs of a higher weight may also be successfully made by this process.
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 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. Other suitable changes, modifications, and variations may also be made without departing from the scope of the invention.