US3009822A

US3009822A - Nonwoven fabrics and methods of manufacturing the same

Info

Publication number: US3009822A
Authority: US
Inventors: Arthur H Drelich; Hector W Griswold
Original assignee: Chicopee Manufacturing Corp
Current assignee: Chicopee Manufacturing Corp
Priority date: 1958-01-28
Filing date: 1958-01-28
Publication date: 1961-11-21
Anticipated expiration: 1978-11-21
Also published as: GB885006A; NL235419A; DE1410252A1

Description

N0V 21, 1961 A. H. DRELJCH ETAL .3,009,822

NONWOVEN FABRICS AND METHODS OF MANUFACTURING THE SAME #Filed Jan. 2a. 1958 l 2 Sheets-Sheet 1 :farm

ATTORN EY Nov. 21, 1961 A. H. DRELICH ETAL 3,009,822

NONWOVEN FABRICS AND METHODS OF MANUFACTURING THE SAME Filed Jan. 28. 1958 2 Sheets-Sheet 2 Man: 77' Kuda',-

ATTORNEY United States Patent O 3,009,822 NONWOVE'N FABRICS AND METHODS 0F MANUFACTURING THE SAME Arthur H. Drelich, Plainfield, and Hector W. Griswold,

Princeton, NJ., assignors to Chicopee Manufacturing Corporation, a corporation of Massachusetts Filed Jan. 28, 1958, Ser. No. 711,580

11 Claims. (Cl. 117-38) The present invention relates to textile fabrics and to their methods of manufacture. More particularly, the present invention is concerned with the so-called nonwoven textile fabrics, i.e., fabrics produced from textile bers without the use of conventional spinning, weaving, knitting or felting operations. Although not limited thereto, the invent-ion is of primary importance in connection with oriented or carded nonwoven fabrics composed of textile bers, the major proportion of which are oriented predominantly in one direction. Typical of such fabrics are the so-called Masslinn nonwoven fabrics, some of which are described in greater particularity in U.S. Patents 2,705,687 and 2,705,688, issued April 5, 1955, to De Witt R. Petterson et al. and I. S. Ness et al., respectively. Another aspect of the present invent-ion is its application to nonwoven fabrics wherein the bers are disposed at random and are not predominantly oriented in any one direction. Typical nonwoven fabrics made by such procedures are described, for example, in U.S. Patents 2,676,363 and 2,676,364, issued April 27, 1954, to C. H. Plummer et al. Still another aspect of the present invention is its application to nonwoven fabrics wherein the bers were originally predominantly oriented in one direction but have been reorganized and rearranged in predetermined designs and patterns of openings and ber bundles. Typical of such latter fabrcis are the so-called Keybak bundled nonwoven fabrics, some of which are described in particularity in pending patent application Serial Number 503,871, filed April 26, 1955.

The conventional base starting material for nonwoven fabrics is a fibrous web comprising any of the common textile-length bers, or mixtures thereof, the bers varying in average length from approximately one-half inch to about two and one-half inches. Exemplary of such bers are the natural bers such as cotton and wool and the synthetic cellulosic bers, notably rayon or regenerated cellulose. To these textile length bers may be added, at an appropriate time during the processing, a minority by weight of bers having an average length of less than about one-half inch and down to about one-quarter inch. These bers, or mixtures thereof, vif they are of textile length, are customarily processed through any suitable textile machinery (e.g., a conventional cotton card or other fibrous web producing apparatus) to form a web or sheet of loosely associated bers, weighing from about 100 grains to about 2000 grains per square yard or even higher. This essentially two-dimensional web or sheet of bers is produced continuously with the bers generally predominantly oriented in the machine direction, i.e., the direction in which the web is formed and is moved continuously from the sheet-forming machine. In such a web, the degree of orientation, or the ratio of oriented to nonoriented bers in the machine direction, may be described for purposes of simplicity as varying roughly from about 60% to about 90%, that is to say that from about 60% to about 90% by weight ofthe bers are substantially oriented or aligned more or less in the machine direction and from about to about 40% by weight of the bers are non-oriented in the machine direction and lie in overlapping, intersecting relationship.

As mentioned above, the principles of the present invention may also be extended to non-oriented brous non- 3,009,822 Patented Nov. 2l, 1961 ICC shorter bers ranging in average length of from ,about 1/2A inch down to about 1A inch, and may even include wood pulp and cotton linters.

The resulting brous web or sheet, regardless of its method of production, is then subjected to at least one of several types of bonding operations to anchor the `individual bers together to form a self-sustaining web. One method is to impregnate the web over its entire surface area with Various wel-known bonding agents, such as natural or synthetic resins. Such over-all impregnation produces a non-woven fabric of good `longitudinal and cross strength, acceptable durability and washability, and satisfactory abrasion resistance. However, the nonwoven fabric tends to be stiff and boardlike, possessing more of the properties and characteristics of paper or board than those of a woven or knitted textile fabric. Consequently, although such over-all impregnated nonwoven fabrics are satisfactory for many uses, they are still basically unsatisfactory as general purpose textile fabrics.

Another well-known bonding method is to print the nonwoven webs with intermittent or cont-inuous straight or wavy lines or areas of binder extending generally transversely or diagonally across the web and additionally, if desired, along the web. The resulting nonwoven fabric, as exemplied by a product disclosed in the Goldman Patent 2,039,312 and sold under the trademark Masslinn, is far more satisfactory as a textile fabric than over-all irnpregnated webs in that the softness, drape, and hand of the resulting nonwoven fabric nearly approach those of a woven textile fabric.

The printing of the binder on these nonwoven webs is usually in the form of relatively narrow lines, elongated rectangular, triangular or square areas, or annular or circular binder areas which are spaced apart a distance which, at its maximum, is preferably slightly less than the average ber lengt-h of the bers constituting the web. This is based on the theory that the individual bers of the web should be bound together in as few places as possible and preferably only at two places, such as one bond near each end of the ber. -It has been believed that such bonding would increase the strength of the nonwoven fabric but retain substantially complete freedom of movement for the individual bers whereby the desirable softness, drape and hand are obtained. This spacing of the binder lines has been `accepted by the industry and it has been deemed necessarily so if the stiff and board-like appearance, drape and hand of the over-all impregnated nonwoven fabrics are to be avoided.

