Title:
HIGH BULK CORRUGATED NONWOVEN FABRIC
United States Patent 3668054
Abstract:
A tough, high bulk, flexible fabric is provided which has a grainy wrinkled texture with a multiplicity of transversely discontinuous furrows and ridges. The fabric is somewhat elastic, especially in the machine direction, and comprises a corrugated web of initially alined textile fibers implanted in a continuous thin film of thermoplastic adhesive, the fiber-adhesive web thereafter being corrugated into a multitude of furrows and grooves with irregularly root- and side-connected convolutions. The fabric is produced by implanting the fibers into the thermoplastic adhesive film, adhering the resulting web onto an abherent heated surface, and advancing the surface against a gathering blade to corrugate the web and form irregularly root- and side-connected sinusoidal convolutions.
US Patent References:
Method of treating webs and product resulting therefrom
Cohn et al. - February 1966 - 3236718
Treatment of sheet materials
Walton - November 1965 - 3220056
Fibrous structural material and method and apparatus for making same
Goldman - September 1946 - 2407548
Method of treating webs and product resulting therefrom
Cohn et al. - February 1966 - 3236718
Treatment of sheet materials
Walton - November 1965 - 3220056
Fibrous structural material and method and apparatus for making same
Goldman - September 1946 - 2407548
Application Number:
05/024197
Publication Date:
06/06/1972
Filing Date:
03/31/1970
View Patent Images:
Export Citation:
Assignee:
Kimberly-Clark Corporation (Neenah, WI)
Primary Class:
Other Classes:
442/149, 156/183, 428/359, 428/473
International Classes:
D04H11/04; D04H11/00; D04H3/00; D04H1/00
Field of Search:
161/128,129,132,133,134,135 156/183,205,206,207,210
Primary Examiner:
Burnett, Robert F.
Assistant Examiner:
Linker Jr., Raymond O.
Claims:
1. A tough, high-bulk, flexible fabric having a grainy wrinkled texture with a multiplicity of transversely discontinuous furrows and ridges, said fabric being somewhat elastic especially in the machine direction, said fabric comprising:
2. A fabric as defined in claim 1 wherein said fabric has been creped to
3. Fabric of claim 1 wherein said textile fibers are fibers of staple
4. Fabric of claim 1 wherein said textile fibers are synthetic plastic
5. Fabric of claim 1 wherein said thermoplastic adhesive is a plastisol.
2. A fabric as defined in claim 1 wherein said fabric has been creped to
3. Fabric of claim 1 wherein said textile fibers are fibers of staple
4. Fabric of claim 1 wherein said textile fibers are synthetic plastic
5. Fabric of claim 1 wherein said thermoplastic adhesive is a plastisol.
Description:
CROSS-REFERENCE TO RELATED APPLICATIONS
Robert J. Stumpf, U.S. application, Ser. Nos. 498,929 filed Oct. 20, 1965, now abandoned, 553,483 now U.S. Pat. No. 3,553,065, 769,959, filed Oct. 23, 1968, now abandoned.
DESCRIPTION OF THE INVENTION
This invention relates to a high bulk corrugated nonwoven fabric, and in particular concerns the fabric and a method of making the same.
A primary object of the present invention is to provide a high bulk, flexible, fabric having a grainy wrinkled texture, the fabric being somewhat elastic especially in the machine direction. The fabric has a grainy wrinkled texture somewhat reminiscent of animal skin, and somewhat resembles a tough creped rubber in appearance but not in weight.
A further object is to provide a high bulk flexible fabric from nonwoven textile material, which fabric offers desirable properties from the standpoint of durability, appearance, and high bulk rendering it useful in such applications as sound-absorbing disposable draperies, wall coverings, thermal insulation, wearing apparel,and the like.
Another object is to provide a method of making such material in a simple, convenient, and highly advantageous manner.
Other and further aims, advantages, and objects of the invention will become apparent as the description thereof proceeds, which description is to be taken with reference to the attached drawings in which:
FIG. 1 is a schematic side elevation of one form of apparatus which may be employed to practice the method of the present invention;
FIG. 2 is a fragmentary plan view of an illustrative web of the novel fabric, somewhat simplified and exaggerated for the sake of clarity of illustration;
FIGS. 3 and 4, respectively, are greatly enlarged, simplified, and somewhat exaggerated sections taken along the longitudinal lines 3-3 and the transverse lines 4--4 in FIG. 2;
FIG. 5 is an enlarged schematic detail in side elevation of the forming drum and gathering blade of the apparatus shown in FIG. 1;
FIG. 6 is a further enlarged schematic side elevation illustrating in somewhat idealized fashion the sequence of corrugating the fiber-adhesive web into a multitude of irregularly root- and side-connected sinusoidal convolutions;
FIG. 7 is an alternative fabric of the present invention in which the corrugated web is creped to form a substantially thicker fabric product; and
FIG. 8 is a greatly enlarged, simplified, and somewhat exaggerated section taken along the longitudinal lines 8--8 in FIG. 7.
Broadly stated, the fabric of the invention is a tough, high bulk, flexible material having a grainy wrinkled texture with a multiplicity of transversely discontinuous furrows and ridges. The fabric is somewhat elastic relative to conventional woven fabrics, and is especially elastic in the machine direction. The fabric itself comprises a corrugated web of initially alined textile fibers implanted in a continuous thin film of a thermoplastic adhesive having an essentially constant thickness. The resulting web-adhesive material is then corrugated to provide the multitude of furrows and grooves, which are irregularly connected near their roots and along their respective sides.
To manufacture the inventive fabric, a web of alined textile fibers is implanted into a continuous thin film of thermoplastic adhesive; the resulting web is adhered onto an abherent surface heated sufficiently to maintain the adhesive in a tacky state; the surface is advanced against a relatively moving gathering blade to loft or corrugate the web into the desired convolutions; and the corrugated web is withdrawn as a bulked fabric.
