US 3509009 A
Description (OCR text may contain errors)
A ril 28, 1970 1.. HARTMANN 3,509,009
NON-WOVEN FABRIC Filed Feb. 6, 1967 6 Sheets-Sheet l I NV'ENT OR LUDW/G HARTMANN ATTORNEYS A ril 28, 1970 L. HARTMANN 3,509,009
NONWOVEN FABRIC Filed Feb. 6, 1967 6 Sheets-Sheet 2 WIHHHJH HW HHHHHWIMU nun-"why INVENT OR LUDW/G HARWANN BY l f ATTORNEYS April 28, 1970 HARTMANN 3,509,009
NON-WOVEN FABR I G Filed Feb. 6, 1967 6 Sheets-Sheet 4,
m s a R; m INVENT OR wow/c HART/MANN ATTORNEYS A ril 28, 1970 L. HARTMANN non-wovm1 name a SheetS- Sheet 5 Filed Feb. 6, 1967 INVENT OR wow/a HA RTMAMV BY 3w? a? ATTORNEYS A ril 28, 1970 L. HARTMANN 3,509,009
NON-WOVEN FABRIC Filed Feb. 6, 1967 6 Sheets-Sheet 6 FIG. /7.
u c o c o INVENTOR LUDWIG HARTMANN BY 3mm Ma4x$mm AT TORNEYS.
United States Patent Int. (:1. D04h 1/04, 3/08 U.S. Cl. 161-150 19 Claims ABSTRACT OF THE DISCLOSURE Apparatus and process for producing a non-woven fabric. The fabric is composed of filaments which are substantially continuous, substantially randomly disposed with respect to each other, randomly intersecting with each other and axially molecularly oriented by drawing at a ratio of at least 30: 1.
This application is a continuation-in-part of application Ser. No. 254,601, filed Jan. '29, 1963, now abandoned; application Ser. No. 302,370, filed Aug. 15, 1963, now abandoned; and application Ser. No. 341,489, filed on Jan. 27, 1964.
This invention relates to the production of non-woven fabric articles from material which can be provided in filament form, as by extrusion. This invention provides a new method for production of filaments, new non-woven fabrics, and new devices for production of such materials.
This disclosure is directed to a process for melt-spinning a polymer into a filament and drawing as well as orienting the filament as spun in a combined spinningdrawing operation. Further described herein is the apparatus in which said spin-drawing is carried out, a non- Woven product which can be produced directly from a multiplicity of such spin-drawn fibers, as Well as some particularly novel uses thereof, such as a cigarette filter. The described process includes melt-spinning immediately followed by impinging a gas along the spun filament, which gas exerts a drawing and orienting effect upon the filament. The described textile non-woven product has substantially randomly disposed, molecularly oriented, substantially continuous filaments which are bonded together at their intersecting points, either by laying the filaments down in a still tacky state and permitting the filaments to fuse-bond to each other at their points of intersection, or by laying down the filaments in a drawn and non-tacky state and bonding them in a second process step.
The starting material for the manufacture of non-woven fabrics is commonly staple fibers which are brought into a fiat assemblage and fixed in place with the aid of bonding agents or by self-adhesion. In general, the high precision required in the manufacture of textile fibers as to uniformity of fiber thickness and length, is not as technically important in the case of non-woven fabrics. Consequently, attempts have been made to produce special fibers for non-woven fabrics, and furthermore, to simplify the processes of making fibers and non-woven fabrics by combining the two processes, i.e., production of fibers and production of fabric, into one operation. Thus, it has been proposed that solutions of high polymers be sprayed through round nozzles placed in a concentric air stream, whereupon fibrous mats are formed. These processes, based on a spray gun principle, have not achieved any great industrial importance because the fibers produced,
3,509,009 Patented Apr. 28, 1970 and hence also the non-woven fabrics made, do not possess enough strength. This is probably due mainly to the poor molecular orientation of the molecular chains in the fibers thus manufactured, which evidently have been drawn very little or not at all. It has been proposed to use in place of the round nozzles, a fiat nozzle. The flat nozzle is formed of two wedges, into which longitudinal grooves have been cut, and the wedges are placed together so that juxtaposed holes are provided. The fused high polymer mass can be injected into two turbulent air currents and blown into fine fibers by means of the air currents. Since the wedges equipped with the longitudinal grooves have to be pressed tightly against one another, struts are required at certain intervals, and the struts hamper the uniform formation of fibers at regular intervals and, due to the turbulence which the struts create, the interfere with the formation of high strength fibers and uniform fabrics of relatively great width. The air streams which pick up the fibers become very turbulent after leaving the spinning nozzle, which also interferes with well defined drawing conditions of the fibers themselves.
The above-mentioned disadvantages are overcome by the following invention, which makes it possible, by spinning fiber-forming high polymers into directed gas current of high velocity, to produce a uniform non-woven fabric of great strength. Furthermore, it has been found surprisingly that, by melt spinning and drawing by means of directed gas currents, fibers of high molecular orientation can be produced. By directed gas currents according to the present invention, we mean those gas currents whose various strata have the same direction of travel over a distance of at least 30 cm.
In the process of this invention, filament material is spun out in such manner that a plurality of continuous filaments is formed simultaneously, said filaments lying rectilinearly alongside one another. This set of filaments is guided within air channels in such a manner that they do not contact one another in the form of strands or cables. This is accomplished by means of currents which pick up the filaments as they leave the spinneret, draw them and solidify them and carry them in parallel paths within air channels in a parallel-wise arrangement, avoiding the combination of a plurality of filaments into a yarn or tow, and they are finally built up by winding, collecting or criss-crossing the parallel rows into a mat of individually interfelted filaments.
Thus, the invention provides a process for spinning of filaments which comprises issuing a fused polymer mass in the form of filaments from several linear rows of spinneret holes of a spinneret head, and directing gas streams into impinging and entraining relation with the issuing fused polymer filaments to draw them and orient polymer molecules in the direction of the filament axis. The mass is drawn to reduce the diameter from the diameter of the spinneret hole in the ratio of at least 30:1, and the filaments are cooled to a set condition wherein the molecular orientation is retained. The filaments are maintained in drawn condition during the cooling by gas streams directed against the filaments to urge them to the drawn condition. In practical application, a multitude of linear, parallel filament rows are simultaneously drawn while keeping them in parallel arrangement within separate air channels, and the drawn and set filaments of the different rows are finally collected on a screen or perforated roll for the formation of a fleece or mat.
In this process, a fiber-forming high polymer can be fed in the form of a melt to a plurality of spinnerets, each of which consists of a linear row or line of more than, for example, holes, and an elongated gas discharge passageway can be provided on each side of the row or line of spinneret holes. The individual spinneret holes can have a diameter of 0.1 to 1.0 mm., preferably 0.2 to 0.5 mm. The length of the holes can be 3 to 6 times the diameter. The distance of the holes from one another can be 1 to 3 mm., and all of the holes in the same spinneret can be the same distance apart. The distance between the row of holes and the slit-like opening for the discharge of gas is more than about 0.1 mm, and preferably is about 0.1 to 1 mm., desirably 0.2 mm. Due to this close spacing, the gas stream does not have to be directed at any angle to the filaments, though an angle of a few degrees can be used in order to increase the pulling force.