The nonwoven fabrics bonded with such line and area binder patterns have had the desired softness, drape and hand and 4have not been undesirably stiff or board-like. However, such nonwoven fabrics have also possessed some disadvantages. For example, although their longitudinal strength has been satisfactory, ltheir cross strength has not been completely satisfactory, Furthermore, the nonwoven fabrics have not been suiciently durable or washable and have not possessed surfcient abrasion resistance. As a consequence, they have been relegated to those uses and applications where launderability, for example, is not a prerequisite. Their utility has therefore been limited to single use disposable products such as sanitary napkin covers, surgical dressings, casket liners, table napkins, hand towels, diapers, curtains, drapery fabrics, shoe cloths, cleaning and polishing rags, and the like.

vIt has been discovered that, although the free distance between the bonded areas of the fibers is still a critical -factor in the bonding of nonwoven fabrics, this free distance need not necessarily be as much as slightly less than the iber length of the fibers constituting the web. As a matter of fact, it has been discovered that, if this free distance between the bonded areas of the fibers is reduced to but a small fraction of the fiber length, while still retaining substantially unbonded portions between the bonded areas, all the desired properties of durability, washability and abrasion resistance are created in the nonwoven fabric while retaining the textilelike softness, hand and drape. Additionally, such has surprisingly led to an increase in the cross strength of the nonwoven fabric without a corresponding loss in the longitudinal strength, and, in fact, occasionally with a slight gain in longitudinal strength.

For the average nonwoven card web of textile or other tibers having average fiber lengths of from about onequarter of an inch to about two and one-half inches for natural fibers, such as cotton and wool, and from onequarter of an inch up to about five inches for artificial bers, such as rayon or regenerated cellulose, there may be as many as from about 8 to about 30 lines of binder areas per inch of nonwoven web, and preferably from about 8 to about 24 lines of binder area per inch of nonwoven web, as measured in the direction of the long axis of the nonwoven fabric. The number of lines of binder areas used in a particular case, however, will depend to a great extent upon the length and type of the fiber used in the nonwoven fabric. The number of lines should be great enough so that substantially all the individual fibers in the nonwoven web will be bonded with as many as from about 5 to about 100 binder areas along their lengths. Within the more commercial aspects of the present inventive concept, however, from about 6 to about 30 binder areas per liber has been found preferable.

The widths of these binder areas (as measured in the machine direction) will depend upon many factors, such as, for example, the properties desired in the ultimate product, the number of binder areas per inch of nonwoven web, the thickness and weight of the nonwoven web, the length andother characteristics of the fibers in the web, and so forth. Widths of binder lines of from about 0.006 inch to about 0.050 inch have been found acceptable, with the preferred range being from about 0.010 inch to about 0.040 inch.

It is not essential that these lines of binder areas be straight, nor that they be continuous. They may be curved, wavy or sinuous and they may be disco-ntinuous. When they are discontinuous, the individual segments thereof should not be separated to such an extent as to weaken the fabric. It has been established that gaps in these lines of binder areas of from about 0.006 inch to about 0.050 inch, and preferably from about 0.020 inch to about 0.040 inch do not create any material loss in strength characteristics. These gaps should be staggered or offset from each other as shown in FIGURES 2 and 4.

The lines of binder areas may extend directly across the width of the nonwoven web at right angles or 90 to the long axis of the web, as shown in FIGURE 2. This, however, is not necessarily so, and the angle of 90 may be changed and decreased to as low as about 30 to the long axis of the web. In the case of nonwoven fabrics wherein the fibers are not oriented, the angle of the elongated lines of binder areas may be reduced to as low as-0, at which time the binder lines will be parallel to the direction of the long axis of the web.

The particular type of binder used in printing the nonwoven web is important and must be of the nonmigratory type. Such a binder, under the printing conditions used, will not migrate or spread more than about 40% of the original width of the applicator print pattern and will show relatively clear cut and sharp boundaries between bonded and bond free portions. This value of 40% is actually a relatively low value when it is realized that other binders, not of the non-migratory type, will migrate up to 200% or more of the originally printed area. Illustrative of such non-migratory binders is regenerated cellulose.

The amount of solid binder add-on will vary within relatively narrow limits depending upon the chemical nature, the solids content, the viscosity and other rheological characteristics of the binder, the thickness and weight of the nonwoven web, the surface area and depth of engraving of the particular binder pattern being used, and so forth. It may be as low as about 1 percent and may be as high as about 7 percent by weight of the dry nonwoven web for the preferred binder which is regenerated cellulose.

The viscosity is also of some criticality. If the binder is too thin, there -is an increased tendency to migration or lateral diffusion into normally unbonded areas. If the binder is too thick, diiculties will be encountered in the pick-up and deposition of the binder agent on, and penetration through the thickness of, the nonwoven web. In the case of viscose, it has been determined that, for balanced control of migration and penetration, the viscosity of the cellulose xanthate or viscose, as applied, should be in the range of from about l0 seconds to about seconds, as determined by the standard falling-ball test used in the viscose industry. As used herein, the viscosity is rated as the number of seconds required for a stainless steel ball having a diameter of s inch and a weight of 0.143 gram to fall 20 centimeters in a 1.5 cm. inside diameter glass tube of the viscose being tested at 20 C.

The viscosity of the viscose or cellulose xanthate is, of course, controllable within specic limits by techniques well known to the art and basically varies depending upon the concentration and chain length of the cellulose, the concentration of caustic in the viscose, the degree of ripening, the time and temperature of ageing, and the temperature of the viscose solution at the moment of its application to the fibers.

The surface coverage of such binder areas will vary depending on the precise properties of strength and softness desired in the final fabric and in practice may be designed within the range of from about 10 percent to about 50 percent of the total surface of the nonwoven web. Within the more commercial aspects of the present inventive concept, however, from about 12 percent to about 35 percent surface coverage has been found preferable.