Various parameters, to be discussed further below, may be chosen to alter the nature and characteristics of the product. Thus, selection of fibers and adhesive, weight and denier of the fibers, thickness (or weight per unit area) of the adhesive, and the like may be chosen with a view toward regulating the properties of the fabric. Additionally, processing conditions such as gathering blade angle with respect to the advancing web-containing surface, corrugated web withdrawal conditions (take-away ratio), and the like permit further alteration of the fabric.
In practicing the method of the present invention in its preferred form, a base web of textile fibers is first prepared and implanted into a continuous thin film of a thermoplastic adhesive.
Different procedures may be used in preparing the base web. For example, textile length, or staple, 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 percent of the fibers may be oriented substantially parallel with the machine direction. It has been found, however, that a product having superior characteristics has been obtained with the method of the present invention by using base webs having a higher percentage of the fibers alined with the machine direction, such as a highly drafted web in which, as a result of the drafting, 80 to 95 percent or more of the fibers are alined with the machine direction.
A variety of different textile fibers, fiber lengths, and fiber deniers are suitable for the present invention. The fibers may be natural or synthetic, and either staple or monofilament, or various blends thereof. Among the suitable fibers are included rayon, polyesters such as polyethylene terephthalate, the acrylics and modacrylics, and the olefins such as polypropylene. If desired, a blend of fibers may be used.
While various known adhesives may be employed, it should be recognized that the particular adhesive selected is dependent upon the characteristics of the textile fibers and the desired end use of the fabric. The adhesive should be thermoplastic, and should soften at temperatures which will not degrade the particular fibrous material being used. In addition, the adhesive should also be applicable to the base web by procedures which will not disarrange the fibrous structure of the web, be reactivatable by reheating in the subsequent adhesive gathering and partial consolidation stage of the process, and form a flexible, generally continuous, film in which the fabric web is secured by partial or complete embedding and adhesive attraction.
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. Those found particularly useful for incorporation in the product of the present 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 may be reactivated by subsequent heating.
It has been found that other adhesive systems may be employed in particular circumstances, such as the organisols utilizing resins such as the vinyl chloride polymers and copolymers. Other adhesives may be employed provided they satisfy the indicated characteristics in the base web forming stage and meet the product requirements of the final fabric. For example, emulsions of thermoplastic resins such as acrylics and rubber-like compounds illustrated by acrylonitrile-butadiene-styrene usually have the requisite properties to serve as the bonding adhesive for the web.
Turning now to the drawings, FIG. 1 schematically illustrates the apparatus for performing the method of the present invention in its preferred form. This apparatus includes a web-forming section 10 and an adhesive-compacting and web-corrugating section 30.
As shown in FIG. 1, multiple slivers 11 of textile fibers are drawn from their respective supply cans (not shown) into a draw frame 12. The fibers may either be staple length or monofilament, and illustratively have a denier ranging from about 1.0 to about 15, although lighter or heavier fibers may be used as determined by the desired characteristics of the final fabric. In the case of staple fibers, the draw frame 12 comprises a series of pairs of grooved rolls 13, the rolls of each pair being driven by appropriate gearing at a peripheral rate of speed slightly faster than the rate of the preceding pair. As the juxtaposed slivers pass through the draw frame 12, the individual fibers are drafted and spread out to form a flat striated web of substantially alined fibers as shown at 14. The web 14 is fed onto a supporting surface 15, the top of which contains a uniform thin film of a thermoplastic adhesive.
In the depicted embodiment, the conveyor surface 15 comprises an endless conveyor belt treated on at least its outer surface with a release agent. One example of such a belt comprises a woven glass fiber with an abherent surface coating of polytetrafluoroethylene resin. Other 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, which either are inherently abherent or else are treated with release agents, may also be used as the carrier or conveyor surface.
Prior to the time the web 14 is picked up by the belt 15, the latter has been coated on its web-contacting surface with a flexible thermoplastic adhesive in a thin film of substantially uniform thickness. Film thickness may be controlled as one of the variables of the process in order to regulate the relative weight ratio of fiber web to thermoplastic adhesive. Ordinarily, the optimum ratio is in the range of about 0.2:1 to about 20:1 in terms of weight of adhesive per unit weight of fiber, but these may be varied within or outside the foregoing limits to regulate the texture of the fabric. It is understood that the adhesive is actually on the underside of the belt 15, which becomes the upper surface after passing around the roll 17 whereby the adhesive 16 directly contacts the fiber web 14.
The belt or conveyor surface 15 is fed around the roll 17 at a speed slightly in excess of the delivery speed of the final pair of rolls 13 in order to maintain the web 14 under slight tension. Thus, the individual highly drafted fibers constituting the web are retained in their alined and tensioned condition. Drive rolls 18, 19 for the conveyor surface 15 are rotated to drive the belt or conveyor surface 15 at a speed sufficient to maintain the proper tension on the web 14.
In the method shown for applying adhesive to the belt or conveyor surface 15, the belt is fed through a nip formed between a printing roll 20 and a back-up roll 21 maintained in very light pressure engagement with each other. The surface of the printing roll 20 is smooth, and as the roll surface rotates adhesive 22 is pumped, from a tank not shown, to a reservoir defined in part by the roll 20 and an inclined doctor blade 24 spaced slightly away from the roll surface. Thus, as the printing roll 20 rotates (in a counterclockwise direction as viewed in FIG. 1), the roll surface is coated with adhesive 22, excess adhesive is removed by the doctor blade 24, and a metered amount of adhesive is then transferred to the underside of the release coated belt 16. The blade 24 may be a wire-wrapped rod of the type commonly used in paint and other surface coating application, so that the thickness and spacing of the wires regulates the amount of adhesive remaining on the roll 20 after it passes the doctor blade 24.