The fused polymer is ejected from the spinneret holes in filament form. The filaments are immediately thereafter seized on both sides by heated gas currents dis charged from the two slit-like openings. The gas velocity is so adjusted that the filaments are carried away from the spinneret without breaking off, and so that the filament diameter decreases within a distance of 5 mm. from the spinneret in a ratio of at least 30:1, but preferably higher. The gas currents producing the great cross-sectional reduction are guided in such a manner that, due to the smooth shape of the slits, turbulence at the outlets of the spinneret is suppressed and a substantially directed flow is obtained. After leaving the spinneret the ribbon of parellel filaments from each individual spinneret, guided by the gas currents surrounding it, is introduced into a separate air channel or guide passageway for the purpose of keeping the filaments, as well as the filament rows, in a parallel arrangement. This is important, not only for the formation of a uniform web, but also for the undisturbed drawing and orienting action of the filaments. After leaving the discharge passageways, the gas currents are no longer heated, but instead cooled oif due to addition of cold secondary air streams in such manner that, at the distance of 5 cm. from the spinneret, the gas current can be chilled from, for example, 300 C. in the slit to 60-100 C. The secondary air streams can conveniently be introduced into the air channels or guide passageways through slot-like openings provided in the side-plates of the channels, so that the air can be added in a direction parallel with the filament row and on both sides of it. The cooling of the air stream is of great importance to the filaments inasmuch as the molecular orientation produced by the great cross-sectional reduction and by the drawing that takes place within a distance of 5 mm. from the spinneret is more or less substantially frozen in. The extent to which molecular orientation is achieved depends on the amount by which the filaments are drawn, which in turn can be controlled by the speed with which the polymers are ejected from the spinnerets and the speed of and the degree of cooling by the gas currents. The gas stream can cool the filaments by more than 100 C. in a distance of about 50 mm. to at least partially set the filaments. The guidance of the filament rows within the separate air channels is of great importance for the drawing and orienting process since it provides for turbulence-free conditions.
In one of the procedures of the invention, non-woven fabrics are manufactured by:
(a) Extruding a material capable of formation into filaments, while in liquid state, through a plurality of juxtaposed openings to provide a plurality of spaced and parallelly disposed nonsolidified filament rows thereof;
(b) passing heated gas streams, and at some distance cool air streams, on either side of the parallelly disposed filaments in impinging and entraining relation with the filaments, the combined gas of the gas streams cooling down and converging with the path of the filaments and urging the filaments in the direction of the extrusion into the air channels while tending to maintain the filaments in said spaced parallel disposed relationship, the filaments at least partially solidifying during the impingement and entrainment with the gas; and
(c) Thereafter and while the filaments are in impinging relation with the gas and after leaving the guide passageways or air channels, collecting the at least partially solidified filaments together to provide a fabric form comprising the filaments. By this procedure, the material forming the filaments can be provided in the fabric form as monofilaments with statistically varying directions of the filaments, such as, for example, in a woven or knit pattern.
Gathering of the filaments together to form a fabric can be performed in various Ways. A third gas stream in addition to the hot and cold gas streams referred to above can be passed into impinging relation with the filament forms along a path at the angle with or perpendicular to the direction of spinning of the filaments. The first and second gas streams referred to above can, and preferably do, provide the filaments in a plane. The third gas stream used to gather the fialments together for the collection thereof into a fabric form, can then be a gas stream which passes through such plane and across the monofilaments, breaking up the plane of the filaments and causing them to cross one another. The filaments can be gathered on a foraminous form which is moved across the path of the filaments and desirably means are provided for oscillating the filaments relative to the form for providing an improved random disposition of the fibers in the fabric. Following the gathering, the fabric form provided thereby can be calendered at, for example, room temperature or steam treated to bond the filaments together. It can also be bonded with synethic resins,
especially if a soft hand is desired.
As well as providing a procedure for the production of non-Woven fabrics, the invention provides a novel fabric structure characterized in that the fabric comprised of monofilament strands gathered together in such a manner as to provide a fabric thereof with randomly varying directions of filaments can be arrayed in a woven or knitlike pattern. Thus, the monofilaments can be collectively arrayed in a fabric pattern, the course of the segments of each filament varying in a statistically random manner. Further, the monofilaments can be gathered together on a form having the shape of a garment, so that a seamless garment can be formed of the nonwoven filament fabric according to the invention. In the production of such garments the form for the garment can be wound with respect to the filaments, so that the monofilaments are gathered on the form in a manner to provide a nonwoven fabric therefrom. For the production of fabrics having a woven or knit-like pattern, the filaments can be collected on a screen, having a woven or knit fabric-like pattern, by drawing gas or vapor through the holes of the screen. A preferred embodiment of the invention is the collection of filaments on a patterned foraminous form or screen, with means to increase the air speed towards the collection spots, as well as means to keep the filaments off and away from the undesired locations. Such means can be pyramidal studs or pins which are located on the collection form or screen wherever the holes or mesh of the woven or knit-like fabric should be. The pyramidal form of these pins or studs tends to guide the filaments into the appropirate interrelationship as well as increases the air speed of the guiding air stream of the filaments toward the collecting spots. The filaments thereby settle in a pattern resembling cloth and can be bonded that way. The resemble cloth in appearance, but are non-woven and have randomly varying directions of the filaments.
The invention will be further described with reference to the accompanying drawings, wherein:
FIGURE 1 is plan view of a spinneret head according to the invention looking toward the spinning nozzles.
FIGURE 2 is a sectional view taken along the line 22 in FIGURE 1.
FIGURE 3 is a schematic representation according to the invention which employs secondary air supply means.
FIGURE 4 is a sectional view taken along line 44 in FIGURE 3, and showing only the guide passageway in cross-section.
FIGURE 5 is a perspective schematic view of a fleece cross-section producing apparatus according to the invention as depicted.
FIGURE 6 is a side elevation of an embodiment of the apparatus according to this invention.
FIGURE 7 is a plan view of an embodiment of the apparatus according to this invention.
FIGURE 8 is a perspective view of an embodiment of the apparatus according to the invention, and schematically indicating use of the apparatus for production of a fleece.
FIGURE 9 is a graph showing birefringence in relation to fiber fineness.
FIGURE 10 is a perspective view, partially in section, showing apparatus according to the invention, wherein a plurality of the ranks of the filaments are simultaneously formed and are guided to a fleece form for collection as a fabric.
FIGURE 11 is a schematic representation of a fleece fabric according to the invention, having a woven-like attern wherein the monofilaments are arrayed in randomly varying directions.
FIGURE 12 is a view similar to FIGURE 11, indicating a fleece in a knit-like pattern.
FIGURE 13 is a perspective view of a foraminous support plate having perforations and pyramidal studs for production of a knit-like pattern as is shown in FIG- URE 12.
FIGURE 14 is a view of a collecting screen with pyramidal plans for the production of a woven-like pattern as is shown in FIGURE 11.