The resulting nonwoven fabrics have been found to possess the required softness, drape and hand and have not been undesirably stiff or boardy. The longitudinal and transverse strengths have been more equalized and the non-woven fabrics have been durable and washable and have possessed excellent abrasion resistance. Unfortunately, however, in some cases, a slight pebbly or nubby elfect has been observed and felt in the nonwoven fabric, which effect has apparently been caused by the relative hardness of the binder areas, as compared to the relative softness of the unbonded fabric areas.

Careful consideration of the nonwoven fabrics bonded with regenerated cellulose by prior art methods has revealed that, although they may be relatively soft in a gross fashion and generally possess satisfactory drape, the actual surfaces of fabric wherein the bond areas are located are hard and harsh. Presence of local harsh areas in an otherwise soft fabric detracts from the utility of these fabrics. This harshness which is readily detected by hand is due primarily to the fact that the aocasaa printed bonded areas are much stiffer segments on the surface of the non-woven fabric. As a result, the fabric does not fold readily or easily, even though the binder segments are relatively small.

It has now been surprisingly found that, if the nonmigratory binder agent is applied to the surface of the nonwoven fibrous web after the web has been sufficiently wetted with aqueous liquids, the binder agent rapidly diffuses and penetrates substantially completely through the wetted nonwoven fabric directly from one surface to the other. The diffusion and penetration takes place substantially in straight-line fashion substantially at right angles to the fabric surfaces, with the binder showing little or no inclination to diffuse or migrate laterally but exhibiting a strong tendency to penetrate straight through the nonwoven web. IFor example, where the binder pattern on the surface applying the binder agent is a rectangle, the binder diffuses rapidly through the nonwoven fabric in the shape of a right rectangular prism. And, where the binder pattern on the surface applying the binder agent is a circle or an irregularly-shaped area, the binder diffuses rapidly through the nonwoven `fabric in the shape of a right circular cylinder or a right irregular cylinder. In this way, the same amount of binder which was formerly relatively densely located as a hard, fiat segment at the surface of prior art nonwoven fabrics is diffused and dispersed thinly as a softer network of binder material extending through the body of the nonwoven fabric of the present invention in substantially a right cylindrical or prismatic shape.

yIt is to be noted that the term right cylindrical is not intended to be limited to cylindrical solids having a circular cross-section. lSuch solids are more properly called right circular cylinders. The term right cylindrical is used herein in its broadest geometric sense, namely, the space or volume lbounded by a cylindrical surface (traced by any substantially straight line called a generatrix or element moving parallel to any xed substantially straight line) and two parallel planes cutting the generatrices or elements at right angles. The intersection of the cylindrical surface with each parallel plane may therefore be a circle, an ellipse, or even an irregular closed geometric line.

The word network actually and literally describes the structure of the bonded area in that the binder agent, in the presence of the added aqueous liquid, appears to follow the fibers themselves through the nonwoven web, coating them and joining them at their interstices as Well as forming thin filmy membranes or structures whereever adjacent fibers are fairly close to each other. The resulting bonded area is consequently relatively soft, flexible and yielding since the fibers are not completely and stiffly engulfed in a solid mass of binder agent lbut are free to shift and yield as a flexible network would function.

The ability to form the clearly defined, relatively soft binder areas of this invention is extremely important where small binder areas are used with small unbonded areas therebetween wherein it is especially desired to have the binder agent penetrate substantially completely through the nonwoven fabric rather than migrate laterally to ood the unbonded areas. It is, of course, also important where heavier -fabrics and larger binder areas are used inasmuch as the penetration of the binder completely through the nonwoven fabric requires the use of only one ybonding from one side of the fabric, in contradistinction to those prior art methods wherein the binder areas were so shallow as to require the application of the binder agent to both sides of the nonwoven fabric in the hope that they would meet in the middle to provide through-bonding to hold the nonwoven fabric together.

Efforts to obtain such through-bonding in the past have been directed to other methods of accomplishing such a desired result. For example, greater amounts of binder agent have been applied which quite often penetrated, albeit rather incompletely, through the nonwoven fabric but which left heavy masses of dense, nubby binder areas. `Such fabrics felt pebbly, nubby and pimply. Quite often, the amounts added were so great that the properties of the bonded areas were predominately those of solid irregular blocks of regenerated cellulose, hence hard and horny.

Other efforts have been directed to the use of greater pressures on the binder pattern printing rolls. Such has not been beneficial toy the nonwoven fabrics and has flattened them and caused excessive loss of loft and bulk as well as occasionally cutting through the fabric.

However, the application of aqueous liquids to the nonwoven webs and their subsequent printing with non-migratory binders while still wet has avoided all these difficulties and disadvantages whereby lesser amounts of binder agents can be used along with average or even decreased pressures on the binder applying means.

The amount of aqueous liquid which is applied to the nonwoven web, prior to the printing of the binder agent thereon, may be varied within relatively broad limits, depending upon the thickness and weight of the nonwoven web, the nature and characteristics of the fibers used therein, the properties, concentration and particularly the viscosity of the binder agent, the physical properties desired in the final fabric product, and so forth. Within the broader aspects of the present invention, from about 70 percent to about 2,50 percent by weight of aqueous liquid may be added, based on the dry weight of the nonwoven web, with preferred commercial ranges extending from about percent to about 210 percent by weight, based on the dry weight of the nonwoven web. If desired, surface active agents, anti-foam agents, etc., may be added to the aqueous liquid or to the non-migratory binder.

It has also been established that the use of rotogravure printing processes for the application of the bonding agent cooperates with and leads to surprisingly excellent results when the nonwoven web is wetted prior to the application of the bonding agent. In rotogravure printing, the bonding agent is carried in etched or engraved depressions in the printing roller or other applicator whereby controlled-volume reservoirs are formed which contact the surface of the wetted nonwoven web and diffuse thereinto, being assisted by the capillary or wicking action of the fibers. This form of binder application is, of course, to be contrasted to letter press printing wherein the bonding agent or other material to be adhered to the base web is applied from the ridges on the surface of a roller or other applicator, rather than from the adjacent depressions. Such a letter press method relies basically on pressure and is wholly different in principle and operation from a rotogravure method.