Since the surface of the belt or conveyor surface 15 is treated with a release coating, the adhesive remains substantially on the surface with no penetration to the interior. The adhesive is applied as a cold viscous (3,500-4,000 c.p.s.) material, and is usually in a somewhat tacky condition before it is cured on the roll 19.
The printed belt is drawn from the printing nip around the roll 17 positioned closely adjacent the output end of the draw frame 12, and, as stated above, travels at a speed slightly in excess of the delivery speed of the last pair of rolls in the draw frame. The fiber web emerging from the draw frame 12 is thereupon deposited onto the tacky adhesive 16 on the conveyor surface or belt 15, and is held in a tensioned engagement by the adhesive and by the above-mentioned speed differential. This continuous tension prevents the fibers in the web from losing their highly drafted and alined condition.
Under optimum practice, the fiber web 14 will have the individual fibers positioned side-by-side with no spaces between fibers. In practice however, this optimum is difficult or impossible to achieve. Accordingly, there inevitably are areas of the web 14 which, on a microscopic scale, have no fibers present and others where the web is several fibers thick. Neither condition is entirely disadvantageous to practicing the invention, and in fact there is sufficient versatility in both the present product and process such that fiber webs with, on the one hand, wide spacing between individual fibers or, on the other, webs of many fibers thick, may be accommodated. In the latter case, it is desirable that a relatively fluid adhesive be selected so that substantially all of the fibers are implanted or embedded in the adhesive layer. It is not essential that all fibers be entirely coated with adhesive, as excellent fabric products have been made which exhibit a glossy top surface characteristic of fibers which have no adhesive coating on their respective top portions.
Following deposition of the web component 14 on the adhesive printed belt or conveyor surface 15, the belt is drawn around a heated drum 29 where fusing and any necessary curing of the adhesive is substantially completed while the web 14 is maintained in firm contact with the adhesive 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 heated drum 29. In the illustrated embodiment, a fly roll 29a is disposed to provide wrap for the combined belt and web as they travel around the drum 29 to insure, so far as possible, complete embedment or at least substantial implantation of the fibers in the adhesive. The fibers of the web 14 are thus bonded together while retaining their highly drafted and substantially alined condition in which they were deposited on the adhesive printed on the conveyor surface or belt 15.
After leaving the fly roll 29a, the combined web 14 and surface or belt 15 are preferably passed over a drive roll 19 which also serves as a cooling drum. This chills the adhesive, thereby causing it to set and lose its tackiness. The bonded web 14 is then stripped from the release coated surface of the belt by the guide roll 31 as the web leaves the cooling drum 19.
At this stage of the process, the web 14 is composed of a web of alined textile fibers implanted in a continuous thin film of hardened thermoplastic adhesive, with both the adhesive and the complete fabric-adhesive web having an essentially constant thickness. In this condition, the web 14 is then fed into an adhesive compacting or consolidating and fiber corrugating section 30 of the apparatus shown in FIG. 1. As portrayed, the web 14 continues directly from the web-forming section 10 to the section 30. It should be appreciated, however, that the web 14 discharged from the section 10 may be rolled up for storage or transport and then subsequently unrolled and fed into the section 30. Also, if desired various other processing treatments may be employed before the web is admitted into the section 30, such as for example printing, dyeing, or the like.
The web 14 while still under tension is fed around an idler roll 32 and onto the surface of a heated forming drum 37. The forming drum 37 is maintained at a temperature which will soften the adhesive to a tacky state so that it adheres to the drum surface. Either the entire drum or the cylindrical surface of the drum 37 is made of an abherent material, or one which has an abherent coating. In its preferred embodiment, the drum 37 is made of a highly polished chromium plated surface which is internally heated. As in the case of the drum 29, the drum 37 is desirably positioned to permit the web 14 to travel a substantial distance around the drum 37, that is, have a relatively high degree of wrap, so as to provide adequate residence and heating time.
As the web 14 is fed onto the drum 37, heat from the drum surface reactivates and re-softens the adhesive on the underside of the web 14, causing it to become tacky. The web accordingly adheres slightly to the drum surface, thereby maintaining the web under constant tension.
In keeping with the invention, the drum 37 surface is moved relative to a gathering blade to corrugate the web into a multitude of irregularly root- and side-connected sinusoidal convolutions. This is accomplished by re-forming the fiber-adhesive web 14 by the cooperative action of the heated drum 37 and a gathering blade 38, parallel to the axis of the drum 37, and having a flat edge 39 (FIG. 5). The blade edge 39 corrugates the web into the desired sinusoidal convolutions and brings adjacent roots, and occasionally adjacent side portions of the convolutions, into contact whereby the adhesive secures the contacting portions together. The thus-corrugated web 14, identified as a fabric 40, then leaves the blade edge 39 onto a flat take-off surface 41 (FIG. 5) and a discharge conveyor 42 (FIG. 1).
Turning now to FIGS. 5 and 6, the method of corrugating the fiber-adhesive web 14 into the desired connected convolutions will be explained in greater detail in connection with an illustrative sequence of the corrugating operation.
Referring to FIG. 6, the series of views in this Figure illustrates how the web is formed into convolutions. As the heated drum carries the fiber-adhesive web 14 against the gathering blade edge 39, increments of the web 14 abut against the edge. At this stage, pressure is being applied to the gathering blade 38 in a direction radially inward of the drum 37 so that essentially all of the adhesive is being scraped from the abherent surface of the drum.
As rotation of the drum 37 continues, successive increments of the web 14 are being brought against the edge 39. These increments are unable to pass beyond the edge 39, and accordingly begin to bunch up, as shown at A in the second view of FIG. 6. While rotation of the drum 37 continues further, the bunching up of the web 14 increment continues, with A gradually forming an open loop P. The loop increases in size as the drum 37 rotates further, but for reasons which are not clear there appears to be a rather definite size of loop P which can form before loop growth terminates and the formation of a new loop begins.
