US3808095A - Wet-formed nonwoven textile fabrics and methods of making the same - Google Patents

Abstract

A FORAMINOUS, WET-FORMED NONWOVEN TEXTILE FARBIC HAVING A UNITARY STRUCTURE, BALANCED CONSTRUCTION, PREDETERMINED DESIRED PROPERTIES IN THE LONG AND CROSS DIRECTIONS, UNIFORMITY, AND GOOD OPACITY AND COVERING POWDER COMPRISING UNCARDED, RELATIVELY STRAIGHT, SMOOTH-SURFACED, SYNTHETIC TEXTILE FIBERS HAVING AN AVERAGE LENGTH OF FROM ABOUT 3/8 INCH TO ABOUT 1 1/2 INCHES OR MORE, THE NONWOVEN TEXTILE FABRIC HAVING TWO MAJOR AXES OF PREDOMINANT FIBER ORIENTATION DIRECTED SUBSTANTIALLY AT RIGHT ANGLES TO EACH OTHER, ONE AXIS BEING DIRECTED GENERALLY IN THE LONG DIREACTION OF THE NONWOVEN TEXTILE FABRIC AND THE OTHER AXIS BEING DIRECTED GENERALLY IN THE CROSS DIRECTION OF THE NONWOVEN TEXTILE FABRIC, A PREPONDERANCE OF THE FIBERS BEING ARRANGED IN GENERALLY PARALLEL ARRAYS OF BUNDLES WHICH ARE ORIENTED IN THE DIRECTION OF ONE OF THE TWO MAJOR AXES OF PREDOMINANT FIBER ORIENTATION, WITH THE BUNDLES HAVING DIAMETERS OF FROM ABOUT 0.04 MM. TO ABOUT 0.6 TO 1 MM. AND EXTENDING GENERALLY FROM ONE SIDE OF THE NON-WOVEN TEXTILE FABRIC TO THE OTHER SIDE THEREOF OR GENERALLY FOR THE FULL LENGTH OF THE NONWOVEN TEXTILE FABRIC, AND CONTAINING FROM ABOUT 3 TO ABOUT 200 OR MORE FIBERS IN EACH BUNDLE AND BEING SPACED APART A DISTANCE OF FROM ABOUT 0.2 MM. TO ABOUT 1.5 MM., ON AN APPROXIMATE CENTERTO-CENTER BASIS. ANOTHER FEATURE IS THE PRESENCE IN THE FIBROUS STRUCTURE OF A VERY LARGE NUMBER OF RADOMLYARRANGED PORES OR OPENINGS WHICH, HOWEVER, ARE SO EXTREMELY SMALL IN DIAMETER THAT THERE IS VERY LITTLE OPEN SURFACE AREA, OR FABRIC AREAS OF ZERO OR LOW FIBER DENSITY. AS A RESULT, THE FIBROUS STRUCTURE HAS EXCELLENT OPOCITY AND COVERING POWER. ALSO INCLUDED ARE METHODS FOR MAKING SUCH WET-FORMED NONWOVEN FABRICS COMPRISING: FORMING AN AQUEOUS SLURRY COMPRISING SYNTHETIC FIBERS HAVING AN AVERAGE LENGTH OF FROM ABOUT 3/8 INCH TO ABOUT 1 1/2 INCHES OR MORE; CAUSING SAID AQUEOUS SLURRY TO FLOW AT A PREDETERMINED VELOCITY IN A THIN, FLAT, SHEET-LIKE PLANAR CONFIGURATION; DISCHARGING THE AQUEOUS SLURRY OF FIBERS DIRECTLY UPON A MOVING FORMING SURFACE HAVING A PREDETERMINED VELOCITY AND FORMING A LOOSELY-ASSEMBLED FIBROUS STRUCTURE THEREON WHEREIN THE INDIVIDUAL FIBERS HAVE A PREDOMINANT ORIENTATION IN THE DIRECTION OF MOVEMENT OF THE FORMING SURFACE; AND ANGULARLY DISCHARGING A SECOND AQUEOUS SLURRY OF FIBERS ALSO HAVING A THIN, FLAT, SHEET-LIKE PLANAR CONFIGURATION AND A PREDETERMINED VELOCITY UPON THE LOOSELY-ASSEMBLED FIBROUS STRUCTURE, TO FORM A SECOND LOOSELY-ASSEMBLED FIBROUS STRUCTURE THEREON WHEREIN THE FIBERS HAVE A PREDOMINANT ORIENTATION WHICH IS DIRECTED IN THE CROSS DIRECTION OF THE FORMING SURFACE, THE FIBERS OF THE SECOND LOOSELY-ASSEMBLED FIBROUS STRUCTURE INTER-MINGLING AND INTERENTANGLING WITH THE FIBERS OF THE FIRST LOOSELY-ASSEMBLED FIBROUS STRUCTURE WHEREBY THERE IS MADE A WET-FORMED NONWOVEN TEXTILE FABRIC HAVING A UNITARY STRUCTURE, BALANCED CONSTRUCTION, PREDETEMINED DESIRED PROPERTIES IN THE LONG AND CROSS DIRECTIONS, UNIFORMITY, AND GOOD OPACITY AND COVERING POWER.

Description

yApril 30, 1914 J. T. MCKNIGHT OF MAKING THE SAME Filed May 13, 1971 WvET-FORMED NONWOVEN TEXTILE-FABRICS AND METHODS gli 1:

United States Patent O 3,808,095 WET-FORMED NONWOVEN TEXTILE FABRICS AND METHODS OF MAKING THE SAME James T. McKnight, Martinsville, NJ., assignor to Johnson & Johnson Filed May 13, 1971, Ser. No. 143,061 Int. Cl. D21f 1/06, 11/04 U.S. Cl. 162--215 19 Claims ABSTRACT OF THE DISCLOSURE A foraminous, wet-formed nonwoven textile fabric having a unitary structure, balanced construction, predetermined desired properties in the long and cross directions, uniformity, and good opacity and covering power comprising uncarded, relatively straight, smooth-surfaced, synthetic textile fibers having an average length of from about inch to about 11/2 inches or more, the nonwoven textile fabric having two major axes of predominant fiber orientation directed substantially at right angles to each other, one axis being directed generally in the long direction of the nonwoven textile fabric and the other axis being directed generally in the cross direction of the nonwoven textile fabric, a preponderance of the fibers being arranged in generally parallel arrays of bundles which are oriented in the direction of one of the two major axes of predominant fiber orientation, with the bundles having diameters of from about 0.04 mm. to about 0.6 to l mm. and extending generally from one side of the non-woven textile fabric to the other side thereof or generally for the full length of the nonwoven textile fabric, and containing from about 3 to about 200 or more fibers in each bundle and being spaced apart a distance of from about 0.2 mm. to about 1.5 mm., on an approximate centerto-center basis. Another feature is the presence in the fibrous structure of a very large number of randomlyarranged pores or openings which, however, are so extremely small in diameter that there is very little open surface area, or fabric areas of zero or low fiber density. As a result, the fibrous structure has excellent opacity and covering power. Also included are methods for making such wet-formed nonwoven fabrics comprising: forming an aqueous slurry comprising synthetic fibers having an average length of from about vS/s inch to about 11/2 inches or more; causing said aqueous slurry to flow at a predetermined velocity in a thin, fiat, sheet-like planar configuration; discharging the aqueous slurry of fibers directly upon a moving forming surface having a predetermined velocity and forming a loosely-assembled fibrous structure thereon wherein the individual fibers have a predominant orientation in the direction of movement of the forming surface; and angularly discharging a second aqueous slurry of fibers also having a thin, flat, sheet-like planar configuration and a predetermined velocity upon the loosely-assembled fibrous structure, to form a second loosely-assembled `fibrous structure thereon wherein the fibers have a predominant orientation which is directed in the cross direction of the forming surface, the fibers of the second loosely-assembled fibrous structure inter-mingling and interentangling with the fibers of the first loosely-assembled fibrous structure whereby there is made a wet-formed nonwoven textile fabric having a unitary structure, balanced construction, predetermined desired properties in the long and cross directions, uniformity, and good opacity and covering power.