FIGURES 15 and 16 are each cross-sectional views of fabric structures provided with an iron-on stiffener formed of monofilaments according to invention.
FIGURE 17 is an elevation partially in section showing a 6-nozzle assembly with air channels.
FIGURE 18 is a schematic drawing of a 7 nozzle row assembly with grouped combinations of spinning orifices shown in relation to a collecting screen.
FIGURE 19 is a schematic representation of a portion of a fleece fabric prepared with the apparatus of FIGURE 18.
The apparatus of the invention can include a spinneret outfitted with a spinneret head having a plurality of spinning orifices disposed in a line, desirably in a substantially straight line, for receiving molten filament-forming mate rial from the spinneret and issuing it in a plurality of molten parallel filament forms, and gas delivering means disposed adjacent the spinneret holes for directing the gas stream into the path of the molten filament-forming material as such issue from the spinning orifices and for entraining the filament-forming material as continuous filaments extending from the spinning orifices and drawing the filaments and cooling them to set conditions while introducing them to the air channels. The apparatus further includes a foraminous support form disposed in the path of the entrained filaments after they leave the air channel from receiving the drawn filaments and collecting them, with the monofilaments disposed in totally random (as in common felt), or random and patterned crossing relation to form a felted fleece, and means for moving the ofrm relative to the entrained, drawn filaments to effect the collection of the filaments as an extended fleece.
As is shown in FIGURE 1, a spinneret head 11 is provided with a multitude of aligned spinning orifices 12, and the head further includes gas discharge passageways 13 which are in the form of elongated passageways having their outlet ends disposed substantially parallel to the spinning orifices 12.
As indicated in FIGURE 3, the spinneret head 11 can be mounted on a spinneret 12 with the spinning orifices 12, disposed for issuing filaments and directing such on to a support form 14 which is rotated in the direction indicated by the arrow. Due to the action of the heated gas streams discharging from the passageways, above and below the spinning orifices 12, the issuing filaments are entrained as a plane of filaments extending substantially horizontally and directed toward the form 14. The filaments pass between the secondary gas supply conduits 15. Cold gas discharging from the secondary air supply conduits 15 along with the filaments enters the guide passageway 39 and in cooperation with the guide passageway serves to maintain the filaments in a plane, accomplishes smooth drawing action cooling down of the filaments and prevent entanglement of the filaments prior to the arrival thereof at the form 14. The form 14 can be a perforated cylinder and suction can be applied to the inside of the cylinder via a suction nozzle 38 so that the gas is drawn through the cylinder; the drawing of the gas through the cylinder will serve to break up the plane of the filaments and to cause the filaments to be arranged in a substantially random and crossing relation on the form 14. Other means can be provided to break up the plane of filaments adjacent the fleece form 14, such as a third air supply means 38a and 38b which supplies air streams traversing the path of the filaments to disrupt the plane thereof. Further, the guide passageway or channel 39 can be rocked so that its discharge end pivots about its inlet end, whereby to facilitate the collection of the monofilaments into a fleece, and to facilitate crossing and mingling as well as pattern-like arrangement of the filaments if desired. In the representation shown in FIGURE 3, the spinneret 12, secondary supply conduits 15, and the air channel are mounted on a base 1 6 by brackets 18 and 19.
In the perspective representation in FIGURE 5, the filaments 21 are issuing from the spinning orifices 12 and are maintained in a plane by gas streams issuing from the gas discharge passageways 13 and the filaments are maintained as a plane as they are moved by the gas stream within the guide passageway 39 to the support form 22, which, in this case is elipsoidal in cross-section, indicating that the fleece form can be of any desired configuration, such as garment form if desired.
As noted above, the spacing of the spinning orifices 12 from the gas passageways 13 can be about 0.1 to 1 mm. This distance is indicated by the dimension S shown in FIGURE 1.
In the apparatus shown in FIGURE 6, FIGURE 7 and FIGURE 8, the device according to the invention includes a hopper 30 for the resin to be used to form the filaments, a conduit 31 leading from the hopper to the feed device 32, which is provided with a drive 33 for controlling the feed rate. The resin is passed from the feed device 32 to the manifold 34 where it is melted by application of heat from a supply source (not shown). Communicating with the manifold 34 are a plurality of spinnerets 35. Each of the spinnerets 35 is provided with a pump (not shown) driven by pump shaft 36, and is provided with a spinneret head as is shown in FIGURE 1. Further, a gas supply line 37 communicates with each of the spinnerets to supply gas for the gas discharge passageways 13 (FIGURE 1) of the spinneret heads. The gas passed through each of the lines 37 is heated by a heater (not shown). A rank 46 of filaments issues from each of the spinneret heads, and the spinnerets are disposed with the heads in parallel relation so that the ranks are in parallel planes. Spaced from each spinneret head in a position to receive the filaments issued thereby, is a guide passageway 39. The guide passageway or air channels 39 guide the fialments from the entrance end of the air channel to the exit end thereof which is disposed adjacent the support form 45, which in the embodiment here illustrated is a screen. The guide passageways serve to prevent entanglement of filaments of one rank with filaments of another rank, and further, serve to prevent entanglement of the various filaments of each rank, and keep them on parallel courses. Also, the air channels serve to keep the air streams directed and to guide the gas streams along the lengths of the filaments so that the gas streams urge the filaments in the direction of travel thereof and tend to urge the filaments in the direction in which they have been drawn and by suppressing turbulence allow for smooth drawing action. The cool secondary air streams are drawn in (injection principle) from the surrounding air together with the filament rows at 46. The amount of secondary air is governed by the speed and amount of primary hot air and by the inner volume and spacing of the guide passageways. The surrounding air is kept at a constant temperature to control the mixing temperature of primary and secondary air streams and thereby the setting of the filaments. In this way, the molecular orientation occasioned by the drawings is maintained during cooling of the filaments to the set condition, while the air stream has a great length of undisturbed filament to which to apply its frictional force.
In this regard, it should be understood that this invention includes the general proposition as set forth above as well as several modifications thereof which constitute separate aspects of this invention and some improvements on the basic concept thereof.
Thus, it is within the scope of this invention to provide each of the air channels 39 as either a single wide channel through which a multiplicity of generally parallel filaments are conducted, or to provide a separate channel for each filament which can be accomplished by providing the channels 39 as shown in FIGURE 8, for example, with dividing members between each filament. It is also within the scope of this invention to provide slot-like openings within the air channels for the introduction of additional air streams along side and parallel to the filament rows to govern the drawing and cooling action.
It is further within the scope of this invention to provide for a single polymer composition to be spun through all of the spinnerets through spinning nozzles of substantially equivalent cross-section. Under these circumstances, the product non-woven fabric will have a substantially uniform filamentary composition, that is, the filaments of the fabric product will all be substantially uniform in structure and composition.
It is, however, also within the scope of this invention to vary the spinning nozzle cross-section either as to size or configuration or both, in order to produce a nonwoven fabric product having individual fibers which vary in their physical configuration, cross-sectional size or both. By selectively placing the varyingly designed spinning nozzles, it is possible to produce a final non-woven product which is relatively uniform in overall composition, but comprises both normally constructed filaments and filaments having physical constructions which are at variance with the normal configuration.