One of the major variables in determining loop size, and consequent fabric thickness, is the angle alpha (FIG. 5) formed between the blade edge 39 and a line T tangent to the surface of the drum 37 at the point of blade contact. The optimum blade angle is generally best determined empirically, depending upon the desired fabric thickness and the interrelationship among fiber stiffness, type and thickness of adhesive, and temperature of the drum 37. Usually alpha angles of from about 20° to 120° may be employed, but the optimum range narrows depending upon the various factors discussed. For most applications, an initial alpha angle of between about 50° to 74° should be selected, and the angle varied to provide the required fabric thickness. Usually, so long as the alpha angle is less than about 90°, fabric thicknesses within the range of about one sixty-fourth-inch to nearly three-eighth-inch may be produced.
Returning to FIG. 6, as the loops P form, the adhesive is in a somewhat tacky condition. As a result, the roots of the respective loops, that is, those areas near the original bunching A of the web, come in contact with each other and are adhesively joined. This joining is usually not continuous over the entire width of the drum 37, and indeed appears to be quite irregular, but since the corrugated fabric is usually stretched immediately after leaving the area of the edge 39, irregular contact at the respective roots is not only permissible but is actually desired.
Further, the sides of the adjacent loops P are likewise in contact with each other during part of the loop-forming steps. To the extent that adhesive has penetrated to the outside of the respective loops P, these outside surfaces also are irregularly connected to each other at randomly spaced intervals. The combination of non-regular adhesive connection at the roots of the successive loops P and along the sides of adjacent loops permits the fabric product, after slight stretching, to exhibit its creped-rubber or animal-like skin appearance, as well as adding to the strength and durability of the fabric.
In the final (right) view in FIG. 6, the loops are irregularly interconnected at their roots and sides. Defining, in cross-section, a series of sinusoidal convolutions (FIG. 3), these loops contribute a light-weight, high bulk, fabric product. By reason of the random nature of the loop-forming steps depicted in FIG. 6, the furrows and ridges on the creped web product 40 are irregular and discontinuous along a direction transverse to the machine direction of the apparatus. The resulting furrows and ridges provide the grainy wrinkled texture illustrated in FIG. 2, and in this regard attention is invited to FIG. 4 illustrating the randomness of an individual sinusoidal wrinkle.
An additional variable in the process of the invention is the speed at which the corrugated web 40 is withdrawn, or taken away, from the edge 39. With the blade 38 having an edge alpha angle within the preferred range, and assuming the take-away surface 41 (FIG. 5) is cooled to substantially an ambient temperature, the optimal ratio of the surface speed of the heating drum 37 to the take-away speed should be maintained in the range of from about 5:1 to about 10:1, with a ratio of about 7 to 8:1 being preferred. By decreasing the ratio, or in other words by increasing the fabric take-away speed, a more open final product is obtained, where the loops or convolutions P tend to be pulled apart. At extremely low ratios, or in other words at take-away speeds approaching the peripheral speed of the drum 37, a point is ultimately reached at which no gathering at the edge 39, and consequent loop formation, occurs.
On the other hand, by increasing the take-away ratio, that is, by slowing down the fabric take-away speed, an interesting effect is produced that is illustrated by the products depicted in FIGS. 7 and 8. Here the corrugated fabric 40 has actually been permitted to crepe by establishing corrugations of the already convoluted and corrugated web.
The slowly withdrawn product of FIGS. 7 and 8 has exceptionally high bulk, and is usually from three to four times the thickness of an uncreped product as depicted in FIG. 2. Thus, merely by utilizing a slow withdrawal rate, as opposed to a rapid one, a fabric is obtained which is sufficiently thick to serve as a protective packaging medium.
Returning to FIG. 1, the corrugated web 40 is withdrawn from the blade edge 39, advantageously immediately after corrugation has been effected. The fabric exit end of the conveyor 42 may be provided with a roll 44 to form a nip, and with a pair of rolls 45 forming a second nip. Drawing is accomplished by driving the rolls 45 at a higher speed in order to open up the corrugations somewhat. If desired, the take-away surface 41 may likewise have an abherent surface to prevent or minimize adhesion of the still hot and tacky adhesive. Further, the belt of the conveyor 52 is desirably cooled, again to minimize adherence, by streams of chilled air blown against the underside of the belt from a suitably placed air nozzle 54. Preliminary heating or cooling of the conveyor may be effected by a nozzle 43 immediately adjacent the blade edge 39.
The invention will be illustrated further in conjunction with specific embodiments directed to the illustrative preparation of high bulk fabrics according to the invention.
EXAMPLE I
In this EXAMPLE, a high bulk uncreped product as depicted in FIG. 2 is prepared.
The apparatus of FIG. 1 is employed. Rayon 40, in the form of three inch staple at 1.5 denier is used as the textile fiber, while the adhesive is a polyvinyl chloride plastisol. Plastisol is formulated from about 100 parts by weight of Geon 135 polyvinyl chloride resin (B.F. Goodrich, Akron, Ohio), about 60 parts of GP-261 dioctyl phthalate plasticizer (Goodrich), about 2.5 parts of Cab-O-Sil pyrogenic silica (Cabot Corp., Boston, Mass.), and sufficient mineral spirits to bring the viscosity into the desired range (generally from about 3 to 5 percent by weight based on total weight of other components) to achieve a viscosity, by Brookfield viscometer with a No. 4 spindle at 20 rpm. of about 3,800 c.p.s.
The weight of the base fiber web alone was about 5-6 grams per square yard, that of the adhesive alone being about 75-74 grams per square yard.
The adhesive curing and preheat drum 29 in the first stage of forming the web was maintained at about 300° F. and operated at a surface speed of 65 feet per minute. The base web 14 was thus carried to the heating drum 37 at a surface speed of 65 feet per minute. The roll 37 temperature was about 250° F.