BACKGROUND Many people have been engaged for many years in the manufacture of nonwoven textile fabrics which can be made without resorting to the spinning, twisting, and

c ICC twining of individual fibers into yarns and strands, and the subsequent weaving, knitting, or other fabricating of these yarns and strands into fabrics.

Such nonwoven textile fabrics have usually been manufactured by laying down one or more fibrous layers or webs of textile length fibers by dry textile carding techniques which normally align the majority of the individual fibers more or less generally lengthwise of the fibrous layer or web being prepared.

The individual textile length fibers of these carded fibrous webs are then bonded by conventional bonding techniques, such as, for example, by intermittent print pattern bonding, whereby a unitary, self-sustaining nonwoven textile fabrics is obtained.

Such manufacturing techniques, however are relatively slow and it has always been desired that manufacturing processes having greater production rates be devised. Additionally it is to be noted that such dry textile carding and bonding techniques are normally applicable only to fibers having a textile cardable length of at least about 1A; inch and preferably longer and are not applicable to short fibers such as wood pulp fibers which have very short lengths of from about 1A; inch down to about 1/5 inch or less.

More recently, people have been engaged in the manufacture of nonwoven textile fabrics by wet-forming techniques on conventional or`modified papermaking or similar machines. Such manufacturing techniques advantageously have much higher production rates and are also applicable to very short fibers such as Wood pulp fibers. Unfortunately, however, difficulties are often encountered in the use of the longer textile length fibers in such wet-forming manufacturing techniques.

One of the most intr-ansigent problems of nonwoven textile fabric manufacture is the inherent tendency of all fibrous web forming processes using textile length fibers to produce a fabric having a majority of the fibers oriented in the machine or long direction. This is particularly true for light weight fibrous webs produced at relatively high speeds. This unidirectional character is a familiar feature of carded fibrous webs and of wetformed fibrous webs using the classic papermaking machine arrangement.

Attempts have been made previously to produce crossoriented fibrous webs of textile length fibers by laminating, needling, or otherwise bounding cross lapped card webs but such procedures have failed to achieve a unitary structure, or good opacity and covering power, or sufficiently high production speeds. Specifically, in many of these attempts, it has been particularly noted that the cross-lapped fibrous webs do not satisfactorily form an integral or unitary structure and considerable delamination problems have results in which the cross lapped fibrous webs have undesirably separated from one another. Also, in many cases it has been noted that the cross-lapped fibrous webs do not possess sufficient opacity and covering power. This is particularly true if the webs are hydraulically rearranged into predetermined patterned apertured nonwoven textile fabrics containing apertures by processes and apparatus more particularly described in U.S. Pat. 2,862,251 which issued Dec. 2, 1958 t0 F. Kalwaites.

Although the nonwoven textile fabrics of the present inventive concept also contain pores or openings, they are extremely small in diameter and are also located at random, whereby the opacity or covering power of the resulting nonwoven textile fabric is not substantially diminished.

THE INVENTIVE CONCEPT It has been found that a foraminous, wet-formed, nonwoven textile fabric having a unitary structure, balanced construction, predetermined desired properties in the long and cross directions, uniformity, and good opacity and covering power comprising uncarded, relatively straight, smooth-surfaced, synthetic textile fibers having an average length of from about 3%; inch to about 11/2 inches or more, the nonwoven textile fabric having two major axes of predominant fiber orientation directed substantially at right angles to each other, one axis being directed generally in the long direction of the nonwoven textile fabric and the other axis being directed generally in the cross direction of the nonwoven textile fabric, a preponderance of the fibers being arranged in generally parallel arrays of bundles which are oriented in the direction of one of the two major axes of predominant fiber orientation, with the bundles having diameters of from about 0.04 mm. to about 0.6- or 1 mm. and extending generally from one side of the nonwoven textile fabric to the other side thereof or generally for the full length of the nonwoven textile fabric and containing from about 3 to about 200 or more fibers in each bundle and being spaced apart a distance of from about 0.2 mm. to about 1.5 mm., on an approximate center-to-center basis may be made by forming an aqueous slurry comprising synthetic fibers having an average length of from about inch to about 11A inches or more; causing said aqueous slurry to flow at a predetermined velocity in a thin, flat, sheet-like planar configuration; discharging said aqueous slurry of fibers directly upon a moving forming surface and forming a loosely-assembled fibrous structure thereon wherein the individual fibers have a predominant orientation in the direction of movement of said forming surface; and angul-arly discharging a second aqueous slurry of fibers also having a thin, flat, sheet-like planar configuration upon the loosely-assembled fibrous structure, to form a second loosely-assembled fibrous structure thereon wherein the fibers of the second loosely assembled fibrous structure have a predominant orientation which is directed in the cross direction of the forming surface, whereby there is made a wet-formed nonwoven textile fabric having a unitary structure, balanced construction, predetermined desired properties in the long and cross direction, uniformity, and good opacity and covering power.

In the following specification and accompanying drawings, there is described and illustrated preferred embodiments of the invention but it is to be understood that the inventive concept is not to be considered limited to the embodiments disclosed, except as determined by the scope of the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS Referring to accompanying drawings:

FIG. 1 is a schematic drawing showing a typical prior art nonwoven textile fabric wherein there is basically only one primary direction of predominant fiber orientation which is directed substantially in the long direction of the nonwoven textile fabric;

FIG. 2 is a schematic drawing showing a typical nonwoven textile fabric of the present invention wherein there are Ibasically two primary directions of predominant fiber orientation which are directed substantially at right angles to each other and are generally in the long and in the cross direction of the nonwoven textile fabric;

FIG. 3 is a schematic drawing showing a typical iiow chart of a portion of a Wet-forming manufacturing process, representing a preferred high velocity embodiment of the present inventive concept;

FIG. 4 is an enlarged drawing of a cross-sectional view of a delivery tray which is a part of the apparatus shown in FIG. 3, taken on the line 4-4 thereof looking in the direction indicated by the arrows;

FIG. 5 is a schematic drawing showing a typical fiow chart of a portion of another web-forming manufacturing process, representing a preferred low velocity embodiment of the present inventive concept; and

FIGS. 6A and 6F are simplified schematic drawings showing a reasonable explanation of the theory involved in the various changes in the fiber configuration and orientation at several stages during the process as applied to to the concept illustrated in FIG. 3.

BRIEF DESCRIPTION OF THE PRODUCT OF THE INVENTION With particular reference to FIG. l, there is schematically shown a typical nonwoven textile fabric of the prior art wherein there is basically only one primary direction of predominant liber orientation which is directed substantially in the long direction of the nonwoven textile fabric. Such a nonwoven textile fabric possesses very high strength, but very low elongation in the long direction, whereas it has very low strength but very high elongation in the cross direction. Additionally, the nonwoven textile fabric is very prone to splitting along a long axis but is very resistant to splitting in the cross direction. This naturally creates an unbalanced and undesirable fabric construction with an unbalanced and undesirable ratio of properties and characteristics inthe long and cross directions of the nonwoven textile fabric.

