US 3042576 A
Description (OCR text may contain errors)
y 1962 c. HARMON EIAL 3,042,576
METHOD AND APPARATUS FOR PRODUCING NONWOVEN FIBROUS SHEETS Filed June 17, 1957 9 Sheets-Sheet 1 a ,i 8 m S a O mm wm VRA MAW m & H 3 aw Y 2 @(L 0am [v 6 wumw qmmm MRQM mmw M m mm om m. J m w Q m h i Q F e h 4 A 90199 9 O \O M O r 1 mm 4.\ m. h mm m mh mm uh nh mmw QmN Omww 7 July 3, 1962 c. HARMQN ETAL 3,042,576
METHOD AND APPARATUS FOR PRODUCING NONWOVEN FIBROUS SHEETS Filed June 17, 1957 9 Sheets-Sheet 2 INVENTORS. CARLYLE HARMON FRANK KALWAITES,
MadorjJ-rmlhf fem/7211b ATTORN EYS.
July 3, 1962 c. HARMON ETAL METHOD AND APPARATUS FOR PRODUCING NONWOVEN FIBROUS SHEETS Filed June 17, 1957 9 Sheets-Sheet 3 Avamx mmavamm m Ms wwm n NMT. 1 vA T HW T I E N. AN KYa RNB/L o 46 m a 3 o 3 F W 6 6m 4 l 5 6 [v 16 v n 1 o M 3%, 7 0 a 0 a 3 V 0 WW 6 o 5 H o 6 I I? w 0 6 .I 3 6 6/ 4 H 6% c. HARMON ET AL 3,042,576
9 Sheets-Sheet 5 ATTORNEYS.
July 3, 1962 METHOD AND APPARATUS FOR PRODUCING NONWOVEN FIBROUS SHEETS Filed June 17, 1957 ww am L F I 9 Sheets-Sheet 6 C. HARMON ET AL METHOD AND APPARATUS FOR PRODUCING NONWOVEN FIBROUS SHEETS July 3, 1962 Filed June 17, 1957 INVENTORS. a CARLYLE HARMON FRANK KALWAITES, sz go/madarfizwlbrffiowidtfi ATTORNEYS- July 3, 1962 c. HARMON EI'AL METHOD AND APPARATUS FOR PRODUCING NONWOVEN FIBROUS SHEETS 9 Sheets-Sheet '7 Filed June 17, 1957 July 3, 1962 c. HARMON ETAL METHOD AND APPARATUS FOR PRODUCING NONWOVEN FIBROUS SHEETS Filed June 17, 1957 9 Sheets-Sheet 8 m s mNfi. N IMMM 5% w r R AR C W 0/ MW w E B ATTORNEYS.
July 3, 1962 c. HARMON ETAL METHOD AND APPARATUS FOR PRODUCING NONWOVEN FIBROUS SHEETS Filed June 17, 1957 9 Sheets-Sheet 9 INVENTORS. CARLYLE HARMON TMZEJ ATTORNEYS,
United States Patent ()fifice 3,042,576 Patented July 3, 1962 3,042,576 METHOD AND APPARATUS FOR PRODUCING NQNWOVEN FIBROUS SHEETS Carlyle Harmon, Scotch Plains, and Frank Kalwaites,
Highland Park, N.J., assignors to Chicopee Manufacturing Corporation, a corporation of Massachusetts Filed June 17, 1957, Ser. No. 666,009 8 Claims. (Cl. 162-114) This invention relates to a new method and apparatus for producing forarninous, nonwoven fibrous sheets, and particularly to the production of nonwoven fibrous sheets comprising spaced, interconnected packed fibrous portions which define openings arranged in a predetermined pattern.
The term nonwoven fibrous sheet as used in this sp ification and in the claims includes any nonwoven fibrous sheet no matter what length the fibers are from which the sheet is fabricated. Products made in accordance with this invention thus include foraminous paper products as well as foraminous nonwoven fibrous sheets having the characteristic hand and drape of conventional textile fabrics.
Invention Sun lmarized The present invention provides method and apparatus for production of a foraminous, nonwoven fibrous sheet from a fibrous slurry, as for example, an aqueous suspension of short cellulosic fibers in either hydrated or unhydrated condition.
In the first step of the method of this invention, liquid is removed from the slurry of fibers to Wet form a layer of superposed fibers that is no longer flowable. In this condition the fibers of the layer are in mechanical and frictional engagement with one another, so as to oppose fiow of the wet layer along a horizontal or inclined surface. If desired, the removal of liquid from the slurry may be stopped while the Wet fibrous layer is still nonself-supporting. On the other hand, the removal of liquid may be carried so far that the fibers are caused to adhere to each other due to the mechanical and frictional engagement between them, and due to surface tension of the wetting liquid, and an integral, self-supporting fibrous Web is formed. In no event, however, is the removal of liquid carried far enough to produce any bonds of the hydration type between fibers of the layer.
In the second step of the method, which is carried out immediately after the wet forming step, the fibers of the wet fibrous layer formed from the slurry of fibers are rearranged to produce a for-aminous, nonwoven fibrous sheet directly, without any additional dewatering, drying or other processing. After the wet fibrous layer of the desired character is wet formed, fiber rearrangement proceeds immediately, resulting in a foraminous nonwoven fibrous sheet of predetermined pattern.
In the third step of the method, the rearranged fibrous sheet is then dried, with or without elevation of the temperature of the sheet above room temperature. This develops any latent interfiber bonds within the layer, thereby providing a nonwoven fibrous sheet possessing adequate tensile properties for a variety of end uses.
The interfiber bonds utilized can be of any suitable type. One method of bonding is to add highly beaten woodpulp fibers to the starting slurry, so that the hydration bonds formed between the dried pulp fibers can provide an adhesive bonding between the other fibers. In those cases in which it is feasible to use all beaten woodpulp fibers in the slurry, the fibers themselves provide their own bonding when, upon drying, hydration bonds are formed between them. In another method of bonding, the rearranged foraminous, nonwoven fibrous sheet may be impregnated with an aqueous dispersion of a suitable adhesive agent, such as polyvinyl acetate, which for-ms the desired adhesive bond upon drying.
In some cases it is necessary to employ a bonding step as a fourth and separate step in the method of this invention. This is the case when a bonding action between fibers is necessary to provide the required strength for the purpose for which the finished fibrous sheet is to be used, but no binder is present in the dried for-aminous, nonwoven fibrous sheet resulting from the third step of this invention. In such cases, an adhesive binder may be added to the fibrous sheet, either in an intermittent pattern or otherwise, to provide the required strength for the purpose for which the sheet is to be used.
In the method of this invention, the starting slurry, the intermediate nonflowable fibrous layer, and the final rearranged fibrous sheet are supported during the entire process upon a continuous carrier. The carrier may be literally continuous in mechanical structure or, as is explained below, effectively continuous because any gaps in the structure are so short that at least dynamic support is provided the material upon the carrier at all points as it moves through the apparatus employed in the invention.
Advantages of This Invention This invention is particularly adapted to the rapid and efficient production of patterned nonwoven fibrous sheets from fibers of papermaking length, for example /a inch or less. Thus one advantage of this invention is that it can utilize inexpensive fibrous starting materials such as woodpulp.
Moreover, if desired, the woodpulp used as a starting material may be hydrated, with the resulting advantage of additional strength in the final product without the disadvantage of permitting hydration bonds to :form before the fibers are in their ultimate positions occupied in the finished fibrous sheet. Thus it is possible with this invention to produce a patterned, forarninous paper product in a single continuous process without any waste of material, instead of by the conventional method of first producing imperforate paper stock in which the fibers are connected by hydration bonds, and then punching out portions of that paper to producethe foramina of the desired pattern.
Another advantage of the present invention is the savings in time resulting from the fact that the steps of (1) preparation of a slurry, (2) wet forming of the intermediate fibrous layer, and (3) rearranging the fibers of that layer to produce a nonwoven fibrous sheet are performed in immediate succession, without the intervention of any additional steps of draining, drying, or other treatment of the fibrous layer.
A corresponding savings in equipment space also results from the economy of steps involved in this invention.
Various Embodiments of the Invention In accordance with a principal embodiment of the invention, a wet, nonfiowable fibrous layer containing a plu rality of superposed fibers is formed by draining and dewatering of a fibrous slurry, and the layer is thereupon introduced into a rearranging region between means defining spaced apertures, on one side thereof, and means defining foramina smaller than said apertures, on the other side thereof. A stream of fluid, preferably water, is then passed through the sandwich formed by the superposed aperture defining means, fibrous layer and foramina defining means. As a result, fiber segments and some of the shorter individual fibers in the fibrous layer are displaced in the hydraulic medium and hydraulically rearranged in new positions in which they are. packed and consolidated with one another. The rearranged fibers take up relaxed and tensionless positions in the resulting fibrous product.
In discussing fiber rearrangement of a type such as just described, the term fiber elements used in this specification and in the claims to include the segments of any fibers flexible enough to be capable of segmented movement, and also any Whole fibers which are of a type that is moved bodily by applied fluid forces.