It has not been definitely established but it is believed that in the use of rotogravure printing processes wherein the printing pressure is not applied to the areas being printed but is applied rather to the portions of the web adjacent to the areas being printed, that such processes and printing pressures assist in the ability of the binder material being printed to penetrate through the web while simultaneously opposing the lateral diffusion of binder into the web areas adjacent to the printed areas. It appears that the pressures applied adjacent to the areas being printed actually prevent migration beyond those areas, when the binder itself does not readily diffuse in water as is characteristic of viscose. This is, of course, to be contrasted to letter press printing wherein the pressure is applied to the areas being printed, thus possibly contributing to` the tendency of the binder to migrate and ignoring the advantages available due to non-diffusibility of the binder in water.

The depth of the etched or engraved depressions in the printing roller or other applicator should be such that the amount of the deposited binder agent is sufiicient to penetrate completely through the nonwoven web. The depth of the depression will vary depending upon many factors, the most important of which are the weight and thickness of the nonwoven web, the particular fibers present therein, and the properties and characteristics of the binder agent. Within the broader aspects of the present invention, depths of from about 0.002 inch to about 0.020 inch have been found practical for nonwoven webs having wegihts of from about 100 to about 2000 grains per square yard. Within the more commercial aspects of the present invention, depths of from about 0.003 inch to about 0.015 inch have been found most practical for nonwoven webs lha-ving weights of from about 150 grains to about 1200 :grains per square yard. As a general rule, it has been found that a depth of from about 0.001 inch to about 0.002 inch is required for each 100 grain weight per square yard of nonwoven web.

The width of the etched or engraved depressions is determined by the width of the binder area which is to be applied to the nonwoven web. Under normal circumstances in cases using low-migratory binders, the width of the etched or engraved depression on the roller or other applicator will be approximately 25% less than the width of desired binder area on the finished nonwoven fabric. With binders that are less migratory in nature, the width of the etched or engraved depression on the applicator will be aproximately less than the width of the desired binder area. The use of a non-migratory binding agent, such as a relatively high` viscosity viscose, has reduced this value on occasion to as low as 1%, in which case it may be practically ignored and the width of the etched or engraved depression on the rotogravure roller made equal to the required width of the desired binder area.

The width of the etched or engraved depressions will therefore be on approximately the same order of the values of the widths of binder lines or areas which, as defined hereinbefore, may range from about 0.005 inch to about 0.045 inch and preferably from about 0.009 inch to about 0.035 inch. Such values have been found practical and commercially satisfactory, particularly for nonwoven fabrics having weights of up to about 1000 grains per square yard. For fabrics heavier than 1000 grains per square yard, the depths of the etched or engraved depressions may begin to approach their widths and the processing speed of the fabric through the bonding apparatus may be decreased to permit complete diffusion and penetration of the binder through the fabric. Such is, of course,` commercially and productively undesirable and in such cases the widths of the etched or engraved depressions and the resulting binder areas may be increased to as much as about 0.100, provided the fiber formulation is such as to permit the indicated average number of bonds per fiber length. As a general rule, it may be stated that the width of the etched or engraved depression should be at least about two times the depth thereof, and usually at least about three or four times. In special designs this ratio may be as large as about twenty times.

With reference tothe drawing setting forth preferred embodiments of the present invention.

FIGURE l is an enlarged plan View of a portion of a nonwoven fabric bonded with wavy or sinuous continuous lines of binder agent extending substantially transversely across the nonwoven fabric and generally at right angles to the longitudinal axis thereof;

FIGURE 2 is an enlarged plan view of a portion of a nonwoven fabric bonded with discontinuous lines of binder agent extending substantially transversely across the nonwoven fabric and at right angles to the longitudinal axis thereof;

FIGURE 3 is an enlarged plan view of a portion of a nonwoven fabric bonded with continuous lines of binder agent extending angularly acnoss the nonwoven fabric;

FIGURE 4 is an enlarged plan view of a portion of a nonwoven fabric bonded with discontinuous lines of binder -agent extending angularly across the nonwoven fabric;

FIGURE 5 is an enlarged plan view of a portion of a nonwoven fabric bonded in a square pattern 'of intersecting parallel rows of circular binder areas;

FIGURE 6 is an enlarged plan view of a portion of a nonwoven fabric bonded in a diamond pattern of intersecting parallel rows of circular binder areas;

FIGURE 7 is an enlarged plan view of a portion of a nonwoven fabric bonded in a square pattern of intersecting parallel rows of square binder areas;

FIGURE 8 is an enlarged cross-sectional view of the portion of the nonwoven fabric illustrated in FIGURE 7, taken on the line 8 8 thereof;

FIGURE 9 is a schematic drawing illustrating conventional apparatus for carrying out the methods of the present inventive concept; and

`FIGURE l0 is a fragmentary schematic drawing showing a conventional etched or engraved roller for use in rotogravure application of the binder agent.

In the preferred embodiments of the present inventive concept shown in the drawings, a portion of a carded, nonwoven textile fabric 10 is illustrated in FIGURE l wherein sinuous binder segments 12 extend generally transversely across the width of the nonwoven fabric 10. 'In this configuration, the wavy binder segments 12 (when considered in gross) are substantially at right angles to the so-called machine-direction or the-long axis of the nonwoven fabric 10. Itis to be appreciated, however, that if an isotropic nonwoven fibrous web made by air deposition or other techniques is employed, or if any n'onoriented fibrous nonwoven fabric is used, the binder segments 12 may extend longitudinally of the length of the fabric, or in its so-called machine-direction. The unbonded portions 14 which extend between the binder segmentslZ are sharply marked and clearly defined. Such a binder pattern is suitable for oriented, non-oriented, or rearranged nonwoven textile fabrics. The binder segments 12 are diffused substantially completely through the nonwoven textile fabric 10 directly in straight lines from one surface of the fabric to the other surface, in the form of relatively soft and flexible, individually distinct open networks of bonded fibers. FIGURE 8 illustrates the directness and sharpness of the diffusion.