The gathering blade 38 was positioned at an angle of 34° and maintained against the heating drum 37 with a pressure of about 28 psi. The drum, nine inches in diameter, was internally heated and maintained at a temperature of about 250° F. The take-away ratio, that is, surface speed around the drum divided by take-away speed in consistent units, was about 7-1/2.
Adhesive was applied to the rotogravure roll 20 with a No. 60 Meyer rod at the end of the doctor blade 24.
The resulting product had a final weight of about 600 grams per yard and was about one-sixteenth-inch-thick. It exhibited a pleasing drape, was slightly porous, and displayed some resiliency in the transverse direction and more in the machine direction.
EXAMPLE II
In this EXAMPLE, using the apparatus of EXAMPLE I, a creped product as depicted in FIGS. 7 and 8 was made. The resulting material had an animal-skin like texture and was an ideal material for women's purses.
All process conditions were as set forth in EXAMPLE I, except that the original adhesive weight was 73 grams per square yard, the original fiber weight was 7 grams per square yard, and the take-away ratio was roughly 15 so as to re-gather the product. The finished material weighed 1,204 grams per square yard.
Thus it is apparent that there has been provided, according to the invention, an exceptional product and method which fully satisfy the objects set forth earlier. While the invention has been described in conjunction with specific embodiments, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in view of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.
Robert J. Stumpf, U.S. application, Ser. Nos. 498,929 filed Oct. 20, 1965, now abandoned, 553,483 now U.S. Pat. No. 3,553,065, 769,959, filed Oct. 23, 1968, now abandoned.
DESCRIPTION OF THE INVENTION
This invention relates to a high bulk corrugated nonwoven fabric, and in particular concerns the fabric and a method of making the same.
A primary object of the present invention is to provide a high bulk, flexible, fabric having a grainy wrinkled texture, the fabric being somewhat elastic especially in the machine direction. The fabric has a grainy wrinkled texture somewhat reminiscent of animal skin, and somewhat resembles a tough creped rubber in appearance but not in weight.
A further object is to provide a high bulk flexible fabric from nonwoven textile material, which fabric offers desirable properties from the standpoint of durability, appearance, and high bulk rendering it useful in such applications as sound-absorbing disposable draperies, wall coverings, thermal insulation, wearing apparel,and the like.
Another object is to provide a method of making such material in a simple, convenient, and highly advantageous manner.
Other and further aims, advantages, and objects of the invention will become apparent as the description thereof proceeds, which description is to be taken with reference to the attached drawings in which:
FIG. 1 is a schematic side elevation of one form of apparatus which may be employed to practice the method of the present invention;
FIG. 2 is a fragmentary plan view of an illustrative web of the novel fabric, somewhat simplified and exaggerated for the sake of clarity of illustration;
FIGS. 3 and 4, respectively, are greatly enlarged, simplified, and somewhat exaggerated sections taken along the longitudinal lines 3-3 and the transverse lines 4--4 in FIG. 2;
FIG. 5 is an enlarged schematic detail in side elevation of the forming drum and gathering blade of the apparatus shown in FIG. 1;
FIG. 6 is a further enlarged schematic side elevation illustrating in somewhat idealized fashion the sequence of corrugating the fiber-adhesive web into a multitude of irregularly root- and side-connected sinusoidal convolutions;
FIG. 7 is an alternative fabric of the present invention in which the corrugated web is creped to form a substantially thicker fabric product; and
FIG. 8 is a greatly enlarged, simplified, and somewhat exaggerated section taken along the longitudinal lines 8--8 in FIG. 7.
Broadly stated, the fabric of the invention is a tough, high bulk, flexible material having a grainy wrinkled texture with a multiplicity of transversely discontinuous furrows and ridges. The fabric is somewhat elastic relative to conventional woven fabrics, and is especially elastic in the machine direction. The fabric itself comprises a corrugated web of initially alined textile fibers implanted in a continuous thin film of a thermoplastic adhesive having an essentially constant thickness. The resulting web-adhesive material is then corrugated to provide the multitude of furrows and grooves, which are irregularly connected near their roots and along their respective sides.
To manufacture the inventive fabric, a web of alined textile fibers is implanted into a continuous thin film of thermoplastic adhesive; the resulting web is adhered onto an abherent surface heated sufficiently to maintain the adhesive in a tacky state; the surface is advanced against a relatively moving gathering blade to loft or corrugate the web into the desired convolutions; and the corrugated web is withdrawn as a bulked fabric.
Various parameters, to be discussed further below, may be chosen to alter the nature and characteristics of the product. Thus, selection of fibers and adhesive, weight and denier of the fibers, thickness (or weight per unit area) of the adhesive, and the like may be chosen with a view toward regulating the properties of the fabric. Additionally, processing conditions such as gathering blade angle with respect to the advancing web-containing surface, corrugated web withdrawal conditions (take-away ratio), and the like permit further alteration of the fabric.
In practicing the method of the present invention in its preferred form, a base web of textile fibers is first prepared and implanted into a continuous thin film of a thermoplastic adhesive.
Different procedures may be used in preparing the base web. For example, textile length, or staple, 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 percent of the fibers may be oriented substantially parallel with the machine direction. It has been found, however, that a product having superior characteristics has been obtained with the method of the present invention by using base webs having a higher percentage of the fibers alined with the machine direction, such as a highly drafted web in which, as a result of the drafting, 80 to 95 percent or more of the fibers are alined with the machine direction.
A variety of different textile fibers, fiber lengths, and fiber deniers are suitable for the present invention. The fibers may be natural or synthetic, and either staple or monofilament, or various blends thereof. Among the suitable fibers are included rayon, polyesters such as polyethylene terephthalate, the acrylics and modacrylics, and the olefins such as polypropylene. If desired, a blend of fibers may be used.