In one specific embodiment of this invention, the fluid is passed in sequence through the aperture defining means, then through the wet fibrous layer and then through the foramina defining means. The hydraulic displacement of fiber elements which results causes the portions of the fibrous layer immediately beneath the apertures to be shifted to the surrounding regions underlying the land areas of the apertured means, where the fibers are packed and consolidated in .a structure having interconnected portions. The rearrwged fibers lie in the resulting nonwoven fabric in relaxed and tensionless condition. The interconnected portions outline and define openings in a unitary nonwoven fibrous sheet, with the openings forming a pattern which corresponds with the pattern of the spaced apertures.
In another specific embodiment of the present invention, fluid streams are passed in sequence through the foramina defining means, then through the wet fibrous layer and then through the aperture defining means. In this embodiment the individual fibers are preferably longer than the largest dimension of the apertures, and also preferably longer than the distance between immediately adjacent apertures in the aperture defining means. The fluid forces move the fibers and segments thereof in directions generally parallel to the apertured means, and into the apertures, to produce there a rearranged packing of buds or tufts which lie outside the plane of the fibrous layer and are interconnected by bands of consolidated and parallelized fibers on the lands between the apertures. Thus, three-dimensional fabrics of a great variety of patterned arrangements may be provided in which packed, tufted, budded, or otherwise rearranged and consolidated fibers out of the plane of the interconnected groups of fibers are joined by said interconnecting fibers in consolidated bands. In this embodiment, as in the first specific embodiment described, there is no substantial tendency for any fiber to return from its rearranged position to its original position in the wet fibrous layer. The fibers forming the tufts or buds lie in a relaxed condition, as do the fibers which bridge across the interconnected areas between adjacent tufts or buds.
Various other expedients may be employed in the method and apparatus of this invention for applying to the fibers of the intermediate, nonflowable fibrous layer rearranging forces which move the fibers into a foraminous pattern where they lie in relaxed and tensionless condition. In every case, the wet, nonflow-able fibrous layer is supported or confined so as to restrict the layer .as a whole against substantial movement in a direction perpendicular to the median section of the layer, without confining the individual fibers against relative movement within the layer with respect to other fibers in the layer.
As used in this specification and in the claims, the term median section of the fibrous layer means the locus of all points midway between the two general boundary surfaces of the layer. The median section of the fibrous layer will often be a plane, and lie parallel to the plane of the foraminous supporting means.
Optimum Conditions for Fluid Rearrangement A uniform or solid stream of a fluid, water for example, may be used to rearrange the fiber elements in the wet, nonflowable fibrous layer utilized in this invention, but an intermittently applied stream, such as a stream of discrete liquid particles, is more elfective in causing the desired rearrangement. As a result of the projection of particles of the fluid stream, preferably a rapid succession of water droplets, there is an intermittent bombardment of the fibers in the region wherein they undergo rearranging movement. This provides a more distinct and a better defined reorientation of the fibers in packed bundles than in the case where a uniform stream of water is used.
When the action of the fluid on the apertured and foraminous means is intermittent, the region between said two means in which the individual fiber elements of the wet fibrous layer are rearranged into the desired pattern may vary in spacing to facilitate movement of the fiber elements. Both the aperture defining means and the foramina defining means may be flexible. If so, suitable tensioning of both these means permits the means farthest from the fluid source, under the applied intermittent forces from bombardment of this flexible means by the particles of strong fluid jets such as water, to belly out from the other means with which it forms the rearranging region. It is seen that the increased spacing between the two means confining the fibrous layer will not only permit easier sidewise movement of individual fibers within the layer but will also permit a slight movement of the layer as a whole in a direction perpendicular to the layer. The median section of the layer, in other words, may be subjected to a slight shift perpendicular to the layer. However, the shift is in no event substantial, else the integrity of the layer may be destroyed.
After the confining foraminous means and apertured means leave the Zone of fluid bombardment, their original spacing is more or less restored, thereby precluding further displacement of the fibers from the desired pattern of the rearranged nonwoven fibrous sheet.
Care is taken that the amount of water and the depth of the rearranging region each be less than would tend to flood the region and thereby displace the rearranged fibers from the desired pattern which they are to occupy or have already occupied. In general, flooding results in a loss of identity of the fibrous layer and the rearranged nonwoven fabric. By flooding is meant a condition wherein the forces exerted by the motion of the water upon the fibers in their rearranged state exceed the forces upon these fibers arising from fiber-to-fiber friction, fiberto-apertured means friction and fiber-to-foraminous means friction, as well as any other restraining forces that may be present.
The optimum spacing and quantity of water employed-depending upon the physical characteristics of the particular fiber used (such as fiber weight, denier, fiber length, frictional characteristics, etc.), the size and spacing of the apertures and foramina, the speed at which fiber rearrangement is to take place, etc.-lie below the flooding condition causing loss of identity of the fibrous layer to be rearranged or of the resulting nonwoven fabric and above the minimum condition, depending upon the same factors, for a desirable rate of fiber rearrangement. These conditions are set out in additional detail in a later part of this specification.
Nature of Fibers The fibers employed as the starting material in the method of this invention may comprise natural fibers, such as cotton, flax, wood, silk, wool, jute, asbestos, ramie, rag, or abaca; mineral fibers such as glass; artificial fibers such as viscose rayon, cuprammonium rayon, ethyl cellulose or cellulose acetate; synthetic fibers such as polyamides, i.e., nylon, polyester, i.e., Dacron, acrylics, i.e., Orlon, Acrilan and Dynel, polyethylene, vinylidene chloride, i.e., Saran, polyvinyl chloride, polyurethane, etc., alone or in combination with one another.
The fibers employed as the starting material in the method of this invention may be of any length desired, so long as a uniform slurry can be formed of the fibers. However, to obtain a product having the characteristic hand and drape of a textile-fabric, it is preferred to include in the fibrous layer textile-type fibers above normal papermaking length and close to normal textile length, say of about A inch to inch or longer.
If a fibrous sheet having the characteristics of paper is desired, fibers below inch in length and within the paper-making range should constitute a major portion of the fibers in the layer.
If a textile-like fabric is desired as the end product, it is preferred that any shorter papermaking fibers included in the layer as a filler be substantially unbeaten or unhydrated. To provide a binder, however, the fibrous layer may contain a proportion of superposed hydrated cellulosic fibers which have been beaten in normal papermaking fashion.
The wet fibrous layer may also include particulate materials such as resin particles, so long as these particles do not cause the individual fibers of the fibrous layer to become bonded together prior to rearrangement of the fibers by the fluid forces.
Mixtures of fibrous materials, natural and/ or synthetic, alone or in combination with resinous and similar plastic particulate materials, may be present in the fibrous layer and can be rearranged in accordance with the present invention.
Formation Wet Nonflowable Fibrous Layer In the first step of the method of this invention, the various types of fibers and particulate masses, if any, desired for inclusion in the fibrous layer are incorporated in a liquid suspension or slurry by conventional papermaking procedures.
To produce a wet nonflowable fibrous layer, the resulting slurry may be placed upon a wire such as a Fourdrinier wire and most of the water or other liquid permitted to drain off. Removal of liquid from the wet fibrous layer is continued until a layer of superposed fibers is formed in which the fibers of the layer are in mechanical and frictional engagement with one another, and the quantity of liquid present in the layer has been reduced at least to the point that treatment with fluid rearranging streams will not produce flooding. Liquid removal must not be carried so far, however, that any bonds of the hydration type are formed between fibers of the layer.
For commercial use, the preferred embodiments of the fluid rearranging apparatus of this invention are constructed to provide continuous, eificient, high speed fiber rearrangement by the application of fluid forces first to means defining spaced apertures arranged in a predetermined pattern then to the wet layer of fibrous starting material positioned or sandwiched in a region between the apertured means and a foraminated backing means having forarnina smaller than said apertures.