In FIGURE 2, a portion of a carded, nonwoven fabric 20 is illustrated wherein the binder segments 22 are discontinuous and appear as rectangular areas on the surface of the fabric 20. The binder segments 22 are spaced apart by gaps of unbonded portions 24. Again, it is to be realized that the discontinuous binder segments 22 may, if desired, extend along the long axis of the nonwoven fabric, rather than across the same, particularly in the case of non-oriented fibrous nonwoven fabrics. Such binder patterns are suitable for oriented non-oriented, or rearranged nonwoven fabrics. Gelometrically speaking, the binder segments 22 are substantially right rectangular prisms having a rectangular base and a rectangular upper surface, as shown in FIGURE 2, and substantially rectangular lateral faces which extend perpendicularly to the surfaces of the nonwoven fabric 20.

In FIGURE 3, a portion of a carded, nonwoven fabric 30 is illustrated wherein the binder agent is in the form of substantially straight, continuous binder segments 32, separated by unbonded portions 34, extending angularly across the width of the librous nonwoven fabric. As shown, the binder segments I32 and the unbonded portions 34 are at an angle of about 75 to the long axis of the web. If desired, this angle may, of course, be decreased to as low as about 0, particularly for non-ori ented nonwoven fabrics. Such a binder pattern is suitable for oriented, non-oriented, or rearranged nonwoven fabrics.

In FIGURE 4, a portion of a carded, nonwoven fabric 40 is illustrated wherein the binder segments 42 are discontinuous, extending angularly across the width of the fibrous nonwoven fabric. Unbonded portions 44 lie between and separate the discontinuous binder segments 42. As shown, the binder segments are at an angle of about 75 to the long axis lof the web. If desired, this angle may be decreased to as low as about particularly in the case of nonoriented nonwoven fabrics. Such a binder pattern is suitable for oriented, non-oriented, or rearranged nonwoven fabrics. Geometrically speaking, the binder segments 42 are right prisms and may appear on the surface of the nonwoven fabric either as parallelograms or rectangles.

IN FIGURE 5, a portion of a random-laid nonwoven fabric 50 is illustrated wherein the binder segments 52 form a square pattern of intersecting parallel rows of circular binder segments which are separated by an unbonded portion 54. The diameters of the circular binder segments are, of course, equivalent in width and spacing to the lines of binder segments previously described. That is, the diameters of the circular binders range from about 0.006 inch to about 0.050 inch and preferably from about 0.010 inch to about 0.040 inch, with from about 8 to about 30 binder segments per inch, and preferably from about 10 to about 24 binder areas per inch, as measured in the long direction lof the nonwoven web. The inter-circular spaces 56 in the lines of the binder areas are of the same order as previously described, namely, from about 0.006 inch to about 0.050 inch, and preferably from about 0.020 inch to about 0.040 inch. `The inter-circular spaces 56 are preferably equal but are not necessarily so. Such a binder pattern is preferred for non-oriented nonwoven fabrics.

In FIGURE 6, a portion of a random-laid nonwoven fabric 60 is illustrated wherein the binder agent forms a diamond pattern of intersecting parallel rows of circular binder areas or segments 62, the diameter and the number of bonds per inch of nonwoven fabric as measured in the direction of the long axis of the web as well as the intercircular distance 66, being within the ranges described in connection with the circular binder pattern of FIGURE 5. Such a binder pattern is preferred for non-oriented nonwoven fabrics.

'In FIGURES 5 and 6 which are plan views, the binder areas or segments 52, 612 have been illustrated and described as circular. In reality, the binders are actually in the form of substantially right circular cylindrical networks of bonded fibers. The binder is diffused substantially uniformly throughout the binder segment and is not concentrated solely on the surface of the nonwoven fabric. As a result, the

binder segments

52 and 62 are neither dense nor solid masses but are relatively soft and flexible and do not create a pebbly or nubby feel.

In FIGURE 7, a portion of a random-laid nonwoven fabric 70 is illustrated wherein the binder agent forms a square pattern of intersecting p-arallel rows of square binder segments 72 separated by an unbonded portion 74. The sides of the squares have lengths of from about 0.006 inch to about 0.050 inch and preferably from about 0.010 inch to about 0.040 inch. The number of binder areas per inch of nonwoven fabric measured along the long axis thereof ranges from about 8 to about 30 and preferably from about l0 to about 24. The inter-square distance 76 between the segments of binder may range from about 0.006 inch to about 0.050 inch and preferably from about 0.020 inch to labout 0.040 inch. Such a binder pattern is preferred for non-oriented nonwoven fabrics.

In FIGURE 7 which is a plan view, the binder segments 72 have been illustrated and described as squares. In reality, the binders are actually in the form of substantially right square prism networks of bonded fibers, the cross-sections of the networks being substantially square from base totop surface. The binder is diffused substantially uniformly throughout the binder segment and is not concentrated solely on the surface of the nonwoven fabric. As a result, the binder segments 72 are v10 relatively soft and iiexible and do not create a pebbly or nubby feel.

In FIGURE 8, there is illustrated a cross-section of the portion of the nonwoven fabric 70 illustrated in 'FIG- URE 7. It is to be observed that the binder segments 72 are `substantially rectangular in cross-Section and that `they extend substantially completely through the nonwoven 'fabric from one surface to the other surface. In some cases, slight concavities have been observed in the upper and lower surfaces of the binder segments but these are relatively small and have no undesirable effect on the properties and characteristics of the nonwoven fabric.

The proportion of the weight of the binder material in the binder segments to the weight of the fibrous material in these binder segments is an important factor in determining the softness, drape and hand of the finished nonwoven fabric and of particular criticality with regard to the pebbly, nubby or pimply feeling. This proportion may be computed by a precise chemical analysis or more quickly with less accuracy by determining the amount of binder add-on in the binder segments from the weight of the nonwoven fabric before and after bonding. IIn the present inventive concept, the binder add-on is from about 1% to about 7% of the weight of the dry nonwoven web. The weight of the fibrous materials in these binder areas is the fractional coverage of the binder multiplied by the weight of the dry nonwoven web. In the present inventive concept, the percent coverage is from about 10% to about 50%, and preferably from about 12% to about 35% of the dry nonwoven web.