It is further possible, practical and, in some cases, desirable to utilize polymers of different chemical composition in the practice of this invention. Thus, while the description of the process of this invention set forth above has indicated that all the filaments which are being spun may have the same composition and thus produce a product non-woven fabric having a substantially uniform composition, there may be circumstances where it is desirable to provide part of the product non-woven fleece filaments of a difierent chemical composition than the other filaments of the fabric. This construction could find great utility where it is desired to provide different dye patterns in the product or where puckered types of fabric are desired. These features can be accomplished, for example, by providing as a portion of the product, fibers which take up dyes at a different pH than the remainder of the fibers and therefor make it possible to dye a single fabric with two or more colors to provide some unusual and. desirable effects. Thus, products may be produced which have one, two or many more dif' ferent chemical composition fibers in the fabric. These different composition fibers may be distributed uniformly in the fabric product or may be disposed in particular limited areas of the product in order to produce a desired pattern thereon. It is also within the scope of this invention to produce fleeces composed of or containing so called hetero filaments, i.e. individual, unitary filaments which are composed of two or more polymers, and collect them to a non-woven fabric.
It is, of course, understood that these embodiments described immediately above, that is, the use of physically different filaments and the use of chemically different filaments, can be combined. Thus, it may be practical to form a non-woven fabric product comprising filaments some of which vary in physical structure and some of which vary in chemical composition. It may also be that the filaments which vary in chemical c0mposition also vary in physical structure.
A screen 45 is moved in the direction of the arrow 50 across the path of the descending ranks of filaments 46 and collects the filaments as a fleece. To improve the distribution of the filaments as well as their interfelting the air channels 39 may be rocked as is indicated by the arrow 44. Thus, each air channel is mounted on a shaft 40 which extends in the direction of the transverse axis of the air channel and a pinion 42, is provided for the rocking action of the air channels.
To further facilitate the obtaining of a suitable distribution of filaments in the fleece, the ranks of fibers are disposed so that horizontal projection thereof in the direction of movement of the screen 45, indicated by the arrow 50 overlap each other. This can best be seen in FIGURE 7.
It can be seen that non-woven fabrics can be manufactured according to this invention by spinning filaments 46 by means of spinnerets 35 through channels 39 onto a suitable substrate 45. It has been found, however, that for certain purposes, a better product is produced by disposing the spinnerets and associated channels at an angle other than perpendicular to the direction of movement of the substrate 45 upon which the nonwoven fabric is layed. This is particularly desirable where it is sought to produce a non-woven product which has a. more uniform overall structure.
Certainly, this aspect of this invention, that is, varying the laydown pattern of the filaments from the spinnerets from parallel to the direction of movement of the substrate to some angle thereto, is applicable to the other aspects of this invention referred to above, that is, varying the individual filament physical structure and/or chemical composition.
It has been found that there is an optimum angle of displacement of the spinnerets with respect to the direction of movement of the substrate. What this optimum angle is in any given case depends upon several factors. Among these factors are the overall construction desired in the final product, the number and spacing of filaments being spun from any single spinneret, the spacing between spinnerets and the angle through which the air channels, and possibly the spinneret directly associated therewith are rocked as outlined above.
Where it is desired to provide a relatively uniformly constructed non-woven fabric product, it has been discovered that the optimum angle of deviation of the spin nerets from perpendicular to the substrate direction of movement is such as will cause the plurality of filaments deposited from any given spinneret to overlap the plurality of filaments deposited from the next adjacent spinneret to a minimum extent. Thus, the optimum situation, in this aspect, is where the end filament on one side of a given spinneret overlaps the end filament on the opposite side of the next adjacent spinneret. In this manner, a substantially uniform-thickness fleece is obtained.
In the embodiment shown in FIGURE 10, the spinneret 12' is outfitted with a plurality of spinneret heads 11 each having a line of spinneret holes 12, and an air passageway 13 is disposed adjacent each row of spinneret holes and on each side thereof. Resin-melt is supplied by conveyor 51 to the pump 52, which in turn moves the melt to the conduit-system 61, whereby the melt is advanced to the spinneret holes 12. Heated primary air for assisting in the drawing of the monofilaments is introduced via conduits 56 and issues from the air discharge passageways 13.
The guide passageway interposed between the spinneret and the fleece form can be a square chamber with a centrally disposed opening for passage of the filaments extending therethrough, and with a plate disposed adjacent the filament path through the chamber on each side of the filament path. Openings can be provided in the plates, the openings being formed to direct cool secondary gas passed therethrough in the direction of and along the filament path.
In the embodiment of FIGURE 10, a plurality of guide passageways, one for each row of spinning orifices is provided in the housing 63. The housing 63 is constructed L with openings 64 extending therethrough for passage through the housing of the filaments. Each of the openings 64 is bounded above and below by a plate 65, and the plates 65 are provided with openings 66. These openings are formed to direct secondary gas, e.g. air, passed therethrough along the path of filament travel through the various passageways 64. Gas for introduction into the openings 66 is introduced into the housing 63 through inlet pipes 58. To provide suitable distribution of the gas, divider plates 67 are provided. Filament ranks 46 issue from the spinning orifices 12 and pass through respective openings 64 in the housing 63, and on the fleece form 14. The fleece form is rotated in the direction indicated by the arrow thereon, and, the filaments from each rank are collected on the fleece form as a layer, providing a fabric of several layers.
A feature of the invention is that the filaments can be deposited in the fabric to provide a fabric having a wovenor knit-like pattern. This can be effected by means of gas or steam currents utilized with an alternation of intensity corresponding to the pattern desired, and/or utilizing a selected pattern for the perforations of the fleece form on which the filaments are collected. This can be accomplished by using a collecting screen or foraminous form which, in the position where the mesh or holes of the woven or knit pattern would be, have elongated guiding studs or pins. These studs or pins can be of pyramidal or other form and as close as possible leaving free and foraminous only the places where filaments would collect in order to produce a wovenor knit-like mesh of strands. The pyramidal or conical forms provide narrowing air passages toward the collection screen, thereby increasing air speed towards the collecting points or lines of the filaments which greatly aid in providing good collection performance. Whereas the fabrics so formed have a wovenor knit-like structure, they differ from the usual woven or knit fabrics in that the individual filaments or collections of filaments, which form the wovenor knit-like pattern, change direction in a statistically random manner. This is indicated for a wovenlike pattern in FIGURE 11, wherein the forms b indicate the overall pattern which, as will be observed, is that of woven goods. The direction of any particular monofilament component through the fabric may be indicated by the dashed line a. The course of a filament is governed by the swinging action of the air channels, with lower swinging speed the course will be more curly, while with higher speeds there is a tendency to more parallel filaments within the strands. Similarly, for knit-like fabrics, the overall pattern of the goods may be as shown in FIGURE 12.