The invention will now be described with reference to the embodiments shown in the accompanying drawings, in which:
FIGURE 1 is a side elevation, partly broken away, of an illustrative apparatus constructed in accordance with the invention including as a portion thereof a papermaking machine of the belt or Fourdrinier type for continuously supplying a wet fibrous layer;
FIG. 2 is a diagrammatic elevation of the right-hand portion of FIG. 1 on an enlarged scale, modified to indicate the inventive construction more clearly;
FIG. 3 is a perspective view of a portion of the apparatus shown in FIG. 2, illustrating vacuum assist in fabric production of a nonwoven fibrous sheet;
FIG. 4 is a vertical schematic section of the fiber rearranging portion of the apparatus shown in FIG. 2;
FIG. 5 is a fragmentary perspective view of a water removal element shown in FIG. 2;
FIG. 6 is a fragmentary, partially cut away schematic plan view of the apertured means and the foraminous supporting means of the apparatus of FIG. 2, with the wet fibrous layer to be transformed into a rearranged fabric interposed therebetween to form a sandwic FIG. 7 is an enlarged fragmentary sectional view taken along the line 77 of FIG. 6;
FIG. 8 is a view similar to FIG. 7, but somewhat enlarged, showing the manner in which fiber elements of the wet fibrous layer are displaced and compacted when fluid is passed, in sequence, through the apertured member, the fibrous layer and the foraminous support;
FIG. 9 is an enlarged fragmentary schematic view of a portion of FIG. 6 illustrating the positioning of the fibers of a wet fibrous layer when treated as shown in FIG. 8 and employing a relatively narrow spacing between the apertured member and the foraminous supporting means;
FIG. 10 is a view similar to FIG. 9 under difierent conditions, namely, a wider spacing between the apertured and foraminous members;
FIG. 11 is a view similar to FIG. 9 under still difierent conditions, namely, a still wider spacing between the apertured and foraminous members;
FIG. 12 is an enlarged view of a portion of FIG. 8 illustrating the packing components of force created by the aforesaid passage of fluid;
FIG. 13 is a vertical section taken on the line 13-13 of FIG. 3;
FIG. 14 is a schematic sectional view showing the action of particles of liquid upon a fibrous layer positioned between loosely spaced apertured and foraminous members;
FIG. 15 is a schematic view as in FIG. 14 but with a tighter spacing between the apertured and foraminous members;
FIG. 16 is an enlarged fragmentary sectional view similar to FIG. 7 but with the apertured member and the formaminous member reversed so that the fluid producing the fluid rearranging force is projected in the opposite direction with respect to those members and the wet fibrous layer positioned between them;
FIG. 17 is an enlarged fragmentary schematic view of a portion of the apparatus of FIG. 16 illustrating the positioning of the fibers of a layer after being treated by passing a fluid through the sandwich shown in FIG. 16 in the direction shown by the arrows in FIG. 17;
FIG. 18 is a schematic sectional view showing the action of particles of liquid upon a fibrous layer treated as shown in FIG. 17;
FIG. 19 is a schematic sectional view similar to FIG. 18 but with wider spacing between the apertured means and foraminous means between which the fibrous layer is sandwiched;
FIG. 20 is a vertical section similar to FIG. 13 when the apparatus of FIG. 3 is modified as shown in FIG.
FIG. 21 is a side elevation, with parts broken away for greater clarity, showing the same general portion of one embodiment of the apparatus of this invention as is shown in FIG. 2 for another embodiment, but with the direction of travel of the fibrous layer through the apparatus reversed in the two showings;
FIG. 22 is a view generally similar to FIG. 4 but with the belts reversed, direction of travel of the fibrous layer reversed, and a modified support means for the wet fibrous layer to be rearranged;
FIG. 23 is a diagrammatic side elevation of a modification of the apparatus of this invention in which fluid is passed upwardly through the fibrous layer with the assistance of vacuum.
FIG. 24 is a fragmentary view on an enlarged scale of the modification of FIG. 23;
FIG. 25 is a diagrammatic side elevation of apparatus which may be used in accordance with this invention to produce a Wet fibrous layer comprising an intimate mixture of a card web and a fibrous slurry and to efiect immediate fluid rearrangement of said layer;
FIG. 26 is a photomicrograph of a typical nonwoven fibrous sheet according to one embodiment of the invention at an original enlargement of approximately 10 to 1; and
FIG. 27 is a photomicrograph of the same nonwoven fibrous sheet further enlarged to an original enlargement of approximately 40 to 1.
Referring to FIG. 1, the center portion thereof diagrammatically depicts the wire portion of a Fourdrinier machine which is adapted to transform a slurry of fibers into a wet nonflowable fibrous layer for utilization in accordance with this invention.
The reference numeral 1 generically indicates a leterally removable table having side beams 2 supporting a plurality of table rolls 4-. The table structure includes the usual suction boxes 5, and a wire passing over the suction boxes and the rolls 4. The wire is also trained around a separately mounted breast roll '7 at the feed end of the table, and around couch roll 8, which acts as a drive roll and forms a part of the rearranging apparatus to be described later, at the other end. The usual wire guiding and tensioning rolls 9 are provided for the lower run of the wire.
The table 1 is supported at its feed end on fulcrum support 12, and at its couch roll end is mounted upon jack screws 13. Tracks 14 and 15 extend transversely of the table 1 so that it can be removed laterally upon flanged wheels 16 and 17 when the table is lowered in the customary fashion.
Breast roll 7 is mounted upon vertical supports 29 which are braced from a head box supporting frame 21 carrying first draining roll 43. Bridge members 28 may be used as disclosed in Berry Patent No. 1,599,402 granted September 14, 1926.
The aforementioned wire, which is designated by the numeral 62, is trained over table rolls 4, around couch roll 8, over and under guiding and tensioning rolls 9 and around first draining roll 43 and breast roll 7. It is the portion of wire 62 between the latter two rolls, in the area indicated in the drawings by the numeral 59, in which the first draining occurs to help transform a dilute aqueous suspension of fibers into the wet, nonflowable fibrous layer which is rearranged in accordance with thi invention.
The dilute suspension of fibers is supplied by head box 48 shown in the left hand portion of FIG. 1. The suspension of fibers passes from head box 48 through valved conduit 51 to adjacent mixing tank 53. A second valved conduit 52 is provided to enable mixing tank 53 to be drained.
The fibers in the fiber suspension supplied from head box 48 may be of paperrnaking length, such as inch or less. The numeral 55 designates a container holding a suspension of longer fibers and particulate solids which, if desired, may be incorporated in the suspension of papermaking fibers by gravity drain from container 55 through downspout 56 to mixing tank 53.
Mixing tank 53 is provided with baflles 57. The tank supplies an intimately mixed suspension in the depositing zone 59 above the conventional sluice 58 located adjacent first draining roll 43.
As this suspension of fibers is deposited at zone 59, it may contain about one-quarter of one percent by weight of fibers. Water immediately begins to drain through wire 62 from the fiber suspension as the wire moves from depositing zone 59 over table rolls 4 toward suction boxes 5. When the fiber suspension or slurry arrives at first suction box 5, the draining of water has ordinarily increased the proportion of fibers in the suspension to more than one percent.
Suction boxes 5, positioned immediately beneath the top reach of wire 62, help to speed further removal of excess water from the fiber suspension or slurry. By the time the slurry reaches the rearranging apparatus shown diagrammatically in the right hand portion of FIG. 1, it is no longer flowable, and ordinarily contains no more than about 300 to 500 percent water based on the dry weight of the fibers contained in the layer.
The wet fibrous layer 60 so produced is continuously supplied to the apertured belt 61 of the rearranging apparatus. Briefly, fibrous layer 60 is confined between the overlying apertured belt 61 and the underlying wire 62 and is continuously conveyed thereby past downwardly directed fluid streams supplied by nozzles 238. Passage of the fluid through fibrous layer 60 and wire 62 is preferably facilitated by the use of suction boxes 5a, located directly beneath the area of the moving fibrous layer upon which the fluid streams impinge.
The patterned fibrous sheet 2% produced by the fiber rearrangement brought about by passage of the fluid streams through layer 6t is discharged from between rolls 26b and 8. Excess water is removed as by mangle roll 262 and endless felt mangling belt 263. The latter is trained about support rolls 264 and tension roll 265. The nonwoven fibrous sheet is then transported to a bondirrg or drying zone (not shown). The detailed construction of the rearranging apparatus is described in a later part of this specification, in connection with the discussion of FIG. 21, where certain additional elements not here described are identified.
Referring to FIGS. 6, 7, and 8, by way of illustration there is shown a Wet fibrous layer of containing superposed fibers deposited on wire 62 of the Fourdrinier machine of FIG. 1, sandwiched between an apertured rearranging member 61 and foraminous supporting means 62 such as a fine mesh screen which is constituted by the wire of the Fourdrinier machine. Rearranging member 61 may have apertures or holes 63 arranged in a definite pattern. The size of these apertures is substantially larger than the openings in the foraminous supporting means, e.g., the wire 62.
Where rearranging member 61 and wire 62 are as shown in FIGS. 1 to 8 and 12 to 15, inclusive, the applied fluid force is directed against the sandwich from the exposed side of apertured member 61 and the rearranged fibers are grouped on wire 62 in the spaces adjacent the land areas of member 61 in bundles to produce a relatively flat, two-dimensional rearranged foraminous, fibrous sheet, as illustrated in FIGS. 8 to 15.
If the apertured rearranging member and the foraminous Wire are reversed with respect to the direction of passage of fluid through the fibrous layer sandwiched therebetween, the wire acts as a spray diffusing member as shown in FIGS. 16 to 20, and an inverted three-dimensional forarninous, fibrous sheet is produced in and between the apertures 63 of member 6'1. The fluid, preferably water, is projected against the spray diffusing member, then passes through the intermediate fibrous layer to be rearranged, and finally passes through the apertured rearranging member to carry into the apertures of that memher a portion of the fibers of the web. As the fibers are carried into the apertures, they intermingle in random arrangement there and become interlocked into a three-dimensional tufted formation, with individual fibers from each tuft of the formation extending in various directions into the adjacent tufts or buds.