It has been established that use of the extremes of these values of binder add-0n and fibrous materials weights in the binder segments will not yield the desired nonwoven fabrics. That is toy say, if 1% binder add-on is desired in combination with 50% surface coverage for a proportion of 1:50 or 2% binder based on the weight of the fibrous material in the binder segment), the resulting nonwoven fabric is not strong, durable, washable, or abra-sion resistant. Similarly, if 7% binder add-0n is used in combination with 10% surface coverage for a proportion of 7:10 (or 70% binder based on the weight of the fibrous material in the binder segment) the resulting nonwoven fabric lis not sutiiciently soft, does not possess good hand, and is pebbly, nubby and pimply. In Isuch cases, serious migration also occurs.

It has been established that proportions of the weight of the binder to the weight of the fibrous materials in the binder segments 0f from about 13% binder by weight based on the dry weight of the fibrous material in the binder segment to about 35% binder by weight based on the dry weight of the fibrous material in the binder segment will yield the desired and required properties and characteristics in the nonwoven fabric, provided `the binder diffuses and penetrates substantially uniformly and completely throughout the nonwoven web. Within the preferred commercial aspects of the present invention, a range of from about 15% to about 30% of binder to fiber weight in the binder segment has been found .most desirable.

In FIGURE 9, there is illustrated one Iform of conventional apparatus suitable for carrying out the improved processes of the present inventive concept. A fibrous nonwoven web W is delivered `from any desired source, such as a carding machine, into the niplvof a pair of adjustable rollers v and 1011, the lower roll 100 being the applicator roll and the upper roll 101 being the back-up roll. Aqueous liquid is picked up from a bath 102 by apick-up roller 103 partially immersed therein and is transferred to the applicator roll 100 and applied to the travelling nonwoven web W passing in co-ntact therewith. The depth of the roller 103 in the bath 102 and the pressure between the roll-s 100 and 101 may be so adjusted as to provide for the controlled application of the desired amounts of aqueous liquid to the nonwoven web W. The surfaces of rolls 100 and 101 are normally smooth and cylindrical to 1 1 provide for an even transfer of liquid to the nonwoven web W.

A second bath 105 containing the desired binding agent is provided whereby the binder is transferred to a pick-up roller 106 partially immersed in the bath 105 to be further transferred to an applicator roll 107 which applies the binder to the traveling nonwoven web W as controlled by a doctor blade 109. A conventional lback-up roll 108 is positioned on the top side of the traveling web W to cooperate with the applicator roll 107 in the application of the binder to the web. The surface of roll 107 is suitably etched or engraved to provide the vdepressions necessary for rotogravure printing of the binder agent on the nonwoven web W. The depths and widths of the etched and engraved patterns on the roller has been described hereinbefore and should need no further description. FIGURE illustrates a portion of one such roll 107 and shows in enlarged scale the relationship of the depth (D) and width (W) dimensions on the surface of the roll.

The treated nonwoven web W may then be passed into a conventional system of baths or other treating devices 110 providing for any necessary chemical processing or conversion of the applied binder agent. In one case of regenerated cellulose, the binder applied from the bath 105 is cellulose xanthate and the system of baths or other treating devices 110 provides for the coagulation, regeneration and washing of the cellulose regenerated from the cellulose xanthate.

The regenerated-cellulose treated nonwoven web W is -then conveyed into a conventional heating and drying means such as an oven 120 which is capable of being maintained by heated air, for example, at any desired temperature such as in the range of from about 200 to about 280 F. to drive off moisture in the nonwoven fabric. A receiving roll 130 is provided to receive and wind the nonwoven fabric as it emerges in relatively dry form from the oven 120.

The invention will be further illustrated in greater detail by the following specific examples. It should be understood, however, that although these examples may describe in particular detail some of the more specific features of the invention, they are given primarily for purposes of illustration and the invention in its broader aspects is not to be construed as limited thereto.

Example I A card web comprising 1.5 denier, 1%6 inch staple length bright viscose rayon, weighing yabout 200 grains per square yard, is wetted with water to a moisture pickup of about 170 percent by weight based on the dry weight of -the card web. The wetted card web is immediately print bonded (before any substantial loss of moisture content) on a rotogravure print unit having 16 lines per inch, with each line 0.015 inch Wide by 0.004 inch deep, spiralled equally spaced at an angle of 45 around the axis of the print roll. The binder agent is cellulose xanthate, 6% caustic, 61/2 cellulose, falling-ball viscosity-60 seconds. The treated web is then immediately introduced into a bath containing sodium sulfate (Na2SO4) and 4% sulfuric acid (H2804), vacuumextracted and washed with water to remove all traces of salt and acid. The nonwoven fabric is then dried on conventional dry cans at temperatures of about 230 F. The resulting nonwoven fabric is soft, possesses good wet abrasion resistance, possesses drape, is strong and is washable in an automatic home laundry machine. The binder segments are relatively soft and flexible and are not harsh or nubby masses of solid binder. The product is useful as a disposable diaper liner.

Examples 2, 3 and 4 The procedures set forth in Example 1 are carried out substantially as set forth therein except that the moisture pickup is controlled to: (1) 100 percent by weight based 'on the dry weight of the card web and viscosity of viscose is 15 seconds by ball-fall test; (2) 140 percent by weight based on the dry weight of the card web and viscosity of binder is 35 seco-nds by ball-fall test; and I(3) 220 percent by weight based on the dry weight of the card web and viscosity of binder is seconds by ball-fall test. The resulting nonwoven fabrics are soft, possess drape, are strong, possess good wet abrasion resistance and are washable in an automatic home laundry machine. The binder lines are relatively soft and flexible `and are not harsh or nubby masses of solid heavy binder. The products are useful as kitchen curtains.

Examples 5 and 6 The procedures set forth in Example 1 are carried out substantially as set forth therein except that the card web comprises a mixture of 50% by Weight of cotton and 50% by weight of 1.5 denier, 1%6 inch staple length dull viscose rayon. The nonwoven web weighs: (l) 400 grains; and (2) 600 grains per square yard. The results are comparable to those set forth in Example 1. The products 'are useful as dinner place mats. in making the 400 grain nonwoven fabric, the rotogravure roll had l2 lines per inch, with each line 0.020 inch wide and 0.006 inch deep. In making the 600 grain nonwoven fabric, the rotogravure roll had 10 lines per inch, with each line 0.025 inch wide and 0.008 inch deep.