While various known adhesives may be employed, it should be recognized that the particular adhesive selected is dependent upon the characteristics of the textile fibers and the desired end use of the fabric. The adhesive should be thermoplastic, and should soften at temperatures which will not degrade the particular fibrous material being used. In addition, the adhesive should also be applicable to the base web by procedures which will not disarrange the fibrous structure of the web, be reactivatable by reheating in the subsequent adhesive gathering and partial consolidation stage of the process, and form a flexible, generally continuous, film in which the fabric web is secured by partial or complete embedding and adhesive attraction.
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. Those found particularly useful for incorporation in the product of the present 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 may be reactivated by subsequent heating.
It has been found that other adhesive systems may be employed in particular circumstances, such as the organisols utilizing resins such as the vinyl chloride polymers and copolymers. Other adhesives may be employed provided they satisfy the indicated characteristics in the base web forming stage and meet the product requirements of the final fabric. For example, emulsions of thermoplastic resins such as acrylics and rubber-like compounds illustrated by acrylonitrile-butadiene-styrene usually have the requisite properties to serve as the bonding adhesive for the web.
Turning now to the drawings, FIG. 1 schematically illustrates the apparatus for performing the method of the present invention in its preferred form. This apparatus includes a web-forming section 10 and an adhesive-compacting and web-corrugating section 30.
As shown in FIG. 1, multiple slivers 11 of textile fibers are drawn from their respective supply cans (not shown) into a draw frame 12. The fibers may either be staple length or monofilament, and illustratively have a denier ranging from about 1.0 to about 15, although lighter or heavier fibers may be used as determined by the desired characteristics of the final fabric. In the case of staple fibers, the draw frame 12 comprises a series of pairs of grooved rolls 13, the rolls of each pair being driven by appropriate gearing at a peripheral rate of speed slightly faster than the rate of the preceding pair. As the juxtaposed slivers pass through the draw frame 12, the individual fibers are drafted and spread out to form a flat striated web of substantially alined fibers as shown at 14. The web 14 is fed onto a supporting surface 15, the top of which contains a uniform thin film of a thermoplastic adhesive.
In the depicted embodiment, the conveyor surface 15 comprises an endless conveyor belt treated on at least its outer surface with a release agent. One example of such a belt comprises a woven glass fiber with an abherent surface coating of polytetrafluoroethylene resin. Other 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, which either are inherently abherent or else are treated with release agents, may also be used as the carrier or conveyor surface.
Prior to the time the web 14 is picked up by the belt 15, the latter has been coated on its web-contacting surface with a flexible thermoplastic adhesive in a thin film of substantially uniform thickness. Film thickness may be controlled as one of the variables of the process in order to regulate the relative weight ratio of fiber web to thermoplastic adhesive. Ordinarily, the optimum ratio is in the range of about 0.2:1 to about 20:1 in terms of weight of adhesive per unit weight of fiber, but these may be varied within or outside the foregoing limits to regulate the texture of the fabric. It is understood that the adhesive is actually on the underside of the belt 15, which becomes the upper surface after passing around the roll 17 whereby the adhesive 16 directly contacts the fiber web 14.
The belt or conveyor surface 15 is fed around the roll 17 at a speed slightly in excess of the delivery speed of the final pair of rolls 13 in order to maintain the web 14 under slight tension. Thus, the individual highly drafted fibers constituting the web are retained in their alined and tensioned condition. Drive rolls 18, 19 for the conveyor surface 15 are rotated to drive the belt or conveyor surface 15 at a speed sufficient to maintain the proper tension on the web 14.
In the method shown for applying adhesive to the belt or conveyor surface 15, the belt is fed through a nip formed between a printing roll 20 and a back-up roll 21 maintained in very light pressure engagement with each other. The surface of the printing roll 20 is smooth, and as the roll surface rotates adhesive 22 is pumped, from a tank not shown, to a reservoir defined in part by the roll 20 and an inclined doctor blade 24 spaced slightly away from the roll surface. Thus, as the printing roll 20 rotates (in a counterclockwise direction as viewed in FIG. 1), the roll surface is coated with adhesive 22, excess adhesive is removed by the doctor blade 24, and a metered amount of adhesive is then transferred to the underside of the release coated belt 16. The blade 24 may be a wire-wrapped rod of the type commonly used in paint and other surface coating application, so that the thickness and spacing of the wires regulates the amount of adhesive remaining on the roll 20 after it passes the doctor blade 24.
Since the surface of the belt or conveyor surface 15 is treated with a release coating, the adhesive remains substantially on the surface with no penetration to the interior. The adhesive is applied as a cold viscous (3,500-4,000 c.p.s.) material, and is usually in a somewhat tacky condition before it is cured on the roll 19.
The printed belt is drawn from the printing nip around the roll 17 positioned closely adjacent the output end of the draw frame 12, and, as stated above, travels at a speed slightly in excess of the delivery speed of the last pair of rolls in the draw frame. The fiber web emerging from the draw frame 12 is thereupon deposited onto the tacky adhesive 16 on the conveyor surface or belt 15, and is held in a tensioned engagement by the adhesive and by the above-mentioned speed differential. This continuous tension prevents the fibers in the web from losing their highly drafted and alined condition.
Under optimum practice, the fiber web 14 will have the individual fibers positioned side-by-side with no spaces between fibers. In practice however, this optimum is difficult or impossible to achieve. Accordingly, there inevitably are areas of the web 14 which, on a microscopic scale, have no fibers present and others where the web is several fibers thick. Neither condition is entirely disadvantageous to practicing the invention, and in fact there is sufficient versatility in both the present product and process such that fiber webs with, on the one hand, wide spacing between individual fibers or, on the other, webs of many fibers thick, may be accommodated. In the latter case, it is desirable that a relatively fluid adhesive be selected so that substantially all of the fibers are implanted or embedded in the adhesive layer. It is not essential that all fibers be entirely coated with adhesive, as excellent fabric products have been made which exhibit a glossy top surface characteristic of fibers which have no adhesive coating on their respective top portions.