In this embodiment of the invention, the fibers utilized are preferably longer than the longest dimension of the apertures and also preferably longer than the distance between immediately adjacent apertures of the apertured rearranging member. However, if the vacuum furnished by suction box 5 in FIG. 20 is not applied for too long a period of time to any given portion of the fibrous layer being rearranged, the fibers may be of shorter lengths.
Whether the spacing between apertured member 61 and wire 62 is loose or tight with respect to the fibrous layer 60, as shown in FIGS. 14 and 15, respectively, the intermittent bombardment of water particles against the sandwiched fibrous layer forces the fibers into bundles or groupings 64 by the component of sidewise force exerted by said fluid particles.
The spacing between apertured member 61 and supporting wire 62 should not be so tight as to prevent rearrangement of the fibers. On the other hand, the spacing should not be so loose as to permit a condition of flooding in which the rearranged fibers are subjected to such strong and unregulated currents that either the fibrous layer or the rearranged nonwoven fibrous sheet loses its identity. Between the limits of tight and loose spacing of the sandwich elements, as indicated above, the fibers are packed into bundles of a flatness and tightness of packing which vary with increase in said spacing. This is schematically illustrated in FIGS. 14 and 15, the former showing a tighter packing of the interconnecting fiber bundles and a higher profile therefor.
As shown diagrammatically in FIG. 8, the fluid such as water, steam, air, or other liquid or gas, or the like, is projected through the apertures 63 in the rearranging member 61 to pass through the fibrous layer 60 and the foraminous supporting means 62. The fluid may be emitted from the apertures in the rearranging member in spaced streams arranged according to the aforementioned pattern.
The liquid may contain an adhesive or a liquid waterproofing or fireproofing composition, etc., if it is desired to apply the properties of these materials to the finished product. The liquid may also contain a dye if it is desired to impart a color to the nonwoven fibrous sheet. The liquid may thus serve a plurality of functions in accordance with this invention.
The liquid streams projected through the fibrous layer move fibers out of their way and into portions 64 of the zone between the streams. The rearranged fibers form a reticular foraminous structure comprising openings or holes arranged in a pattern corresponding in general with the pattern in the apertured rearranging member.
By the method and apparatus of the present invention, the fibers in the fibrous starting material are rapidly and efliciently relocated into new, relatively unstressed positions where they lie in a state of mechanical equilibrium. In the relocated positions, the fibers are mechanically engaged, both frictionally and/ or by interlocking of the fibers. Of basic importance in the product produced by the method and apparatus of this invention is the fact that the new arrangement of the fibers is one of equilibrium, the rearranged or relocated fibers having substantially no in-built tendency to revert to their original arrangement.
The action of the fluid upon the fibers and the extent to which the fibers are moved are functions of the hydraulic fluid forces acting in or parallel to the median section of the fibrous layer to which the fluid rearranging forces are applied. The distance between the adjacent surfaces of the apertured rearranging member and the foraminous supporting means, the velocity of the fluid, the weight of the starting web, the nature of the fibers, and other factors, as hereinafter set forth, aifect these forces.
If the wire 62 is maintained fairly tightly against the under surface of the apertured member 61, the fibers formerly in the Way of the apertures 63 will not move much farther than the edges of the apertures and the openings 65 formed in the fibrous layer will correspond quite closely with the holes in the perforated plate, as shown in FIG. 9.
If the wire 62 is moved away slightly from the .apertured member 61, the space within which the streams may move sidewise is increased. These streams which move sidewise are constituted of the streams passing through the apentured member which are deflected in a sidewise direction from the edges of the apertures, and the streams which are deflected in a sidewise direction from the foraminous supporting means. The resulting sidewise motion of these streams causes the fibers to move away from the edges of the apertures 63 and into closer contact with one another in the areas surrounding the holes, in the manner shown in PEG. 10.
in that figure, the fibers have been moved away from the centers of the apertures to form closely assembled substantially parallelized groups 66 lying in the shortest spans A between holes, interconnected by fibers extending in a plurality of diverse directions in web-like areas 67 lying in the longest spans B between the holes. The fiber portions at 66 in FIG. 10 have been moved quite close together, but the openings 65 formed in the fibrous layer still are substantially round, corresponding in shape to the holes in the apertured rearranging member.
The distance between the apertured member and the suppcnting means may be increased to the point where further movement of fibers in the shortest spans between holes can no longer take place, but the fibers are free to move together to minimize the web-like areas 67 in the longer spans between holes, with the result shown in HG. 11. Thus, the openings 65 in the fibrous layer tend to become square, as shown in FIG. 11, and the fibers between holes tend to achieve a maximum degree of parallelism in the groups 66.
It appears that the foraminous supporting means with its relatively small openings resists the passage of the streams therethrough and diverts a portion thereof in a sidewise direction. The sidewise components of adjacent streams act in opposition on the fibers between them, balancing one another as the fibers are compacted, and then pass through the openings in the foraminous means. Those portions of the streams which are not diverted in a sidewise direction pass directly through the openings in the foraminous means. if the space between the apertured member and the foraminous supporting means is increased sufficiently, the sidewise components of the fluid will move the fibers into even :closer association with one another, as seen in FIG. 11, forming yarn-like groups 66 of substantially parallel fiber segments half way between the holes.
if the apertured member 61 and the foraminous means 62 are moved much farther apart, while m'aintaing the same flow conditions as would cause the formations illustrated in FIGS. 9 through 11, the streams will tend to flow together, produce flooding, and destroy the reticular fibrous structure. The optimum range for spacing these means will depend upon the velocity of the fluid passing through the apertured member, the nature of the foram inous means and the size and extent of its openings, as well as other factors including the thickness or density of the layer of starting material.
The for-aminous means 62 must be capable of supporting the fibrous layer 60 and yet passing the fluid streaming through it. Its openings or holes, not shown, must be small enough to prevent fibers from being washed through it. However, if they are too small or perhaps too Widely spaced, so much resistance may be offered to the passage of fiuid that it may back up or fiow sidewise to too great an extent and prevent the production of the desired rearranged nonwoven fibrous structure. For given fiuid velocities, as the foraminous means offers more resistance to passage, the sidewise components of the streams may increase in intensity with the result that the maximum practical spacing between the apertured member 61 and the supporting means 62 must be decreased.
In general, it is preferred that the dimension of the openings in the foraminous backing means 62 be substantially less than the dimension of the apertures in the ape-rtured rearranging member 61. For example, with an apertured member having uniform apertures in the order of about to A1 of an inch in diameter, good results may be obtained where openings in the foraminous backing means vary from about 900 openings per square inch to about 50,000 openings per square inch.
It is also important that the inner surface of the supporting means he sufliciently smooth to allow general movement of fibers along its surface. If the surface is too uneven or rough, as might be the case with relatively large mesh screening, production of the desired nonwoven fibrous sheet may be retarded and clear openings may not form due to fibers which stick on the supporting means in the way of the apertures 63 in the rearranging member.
The smoothness or evenness of the backing means may affect the rate of production of the rearranged nonwoven fibrous sheet in accordance with the invention. Woven screening may be employed, the evenness or smoothness of the screen being in part a function of its mesh. A finer screen will tend to be more even and thereby more readily allow the motion of fibers along its surface. A coarse screen may trap fibers and cause them to stick in the screen in the Way of the apertures in the apertured member.
Foraminous backing means 62 may be made of any suitable material. A screen belt in Woven form gives excellent results. However, a woven belt is not essential since the belt may have the openings punched or etched in the material. The belt, in screen form, may be made of stainless steel, bronze, copper, alloy, nylon, synthetic resinous fibrous materials such as fibers sold by the E. I. du Pont Co. under the trademark Orlon, or the like. It can be in the form of a flexible punched plate of steel, plastic or other material which is sufficiently foraminous to allow passage of the fluid but sufficiently impervious and smooth to permit the rearranging fluid to effect the desired rearrangement of the fibers over its surface without washing them away.
The patterned apertured member employed with this invention may take many forms such as, for example, disclosed in the aforementioned copending Kalwaites application S. N. 567,275, now US. Patent No. 2,862,251. The embodiment of the present invention being described includes a flexible belt having apertures larger than the holes in the screen backing member or wire 62.
In accordance with this embodiment of the invention, the wet fibrous layer is continuously formed and subjected to the jets of the applied fluid, preferably water, which are applied intermittently and simultaneously over successive portions of the moving fibrous layer and at right angles to the moving layer. The production of the rearranged nonwoven fibrous sheet according to this invention may occur at any of a plurality of spray regions or at a particular segment of travel of the sandwich.
FIGS. 3, 4, and show certain details of the rearranging portion of the apparatus of FIG. 1. FIG. 3 shows, for example, vacuum dewatering means 5 directly below the zone of fiber rearrangement, i.e., directly below the area impinged upon by the particles of water from the jets. This permits attainment of greater clarity of fiber rearrangement. It also permits use of higher speeds at the discharge end of the belt without damage to the rearranged fabric structure, since the improved dewatering of the rearranged product resulting from use of vacuum assist materially increases the strength of the fabric. The use of vacuum dewatering devices is thus a preferred modification for commercial use. As many of these vacuum devices may be used for each zone as desired, in the light of the spray conditions which are found desirable.