The monofilaments are disposed to provide the fabric form b and the varying directions and paths of the monofilaments in the goods is illustrated by the dashed a for one particular filament. A pattern for drum perforations and guiding studs corresponding to the knit-like pattern shown in FIGURE 12, is shown in FIGURE 13. The drum 70 is provided with perforations 71 and the projections 72 which have the form of a cone. For producing a woven-like pattern, as is shown in FIGURE 11, the surface on which the filaments are collected can be formed of a screen having pyramid-like projections 74.
The use of guide passageways or air channels according to the invention has been found to provide maximum uniformity of the fiber web over the entire width of the material. The swinging of the guide passageways provides for a method of determining the parallelism of filaments within given strands in wovenor knit-like patterns. The higher the swinging speed, the more uniformly the mesh of wovenor knit-like pattern. With low swinging speeds, a more curly pattern of filament deposition is obtained.
With the gas currents, according to the invention, filaments of 6 microns in diameter and less can be drawn directly from, for example, 400 micron spinneret holes. Such a reduction in combination with rapid cooling results in high orientation of long chain molecules.
In the rior art spinning processes, such great drawing from the spinneret holes by mechanical devices resulted in the breaking of filaments. The present process is furthermore characterized by the fact that the gas currents which cause drawing of the filaments out of the spinning orifices and which provide the parallel guidance thereof, should impinge and entrain the filaments in the form of rows for a distance of at least 300 mm., and preferably 600 mm. without the individual filaments being put together to strands or cables. The use of air channels with primary and secondary air streams enables the formation of strong filaments as well as uniform nonwoven fabrics therefrom.
The great cross-sectional reduction produces an orientation of the polymer molecules, and the finer the filament is drawn, that is, the greater the gas pull is, the greater the orientation will be. As the fineness of the filament increases, the specifi strength of the filament increases. The following tables list strengths of filaments which were spun from polycaprolactam according to Example 1 below.
Table I shows how the fiber thickness varies with the rate of flow of polymer per spinneret hole, the gas currents remaining constant:
TABLE I Rate of flow per ce./min. the slots in m./sec. microns TABLE II Fiber thickness in Tensile strength in microns grams per denier Fineness in deniers The curve in FIGURE 9 shows the birefringence of polycaproamide fibers in relation to fiber fineness. It is apparent from this that, in the case of fine fibers, birefringence values are achieved which correspond to those of normally spun and then mechanically cold drawn fibers. If no special precautions are taken the flow of polymer as well as gas over the width of the long linear nozzle shows irregularities especially towards the ends of the slots. This results in having different degrees of air and polymer speeds, for instance, in the middle of the nozzle as compared to the ends of the nozzle, a characteristic which becomes specially dominant in long nozzles. This results in the production of a spectrum of fiber thicknesses. It has been found that the birefringence of these different filaments increases with decreasing thickness, indicating increasing polymer molecule orientation. Production of a uniform non-woven fleece is possible by swinging the guide passageways so that a given line on the collecting screen is served by several spinning orifices. This difference in filament thickness can be avoided by having longer air slots 13 than spinning rows 12 (FIGURE 1) in order to put the decrease in air speed to a place where no filaments are formed and by having smaller spinning orifices. However, it has been found in some cases desirable having different filament characteristics within one fabric. Fibers of different thick nesses give a better closed surface. The thicker fibers have higher elongations because of lower drawing ratios and give the fabric a certain toughness, because when stress isapplied, they will elongate.
The felting of the individual filaments into a non-woven fabric takes place on the basis of various principles. On the one hand, the spinning speed is substantially higher than the speed with which the fabric is taken out, the two speeds being in a ratio of approximately 100:1. Thus, if the web of filaments is blown onto a screen belt with a suction behind it, the filament can be laid on in loops of a diameter always greater than 1 mm., i.e., greater than the filament spacing, so that adjacent loops overlap. Another factor that contributes to the felting is the turbulence of the gas current after leaving the guiding channels and striking the screen belt. The turbulence also increases as the deposition of fibers on the screen belt increases. The felting together of the ranks of filaments from different spinnerets is, according to the invention, brought about by swinging the guiding channels of passageways. The ranks of filaments follow the swinging movement without intertwining inside of the channels. A frequency of as many as 3 to-and-fro movements per second is appropriate. In this manner, the point of deposit of a particular filament can be displaced several times per second into the area of the adjacent spinneret and back, so that a satisfactory interfelting is achieved.
The bonding of the non-woven fabric thus produced can be brought about by various methods. The filaments can be welded together by heat treatment or with the aid of swelling substances. Secondary bonding agents in the form of dispersons or solutions can also be added. The fabric can be needled. Particularly desirable effects can be achieved by printing-on the bonding agents in certain patterns, because this especially preserves the inherent textile-like character of the goods. All fiber-forming polymers that can be melted without decomposition can be used as raw materials for the present process.
The following table gives a perspective of a number of fiber characteristics obtained with various raw materials:
81 is mounted on the spinning beam 82, which serves also as heating chamber for the nozzles. Each nozzle is fed with polymer melt 83 with the help of the spinning pumps 84. The filaments 86 leave the nozzles through the spinning orifices drilled intothe nozzle tip 85. On both sides of the spinning orifices are the slots 87 for the heated primary air. The primary air is fed into the nozzles from the small sides of each nozzle, as indicated at FIGURE 1. After leaving the spinning orifices, the filaments are guided into the air channels, so that each row of filaments has its own air channel. Cool secondary air is fed through slots 88 into the air channels. The primary air is also fed into the air passageways from both small sides of the air channels, so that could not be shown in this figure. It is similar to the feeding device of the nozzle indicated at 37, FIGURE 1.
This secondary air cools down the filaments, increases the spinning speed and keeps the individual rows of filaments on parallel course. As mentioned above, the filaments are collected on a moving screen which moves towards the observer of the picture. The air stream which flows on both sides of the filament rows starts to expand right after leaving the air channels 92. During this expansion it looses speed, while the spinning speed of the filaments remains constant. At a certain distance 89 from the end of the air channels turbulence causes the filaments to oscillate to such a degree that such is clearly visible. At a further distance 90 the filaments are collected. The distance 89+90 is important to the web structure and degree of intermingling of the different filaments. If they are collected at the distance 89 the filaments show little intermingling and interfelting so that the loose web thus formed can be pulled apart quite easily. If the distance 894-90 is too great, there is too much turbulence and web distortion. The distance between the end of air channels and collecting screen must be chosen for each spinning speed and product. The distance, however, should not be smaller than about mm. and should not be greater than about 1000 mm. As a spinning speed of 1000 m./min. with spinnerets of orifices each, and air channels of 30 mm. width, 380 mm. length, and 1015 mm. height, a distance of 350 mm. was found to be best suited to use in this apparatus. In actual operation the air channels are rocked in parallel fashion as indicated at 91 with the help of the guiding pins 93.