Following deposition of the web component 14 on the adhesive printed belt or conveyor surface 15, the belt is drawn around a heated drum 29 where fusing and any necessary curing of the adhesive is substantially completed while the web 14 is maintained in firm contact with the adhesive 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 heated drum 29. In the illustrated embodiment, a fly roll 29a is disposed to provide wrap for the combined belt and web as they travel around the drum 29 to insure, so far as possible, complete embedment or at least substantial implantation of the fibers in the adhesive. The fibers of the web 14 are thus bonded together while retaining their highly drafted and substantially alined condition in which they were deposited on the adhesive printed on the conveyor surface or belt 15.
After leaving the fly roll 29a, the combined web 14 and surface or belt 15 are preferably passed over a drive roll 19 which also serves as a cooling drum. This chills the adhesive, thereby causing it to set and lose its tackiness. The bonded web 14 is then stripped from the release coated surface of the belt by the guide roll 31 as the web leaves the cooling drum 19.
At this stage of the process, the web 14 is composed of a web of alined textile fibers implanted in a continuous thin film of hardened thermoplastic adhesive, with both the adhesive and the complete fabric-adhesive web having an essentially constant thickness. In this condition, the web 14 is then fed into an adhesive compacting or consolidating and fiber corrugating section 30 of the apparatus shown in FIG. 1. As portrayed, the web 14 continues directly from the web-forming section 10 to the section 30. It should be appreciated, however, that the web 14 discharged from the section 10 may be rolled up for storage or transport and then subsequently unrolled and fed into the section 30. Also, if desired various other processing treatments may be employed before the web is admitted into the section 30, such as for example printing, dyeing, or the like.
The web 14 while still under tension is fed around an idler roll 32 and onto the surface of a heated forming drum 37. The forming drum 37 is maintained at a temperature which will soften the adhesive to a tacky state so that it adheres to the drum surface. Either the entire drum or the cylindrical surface of the drum 37 is made of an abherent material, or one which has an abherent coating. In its preferred embodiment, the drum 37 is made of a highly polished chromium plated surface which is internally heated. As in the case of the drum 29, the drum 37 is desirably positioned to permit the web 14 to travel a substantial distance around the drum 37, that is, have a relatively high degree of wrap, so as to provide adequate residence and heating time.
As the web 14 is fed onto the drum 37, heat from the drum surface reactivates and re-softens the adhesive on the underside of the web 14, causing it to become tacky. The web accordingly adheres slightly to the drum surface, thereby maintaining the web under constant tension.
In keeping with the invention, the drum 37 surface is moved relative to a gathering blade to corrugate the web into a multitude of irregularly root- and side-connected sinusoidal convolutions. This is accomplished by re-forming the fiber-adhesive web 14 by the cooperative action of the heated drum 37 and a gathering blade 38, parallel to the axis of the drum 37, and having a flat edge 39 (FIG. 5). The blade edge 39 corrugates the web into the desired sinusoidal convolutions and brings adjacent roots, and occasionally adjacent side portions of the convolutions, into contact whereby the adhesive secures the contacting portions together. The thus-corrugated web 14, identified as a fabric 40, then leaves the blade edge 39 onto a flat take-off surface 41 (FIG. 5) and a discharge conveyor 42 (FIG. 1).
Turning now to FIGS. 5 and 6, the method of corrugating the fiber-adhesive web 14 into the desired connected convolutions will be explained in greater detail in connection with an illustrative sequence of the corrugating operation.
Referring to FIG. 6, the series of views in this Figure illustrates how the web is formed into convolutions. As the heated drum carries the fiber-adhesive web 14 against the gathering blade edge 39, increments of the web 14 abut against the edge. At this stage, pressure is being applied to the gathering blade 38 in a direction radially inward of the drum 37 so that essentially all of the adhesive is being scraped from the abherent surface of the drum.
As rotation of the drum 37 continues, successive increments of the web 14 are being brought against the edge 39. These increments are unable to pass beyond the edge 39, and accordingly begin to bunch up, as shown at A in the second view of FIG. 6. While rotation of the drum 37 continues further, the bunching up of the web 14 increment continues, with A gradually forming an open loop P. The loop increases in size as the drum 37 rotates further, but for reasons which are not clear there appears to be a rather definite size of loop P which can form before loop growth terminates and the formation of a new loop begins.
One of the major variables in determining loop size, and consequent fabric thickness, is the angle alpha (FIG. 5) formed between the blade edge 39 and a line T tangent to the surface of the drum 37 at the point of blade contact. The optimum blade angle is generally best determined empirically, depending upon the desired fabric thickness and the interrelationship among fiber stiffness, type and thickness of adhesive, and temperature of the drum 37. Usually alpha angles of from about 20° to 120° may be employed, but the optimum range narrows depending upon the various factors discussed. For most applications, an initial alpha angle of between about 50° to 74° should be selected, and the angle varied to provide the required fabric thickness. Usually, so long as the alpha angle is less than about 90°, fabric thicknesses within the range of about one sixty-fourth-inch to nearly three-eighth-inch may be produced.
Returning to FIG. 6, as the loops P form, the adhesive is in a somewhat tacky condition. As a result, the roots of the respective loops, that is, those areas near the original bunching A of the web, come in contact with each other and are adhesively joined. This joining is usually not continuous over the entire width of the drum 37, and indeed appears to be quite irregular, but since the corrugated fabric is usually stretched immediately after leaving the area of the edge 39, irregular contact at the respective roots is not only permissible but is actually desired.