FIGS. 21 and 22 show more specifically the rearrangeing portion of a preferred embodiment of the apparatus of this invention, which may be used as a part of the machine shown diagrammatically in FIG. 1. When the apparatus shown in FIG. 21 is considered in connection with the machine of "FIG. 1, it should be noted that the feed and discharge ends are reversed in the two drawmgs.
The details of construction of the apparatus of FIG. 21 are more fully described in the copending Kalwaites application S. N. 567,275, now U.S. Patent No. 2,862,251 to which reference is here made. Particular attention is directed to FIGS. 22 through 25 of that application.
The machine shown in FIG. 21 is mounted on vertitical frame members 247 (at the left of FIG. 21) and vertical support members 256 (at the center and right of the figure). Fixed to members 256 is the horizontal fixed frame member 246 which carries, at its upper flange, fixed wall 289. Manifolds 287a, 287b, and 2870 of the spray jets are attached to wall 289 by the respective flange mountings 288.
The upper belt 61 and lower belt or wire 62 are mounted on the respective drive rolls 260 and 8. Upper belt 61 is also mounted on upper follower roll 258 within the framework provided by the vertical supports 256, the horizontal fixed frame member 246 and the first fixed wall 289. Lower belt 62 is supported by table rolls 4.
The top flight of upper belt 61 travels under and in contact with belt tracking roll 258a. Tracking roll 258a is mounted for rotation on shaft 225 which extends transversely of the machine. The shaft 225 is pivotally mounted at one end for angular adjustment to cause the proper travel of belt 61 with respect to the face of the rolls on which it is mounted. In that part of the path of Wire 62 which passes through the Fourdrinier type machine, wire 62 is controlled in the conventional man ner.
The wet fibrous layer 60 is sandwiched between flexible, apertured rearranging belt 61 and the flexible foraminous backing belt or wire 62. The apertured belt is preferably a metal screen, whereas the foraminous backing belt is preferably of nylon. As shown in FIG. 21, table rolls 4 serve to support the sandwich so formed. The table rolls prevent sagging of the belts during impingement of the jet streams on the sandwich in the rearranging areas.
Fibrous layer 60 is subjected during its travel between apertured rearranging belt 61 and the backing belt or wire 62 to the action of jet sprays 201 of a fluid, preferably water, which impinge upon and through the sandwich. In the embodiment shown, the water from the sprays passes first through the larger apertures '63 in belt 61, then through the fibrous layer, and finally through the smaller foramina in the belt or wire 62.
The jet sprays from the three successive nozzles 238 provide three successive rearranging zones. However, more or less of these rearanging zones may be utilized as desired depending upon the fineness of the fiber rearrangement which is desired, the density of the web, the material of which the web is formed, and other factors.
Apertured rearranging belt 61 is tensioned during its travel by means of upper roller tensioning devices 259 at each end of shaft 297 for upper belt tensioning roller 258. Shaft 297 does not rotate, roller 258 being rotatably mounted upon it. Tensioning device 259 comprises an adjusting screw member 283 which at one of its ends is keyed into shaft 297 and also into a square sleeve around the shaft. At the other end of screw member 283 there is provided an adjusting knob or wheel 285, which serves to thread the screw shaft 297 to pull back the shaft in a direction toward wheel 285. By the means described, tensioning roller 258 may be moved in a direction away from fixed roller 260.
The lower belt or wire 62 is tensioned by the roller 43 of the machine (see FIG. 1) in the customary manner as with a Fourdrinier type wire.
At the exit of the rearranged nonwoven fibrous sheet from the end nip of upper belt 61 and lower belt or wire 62 around upper and lower rolls 260 and 8, respectively, the sheet passes between mangle roll 262 and endless felt mangling belt 263. The outer surface of mangle roll 262 is preferably formed of rubber, metal or stone. After the fibrous sheet leaves the mangling zone, it moves to a bonding or drying zone (not shown) of conventional type.
To drive the flexible belt machine, a power source (not shown) such as an electric motor drives the shaft 203 of the first support roll 264 around which felt mangling belt 263 is trained. On the same shaft 263 of the first felt covered mangle roll 263 there is mounted gear 200 which is fitted with a chain 235, said chain connected at its other end to the lower belt driving gear 204 on the shaft 279 of the lower fixed roll 8. Gear 204 in turn drives gear 261 fixed to the shaft 28% of the upper belt fixed roll 269 to provide uniform movement of both upper and lower belts of the machine.
As shown by the direction of the arrows in FIG. 21, the
despite the open formation of the screen.
belts travel to move fibrous layer 60 through the successive rearranging zones, and to move the rearranged fibrous sheet out of the nip at the belt exit into the nip of mangle roll 262 and felt mangling belt 263. The drive effectively pulls the fibrous layer and upper and lower belts as one sandwich from the feed zone through the rearranging zones to couch roll 8, and from there leads the rearranged fibrous sheet between mangling roll 262 and felt mangling belt 263, the latter being geared to move at the same linear velocity as that at which the couch roll revolves.
A common header 2% for the water manifolds is fed from a water inlet 207 which may be either from a pump (not shown), or optionally from a water reservoir (not shown) which may include a filter and pump in which the liquid from the flexible belt machine is filtered and recycled by pumping to be returned to feed the nozzle jets 238. Respective valves 209a, 2119b, and 2%90 are provided in the three connecting conduits Zlfia, 21%, and 210c for independent control of water from the common header 208. Each of the spray devices 238 is provided with its own manifold.
Water from the spray nozzles which passes through the belts and fibrous layer is collected and flows to an outlet. If desired, the water from the outlet may be recycled after filtering it to remove any fibers that may be lost from the sandwich.
Although only three fiber rearranging zones are shown, any number of Zones may be employed simply by supplying more jets and using longer belts. The number to be used depends. upon the type of control required in view of the thickness of the fibrous starting material and the desired clarity, distinctness and packing density of the interconnecting packed bands between fiber intersections. Tension on belts 61 and 62 is regulated to provide the necessary spacing in the region where fiber rearrangement occurs. The adjustment of this spacing is desirable particularly since the production of twodimensional or three-dimensional nonwoven fibrous sheets each imposes different requirements on the amount of Water used and other variables which have been mentioned above.
As already stated above, the removal of Water after the final stage of rearrangement facilitates more rapid removal of the fibrous sheet from the machine. It has been found that the Vacuum dewatering device 460 illustrated in FIG. 21 and in enlarged fragmentary perspective in FIG. 5, comprising a slotted pipe having cylindrical vacuum connection 402, is effective for this purpose. The sandwich passes over the slot 399 of dewatering device 400 and the vacuum diminishes the moisture from about 1200 percent of water, for example, to about 250 percent. The employment of this vacuum dewatering device permits a degree of dryness to be attained in the finished fibrous sheet which may render mangling unnecessary.
The flow of water projected at the assemblage of apertured belt 61, fibrous layer 641, and backing screen 62 is controlled to provide sufficient force to move the fibers readily into the desired rearranged positions, and at the same time to avoid an amount of water which would cause flooding at the region of the screen. Flooding is objectionable since, as already explained above, it serves to carry away fibers and prevent their rearrangement into the desired structure.
Flooding at the region of the screen may be avoided in a number of ways. For example, flooding may be avoided by draining away the water from the backing screen as rapidly as it begins to build up at the screen This draining may be aided by suction, for example, by the expedient of suction boxes immediately beneath the backing screen and intermediate the table rolls, where table rolls are used to support the screen. With the aid of vacuum assists 401, such as suction boxes, as illustrated in FIG. 3, it is possible to project the water to form a rearranged nonwoven fibrous sheet as shown in FIGS. 26 and 27 at pressures varying from about 70 to 100 pounds per square inch, and amounts of water from about 1.1 gal. to about 1.7 gal. per minute per nozzle.
Dewatering of the product is thus effected by the mangling arrangement or by vacuum, or a combination of both.
In general, where vacuum is utilized to avoid flooding conditions and to aid fabric rearrangement, the amount of vacuum to be applied to the sandwich is preferably equivalent to about /2 inch mercury to about 8 inches mercury. The amount of vacuum to be applied to the wet fibrous layer to assist in draining water from the layer in the production of the three-dimensional budded fibrous sheet of the above-mentioned alternative embodiment of this invention must be limited to avoid disruptive forces on the fibers within the sheet of such magnitude as to pull them entirely away and thus destroy the unity of the product.
An alternative method of the present invention which is illustrated in FIG. 22 is the rearrangement of a layer of fibers into a three-dimensional nonwoven fibrous sheet. This is effected by the utilization of the pair of opposed flexible foraminated belts, upper belt 62 being a spray diffusion belt for the liquid jets and bottom belt 61 being the apertured rearranging belt.