EXAMPLE 1 Granulated polyamide (polycaprolactam, melting temperature 210 (3., relative viscosity 2.28) was melted in an extrusion worm press at temperatures increasing forwardly at 200, 220, 250 and 270 C. and fed to four spinning pumps. The spinning pumps pumped the material to four spinnerets heated to 220 C., each of which consisted of a row of 160 orifices of a diameter of 0.3 mm. and spaced at distance of 2 mm. Each row of spinning TABLE III Rate of now Velocity Fiber through of gas in Primary Spinueret strength, Fiberspinneret, the slit, gas temp, temp, g. per thickness Polymer ceJmin. m./sec. 0. C. denier in microns Polycaprolactam 0. 1 270 260 240 3. 2 ll. 5 Polypropylene; 0. 065 150 260 265 5. 0 8. 0 Polyethylene-terephthalate 0. 1 300 290 3. 5 13. 0 Polystyrene 0. 005 375 248 1. 5 13. 0
The different filaments within the row as well as the different rows of filaments are collected on the form 45 after leaving the air channels and passing through open air for some distance. This distance is important for several reasons. The air streams which leave the channels expand and lose some of their linear speed. This is shown in FIGURE 17.
orifices had air slots of 0.2 mm. height, spaced at a distance of 0.4 mm. on both sides thereof, along its entire length. The continuous filaments issuing from the nozzles in the form of broad, non-cohering parallel bands were each seized above and below by air currents of 200 m./ sec. speed which were leaving the slots heated at 220 C. and pulled forward thereby. The filaments were thereby ac- The assembly of the six spinning orifices or nozzles 75 celerated from a speed of l m./mm. without the nozzles to about 1200 m./min. within a distance of 3 mm. from the nozzle exit. In a distance of 30 mm. from the nozzle exit, each row of filaments together with its air streams was brought into its air channel, which consisted of box-like ducts with the dimensions of 35 cm. width, 3 cm. height and 58 cm. length and which were open on the side which was opposite the noule (entrance) and on the outer side opposite the filament receiving screen (exit). Each nozzle had its own air channel which kept the filaments from each nozzle separated as well as parallel. Secondary air at a temperature of 40 was also drawn into the air channels in the direction of filament flow in a volume ratio of 1:10 to primary air, so that at the inside of the air channel was a temperature of 80. The air channels were rocked around an axis which was on the entrance side, so that they were swinging back and forth about 5 cm. on the exit side and indicated in FIGURE 8. The swinging of the four air channels was parallel. The filament rows were allowed to pass through the open air for 30 cm. after leaving the air channels.
The filament also moved in a swinging fashion after leaving the air channels since the air channels imparted their direction of motion. The filaments finally collected on a moving screen which had a suction device thereunder. The screen was moved forward with a speed of m:min., while the four different rows of filaments coming from the four nozzles were interfelted to a cohering non-woven fabric. The fabric was impregnated with a -percent dispersion of polyacrylate resin (butyl acrylate) and dried giving a fabric of 30 g./ square meter of fiber weight and 10 g./ square meter of bonding resin weight.
EXAMPLE 2 A granulate of polycaprolactam (rel. viscosity 2.28) was melted on a worm gear press, and fed to four spinning pumps, at a temperature of 260 C. The spinning pumps fed the melt to four spinnerets heated to 230 C. Each of the spinnerets consisted of a rectilinear line of orifices, 160 in number, each having a diameter of 400, and spaced from each other at 2 mm. The row of orifices was bounded on both sides, at a distance of 0.4 mm., by air slots each 330 mm. in length, in each case, and air currents were forced out of the said air slot after being heated, to 230 C., at a rate of speed of 200 m./ sec. The filaments issuing from the holes were seized by the bilateral air currents and thrust forward, whereby at a distance of about 3 mm. from the spinneret they Were accelerated from a rate of speed of 1 m./ min. at the orifice, to 1000 m./min. At a distance of 5 cm. from the spinneret, the filaments of each individual spinneret were introduced into a lengthwise air duct registering with it, the inner dimensions of said duct being about 3 x cm. and having a length of 58 cm. Secondary air at a temperature of C. was fed into the air duct in a volume ratio of 1:10 to the primary air.
The air ducts assured that along the further path, the individual filaments also remained separated from each other, while the set of filaments of each individual spinneret remained separate from the sets of filaments of the adjacent spinnerets. This made it possible to determine in advance the collection place of the filaments and particularly to facilitate patterned collection. The filaments issuing from four air ducts were captured by a screening drum, having holes (perforations) of about 2 mm. in diameter, arranged in a knit pattern. In checkerboard fashion the holes were surrounded by cones of 2 mm. base diameter and 4 mm. height.
By blowing through hot air currents, both during and after collection, the filaments assumed an arrangement in accordance with the layout of the perforations on the collecting drum, and under the effect of the heat, the filaments became bonded together. In this manner, there was produced a type of textured (knit-like) fabric structure with statically alternating directions of the endless filaments.
The non-woven fabric articles of the invention have a soft hand-like woven or knit goods feel, and can, there fore, be used wherever woven or knit goods or other such interlaced fabrics are used at the present time. The new process, however, substantially simplifies the manufacture of such textile products, since the manufacturing process is coupled with the production of the fabric. In other words, it is not necessary for fibers to be made and then drawn and treated with spinning oil and adjuvant agents in a first series of procedures, and then to spin the fibers into yarns which then are used for the production of woven or knit goods.
The process also differs from the prior art production of non-woven fabrics wherein the starting material is staple fibers which are made into a fleece and cemented together with the aid of binding agents. In processes of that kind, it is necessary to produce a relatively high number of bonds, in order to prevent individual fibers from working out of the fabric and fuzzing up the surface, a phenomenon which not only results in the destruction of the fabric, but also is a nuisance when the free fibers migrate, for example, to the outside of an outer wear fabric. Consequently, a relatively high proportion of binding agent is required for the adequate fixation of the staple fibers. The result in many cases is a stiffening of the fabric or a loss of its soft feel.
In the process of the invention, these disadvantages are avoided and a simplified manufacture of non-woven fabric articles is achieved. The starting materials can be polymers such as polyamides, polyesters, polyolefins, as well as mixtures of polymers. These materials can be spun into continuous filaments by the melt spinning process. In contrast to the prior art spinning methods, the process of the invention uses directed gas currents as drawing medium while spinning from several linearly arranged parallel rows of holes and whereby each row has two air slots, and an air channel. The air slots are parallel on opposite sides of each row. Preferably, spinnerets are used Which have more than about orifices in each. The spinning speed can be, for example, between about 1000 and 6000 meters per minute, according to the thickness of tthe fibers. The band of filaments of each individual row of spinning orifices, upon leaving the spinneret, is seized on opposite sides by a primary current of gas and accelerated, resulting in a reduction of the filament cross-section from, for example 300 microns, to 15 microns. The purpose of the primary gas or vapor current is to perform this drawing action and keep the filaments separate from one another. Furthermore, the primary gas or vapor current in many cases causes a solidification of the filaments, at least on the surface. The primary gas currents are preferably heated to avoid cooling down of the spinning nozzles and to improve the drawing step of the filaments. Then the bands of filaments are introduced into the air channels and seized by secondary gas or vapor currents which produce a final solidification and guide the filaments on their parallel course and prevent them from combining and entangling. The gas or vapor currents have a velocity greater than the filament speed, so that they not only stretch the plastic substance as it comes from the spinneret, but also solidify and draw the filaments. In the case of thermoplastics, the filaments are solidified by cooling from the molten state. The filaments, however, may also be solidified by precipitation by using, for the acceleration and guidance of the band of filaments, vapors, which precipitate solutions of high polymers in filamentary form. The solidification of the filaments coming from the spinneret can also be accomplished by chemical action, by using acid vapors.