With reference to FIG. 2, there is schematically shown a typical nonwoven textile fabric of the present invention wherein there are basically two primary directions of predominant fiber orientation which are directed at right angles to each other. As indicated by the arrows, one primary direction of predominant fiber orientation is gentrally in the long direction of the nonwoven textile fabric whereas the other primary direction of predominant fiber orientation is generally in the cross direction of the nonwoven textile fabric.

Each of these primary liber orientations may be considered to be a property and characteristic vector, one in the long direction and the other in the cross direction of the nonwoven textile fabric. It is to be noted at once that if these vectors are equal, the properties and characteristics of the nonwoven textile fabric in the long direction are substantially equal to the properties and characetristics of the nonwoven textile fabric in the cross direction.

The result is a balanced and desirable fabric construction wherein the strength, elongation, resistance to splitting, and other properties and characteristics are generally balanced and equal in the long and cross directions.

However, if a larger number of fibers is laid down in a particular direction, or if heavier, longer or stronger fibers are used in that particular direction, then the tensile component and resistance to elongation or splitting in that particular direction will be greater. As a result, desired physical and chemical properties and characteristics can be designed and built into the nonwoven textile fabric, as desired or required. Thus, the selection of the particular type of fiber, or its fiber density or concentration, or its size, length, or strength will determine the physical and chemical properties and characteristics which are ultimately obtained.

BRIEF DESCRIPTION OF THE PROCESS OF THE INVENTION With particular reference to FIG. 3, there is shown the discharge portion of a dispersion tank 10 which is suitable for forming a substantially uniform aqueous dispersion of the fibers to be used in the formation of the nonwoven textile fabric of the present invention.

FIBERS USED The fibers which are dispersed in the dispersion tank 10 Imay comprise 100% uncarded, relatively straight, smooth-surfaced synthetic textile length fibers having an average length of from about inch to about 11/2 inches or more, or, if so desired or required, the dispersion may comprise a mixture of at least about 50% by weight of such textile length synthetic fibers and less than about 50% by weight of relatively unbeaten and unrefined short fibers having an average length of from about 1/6 inch (0.167 inch) to about 1/25 inch (0.040).

TEXTILE LENGTH SYNTHETIC FIBERS The textile length fibers may be selected from a large group of synthetic o r man-made fibers such as: the cellulosic fibers, notably regenerated cellulose (both viscose and cuprammonium processes), cellulose acetate, and cellulose triacetate; the non-cellulosic fibers such as: the polyamide fibers, notably nylon 6,6 and 6; the polyesters, notably Dacron, Fortrel and Kodel; the acrylics, notably Creslan, Acrilan and Orlon; the modacrylics, notably Dynel and Verel; the polyolefins, especially polypropylene and polyethylene, notably Vectra and Herculon; the spandexes, notably Lycra and Unel; the fluorocarbons, notably Teflon TEE and FEP; etc. These fibers may be used by themselves, or in various combinations and blends of two or more species in varying percentages, as desired or required.

The denier of the synthetic or man-made textile length fibers may be varied relatively widely, depending on the circumstances, and vary from about 11/2 denier to about 6 denier, with low deniers to about 1 or less, and higher deniers to about 9, 15, or more, being of use in special circumstances.

SHORT FIBERS The remaining fibers of the aqueous dispersion, if other fibers are used, are wood pulp fibers or other short fibers.

Unbeaten or unrefined wood pulp fibers, or at least relatively unbeaten or unrefined wood pulp fibers, are preferably used inasmuch as beating and refining are rather severe mechanical treatments, and beat and macerate the fibers whereby enhanced hydration bonding is obtained in the nal product which is not desired in the present inventive concept and which leads to a product which undesirably has increased stiffness, harshness and a papery hand.

However, in some circumstances, it may be desired to include a small amount, say, up to about by weight of thoroughly beaten, thoroughly hydrated fibrillated wood pulp fibers which will act as a bonding agent, in order to unify the nonwoven textile fabric and to increase its cohesive properties.

Although softwood sulfate pulp will be disclosed as the preferred type of wood pulp fiber used in the application of the present invention, substantially any type of wood pulp, either hardwood or softwood, is of use. Examples of other types of Wood pulp are: sulfte pulps in which the cooking liquor, calcium or magnesium bisulfite, is acid, or sodium sulfte which is neutral or slightly alkaline; soda pulps in which the cooking liquor, caustic soda, is alkaline; kraft or sulfate pulps in which the cooking liquor, sodium hydroxide and sodium sulfide, is alkaline, etc.

Although wood pulp fibers are preferred in the application of the present inventive concept, other short fibers or fibrous materials are of use. Examples of such short fibers or fibrous materials having lengths of from about 1/s inch to about 1,425 inch or less are: cotton linters, bagasse, iiax, jute, straw, bamboo, esparto grass, rayon, and the like.

It is essential that all the fibers used in the application of the principles of the present invention be capable of being dispersed substantially uniformly in the aqueous slurry. The concentration of the fibers in the liber dispersion varies widely and normally is in the range of from about 0.02% by weight to about 0.2% by weight, based on the dry weight of the fibers. Greater or lesser fiber concentrations may be used for special circumstances.

DISPERSION AIDS Dispersion aids are used in the aqueous slurry in order to assist or promote the desired uniformity of fiber dispersion. Examples of such dispersion aids are: collagen;

Cytame 5 and Cytame 6, which are water-soluble synthetic anionic polyacrylamide linear polymers having extremely high average molecular weights of about 15 million; Polyox FRA and Polyox coagulants, which are water-soluble ethylene oxide polymers having an average molecular weight of about 7 million and 5 million, respectively; Reten 210, which is a synthetic strongly cationic polyamine having an average molecular weight of at least about 1 million; etc.

The concentration of the dispersion aid in the aqueous slurry varies widely depending on the type and concentration of the fibers used, the effectiveness of the dispersion aid itself, and the dispersing effect desired or required, etc. Normally, from about 5 parts per million to about 500 parts per million of dispersion aid, based on the weight of the aqueous dispersion, is satisfactory with lesser or greater concentrations being of use in special circumstances.

THE DELIVERY TRAY Having formed the substantially uniform, aqueous dispersion or slurry of fibers in the dispersion tank 10, the aqueous slurry is then delivered through the discharge portion of the dispersion tank to a relatively fiat, shallow delivery tray 12. The delivery tray 12 is best shown in FIG. 4 and it is to be noted that its width is many times its depth whereby the aqueous slurry of fibers which flows therein possesses a laminar flow substantially in a fiat, sheet-like plane. Turbulence, eddy currents, and other disruptive effects are reduced to a minimum.

The ratio of the width of the delivery tray to its depth, or more importantly the ratio of the width of the aqueous slurry therein to its depth is normally on the order of at least about 20 to 1 and preferably 100 to l, or even higher. For example, delivery trays having a width of about 36 inches normally carry an aqueous slurry having an average depth of from about 1A inch to about 3%; inch which are equivalent to widthzdepth ratios of 144:1 and 48:1, respectively.