Example 7 A non-oriented web is formed by a rHuid deposition papermaking process from 1.5 denier, 3A" length bright viscose rayon and Weighs about 350 grains per square yard. To impart strength for ease of handling and printing the web is impregnated with 1/2 polyvinyl alcohol solution, a transient binder. The moisture pickup is controlled to about percent, based on the dry weight of the non-oriented web. The procedures of Example l are followed further, using la rotogravure print roll having 16 lines per inch, with each line 0.016 inch wide and 0.005 inch deep. The nonwoven fabric is relatively soft and has a textile-like hand; it is durable, has wet abrasion resistance and is washable. No nubby or pebbly feeling or any solid masses of heavy binder `are detectable.

Example 8 The procedures of Example 7 are followed substantially as set forth thereon except that air-depositon techniques (U.S. Patents 2,676,363 and 2,676,364) are followed. Moisture pickup and bonding take place as described in Example 7. No nubby or pebbly feeling or 'any solid clumps of binder masses are detectable in the -nal product.

Example 9 The procedures of Example 1 are followed substantially as set forth therein except that wool iibers are substituted for the viscose rayon fibers. The binder adheres the fibrous wool web together into a soft nonwoven fabric which possesses good web abrasion, drape and hand.

Example 10 The procedures set forth in Example 1 are followed substantially as set forth therein except that the card web is replaced by a rearranged, originally oriented card web such as described in patent application Serial Number 503,871, tiled April 26, 1955.

Although the present invention has been described with particular reference to natural cellulosic fibers, such as cotton, and other natural fibers such as wool, and artificial cellulosic fibers, notably rayon fibers, it is to be appreciated that blends of these fibers as well as blends with other fibers may be utilized. Such other fibers include iiax, hemp, nylon; cellulose acetate polyester fibers such as Daeron, acrylic bers such as Dyne, Orion and Acrilan; vinyl bers such as Vinyon; etc. When such other fibers are used, they may be included in amounts as low as about 5 percent by weight up to as much as about 60% by weight, depending upon the requirements of the particular product.

With particular regard to rayon fibers, such is intended to cover regenerated cellulosic fibers, whether derived from the viscose process, the cuprammonium process, or other regenerative or saponifying processes.

Although several specific examples of the inventive concept have been described, the same should not be construed as limited thereby nor to the specific substances mentioned therein but to include various other compounds of equivalent constitution as set forth in the claims appended hereto. It is understood that any suitable changes, modifications and variations may be made without departing from the spirit and scope of the invention.

What is claimed is:

1. A bonded fibrous nonwoven textile fabric having textile like softness, drape and hand without a pebbly or nubby feel comprising a web of overlapping, intersecting cellulosic fibers; and a non-migratory regenerated cellulose binder distributed throughout said web in an amount of from about 1% to about 7% by weight, based on the weight of the dry web in a predetermined pattern of spaced binder segments in bonding relationship with the cellulosic fibers passing through said segments, said segments being diffused substantially completely through the web from one surface thereof to the other surface in the form of relatively soft and fiexible, individually distinct open networks of bonded cellulosic fibers, said binder beingt distributed throughout said binder segments in an amount of from about 13% to about 35 by weight, based on the weight of the fibers in said binder segments.

2. A bonded fibrous nonwoven textile fabric having textile-like softness, drape and hand without a pebbly or nubby feel comprising a web of overlapping, intersecting cellulosic fibers; and a non-migratory regenerated cellulose binder distributed throughout said web in an amount of from about 1% to about 7% by weight, based on the weight of the dry web in a predetermined pattern of spaced binder segments in bonding relationship with the cellulosic fibers passing through said segments, said segments being diffused substantially completely through the web from one surface thereof to the other surface in the form of relatively soft and flexible, individually distinct open networks of bonded cellulosic fibers, said binder being distributed throughout said binder segments in an amount of from about 15% to about 30% by weight, based on the weight of the fibers in said binder segments.

3. A bonded fibrous nonwoven textile fabric having textile-like softness, drape and hand without a pebbly or nubby feel comprising a web of overlapping, intersecting cellulosic fibers; and a non-migratory regenerated cellulose binder distributed throughout said web in a predetermined pattern of spaced binder segments in bonding relationship with the cellulosic fibers passing through said segments, said segments being diffused substantially completely through the web from one surface thereof to the other surface in the form of relatively soft and fiexible, individually distinct open networks of bonded cellulosic fibers, said binder being distributed throughout said binder segments in an amount of from about 13% to about 35% by weight, based on the weight of the fibers in said binder segments.

4. A bonded fibrous nonwoven textile fabric having textile-like softness, drape and hand without a pebbly or nubby feel comprising a web of overlapping, intersecting cellulosic fibers; and a non-migratory regenerated cellulose binder distributed throughout said web in a predetermined pattern of spaced binder segments in bonding relationship with the cellulosic fibers passing through said segments, said segments being diffused substantially completely through the web from one surface thereof to the other surface in the form of relatively soft and exible, individually distinct open networks of bonded 14 cellulosic fibers, said binder being distributed throughout said binder segments in an amount of from about 15 to about 30% by weight, based on the weight of the fibers in said binder segments.

5. A method of forming a bonded fibrous nonwoven textile fabric having textile-like softness, drape and hand without a pebbly or nubby feel which comprises: wetting a web of overlapping, intersecting cellulosic fibers; and rotogravure printing the wetted web with a non-migratory regenerated cellulose binder in a predetermined pattern of spaced binder segments, whereby the regenerated cellulose binder diffuses substantially completely through the wetted web from one surface thereof to the other surface and bonds the cellulosic bers in said binder segments into relatively soft and fiexible open networks of bonded fibers, said binder being distributed throughout said binder segments in an amount of from about 13% to about 35% by weight, based on the weight of the fibers in said binder segments.