When the band of filaments are collected, for example, by a screen with vacuum apparatus behind it, the individual filaments are superimposed by criss-crossing or winding entanglement, and are stripped off in the form of a jumbled structure. The stripping speed is always lower than the spinning speed. To increase the strength, the fleece, for example, that has been formed from continuous filaments can be needled, by means, for example, of the needle punching apparatus described in Textile Industries, September 1958, page 117, wherein needles equipped with barbs are used, which catch certain filaments and push them through the fleece, whereby a loop of continuous filaments is formed. It the material has been pr )perly compressed, a drawing of the filaments takes place which is particularly effective if the needling process is repeated several times. This process results in a considerable further strengthening of the fabric. The materials thus manufactured distinguish themselves by a combination of high strength with a soft, pleasant clothlike hand. Nevertheless, they can be further improved for the achievement of special properties. For example, it is possible to achieve woven fabric-like materials by calendaring with embossed rollers; this gives the material a better hand, and it can be sewn rapidly and securely. It has furthermore been found that the filaments in the materials of the invention are welded to one another by calendering at room temperature in such a manner that firm bonds result. It is possible in this manner to produce paper-like materials.
Binding agents which are appropriate can be used to effect such bonding as is desired, though, as it noted above, substantially less bonding agent is required than in the case of non-Wovens formed of staple fibers. Heatbonding can also be used, and it has been found desirable to employ steam or other hot gases to bond the filaments since this assures satisfactory heat transfer through a substantial thickness of fleece.
By subsequent impregnation with synthetic resins or sizes, the properties of the products of the invention can be improved. For example, impregnation with silicone resins has resulted in an improvement in ironability. Thermal post-treatment is often desirable. If, for example, the product is made by the spinning of polyvinyl alcohol, the finished product can be made more ironable by tempering at elevated temperatures. A substantial improvement in launderability has been achieved by treatment with cross-linking resins, such as those containing free methylol groups, or the like depending upon the chemical composition of the fibers.
After appropriation pore filling and compression, the materials can be surface-coated to produce leather-like materials. The advantage of the fibrous materials of the invention in this case is also and especially the fact that the continuous filaments do not contain any average agents and thus have an outstanding ability to adhere to the bonding agents used in the manufacture of artificial leather. This adhesion can be still further improved by performing the spinning process with a slight-oxidation of the fiber surface as for instance taking place by spinning under oxygen atmosphere. It has been found that, when the fibrous materials of the invention are used, for example, for the production of artificial leather products, especially smooth, uniform materials are obtained.
Further, paper-like products can be produced by calendering fleeces according to the invention. Suitable materials can be used as fillers to fill the pores for appropriate consolidation, and by such procedure, it is feasible to produce fully synthetic, paper-like materials with a high degree of strength.
It has been discovered, and is an important aspect of this invention, that non-woven fibrous batts made according to this invention are most eminently suited to use in the manufacture of filters. This is principally because the non-woven batting produced by the practice of this invention has a substantially ideally random fiber lay. That is, there is substantially no directional pattern amongst the filaments of a non-woven batting prepared according to this invention.
Cigarette filters may thus be produced by first feeding 16 the batting of this invention into a funnel-shaped apparatus wherein a dimensionally stable rod-form fibrous article is created from the batting which may then be Wrapped in cigaret paper as is now conventionally done or may be self-bonded on the periphery thereof to produce a filter adapted to use in connection with a cigaret.
In order to lend greater stiffness to the filter rod formed from these random batts, it is recommended to rufile these batts additionally. In other words, the batt is made to run through a pair of steel rollers heated to from to 150 C., in which at least one roll has a pattern such as the one that can be seen, for example, in FIGURES 2 and 3 of British Patent 898,432. However, other patterns are also suitable. In any event, provision is made that the roll has approximately five punctiform elevations per linear centimeter. Upon passing through the roll gap, the fibers in the batt are additionally joined together on the elevated points.
Such punctiform welding can also be achieved if the filaments emerging from the spinneret are formed into a batt at a time when they have not yet cooled. If they are deposited in the hot state, the filaments are still soft on the surface and thus partially become Welded to one another i.e., so-called spin-bonding.
Needless to say, the two methods of punctiform batt consolidation can be combined, that is, first deposit the filaments in the hot state and then rufiie them.
According to the invention, polyolefins free of plasticizers, especially polyethylene and polypropylene are preferred. By using thermoplastics containing no plasticizers, the filaments are kept from sticking together excessively after being twisted into a strand, thereby greatly reducing air permeability. Therefore, the danger does not exist in plastici'zer free filters that the plasticizer, which is always substantially more volatile than the thermoplastic filament material, will be inhaled together with the tobacco smoke.
The diameter of the filaments in the random batts (and ultimately in the filters) can be varied as desired. Usually, diameters between 5 and 50 microns are selected for use.
The use of filaments having a star-shaped cross-section has proven particularly good. Such a cross-section, of course, results in a filament whose surface area is greater than that of a filament having the customary round crosssection.
The manufacture of filaments with a non-circular crosssection by the use of spinnerets having the appropriate non-round cross-section when spinning the thermoplastics, by the methods described, for example, in French Patents 1,402,829 and 1,364,916, or in East German Patent 44,610, may be utilized in this invention. The depositing of such filaments to form a batt and their further working to form a cigarette filter are performed as stated above.
The filtering action of the filters according to this aspect of the instant invention can be further enhanced by applying to the filaments other adsorbents, such as charcoal, for example.
The cigarette filters according to the invention using polyolefin filaments absorb up to percent more tar and nicotine than a cigaret of equal length, equal diameter and equal thickness. At the same time, the air resistance in the filters according to the invention is lower than in any other known cigaret filters. If desired, the filaments used to produce this filter may be crimped.
The invention has special application to the production of iron-on interlinings, or to joining webs.
Recently, resort has been had in the processing of textiles to linings and interlinings which are not sewn on,
- but rather are secured to the base cloth by an ironing process. Generally speaking, these linings consist of fabrics or webs which are coated with a thermoplastic adhesive mass. The adhesive mass must be deposited, preferably not in the form of a sheet, but, for example, in a dotwise coating, in order to obtain porosity in the finished product, for example, articles of clothing. The web or the fabric serves in many instances only as a supporting material for the adhesive masses. As an appreciable simplification, it has been proposed to dispense with the supporting material. This could be accomplished, for example, by producing the ironable webs from thermoplastic fibers, which can be ironed on by applying an appropriate heat on the base cloth, which is to be supported. This simplification has not been successful inasmuch as the thermoplastic fibers produced heretofore could not be ironed on at sufficiently low temperatures to the base cloth with a sufficient degree to adhesiveness, or because the adhering surface was not resistant to cleaning or washing.