For very large commercial installations employing very wide Fourdrinier wires at extremely high Wire velocities, it is advisable to use very wide delivery trays which may be as wide as about 40 feet and wherein the fiber slurry may have a depth of as little as 1A inch to 1/2 inch. Such an arrangement would create a Width to depth ratio as high as 1920z1 or 960:1, respectively. Such an arrangement would provide for the discharge of very large volumes of fiber slurry at relatively low slurry velocities and thus create smooth, even, non-turbulent flow.

The length of the delivery tray 12, when combined with the length of the discharge portion of the dispersion tank 10, should be long enough to provide a smooth, nonturbulent flow in the slurry as it moves to the end portion 16 of the delivery tray 12. Under normal circumstances, a length of vat least about l or 2 feet is sufiicient.

The velocity of the fibers of the aqueous slurry in the delivery tray 12 may also be varied relatively widely and normally is in the range of from about 20 feet per minute to about 260 feet per minute and preferably from about 100 to about 200 feet per minute. The velocity of the fibers as they move in the delivery tray is an important factor affecting the properties and characteristics of the resulting nonwoven textile fabric.

Inasmuch as the velocity range of from about 20 feet per minute to about 260 feet per minute represents a relatively wide velocity range for the fiber slurry, a more detailed breakdown of this velocity range is deemed advisable. Fiber slurries in the low range of from about 20 feet per minute to about 65 feet per minute are normally used with high angles of approach of from about to about (to be defined in greater detail hereinafter) and with low Fourdrinier wire velocities (also to be defined in greater detail hereinafter). Fiber slurry velocities in the high range of from about 65 feet per minute to about 260 feet per minute are normally used with low angles of approach of from about 10 to about 80 and Vwith high Fourdrinier wire velocities.

The delivery tray 12 is positioned with its longitudinal axis directed angularly with respect to the direction of movement of a Fourdrinier wire 14 which is located adjacent thereto, whereby the at, sheet-like planar flow of the aqueous slurry and the fibers therein approach the Fourdrinier wire 14 at a predetermined angle a. The delivery tray 12 is adjustably mounted so that it can be positioned at various angles to the Fourdrinier wire 14 so that the angle of approach a of the aqueous slurry can be selectively predetermined for reasons to become clear from the description which follows. As shown in FIG. 3, the angle of approach of the fiber slurry is 45 but this angle is merely illustrative of one embodiment of the invention and is not to be construed as limitative thereof.

In general, angles of approach a fall within the range of from about 10 to about 100, as measured clockwise with respect to the long axis of the Fourdrinier wire, and depend upon many factors, primarily the velocity of the aqueous slurry in the delivery tray and particularly the velocity of the Fourdrinier wire.

The angle of approach a is an important factor affecting the properties and characteristics of the resulting nonwoven textile fabric.

Inasmuch as the range of the angles of approach of the fiber slurry of from about 10 to about 100 represents a relatively wide range, a more detailed breakdown is deemed advisable. Low angles of approach of from about 10 to about 80 are normally used with high fiber slurry velocities of from about 65 feet per minute to about 260 feet per minute and with high Fourdrinier wire velocities to be defined hereinafter. High angles of approach of from about 80 to about 100 are normally used with low fiber slurry velocities of from about feet per minute to about 65 feet per minute and with low Fourdrinier wire velocities.

The front or delivery end of the delivery. tray 12 preferably possesses an angular edge 16 whereby the aqueous slurry is capable of being delivered substantially uniformly across the full width of the Fourdrinier wire 14. Such an angular cut to the front edge of the delivery tray 12 serves to deposit on the Fourdrinier wire a substantially uniform array of fibers across the width of the Fourdrinier which normally would not be possible if all the aqueous slurry were to be delivered at one edge of the Fourdrinier wire 14 and compelled to flow completely across the full width thereof.

The use of such an angular front edge 16 is of particular advantage when wide Fourdrinier wires are used. The advantages are, of course, less when medium width Fourdrinier wires are used and may be dispensed with completely for narrow Fourdrinier wires. As shown, the front edge 16 is cut at an angle of about 45 to the longitudinal axis of the delivery tray 12 but this angle may be changed within a range of from about 0 to about 75, as measured normal to the fiber flow, as desired or required, depending on the factors mentioned hereinbefore, and particularly the velocity of the Fourdrinier w1re.

THE FOURDRINIER WIRE The Fourdrinier wire 14 passes directly under the delivery end of the delivery tray 12 and is sufficiently close thereto, as measured in the vertical direction, as to substantially reduce the fluid head of the aqueous slurry to a matter of less than about 1 inch of fluid head or preferably even less and to thereby minimize the waterfall effect of the slurry as it is delivered from 'the delivery tray 12 to the Fourdrinier wire 14. This also serves to lessen the turbulence, swirling and eddying in the aqueous slurry in the area of aqueous slurry transfer and to reduce the tendency of the fibers to move about into undesired orientations.

The Fourdrinier wire is a standard or conventional finely woven metal or synthetic fiber cloth which permits rapid drainage of water but retains fibers. The mesh size is preferably relatively coarse and is in the range of from about 15 mesh to about 120 mesh.

The velocity of the Fourdrinier wire 14 may be varied relatively widely but is normally in the range of from about 20 feet per minute to about 260 feet per minute. Higher or lower speeds may be used for special circumstances.

Inasmuch as the velocity range of the Fourdrinier wire of from about 20 feet per minute to about 260 feet per minute represents a relatively wide range, a more detailed breakdown of the range is deemed advisable. Low Fourdrinier wire velocities of from about 20 feet per minute to about 80 feet per minute are normally used with low fiber slurry velocities of from about 20 feet per minute to about feet per minute and with high angles of approach of from about to about 100. High Fourdrinier wire velocities of from about 80 feet per minute to about 260 feet per minute are normally used with high fiber slurry velocities of from about 65 feet per minute to about 260 feet per minute and with low angles of approach of from about 10 to about 80.

The following table shows the relationship between these factors and the drawings illustrating the particular processes involved.

FIBER ORIENTATION The 'fibers of the aqueous slurry deposited on the Fourdrinier wire assume a angular position thereon, as shown, with respect to the direction of movement of the Fourdrinier wire 14. It is believed that this 90 angular configuration is due primarly to the effect on the fibers of: (l) the velocity of the fibers in the planar flow in the delivery tray; (2) the angle of the delivery tray to the Fourdrinier wire; (3) the velocity of the Fourdrinier wire; (4) the mesh of the Fourdrinier wires; etc. The particular angular deposition illustrated in FIG. 3 of approximately 90 represents a preferred embodiment of the present invention.

Such a fibrous structure possesses excellent strength in the cross direction but very little strength in the long direction. Its other properties and particularly its elongation characteristics are similarly unbalanced. However, a balanced construction with predetermined desired properties in the long and cross directions, uniformity, and good opacity and covering power is obtained by combining this fibrous structure with a fibrous structure wherein the fibers -lie generally at 0 to the long direction of the fibrous structure.

This is done either by depositing such a 0 fibrous structure on top of the 90 cross-laid fibrous structure, or by reversing the process and depositing the 90 cross-laid fibrous structure on top of the 0 fibrous structure. This latter process is illustrated in FIG. 3.

As shown in that ligure, a dispersion tank 20 equipped with a relatively flat, shallow delivery tray 22 having a front discharge edge 26 is provided for depositing an aqueous slurry of fibers on the moving Fourdrinier wire.