Further, the sides of the adjacent loops P are likewise in contact with each other during part of the loop-forming steps. To the extent that adhesive has penetrated to the outside of the respective loops P, these outside surfaces also are irregularly connected to each other at randomly spaced intervals. The combination of non-regular adhesive connection at the roots of the successive loops P and along the sides of adjacent loops permits the fabric product, after slight stretching, to exhibit its creped-rubber or animal-like skin appearance, as well as adding to the strength and durability of the fabric.
In the final (right) view in FIG. 6, the loops are irregularly interconnected at their roots and sides. Defining, in cross-section, a series of sinusoidal convolutions (FIG. 3), these loops contribute a light-weight, high bulk, fabric product. By reason of the random nature of the loop-forming steps depicted in FIG. 6, the furrows and ridges on the creped web product 40 are irregular and discontinuous along a direction transverse to the machine direction of the apparatus. The resulting furrows and ridges provide the grainy wrinkled texture illustrated in FIG. 2, and in this regard attention is invited to FIG. 4 illustrating the randomness of an individual sinusoidal wrinkle.
An additional variable in the process of the invention is the speed at which the corrugated web 40 is withdrawn, or taken away, from the edge 39. With the blade 38 having an edge alpha angle within the preferred range, and assuming the take-away surface 41 (FIG. 5) is cooled to substantially an ambient temperature, the optimal ratio of the surface speed of the heating drum 37 to the take-away speed should be maintained in the range of from about 5:1 to about 10:1, with a ratio of about 7 to 8:1 being preferred. By decreasing the ratio, or in other words by increasing the fabric take-away speed, a more open final product is obtained, where the loops or convolutions P tend to be pulled apart. At extremely low ratios, or in other words at take-away speeds approaching the peripheral speed of the drum 37, a point is ultimately reached at which no gathering at the edge 39, and consequent loop formation, occurs.
On the other hand, by increasing the take-away ratio, that is, by slowing down the fabric take-away speed, an interesting effect is produced that is illustrated by the products depicted in FIGS. 7 and 8. Here the corrugated fabric 40 has actually been permitted to crepe by establishing corrugations of the already convoluted and corrugated web.
The slowly withdrawn product of FIGS. 7 and 8 has exceptionally high bulk, and is usually from three to four times the thickness of an uncreped product as depicted in FIG. 2. Thus, merely by utilizing a slow withdrawal rate, as opposed to a rapid one, a fabric is obtained which is sufficiently thick to serve as a protective packaging medium.
Returning to FIG. 1, the corrugated web 40 is withdrawn from the blade edge 39, advantageously immediately after corrugation has been effected. The fabric exit end of the conveyor 42 may be provided with a roll 44 to form a nip, and with a pair of rolls 45 forming a second nip. Drawing is accomplished by driving the rolls 45 at a higher speed in order to open up the corrugations somewhat. If desired, the take-away surface 41 may likewise have an abherent surface to prevent or minimize adhesion of the still hot and tacky adhesive. Further, the belt of the conveyor 52 is desirably cooled, again to minimize adherence, by streams of chilled air blown against the underside of the belt from a suitably placed air nozzle 54. Preliminary heating or cooling of the conveyor may be effected by a nozzle 43 immediately adjacent the blade edge 39.
The invention will be illustrated further in conjunction with specific embodiments directed to the illustrative preparation of high bulk fabrics according to the invention.
EXAMPLE I
In this EXAMPLE, a high bulk uncreped product as depicted in FIG. 2 is prepared.
The apparatus of FIG. 1 is employed. Rayon 40, in the form of three inch staple at 1.5 denier is used as the textile fiber, while the adhesive is a polyvinyl chloride plastisol. Plastisol is formulated from about 100 parts by weight of Geon 135 polyvinyl chloride resin (B.F. Goodrich, Akron, Ohio), about 60 parts of GP-261 dioctyl phthalate plasticizer (Goodrich), about 2.5 parts of Cab-O-Sil pyrogenic silica (Cabot Corp., Boston, Mass.), and sufficient mineral spirits to bring the viscosity into the desired range (generally from about 3 to 5 percent by weight based on total weight of other components) to achieve a viscosity, by Brookfield viscometer with a No. 4 spindle at 20 rpm. of about 3,800 c.p.s.
The weight of the base fiber web alone was about 5-6 grams per square yard, that of the adhesive alone being about 75-74 grams per square yard.
The adhesive curing and preheat drum 29 in the first stage of forming the web was maintained at about 300° F. and operated at a surface speed of 65 feet per minute. The base web 14 was thus carried to the heating drum 37 at a surface speed of 65 feet per minute. The roll 37 temperature was about 250° F.
The gathering blade 38 was positioned at an angle of 34° and maintained against the heating drum 37 with a pressure of about 28 psi. The drum, nine inches in diameter, was internally heated and maintained at a temperature of about 250° F. The take-away ratio, that is, surface speed around the drum divided by take-away speed in consistent units, was about 7-1/2.
Adhesive was applied to the rotogravure roll 20 with a No. 60 Meyer rod at the end of the doctor blade 24.
The resulting product had a final weight of about 600 grams per yard and was about one-sixteenth-inch-thick. It exhibited a pleasing drape, was slightly porous, and displayed some resiliency in the transverse direction and more in the machine direction.
EXAMPLE II
In this EXAMPLE, using the apparatus of EXAMPLE I, a creped product as depicted in FIGS. 7 and 8 was made. The resulting material had an animal-skin like texture and was an ideal material for women's purses.
All process conditions were as set forth in EXAMPLE I, except that the original adhesive weight was 73 grams per square yard, the original fiber weight was 7 grams per square yard, and the take-away ratio was roughly 15 so as to re-gather the product. The finished material weighed 1,204 grams per square yard.
Thus it is apparent that there has been provided, according to the invention, an exceptional product and method which fully satisfy the objects set forth earlier. While the invention has been described in conjunction with specific embodiments, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in view of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.