With a rearranging belt having uniformly spaced openings A inch in diameter arranged 50 per square inch, a permeable spray diffusing belt, nozzles of the convenrtional solid cone type, and vacuum assist, there is no flooding if the water is delivered from each nozzle at a rate varying approximately from 0.5 to 2 gallons per minute. Proper fiber rearrangement takes place with this amount of Water where the nozzles deliver the water at a rate of about 50 to 20 feet per second at the delivery end of the nozzles, when the delivery end of the nozzles is spaced about four inches from the spray diffusion belt.
The spray diffusion belt must not be in such close contiguity to the rearranging belt as to preclude the movement of fibers under the influence of the water into the three-dimensional budded formation. At the same time, the spacing of the belts should generally not be so great as to permit gross displacement of fibers from the plane of the fibrous layer as a result of upward components of forces resulting from the impact of the liquid on the imperforate portions of the rearranging screen.
The use of vacuum for the purpose of aiding fiber rearrangement is applicable to all of the various devices, as, for example, the embodiment now being described, which can be used for producing a nonwoven fibrous sheet in accordance with the present invention. A more distinct and better defined fiber rearrangement takes place, while at the same time the advantage of a more cohesive structure is obtained which prevents impairing the rearranged fibrous sheet during handling. Using a plurality of vacuum assists permits the handling of larger amounts of water and effects more rapid fiber rearrangement in each rearranging zone.
The function of vacuum in the operation is schematically illustrated in FIGS. 13 and 20 with respect to the production of flat and three-dimensional fabrics, respectively.
In FIG. 13 there is shown the production of a foraminated, nonwoven fibrous sheet of the type illustrated in FIGS. 9, 10, and 11, in which the rearranged bundles of fibers are packed behind the land areas of the apertured rearranging member 61. Vacuum assist 5 in contact with and below wire 62 assists in drawing off the water particles through the openings in the foraminated wire screen. As a result, components of force as shown by the arrows in vacuum assist 5 are provided in addition to the components of force of the fluid particles flowing into the regions underlying apertures 63.
In this connection, FIGS. 14, 15, and 18 illustrate what are believed to be highly idealized conditions for the passage of water droplets through apertures 63 in rearranging member 61 and the holes in wire 62, and the spas,
spreading of the droplets as they pass through the sandwich of the fibrous layer and these two means. Depending upon the spacing between apertured member 61 and Wire 62, as shown in FIGS. 14 and 15, the bundles of fibers are packed in accordance with the sidewise components of force exerted by the droplets of water. The fibers assume a packing which may have a relatively high profile as shown in FIG. 14 or a flat profile as shown in FIG. 15. By employing the vacuum assist of FIG. 13, the droplets are each caused to move faster as separate bombarding particles through the upper apertures and through the lower openings in wire 62, and ther results thereby a more rapid intermittent bombardment of the fibers in a sidewise direction.
Turning now to the reversal of belts as illustrated in FIG. 22, upper roller 258 is provided with foraminated belt 62 having smaller openings than lower apertured belt 61, on roll 257. Thus jet 261 impinges on the sandwich containing wet fibrous layer 66 in a reversed position as compared to that in FIG. 4.
By the action of the intermittent bombardment of the fluid particles, fibers bridge the larger apertures 63 of apertured rearranging belt 61. The smaller foramina in the foraminated belt 62 serve as spray diffusin g means to break the stream of fluid particles into even smaller particles. Sidewise components of force are exerted to push some of the fibers into areas immediately adjacent the apertures and between immediately neighboring apertures, while other portions of the fibers are pushed into the apertuers of 63 in a downwardly tufted pattern. As seen in FIG. 18, wet fibrous layer 60 assumes a generally sinusoidal shape in cross-section, having packed tufted portions representing a greater concentration of fibers which protrude downwardly between the side walls of apertures 63.
It is important that fiber movement be permitted to occur easily on the inner surface of apertured rearranging member 61. For this reason its surface should be smooth and have no sharp corners, in order to facilitate movement of the fibers into the desired position.
Assisting the production of the three-dirnensional nonwoven fibrous sheet is the use of the vacuum assist 5 as shown in FIG. 20. Here, the droplets of water as indicated in FIG. 18 are quickly moved out of the tufted areas in the apertures of the rearranging member 61 and removed through vacuum assist 5. Better packing of the three-dimensional fibrous sheet and improved dryness are attained by the use of such assist.
Illustrated in FIGS. 12 and 17 are additional highly idealized and exaggerated schematic views of the fiber rearrangement which takes place during the projection of fluid particles through the sandwich. In FIG. 12 individual force components above the plane of apertured member 61 are shown by arrows. These components enter apertures 63 as illustrated, strike the solid portions of foraminated backing member or wire 62 and deflect from said solid portion to move fibers from the area below the apertures into packed bundles beneath the land areas of apertured member 61. Under the land area on the right-hand side of the drawing there is shown a crosssection of a single fiber 64a which is just being moved into a position at the bottom of the bundles of fibers packed under the right-hand land.
With screen 62 and apertured member 61 reversed as shown in FIG. 17, individual fibers of fibrous layer 69 are moved along the land areas and concentrated and packed in tufts or bundles which fill the apertures 63. Some of the fibers, particularly the long fibers, bridge across the land areas of apertured member 61. The forces from the fluid applied through the apertures of the foraminated member 62 are illustrated in FIG. 17 by arrows passing through the openings in said forarninated member. These forces tend to move the individual fibers sidewise to pack them in the form of tufts at least partially within apertures 63.
Because the fibers are present in the layer to a large extent in random relationship, there is sufiicient intertangling of such fibers that under properly controlled spray conditions there is surprisingly little fiber loss due to fibers being washed entirely through apertures 63. Such loss as may tend to occur may be minimized by controlling the tension between members 61 and 62 as shown in FIGS. 18 and 19. Movement into the openings or apertures of rearranging member 61 is enhanced by providing a larger spacing between forarninated member 62 and apertured member 61 as shown in FIG. 19, and such movement is somewhat decreased with the smaller spacing as shown in FIG. 18.
Referring again to FIG. 22, the belts are shown reversed with the foraminous belt 62 being the upper belt and the apertured belt 61 being the lower belt and the fluid from spray 261 being passed downwardly through the sandwich including wet fibrous layer 66 to produce a tufted nonwoven fibrous sheet. The arrangement shown is preferred since it is generally desirable to apply the fluid force in a downward direction. A suction box 5 is provided to assist dewatering of fibrous layer 60 and production of the tufted structure.
In order to proceed as shown, and because a suitable wire 62 of the Fourdrinier machine would not normally possess the apertured structure desired for the lower belt, water is removed from fibrous layer 60 at least to an extent sufiicient to permit the fibrous layer to be trans ferred from couch roll 8 at the high speeds achieved by the invention. To this end, the horizontal distance of transfer is preferably reduced to a minimum.
If it is not desired to remove water from the originally formed fibrous layer to an extent sufficient to permit such transfer, budded or tufted nonwoven fibrous sheets may be produced using a fibrous layer transported by the wire upon which it was formed in the manner illustrated diagrammatically in FIGS. 23 and 24. Referring to those figures, the numeral 366 indicates a wet fibrous layer carried by wire 362 which is trained over table rolls 4 and couch roll 368. In FIGS. 23 and 24 all details of the wire mounting and fibrous layer deposition have been omitted. Vacuum boxes 5 are provided to suitably dewater the fibrous layer 360.
Aperturcd belt 361 is trained around rolls 35 8 and 359, and wire 362 with fibrous layer 360 thereon is advanced beneath belt 361 to form a sandwich. A spray of water is directed upwardly toward the undersurface of wire 362 and this is preferably accomplished in separated zones spaced along the length of superposed belts 361 and 362. Thus water is supplied through manifolds 387a, 387b, and 3870 and projected through nozzles 338 in the form of a spray. Vacuum boxes 5a, 5b, and 5c are positioned directly above the lower run of the apertured belt 361 in the path of the spray from the respective manifolds 387a, 33712, and 387C.
Vacuum dewatering means comprising vacuum means 400 coupled to vacuum conduit 4fi2 may be positioned beneath wire 36 2 following the last rearranging zone to reduce the proportion of water in the patterned fabric which is produced. The rearranged fibrous sheet, identified by the numeral 393, is dried in a manner which does not disturb the three-dimensional tufted configuration, as by the passage of heated gases therethrough or by the application of radiant heat.
As a result, tufted or budded nonwoven fibrous sheets are produced with direct utilization of a fibrous layer on the wire upon which it was originally deposited and formed.
FIG. 25 gives a diagrammatic side elevation of apparatus which may be used in accordance with this invention to produce a wet fibrous layer including fibers from both a card web and a fibrous slurry, and to effect fluid rearrangement of the fibrous content of the layer.
The apparatus shown in FIG. 25 is a modification of the apparatus shown in FIG. 1 in which card web 463 is continuously fed from a conventional source (not shown) onto foraminous support wire 62. In this case, the fibers of the slurry and the card web together form wet, nonflowable fibrous layer 60, which is fed into the rearranging region shown in the right hand portion of the figure.