T he dispersion tank 20 is similar in function and operation to the dispersion tank 10 described previously and is suitable for forming a substantially uniform aqueous dispersion of the fibers to be used in the formation of the nonwoven textile fabric of the present invention. The fibers used, including the textile length synthetic fibers and the short fibers, are similar to those described previously. Dispersion aids may be used, as desired or required. i

The delivery tray 22 is similar basically to the delivery tray 12 described previously except that delivery tray 22 delivers an aqueous dispersion of fibers directly on to the Fourdrinier wire 14 at a 0 direction, rather than angularly as disclosed for delivery tray 12.

The result is, of course, a fibrous structure in which the primary direction of predominant ber orientation is in the direction, that is, in general alignment with the long or machine direction of the nonwoven textile fabric.

The `fibrous structure formed on the Fourdrinier wire 14 by the aqueous slurry delivered by the delivery tray 22 is dewatered by drainage through the Fourdrinier wire and is carried forwardly under the delivery tray 12 and the second aqueous slurry deposited thereon, thus forming the nonwoven textile fabric of the present invention. As a matter of fact, in the event that the aqueous slurries are alike, one dispersion tank may be used to feed both delivery trays, or a plurality of such trays, if more than two are used.

In the normal course of events, however, it has been desirable that two or more separate dispersion tanks be used and that the fiber consistency in the first dispersion tank be less than that in the second dispersion tank and that, if there are three dispersion tanks, that the fiber consistency in the second tank be less than that in the third tank, and so forth.

It is to be recalled that the first aqueous slurry is discharged directly onto the Fourdrinier wire which possesses certain drainage properties and characteristics. The second aqueous slurry, however, is discharged on top of the fibrous array or stucture formed by the first aqueous slurry and hence its drainage is markedly different and considerably slower since the water must pass through the fibrous array or structure before draining through the Fourdrinier wire. Additionally, there may be more overliow over the sides of the Fourdrinier during the second drainage situation.

The overall range of fiber consistencies is from about 0.02% by weight to about 0.2% by weight, on a dry fiber basis, with the liber consistency in the first dispersion tank being in the range of from about 0.02% by weight to about 0.15% by weight and the fiber consistency in the second dispersion tank being in the range of from about 0.05% by weight to about 0.20% by weight. Normally, however, the second fiber consistency is from about 25% to about 200% greater than the first fiber consistency.

The aqueous slurry of fibers from the second delivery tray 22 also has a flat, substantially planar flow and its deposition on the Fourdrinier wire is similar to the deposition of fibers from the first delivery tray 12 with one very notable exception. Specifically, the direction of the flow of the fibers in the second delivery tray is basically 0 in orientation whereas the fibers delivered from delivery tray 12 take a 90 direction to the Fourdrinier wire movement. As a result, the fibers deposited from the second delivery tray are positioned approximately 90 out of phase with the fibers deposited from the first delivery tray. The fiber orientations are thus at right angles to each other, as shown in FIG. 3.

Additionally, during the deposition of the second fiber slurry, there is sufficient intermingling and interentangling with the fibers of the first slurry that a significant number of the fibers intermix particularly at the slurry interfaces, to form a unitary structure which subsequently can be demonstrated as resisting separation or delamination. This significant intermingling of the fibers of each of the portions laid down by the delivery trays is an important and very desirable feature of the present invention.

The resulting nonwoven textile fabric is found to possess two major axes of predominant fiber orientation directed substantially at right angles to each other and with the fibers thereof substantially uniformly intermingled and interentangled withveach other in a substantially planar configuration. The result is a foraminous, Wetformed nonwoven textile fabric having a unitary structure, balanced construction, predetermined desired properties and characteristics in the long and cross directions, uniformity, and good opacity and covering power.

Rotation of the delivery tray 12 to different angular relationships other than the 45 illustrated in FIG. 3 will result in a change in the angular deposition of the fibers with respect to the direction of movement of the Fourdrinier wire unless the slurry velocity is changed, or unless the Fourdrinier wire velocity is changed, whereby the angular orientation and deposition can be maintained.

LOW VELOCITY TECHNIQUES Thus far, the emphasis has been placed primarily on process and apparatus suitable for application under high velocity conditions. In FIG. 5, there is illustrated process and apparatus suitable for application of the low velocity principles. In this figure, there is disclosed the discharge portion of a first dispersion tank 40 which leads to a first delivery tray 42 having a front discharge edge 46 extending directly in alignment with and over a moving Fourdrinier Wire 44. The first aqueous slurry prepared in the first dispersing tank is delivered in typical fiat, sheet-like planar configuration to the Fourdrinier Wire at an angle of discharge of about 0 to the direction of movement of the Fourdrinier wire. The directions of liow and the fiber orientation are as indicated.

A second dispersion tank 50 supplies a second aqueous slurry to a second delivery tray 52 having a front edge 56 which also extends over the moving Fourdrinier wire 44 although angularly with respect to its direction of movement. The second aqueous slurry prepared in the second dispersing tank is delivered in a fiat, sheetlike planar configuration to the Fourdrinier wire at an angle of discharge of about 90, as measured clockwise to the direction of movement of the Fourdrinier wire. And, it is delivered, as described previously, on top of the first fibrous array or structure formed from the first aqueous slurry. Again, the directions of flow and the fiber orientation are as indicated. The primary directions of predominant orientation are represented at the right end of the nonwoven textile fabric.

It is to be noted that, under the low velocity techniques, the individual fibers are delivered at a specific angle to the Fourdrinier wire and that they are deposited and remain at that angle as the fibrous array or structure is drained and dewatered and moved forwardly.

FORMATION OF FIBER BUNDLES An additional feature and result of the liuid interaction between (1) the substantially planar flow of the aqueous slurry and (2) the operating variables of slurry velocity, angle of approach, and Fourdrinier velocity and surface characteristics is the surprising and unexpected formation of the individual fibers into substantially parallel arrays of bundles or groups of bers aligned generally in the primary directions of predominant fiber orientation.

These fiber bundles are of continuous length and extend the full length of the nonwoven textile fabric as well as angularly at 90 from one side of the nonwoven textile fabric to the other side. Usually, there are up to about 20 fiber bundles per inch. Normally, they are parallel and are spaced from one another by a distance of from about 0.2 to about 1.5 mm., center-to-center. Each bundle contains from about 3 to about 200 or more individual fibers with approximately 50% of the 'fibers in a bundle in multi-point, almost continuous contact for a distance of 1A inch or more. The bundles have an approximate range of diameters of from about 0.04 millimeter to labout 0.6 or 1 millimeter or more. Within a given fibrous structure, approximately 50% of the fibers in Ia given fiber bundle may participate in branching from one bundle to other adjacent bundles in a length of about 1A inch. This branching is at an angle of about 35 or less to the primary direction of predominant fiber orientation. Other than that small portion of their length which is proceeding from one fiber bundle to other adjacent fiber bundles, the fibers in the primary fiber bundles are in multi-point, almost continuous contact with the same adjacent fiber or fibers for a distance of about 1A inch or more. These continuous fiber bundles run the entire length and width of the nonwoven textile fabric. Within a given layer, the adjacent parallel fiber bundles are also linked by from about 20 to about 200 fibers in a distance of about 1/1 inch at an angle of about 60 or more to the primary direction of predominant fiber orientation. These linkages are in laddition to the branching described previously. These connecting fibers which intersect the primary fiber bundles at a large angle, approaching about 90 extend in this general direction for a large fraction of their length, perhaps as much as about 3/s inch.