6. A method of forming a bonded fibrous nonwoven textile fabric having textile-like softness, drape and hand without a pebbly or nubby feel which comprises: wetting a web of overlapping, intersecting cellulosic fibers; and rotogravure printing the wetted web with a non-migratory regenerated cellulose binder in a predetermined pattern of spaced binder segments, whereby the regenerated cel lulose binder diffuses substantially completely through the wetted web from one surface thereof to the other surface and bonds the cellulosic fibers in said binder segments into relatively soft and flexible open networks of bonded fibers, said binder being distributed throughout said binder segments in an amount of from about 15 to about 30% by weight, based on the weight of the fibers in said binder segments.

7. A method of forming a bonded fibrous nonwoven textile rfabric having textile-like softness, drape and hand without a pebbly or nubby feel which comprises: wetting a web of overlapping, intersecting cellulosic fibers; and rotogravure printing Ithe wetted web with from about 1% to about 7% by weight, based onthe weight of the dry web, o-f a non-migratory regenerated cellulose binder in a predetermined pattern of spaced binder segments, whereby the regenerated cellulose binder diffuses substantially completely through the wetted weby from one surface thereof to the other surface and bonds the cellulosic fibers in said binder segments into relatively soft and fiexible open networks of bonded fibers, said binder being distributed throughout said binder segments in an amount of from about 13% to about 35 by weight, based on the weight of the fibers in said binder segments.

8. A method of forming a bonded fibrous nonwoven textile fabric having textile-like softness, drape and han-d without a pebbly or nubby feel which comprises: wetting a web of overlapping, intersecting cellulosic fibers with from about 70% to about 250% by weight of an aqueous liquid, based on the weight of the dry web; and rotogravure printing the wetted web with a non-migratory regenerated cellulose binder in a predetermined pattern of spaced binder segments, whereby the regenerated cellulose binder 'diffuses substantially completely through the wetted web from one surface thereof to the other surface and bonds the cellulosic fibers in said binder segmen-ts into relatively soft and flexible open networks of bonded fibers, said binder being distributed throughout said binder segments in an amount of from about 13% to about 35 by weight, based on the weight of the fibers in said binder segments.

9. A method of forming a bonded fibrous nonwoven 'textile fabric having textile-like softness,ldrape and hand without -a pebbly or nubby feel which comprises: wetting a web of overlapping, intersecting cellulosic fibers with from about 70% to about 250% by weight of an aqueous liquid, based on the weight of the dry web; and rotogravure printing the wetted web with from about 1% to about 7% by weight, based on the weight of the dry web, of a non-migratory regenerated cellulose binder in a predetermined pattern of spaced binder segments, whereby the regenerated cellulose binder diuses sub stantially completely through the wetted web from one surface thereof to the other surface and bonds the cellulosic lbers in said binder segments into relatively soft and -eXi-ble open networks of bonded bers, said binder being distributed throughout said binder segments in an amount of from about 13% to about 35% by weight, based on the Weight of the fibers in said binder segments.

10. An `all-cellulosic, bonded fibrous nonwoven textile fabric having textile-like softness, drape and hand without a pebbly or nubby feel consisting of a web of overlapping, intersecting cellulosic bers; and a non-migratory regenerated cellulose binder distributed throughout said web in an amount of from about 1% to about 7% by weight, based on the weight of the dry web, in a predetermined pattern of spaced binder segments in bonding relationship with the cellulosic fibers passing through said segments, said segments being diffused substantially completely through the web from one surface thereof to the other surface in the form of relatively Soft and exible, individually distinct open networks of bonded cellulosic tibers, said binder being distributed throughout said binder segments in an amount of from about 13% to 16 about 35% `by weight, based on the weight of the fibers in said binder segments.

11. An al1-cellulosic, bonded brous nonwoven textile fabric having textile-like softness, drape and hand Without a pebbly or nubby feel consisting of a web of overlapping, intersecting cellulosic fibers; and a non-migratory regenerated cellulose binder distributed throughout said web in an amount of from about 1% to about 7% by weight, based on the weight of the dry web, in a predetermined pattern of spaced binder segments in bonding relationship with the cellulosic fibers passing through said segments, said segrrents being diffused substantially completely through the web from one surface thereof t0 the other surface in the form. of relatively soft and flexible, individually distinct open networks of bonded cellulosic fibers, said binder being distributed throughout said binder segments in an amount of from about 15% to about b-y weight, based on the weight of the tibers in said binder segments.

References Cited in the file of this patent UNITED STATES PATENTS 2,670,315 Rider Feb. 23, 1954 2,782,130 Ness et al. Feb. 19, 1957 2,880,111 Dreliok et al. Mar. 31, 1959

Claims

1. A BONDED FIBROUS NONWOVEN TEXTILE FABRIC HAVING TEXTILE LIKE SOFTNESS, DRAPE AND HAND WITHOUT A PEBBLY OR NUBBY FEEL COMPRISING A WEB OF OVERLAPPING, INTERSECTING CELLULOSIC FIBERS; ANS A NON-MIGRATORY REGENERATED CELLULOSE BINDER DISTRIBUTED THROUGHOUT SAID WEB IN AN AMOUNT OF FROM ABOUT 1% TO ABOUT 7% BY WEIGHT, BASED ON THE WEIGHT OF THE DRY WEB IN A PREDETERMINED PATTERN OF SPACED BINDER SEGMENTS IN BONDING RELATIONSHIP WITH THE CELLULOSIC FIBERS PASSING THROUGH SAID SEGMENTS, SAID SEGMENTS BEING DIFFUSES SUBSTANTIALLY COMPLETELY THROUGH THE WEB FROM ONE SURFACE THEREOF TO THE OTHER SURFACE IN THE FORM OF RELATIVELY SOFT AND FLEXIBLE, INDIVIDUALLY DISTINCT OPEN NETWORKS OF BONDED CELLULOSIC FIBERS, SAID BINDER BEING DISTRIBUTED THROUGHOUT SAID BINDER SEGMENTS IN AN AMOUNT OF FROM ABOUT 13% TO ABOUT 35% BY WEIGHT, BASED ON THE WEIGHT OF THE FIBERS IN SAID BINDER SEGMENTS.