When the streams of rearranging fluid strike fibrous layer 60, constituted both of fibers derived from the slurry and fibers derived from the card web, the two types of fibers are intermingled to form a more or less intimate mixture. This fibrous mixture is at the same time rearranged into the foraminous patterned nonwoven fibrous sheet of this invention.
The resulting product is removed from the rearranging region, after which it may be dewatered by passing over vacuum box 400 and mangled by passing between felt mangling belt 404 and metal mangling roll 262, as shown in FIG. 25. Mangling belt 404 is an endless felt belt trained around support rolls 405 and tensioning roll 406. If desired, a similar endless felt belt may be substituted for metal mangling roll 262. The finished foraminous, nonwoven fibrous sheet is then removed to a bonding or storage zone (not shown). In the bonding zone, adhesive binder may be added to the fibrous sheet by any conventional method.
Since shorter fibers of the type from which a slurry can be formed are furnished from mixing tank 53, and longer fibers of the type from which a card web can be formed are provided by web 403, wet fibrous layer 60 and the nonwoven fibrous sheet produced by use of this embodiment contain predetermined proportions of various length fibers as desired. Moreover, in the final nonwoven sheet all these fibers are uniformly and intimately mixed throughout the product.
The invention will now be illustrated by the following specific examples:
EXAMPLE 1 A stock furnish containing 100% lightly beaten cellulosic papermaking fibers of 2' to 3 millimeters average length is water-laid to provide a fibrous layer, the fibrous portion of which has a grain weight of 250 grains per square yard.
The rearranging apparatus of FIGS. land 2 is employed to produce a foraminous product from the wet formed fibrous layer. In the apparatus, wire 62 is provided with 10,000 openings per square inch and apertured belt 61 is made of thin stainless steel provided with about 225 openings per square inch. Each opening in the belt is about 0.040 inch in diameter. In place of the metal belt, a plastic belt having the same number and type of openings may be used.
Draining and dewatering of the fibrous layer is carried out at such a rate that the water content of the layer as it enters the space beneath belt 61 is approximately 300% based on the weight of said fibrous portion.
Wire 62 and apertured belt 61 are moved beneath three spaced banks of solid cone nozzles at a velocity of approximately 180 feet per minute. The resulting zones of fluid application are each approximately 1.5 feet in length. The nozzles are located approximately 4 inches above belt 61, and water is delivered at a rate varying from about 50 feet per second to 200 feet per second. Good fiber rearrangement is provided throughout this range. The amount of water delivered by each nozzle is about 1.3 gallons per minute.
During the fluid treatment, the water content of the fibrous layer increases to about times the weight of the fibrous portion. However, this water content is maintained for only a brief period because the tension on wire 62 and belt 61 is such as to reduce this to about 7 to 9 times the weight of the fibrous portion.
The rearranged nonwoven product is then mangled to reduce its water content to about 250% to 300% of the dry weight of the fibrous content, at which point the foraminous paper sheet is sutficiently self-sustaining to permit it to be dried by passage around heated rolls.
18 EXAMPLE 2 This example is the same as Example 1, except that a mixture containing 25% cellulosic papermaking fibers of 2 to 3 millimeters average length and 75% of inch, 1.5 denier viscose rayon fibers is employed, and the water content of the fibrous layer during rearrangement is higher than in Example 1. In the present example, the water content rises to about 15 to 30 times the weight of the fibrous portion during fluid treatment, and is thereafter reduced by the tension on wire 62 and belt 61 to about 7 to 15 times the weight of the fibrous portion.
The resulting unitary fibrous sheet possesses great softness and excellent hand and drape. The sheet has the appearance of a woven fabric, and is considerably stronger than a sample made by simply drying the fibrous layer of the example without rearranging the fibers. The surface of the fabric-like sheet is extremely smooth and lustrous, and the fibers in the interconnected packed portions do not tend to spring outwardly away from the packed portions.
EXAMPLE 3 This example is the same as Example 1, except that a mixture containing cellulosic papermaking fibers of 2 to 3 millimeter average length and 10% of inch, 1.5 denier viscose rayon fibers is employed.
The resulting foraminous nonwoven fibrous sheet possesses unusual strength considering the very small proportion of long fibers which are employed. The softness and hand are exceptional when the strength and small proportion of long fibers are taken into consideration.
EXAMPLE 4 This example is the same as Example 3, with the addition in the starting material of 4% by weight based on the dry fibrous mixture set forth in Example 3 of a uniformly dispersed highly beaten or hydrated.Mitscherlich woodpulp binder, and with the water content of the fibrous layer at the time apertured belt 61 is superposed thereon reduced to only about 500%.
The resulting foraminous nonwoven fibrous sheet is similar to the product of Example 3. The Mitscherlich binder has no substantial effect on the appearance or hand of the sheet, which is rearranged to substantially the same extent as the product of Example 3. There is, however, a significant enhancement in tensile strength.
EXAMPLE 5 This example is the same as Example 1, except that thebelts are reversed and vacuum devices are employed in the rearranging zone, both as shown in the modification illustrated in FIG. 22, and the water content on the wire is reduced to approximately 300% to enable the fibrous layer to be transferred to apertured belt 61 from moving wire 62 on which it is formed.
The resulting patterned nonwoven fibrous sheet is a tufted, three-dimensional product, the tufts being regular and well defined.
The rearranged fibrous sheet of this example is not mangled. Instead, vacuum is employed to reduce the water content and the sheet is then transferred to a traveling screen upon which it is dried by the passage of heated air thereover.
EXAMPLE 6 This example is the same as Example 5, except that a mixture of 75 cellulosic papermaking fibers. of 2 to 3 millimeters average length and 25% viscose rayon fibers of an average length of inch and a denier of 1.5 is employed.
The resulting fibrous sheet is similar to that produced in Example 5, but the interconnecting bands between the tufts are thinner to provide a more openwork appearance.
An important factor affecting both the rate and clarity of fiber rearrangement under the application of fluid rearranging forces is the degree of mechanical tensioning of the belts defining the rearranging zone. The fibrous layer located between the belts is mechanically compacted due to the tension of the upper and lower belts on opposite sides of the fibrous layer. An important factor affecting the clarity of definition of the rearranged fabric is the rate of travel of the fibrous layer through the rearranging zone, for if the fibers are exposed to the fluid forces applied in the rearranging zone for too short a period, the desired degree of fiber rearrangement will not be produced. These two factors are controlled to produce a rapid yet sharply defined fiber rearrangement. In the foregoing examples, the speed of travel of the wire and the fibrous layer is about 100 feet per minute to about 600 feet per minute, with the attainment of good clarity and definition of the foramina in the resulting fabric.
Depending upon the kind of fiber (its physical properties, density, water absorption, dimensions, denier, length, surface properties, etc.) and also depending on the relative spacing between the apertured rearranging member and the other foraminous member, the amount of water which is contained in the fibrous layer in the fiber rearranging region in the method of this invention may be as high as about 3,000 percent or more without encountering conditions which prevent fiber rearrangement.
Woodpulp fibers, 2 to 3 mm. /32 inch to A2 inch) average length, will handle properly in the rearranging area if there is no more than about fifteen times their own weight of water present. These fibers are relatively stiff and coarse. However, shortly after leaving the rearranging Zone, the belt tension should reduce the moisture content to less than about eleven times fiber Weight.
When a substantial proportion of fibers such as inch 1.5 denier viscose rayon is mixed with papermaking fibers, the limits of moisture appear to be about 20 times (or more) of fiber weight in the rearranging area before the fibrous layer loses its integrity, decreasing to less than about 12 times fiber weight as the fibrous layer leaves the rearranging zone.
After the rearranged fibrous sheet resulting from this invention is dried, it may be treated with an adhesive, dye, or other impregnating or coating material by passing it, for example, between the rolls of conventional padder. If desired, there are a number of suitable adhesive bonding materials or binders which may be em ployed in aqueous or non-aqueous media in the padder to strengthen the rearranged sheet.
Thermoplastic binders may, if desired, be applied to the rearranged product in powder form and then fused to bond the fibers.
For three-dimensional fibrous sheets, it is essential to use an apertured rearranging member which has a relatively smooth surface upon which the fibrous layer is to be supported and rearranged. Three-dimensional buds may be produced in the fibrous layer with a variety of sizes of openings and with any arrangement of openings, but voids in addition to three-dimensional buds are produced only where the distance between the openings, the size of the opening and the length of the fibers in the fibrous layer are such as to enable the fibers to consolidate as bands in zones which extend between adjacent openings.
Nonwoven fibrous sheets produced according to this invention have a wide variety of uses. Thus, paper products that can be produced by the method of the invention include table mats, doilies, decorative paper packaging, filter elements, and the like. Due to their structure and appearance and other qualities, textile-like fabrics produced by the method of this invention are particularly adapted for use in surgical dressings, absorbent dressings such as sanitary napkins, and diapers, wiping cloths, toweling, filter materials, drapes, and lining materials, industrial base fabrics, as a substitute for gauze and gauzelike fabrics in general, and in a variety of other applications.