A relatively large number of these fibers are actually interwoven and pass over and under other fibers in a random fashion with the primary fiber Ibundles, i.e., these connecting fibers which lie across the primary direction pass over, under, and through the primary fiber bundles.

PORES OR OPENINGS OF THE FIBROUS STRUCTURE Still another feature and result of the relationship between (l) the substantially planar ow of the aqueous slurry and (2) the opel-ating variables of slurry viscosity, angle of approach, and velocity and surface characteristics of the wire is the formation of a very large number of very small pores or openings randomly arranged or distributed in the fibrous structure.

These pores or openings are so small in diameter that, even though they are very many in number, they do not create very much open surface area, that is, areas which have substantially zero fiber density. As a result, the resulting fibrous structure possesses good opacity and covering power.

The determination of the number of pores or openings in the fibrous structure is a very difficult matter to determine inasmuch as the greater the magnification of the fibrous structure, then the greater is the number of pores or openings which can be detected. Basically, it resolves to a definition as to what is considered to be a pore Within the scope of the present invention, therefore, a pore or opening is herein defined as an area of substantially zero fiber density and which possesses a diameter larger than 0.005 inch.

The fibrous structure of the present invention has substantially none, or at the very most, a very low number of pores or apertures which have diameters equal to or greater than about 0.015 inch. This very low number is less than about 4% of the total number of pores or openings in the fibrous structure, and is normally on the order of about 1% or 2%.

More specifically, the vast preponderance of the randomly-distributed pores or openings in the fibrous structure range in diameter from about 0.005 inch to about 0.015 inch and normally from about 0.005 inch to labout 0.010 inch.

The total amount of open surface area created by the total number of pores or openings, that is, the total surface coverage of the areas which have substantially zero fiber density in the fibrous structures of the present invention is less than about 10%, and more likely, on the order of less than about 5%.

The total number of pores or openings in the fibrous structure is on the order of from at least about 600 to about 1500 or more pores per square inch in the range of from 'about 0.005 inch to about 0.010 inch diameter, from about 100 to about 400 pores per square inch in the range of from about 0.010 inch to about 0.015 inch diameter, and from about 20 to 60 pores per square inch in the range of slightly greater than 0.015 inch diameter.

The following table sets forth these values in percentage values:

Number of Diameter of pores pores Percentage The exact mechanism whereby the novel and patentable results of the present inventive concept are obtained is not precisely known but it is believed that the following is a reasonable explanation thereof with particular reference to the concept illustrated in FIG. 3.

Consideration of the nature of viscous laminar flow of the aqueous slurry makes it clear that the bottom layers of fiber dispersion flowing down the fiat, shallow delivery tray Iwill be fiowing much slower than the upper layers and therefore any fibers which extend from layer to another will be straightened out in the machine or long direction. When this planar iiow contacts the Fourdrinier wire, two new motions will be introduced into the fiber dispersion to varying extents in the various layers. These two new directions are: (l) down through the wire at a very slow rate; and (2) in the direction of the Fourdrinier wire at a much faster rate. However, the very upper layers of the aqueous fiber dispersion remain essentially unaffected by the movement through or With the Fourdrinier wire.

At the very bottom layers, the fiber orientation and the ow downwards means that leading end of the fiber will be caught by the lower layers of fiow moving in the direction of the Fourdrinier wire before the trailing end of the fiber is affected. The intermediate portion of the fiber will be affected by the fiow directions of the intermediate layers which will be in between the fiow direction and the machine direction.

The results, as set forth in FIGS. 6A through 6F, of the movement of the segments of the fiber in several directions is a fiber orientation at about if the Fourdrinier wire and the slurry fiow speeds are in the proper ranges.

FIG. 6A discloses the directions of the Fourdrinier wire motion and the flow of the aqueous slurry of fibers. FIG. 6B discloses the fiber configuration and orientation as it is moving in the direction of movement of the aqueous fiber slurrry. This is the fiber configuration before the fiber is deposited on the Fourdrinier wire. FIG. 6C illustrates the fiber configuration as it exists when the fiber tip a first contacts and is affected by the movement of the Fourdrinier wire. The curving of the leading end a of the fiber and the direction of the trailing end b is to be noted especially.

FIG. 6D represents the fiber configuration as the fiber is being laid down on the Fourdrinier wire. Notice the increase in curvature. FIG. 6E represents the fiber configuration at a moment in time slightly after the time represented in FIG. 6D. Again, note the increase in the change in curvature. FIG. 6F represents the fiber configuration and orientation as the fiber finally comes to rest in its final position on the Fourdrinier wire.

These figures illustrate the mechanism for obtaining the primary directions of predominant fiber orientation using a smooth, fiat, shallow delivery tray having a relatively high width to depth ratio for the aqueous slurry. This mechanism also accounts for the presence of a considerable amount of interweaving of the fibers which is noted in the final product. Such interweaving is brought about since some of the fibers may be deposited on the Fourdrinier wire before they have completed the reorientation process. As such, they thus partially lie across the primary orientation and are subsequently covered over by the other oriented fibers.

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.

13 Example I The apparatus illustrate in FIG. 3 of the drawings is used. Standard finished 3A inch, 1.5 denier tow cut rayon fibers are dispersed in the first dispersing tank to a fiber consistency of 0.03% by weight on a dry fiber basis in the slurry by means of gentle, non-turbulent stirring of a larger beater bar. Sixty parts per million of a dispersion aid Cytame 6 is used to assist in the formation of a uniform dispersion of the fibers.

The first fiber dispersion is delivered from the dispersion tank to a first, fiat, shallow delivery tray having a front delivery edge cut at an angle of as shown. The width of the delivery tray is 3 feet and the depth of the fiber dispersion in the delivery tray is about '1/2 inch. The slurry width:depth ratio is about 72: 1. The velocity of the fiber slurry is approximately 90 feet per minute. The first delivery tray is positioned at an angle of about 0 to the direction of movement of the closely-adjacent Fourdrinier wire ywhich is travelling at a high velocity of about 154 feet per minute.

The fiber slurry has a substantially flat, sheet-like planar flow and is discharged directly by the fiat, shallow delivery tray onto the closely-adjacent moving Fourdrinier wire to form a fibrous array or structure thereon wherein the fibers have a predominant orientation also directed at an angle of 0 to the direction of movement of the Fourdrinier wire.

The Fourdrinier wire carries the fibrous array or structure forwardly and is passed directly under the angular discharge portion of another delivery tray which is discharging a similar fiber slurry under similar conditions except that the fiber consistency of the second aqueous slurry is about 0.1% by weight.

In the case of the first delivery tray, the angle of approach of the aqueous slurry is 0 to the direction of movement of the Fourdrinier wire. In the case of the second delivery tray, the aqueous slurry of fibers has an angle of approach of 45 as measured clockwise to the direction of movement of the Fourdrinier wire. As a result, the fiber slurry delivered from the second delivery tray forms a fibrous structure wherein the fibers have a predominant orientation directed at an angle of 90 as measured clockwise to the direction of movement of the Fourdrinier wire.

The direction of the predominant orientation given to both fibers is indicated at the right hand end of the Fourdrinier wire illustrated in FIG. 3.