The description of the present invention as it relates to fluid fiber arrangement which has been given thus far involves the use of two means defining between them a rearranging region within which the fibers of the Wet fibrous layer produced in the first step of the invention can be rearranged by applied fluid forces. However, the invention is also useful in cases involving fluid fiber rearrangement in which only one means, a permeable backing member upon which the wet, nonflowable fibrous layer is supported, is employed to define the rearranging region. As an example, under proper conditions, a tufted three-dimensional fabric can be made employing only an apertured rearranging member, applying water sprays directly to the fibrous layer rather than first against a foramina defining means as a dispersing screen.
In every case, whether the fluid rearranging .zone is defined by a pair of members or by a single member, the rearranging fluid forces are applied to the wet fibrous layer in a predetermined pattern while the layer is supported on a permeable backing member having a predetermined topography and a predetermined arrangement of passages therethrough. Supporting the wet, fibrous layer upon the backing member restricts the layer as a whole against substantial movement in a direction perpendicular to the median section of the year, without confining the individual fibers against relatively movement within the layer. Because of the predetermined topography of and predetermined arrangement of passages through the permeable backing member, fluid directed toward the fibrous layer and permeable backing member will be redirected into channels having predetermined directions. The predetermined pattern of application of fluid forces may involve spaced zones of direct fluid application separated by zones of no direct fluid application, as for example, when the fluid first passes through an apertured rearranging member or a foraminous dispersing screen as part of a sandwich" before it strikes the fibrous layer to be rearranged. The pattern of fluid application may also be a substantially solid one in which the fluid particles strike continuously and at random all the various areas of the fibrous layer.
In the case of spaced zones of fluid application, no fluid stream can pass directly through the fibrous layer and backing member in those areas in which there is no direct application of fluid forces. This is the situation, for example, with the various embodiments of apparatus shown in FIGS. 1 to 15 and described above. However, as there explained, particularly in connection with FIGS. 7 through 15, side currents or backwash may in some cases flow into the areas of no direct fluid application from adjacent portions of vhte fibers against which the patterned fluid forces are directed applied. In such cases, indirect fluid flow may occur through those portions of the fibrous layer and backing member not directly exposed to the applied fluid forces.
The course or channel followed by the applied fluid as it passes through the fibrous layer, and then over and through the permeable backing member upon which the fibers are supported, is determined by 1) the predetermined pattern of fluid application, (2) the topography of the backing member, and (3) the arrangement of the passages which permit flow of fluid through the backing member. One portion of the fluid may be diverted to the left of a given protuberance or high point on the backing member, for example, while another portion is diverted to the right. These separate streams may then flow by way of separate passages through the backing member, or may in some cases be reunited to pass through a single passage, all depending upon the overall topography of the whole backing member. The fluid passing through the wet fibrous layer and the permeable backing member supporting it is divided in the manner explained into a large number of separate streams, each following a characteristic course determined by the pattern of fluid application and the configurations and dimensions of the backing member.
Individual fibers of the wet, nonflowable fibrous layer are all capable of movement under the influence of an applied fluid or other rearranging force. They are thus rearranged by the applied fluid as it flows along the various courses determined by the factors mentioned. The individual fibers may be effectively picked up and swept along upon, or in the wake of, the various fluid streams passing through the fibrous layer and backing member. A fiber so moved may be transported bodily in a single direction, or part of it may be moved in one direction while other parts or segments are moved in one or more other directions. In any event, the fiber will continue to move under the influence of various fluid streams until its further movement is stopped (I) by the obstruction presented by the land areas of the permeable backing member that surround and define the open passages through the backing member, (2) by the presence of other fibers, or (.3) by the establishment of hydraulic equilibrium about the longitudinal axis of a group of bundled fibers.
On the other hand, instead of being swept along the path of various fluid streams passing through the fibrous layer and the permeable backing member, the individual fibers may be largely simply swept aside, out of the course of the onrushing streams, into quiescent zones to which no fluid forces are directly applied. Whether this is the case depends, among other things, upon the relative dimensions of the individual fibers and of the passages through the permeable backing member, the relative prominence of any protuberances upon 'the surface of the backing member, and the relative size of the areas to which fluid forces are directly applied in comparison to the size of the passages through the backing member.
This latter type of fiber movement, it will be recognized, is the type occurring during production of fibrous sheets such as that shown in the photomicrographs of FIGS. 26 and 27. The product shown in those photographs is made, by a method similar to that described in Example 1 above, from a slurry containing solely woodpulp fibers. T he rearranging member used for production of this fibrous sheet contained about 22.5 holes per square inch, each approximately 0.045 inch in diameter. The backing member was approximately 7,000 mesh nylon screening.
Regardless of the type of rearranging forces applied to the wet, nonflowable fibrous layer utilized in the second I step of this invention, the resulting rearrangement of fibers is brought about in the same general way. in every case, the fiber rearrangement results from the action of lateral translatory components oi the rearranging forces acting parallel to the median section of the fibrous layer and other cooperating components of those forces causing individual fibers to move, with respect to other fibers in the layer with which they are mechanically and frictionally engaged, in the direction of their respective longitudinal axes.
The type of movement just described will permit segments of the individual fibers to remain in mechanical equilibrium and in relatively unstressed condition in the most extreme lateral positions into which they are moved, as for example, in FIG. 11, by the rearranging forces. The fibers will thus remain in positions such as shown in FIG. 11 with substantially no in-built tendency to depart from their configurations in the fibrous sheet.
In effect, individual fibers are caused to slide along their longitudinal axes through the other fibers of the layer with which they are initially mechanically and frictionally engaged, so that there is substantially no force acting upon them to tend to cause them to return to their original positions. The cooperating components of force which help to produce this sliding movement of individual fibers may include vibrational components or rotational components, or both, depending upon the type of re arranging forces employed and the direction of application of the forces to the fibrous layer.
The above-detailed description of this invention has been given for clearness of understanding only. No unnecessary limitations should be understood therefrom, as modifications will be obvious to those skilled in the art.
1. Apparatus for the production of a unitary, nonwoven patterned fibrous sheet from an aqueous slurry of fibers which comprises: permeable, flexible, papermaking means extending through a draining zone and a rearranging zone, said papermaking means having openings therein for the drainage of water therethrough, said openings being of smaller size than the hereinafter referred to apertures, said papermaking means having a surface substantially free of obstacles to the movement of fibers there along under the influence of fluid deflecting forces; means for depositing an aqueous slurry of fibers upon said papermaking means; means for moving said papermaking means, first, with said slurry supported thereon, through said draining zone to remove water from the slurry and thus form a layer of wet fibers in mechanical and frictional engagement but capable of movement under the influence of an applied fluid force and, second, with said wet fibrous layer supported thereon, from said draining Zone to and through a rearranging zone defined by said papermaking means and means defining space-d apertures arranged in a pattern; means to move said apertured means along a path closely adjacent to and parallel with the path of the papermaking means through the portion of the apparatus constituting said rearranging zone, so that said apertured means, the fibrous layer and the papermaking means together form a movable sandwich; spray means directed toward said sandwich; means to supply a liquid to said spray means; and a vacuum means mounted adjacent the side of said sandwich opposite said spray means, said spray means being directed toward said vacuum means so that liquid issuing from said spray means will pass through said sandwich.
2, Apparatus for the production of a unitary, nonwoven patterned fibrous sheet from an aqueous slurry of fibers which comprises: permeable, flexible, papermaking means extending through a draining zone and a rearranging zone, said papermaking means having openings therein for the drainage of Water therethrough, said openings being of smaller size than the hereinafter referred to apertures, said papermaking means having a surface substantially free of obstacles to the movement of fibers therealong under the influence of fluid deflecting forces; means for depositing an aqueous slurry of fibers upon said papermaking means; means for moving said papermaking means, first with said slurry supported thereon, through said draining zone to remove water from the slurry and thus form a layer of wet fibers in mechanical and frictional engagement but capable of movement under the influence of an applied fluid force and, second, with said wet fibrous layer supported thereon, from said draining zone to and through a rearranging zone defined by said papermaking means and means defining spaced apertures arranged in a pattern; means to move said apertured means along a path closely adjacent to and parallel with the path of the papermaking means through the portion of the apparatus constituting said rearranging zone, so that said apertured means, the fibrous layer and the papermaking means together form a movable sandwich; means for supplying a fluid under force toward said sandwich; and a vacuum means mounted adjacent the side of said sandwich opposite said fluid means so that fluid issuing from said fluid means will pass through said sandwich.
3. Apparatus for the production of a unitary, non- Woven patterned fibrous sheet from an aqueous slurry of fibers which comprises: permeable, flexible, paperrnaking means extending through a draining zone and a rearranging zone, said papermaking means having openings therein for the drainage of water therethrough, said openings being of smaller size than the hereinafter referred to apertures, said papermaking means having a surface substantially free of obstacles to the movement