Inasmuch as the fibrous structure deposited by the first delivery tray has just been formed and is not completely drained of water and has not set when the second fibrous slurry is deposited thereon, the fibers of both deposited slurries become substantially uniformly intermingled and interentangled with one another and form a substantially planar configuration. The fibers of the first formed portion extend upwardly and into the second formed portion and similarly the fibers of the second formed portion extend downwardly into the first formed portion. A completely integral and unitary structure is thus obtained wherein the two portions are interentangled to such an extent that is substantially impossible or at least extremely difficult to delaminate the resulting product.

Analysis of the nonwoven textile fabric reveals that there are about 700 pores or openings per square inch and that the pores or openings have diameters in the range of from about 0.003 inch or less up to a maximum of about 0.015 inch with an average diameter of about 0.006 inch. These pores or openings are distributed at random. The amount of open space of such a fabric based on the number and size of these pores and openings is approximately 2%.

The fiber bundles are substantially of continuous length and extend generally either along the long axis of the nonwoven textile fabric or generally along the cross axis from one side of the nonwoven textile fabric to the other side. Normally, they are approximately parallel in each array of bundles and are spaced from one another by a distance of from about 0.2 to about 1.5 mm., center-tocenter. Each bundle contains from about 3 to about 200 or more individual fibers with approximately 50% of the fibers in a bundle in multipoint, almost continuous contact along their entire lengths. The bundles have an approximate range of diameters of from about 0.04 mm. to about 0.6 mm. within a given fibrous structure and the adjacent parallel fiber bundles are linked and interconnected to each other by from about 5 to about 50 individual fibers branching from one fiber bundle to another along about lA of their length.

There are a very large number of very small pores or openings randomly arranged in the fibrous structure. Less than about 1% fall in the diameter. size of 0.016 inch or greater. More than 99% are less than 0.015 inch. The vast preponderance is in the range of from about 0.005 inch to about 0.010 inch.

The resulting nonwoven textile fabric is found to be self-sustaining and basically of single-ply construction. It has balanced physical properties and characteristics in both the long and cross directions. It has excellent uniformity and has excellent opacity and covering power.

Example II The procedures of Example I are followed substantially as set forth therein with the exception that the apparatus of FIG. 5 is used. In this case, the velocity of the Fourdrinier wire is decreased from a high value of 154 feet per minute to a low value of 30 feet per minute. The angle of approach of the second aqueous slurry of fiber is The front discharge end of the second delivery tray is cut at an angle. The water depth in the delivery tray is about 3A; inch. The delivery tray has a width of 15 inches. The slurry velocity is 50 feet per minute. The slurry consistencies are 0.02% and 0.05%, respectively. The dispersant aid is 250 parts per million of an acid swollen fibrillar collagen. The fibers are the same as in Example I. The results are generally similar to those obtained in Example I and the properties and characteristics of the resulting nonwoven textile fabric are generally comparable to those obtained in Example I.

Example III The procedure of Example II are followed substantially as set forth therein with the exception that the dispersant aid is 10 parts per million of Cytame 5.

The resulting nonwoven textile fabric is found to be generally comparable to the nonwoven textile fabric of Example II.

Example IV The procedures of Example I are followed substantially as set forth therein with the exception that the fiber consistency in the first dispersion tank is increased from 0.04% to 0.06% by weight and the fiber consistency in the second dispersion tank is increased from 0.1% by weight to 0.12% by weight. These changes increase the basis weight of the resulting product.

The results are generally comparable and the resulting nonwoven textile fabric possesses generally comparable physical properties and characteristics.

Example V The procedures of Example I are followed substantially as set forth therein with the exception that the fiber consistency in the first dispersion tank is increased from 0.04% to 0.1% by weight and the fiber consistency in the second dispersion tank is increased from 0.1% by weight to 0.15% by weight. These changes increase the basis weight of the resulting product.

The results are generally comparable and the resulting nonwoven textile fabric possesses generally comparable physical properties and characteristics.

15 Example VI The procedures of Example I are followed substantially as set forth therein with the exception that the rayon fibers used in Example I are replaced by a mixture of fibers which comprises 60% by weight of polypropylene fibers and 40% by weight of rayon fibers. These fibers have a length of 3A" and have a denier of 1'1/2. The fiber consistency in the aqueous slurry in the first dispersion tank is 0.1% by weight on a dry fiber basis and the fiber consistency in the second aqueous slurry is 0.15% by weight on a dry liber basis.

The results are generally comparable to those set forth in Example I and the resulting product has generally similar properties and characteristics comparable to the product resulting from Example I.

Example VII The procedures of Example I are carried out substantially as set forth therein with the exception that the rayon fibers used in Example I are replaced by la mixture of 50% by weight of 1%", 1.5 denier rayon and 50% by weight of a softwood sulfate wood pulp fiber. The fiber consistency in the first aqueous slurry is about 0.12% by weight and the fiber consistency in the second aque` ous slurry is 0.18% by weight.

The results are generally comparable to those set forth in Example I and the resulting product has generally similar properties and characteristics comparable to the product resulting from Example I.

Example VIII The procedures of Example I are followed substantially as set forth therein with the exception that the concentration of the dispersing aid (Cytame 6) is increased to 100 parts per million. The results are generally comparable to those obtained in Example I and the resulting nonwoven textile fabric is generally similar to the nonwoven textile fabric of Example I.

Example IX The procedures of Example I are followed substantially as set forth therein with the exception that 60 parts per million of Polyox FRA is used as the dispersing agent. The results are generally comparable to those obtained in Example I and the resulting non-woven textile fabric is generally similar to the nonwoven textile fabric in Example I.

Example X The procedures of Example I are followed substantially as set forth therein -with the exception that 25 parts per million of Cytame is used as the dispersing aid. The results are generally comparable to those obtained in Example I and the resulting nonwoven textile fabric is generally similar to the nonwoven textile fabric obtained in Example I.

Example XI The procedures of Example I are followed substantially as set forth therein with the exception that 250 parts per million of acid swollen fibrillar collagen is used as the dispersion aid. The results are generally comparable to those obtained in Example I and the resulting nonwoven textile fabric is generally similar to the nonwoven textile fabric of Example I.

As used herein, the terms two primary directions of predominant fiber orientation or two major axes or like terms does not mean that every fiber in the fibrous structure is aligned in either of the two directions. There will be fibers which are basically aligned in other directions. However, the preponderance of the fibers is aligned in the two directions and other fibers are definitely of a secondary or minor nature.

Although several specific examples of the inventive concept have been described, the same should not be construed as limited thereby nor to the specific features mentioned therein but to include various other equivalent features 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 foraminous, wet-formed fibrous structure of use in the manufacture of a nonwoven textile fabric comprising relatively straight, synthetic textile fibers having an average length of from about inch to about 11/2 inches or more, said fibrous structure having a major axis of predominant fiber orientation directed at an angle of from about to about 100 to the long direction of said fibrous structure, said fibrous structure comprising bundles of fibers aligned generally in the direction of the major axis of predominant fiber orientation, said bundles including fibers disposed in a generally linear, substantially parallel relationship, said bundles being interconnected by branched portions of fibers common to a plurality of bundles, none of said branched portions forming an angle greater than 35 to the major axis of predominant fiber orientation, with said bundles having `diameters of from about 0.04 mm. to about 1 mm. and extending generally from one side of the fibrous structure to the other side thereof and containing from about 3 to about 200 or more fibers in each bundle and being spaced apart a distance of from about 0.2 mm. to about 1.5 mm., on an approximate center-to-center basis.

2. A foraminous, wet-formed fibrous structure as defined in claim 1 wherein the major axis of predominant fiber orientation is directed at an angle of about to the long direction of the fibrous structure.

3. A foraminous, wet-formed fibrous structure according to claim 1 wherein said bundles of fibers are also linked by fibers disposed at an angle of about 60 or more to the major axis of predominant fiber orientation.

4. A foraminous, wet-formed nonwoven textile fabric having a unitary structure, balanced construction, predetermined desired properties in the long and cross drections, uniformity and good opacity and covering power comprising relatively straight, synthetic textile fibers having an average length of from about A inch to about 11/2 inches or more, said nonwoven textile fabric having two major axes of predominant fiber orientation directed at right angles to each other, one axis directed in the long direction of said nonwoven textile fabric and the other axis being directed in the cross direction of said nonwoven textile fabric, said fibrous structure comprising bundles of fibers, said bundles including fibers disposed in a generally linear, substantially parallel relationship, said bundles being interconnected by branched portions of fibers common to a plurality of bundles, none of said branched portions forming an angle greater than 35 to a major axis of predominant fiber orientation, some of said bundles being aligned generally in the direction of one of the major axes of predominant fiber orientation and other of said bundles being aligned generally in the direction of the other of the major axes of predominant fiber orientation, with said bundles having diameters of from about 0.04 mm. to about 1 mm. and extending generally from one side of the nonwoven textile fabric to the other side thereof and generally for the full length of the nonwoven textile fabric and containing from about 3 to about 200 or more fibers in each bundle and being spaced apart a distance of from about 0.2 mm. to about 1.5 mm., on an approximate center-by-center basis, said nonwoven textile fabric also possessing at least about 600 randomly-distributed pores per square inch, the diameters of at least about 96% of said pores being less than 0.016 inch.

5. A foraminous, wet-formed nonwoven textile fabric as defined in claim 4 wherein the major axes of predominant fiber orientation are directed at an angle of approximately 0 and approximately 90 to the long direction of the nonwoven textile fabric.

6. A method of making a foraminous, wet formed fibrous structure of use in the manufacture of a nonwoven textile fabric comprising:

forming an aqueous slurry comprising relatively straight, synthetic fibers having an average length of from about As inch to 1-1/2 inches;

causing said aqueous slurry to flow at a predetermined velocity in a thin, fiat, sheet-like planar configuration; and

angularly discharging said aqueous slurry of fibers having a thin, fiat, sheet-like planar configuration directly upon a moving forming surface having a predetermined velocity, said angle of discharge being from about to about 100 with respect to the longitudinal axis of said forming surface, and forming a fibrous structure thereon wherein the individual fibers have a predominant orientation substantially perpendicular to the direction of movement of said forming surface.

7. A method as defined in claim 6 wherein said angle of discharge is from about 80 to about 100.

8. A method as defined in claim 7 wherein the predetermined velocity of the aqueous slurry is in the range of from about 20 feet per minute to about 65 feet per minute.

9. A method as defined in claim 8 wherein the predetermined velocity of the moving forming surface upon which the aqueous slurry is discharged is in the range of from about 20 feet per minute to about 80 feet per minute.

10. A method as defined in claim 6 wherein said angle of discharge is from about 10 to about 80.

11. A method as defined in claim 10 wherein the predetermined velocity of the aqueous slurry is in the range of from about l65 feet per minute to about 260 feet per minute.

12. A method as defined in claim 11 wherein the predetermined velocty of the moving forming surface upon which the aqueous slurry is discharged is in the range of from about 80 feet per minute to about 260 feet per minute.

13. A method of making a wet-formed nonwoven textile fabric having a unitary structure, balanced construction, predetermined desired properties n the long and cross directions, uniformity and good opacity and covering power comprising:

forming an aqueous slurry comprising relatively straight, synthetic fibers having an average length of from about 1% inch to about 11/2 inches; causing said aqueous slurry to flow at a predetermined velocity in a thin, at, sheet-like planar configuration; discharging said aqueous slurry of fibers having a thin, fiat, sheet-like planar configuration directly upon a moving forming surface having a predetermined velocity, said aqueous slurry being discharged in a direction substantially parallel to the direction of movement of said moving forming surface, and forming a loosely-assembled brous structure thereon wherein the individual fibers have a predominant orientation in the direction of movement of said forming surface;

angularly discharging, at an angle of from about 10 to about 100 to the longitudinal axis of said moving forming surface, another aqueous slurry of relatively straight, synthetic fibers also having a thin, fiat, sheet-like planar configuration and a predetermined velocity upon said loosely-assembled fibrous structure to form another loosely-assembled fibrous structure wherein the fibers have a predominant orientation which is directed in the cross direction of said forming surface, said another loosely-assembled fibrous structure intermingling and interentangling with said loosely-assembled fibrous structure whereby there is made a wet-formed nonwoven textile fabric having a unitary structure, balanced construction, predetermined desired properties in the long and cross directions, uniformity and good opacity and covering power.

14. A method as defined in claim 13 wherein said angle of discharge of said another aqueous slurry is from about 80 to about 100.

15. A method as defined in claim 14 wherein the predetermined velocity of said another aqueous slurry is in the range of from about 20 feet per minute to about 65 feet per minute.

16. A method as defined in claim 15 wherein the predetermined velocity of the moving forming surface is in the range of from about 20 feet per minute to about 80 feet per minute.

17. A method as defined in claim 13 wherein said angle of discharge of said another aqueous slurry is from about 10 to about 80.

18. A method as defined in claim 17 wherein the predetermined velocity of said another aqueous slurry is in the range of from about feet per minute to about 260 feet per minute.

19. A method as defined in claim 18 wherein the predetermined velocity of the moving forming surface is in the range of from about feet per minute to about 260 feet per minute.

References Cited UNITED STATES PATENTS 3,150,416 9/1964 Such 162-114X 3,081,515 3/ 1963 Griswold et al. 162-114X 2,139,874 12/ 1938 Berry 162-345 X 989,461 4/1911 White 162-336 1,799,350 4/ 1931 Barnes 162-131 3,691,009 9/ 1972 Opderbeck et al. 162-146 3,720,578 3/ 1973 Heling et al. 162-203 X S. LEON BASHORE, Primary Examiner R. H. TUSHIN, Assistant Examiner U.S. Cl. X.R. 19-161 P; 161-153, 169; 162-131, 146

gg@ UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3608x095 Dated A Pl Boy-197)* Inventor(s) Jams-.S I'. McKnight It is certified 'that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In Column E, line l5, there should be one comme. after the word ,"however".

In com@ 2, lineal, "high" Should read u higher In Column 2, Vline L6, "bounding".shou1a read bfmding M In Column line 257-28, "gentrally" should read ger1erell;.y

ln Column LL, line 143, "cheracetristics" should read M- characteristics In column 5, line 2, "(0.0%)". Should read (0.01m inch) or less In culumnfj, 1in@ 16, "TEE" should read. TEE

lo Column 6, line 1%-, "coegulants" should reed coagulent In Column l2, line 16, "from layer" should read from one layer In yColumn 13, line 2, "illu-strate should read illustrated In Colufmel line T, "lenrgerm should read e large In Column 13,` line 60, "that is"hsh@u1d ma@ that it is 'In Column l, line 32, "fiber" should read fibers up.

ln Column lll, line lr6, "procedure" should read procedures L Slgned and sealed this 17th day of December E974 (SEAL) Attest:

PcCOY M. GIBSON JR. C., MA -TSHALL DANN attesting Officer Commissioner of Patents

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