On the other hand, polymers or polymer mixtures which can be ironed on, even at lower temperatures, and which are at the same time also resistant to washing or cleaning, are known. However, these substances cannot be processed by the conventional spinning methods to yield fine fibers or sufficient strength to produce textile webs.
These drawbacks have been obviated by the present invention. Pursuant to it, a fibrous web is produced by spinning of such chemical substances as can be ironed on at temperatures ranging from 110180 C. and which are resistant to washing and cleaning.
The advantages of such a material as compared to materials known hitherto also reside in that such is adhesive on both sides, and that, owing to the absence of a carrier or supporting fabric, it does not make the end product too stiff or bulky. The spinning process is conducted in the manner described above wherein the filaments are spun out of special spinnerets with the aid of directed air currents. The oriented air currents serve in this connection as drawing and stripping devices. The advantage of spinning with oriented air currents resides in the fact that the iron-on substances, which generally tend to breakage of the yarn, can be spun out without breaking to textile webs. Such air currents are in contrast to strongly eddying air currents which would snap off the spinning mass upon issuing from the spinning holes. Thus, it becomes feasible to spin into textile webs built up of yarns, even such substances which have but a slight tendency to the formation of fibers.
In this connection, the process is conducted in such a manner that melts or solutions, or mixtures containing plasticizing agents or plasticizers, and consisting of adhesive high polymers, are spun with the aid of spinnerets into lengthwise chambers, as are described hereinbefore and as are disclosed in application Ser. No. 302,370, filed Aug. 17, 1963. In the chambers or guide passageways the filaments are maintained mutually separated, and are drawn and solidified with the aid of the oriented air currents. In this connection, the velocity of the air can be fixed in such a manner that the layer of air closest to the filaments at the outlet of the spinneret (i.e., the initial velocity of the air), has more than 100 times the velocity of the filament, preferably so that the speed of the filament commencing with the spinneret gains 500-fold within a distance of cm., owing to the lag caused by the frictional forces of the air currents. The expression oriented air current is intended to have reference to air currents which exhibit markedly identical directions of flow at the different layer levels. The oriented air currents render it possible to obtain a great elongation in the spinning and drawing of complex mixtures, and also permit collection as webs of desired form.
Apparatus as is described hereinbefore can be utilized for production of the iron-on stiifeners. Desirably, the air jet above and the air jet below the filaments are oriented air currents, and the velocity in each can be such that the velocity in the stratum adjacent the filaments is highest, and the velocity decreases from stratum to stratum in the direction away from the filaments. Multiple slots or nozzles can be used to produce each air stream to facilitate obtaining the desired gradient in velocity. Upon issuing from the guide passageways, the filaments can be picked up with the aid of a suction device as is shown in FIGURE 3 and can then be consolidated to a continuous web. The consolidation takes place, for example, with the aid of heated rollers whereby the filaments are made to adhere to each other by virtue of their natural adhesiveness. However, any other consolidating method can be resorted to. Generally such methods are preferred as do not require any additional binding agents, except where special effects are sought by means of binding or finishing means.
The iron-on fabrics of the invention can be utilized entirely as a binder since no backing or support is required or, alternatively, as binder and support. In FIGURE 15, a base fabric 78 of polycaprolactam is stiffened by a fleece 79 made, for example, according to Example 4 hereof, and ironed on by application of a heating instrument to the surface of the fabric 78 opposite the fleece 79. A sandwich structure as is shown in FIGURE 16, can also be made. The outer and inner fabrics 78 and 80 are bonded by the fleece 79. Fabric structure, such as those shown in FIGURES 15 and 16, can be porous since the fleece can be applied so that an impermeable film-like layer is not formed from the fleece. The bonding by the monofilament fleece of the invention is a direct bonding of the fleece to the contiguous material. The ironing-on can be by any suitable means for softening the fleece to permit adhesion thereof to the adjacent material.
EXAMPLE 3 A granulate of high-pressure polyethylene (melting index 72), was melted starting at a temperature of C. and fed to a spinneret at 260 C. The spinneret consisting of row of 20 holes with a diameter of 0.4 mm. and a spacing between the holes of 3 mm. On each side of the row of holes at a distance of 0.2 mm. an air slot which was 0.3 mm. in height and 68 mm. in length was positioned. Two air jets, each one of them at 260 C. were forced through the two air slots, these air jets seizing the melts issuing from the spinning holes and drawing them in the forward direction to form filaments. At a distance of 3 cm. from the spinneret head, the filaments entered a guide passageway with a plate spacing of 30 mm. The air jets were developed by a pressure of 1 atmosphere and caused an acceleration of the filaments from 1 m./min. in the spinneret bore to 500 m./min. at a distance of 10 mm. from the spinneret. Commencing with a distance of 60 cm. from the spinneret, the filaments are captured by means of steam treatment wherein steam was passed through the web to effect a suitable bonding.
EXAMPLE 4 A mixture of 1 part of a polyamide mixture of polycaproamide and polyhexarnethylene adipamide and 1 part of 2-ethyl-hexanol-para-oxybenzoic acid ester was melted in a worm gear press at a temperature of C. The melt was supplied to a spinneret heated to C. The spinneret was mounted as indicated in Example 3, but the air jets on leaving the slot exhibited a temperature of 160 C. The air jets were produced with the aid of a pressure of 1.2 atmospheres on the slots. The fleece, produced in accordance with Example 3, exhibited an adequate initial adhesiveness on reaching the screening drum to assure mutual consolidation of the fibers.
EXAMPLE 5 A mixture of 1 part of cellulose acetate (39% acetyl) and 1 part of diethylphthalate was melted in a worm gear press at a temperature of C. The melt was supplied to a spinneret which had been heated to C. The spinneret was mounted as indicated in Example 3,
19 and the air jet, on leaving the slots exhibited a temperature of 190 C. The air jets were produced by means of a pressure on the slot of 1 atmosphere. The fleece produced on the screening drum by suction was consolidated by routing through rollers heated at 150 C.
The iron-on fieece can be of any suitable weight for the task to be performed. Thus, the weight can be such as to provide a desired stiffening effect. Where the fleece is to serve merely the function of joining two webs to form a sandwich, the fleece can appropriately be light. The fleece can be, for example, 5-50 grams per square yard, and 'will commonly preferably be 5-"5 grams per square yard. The fineness in denier can be in the order of tenths and above, for example, 0.3 and above. As a range the denier can be about 0.3-5, preferably 0.5-3.
As to the composition of the monofilaments, this can be any one of a wide range of materials and mixtures. The composition should have a softening range of about llO-180 C. and should be formable into monofilaments by the process of the invention to provide monofilaments of great length, i.e., it should be possible to continuously spin .the composition by the process of the invention utilizing oriented air jets, without substantial breakage of the monofilaments. Examples of suitable compositions are polymers and polymer-plasticizer mixtures, such as branched polyethylene preferably having a melt index in excess of 70, polyamides and plasticizers preferably mixed polyamides and ester-plasticizers, and mixtures of cellulose acetate with plasticizers.
It has been found that the usefulness of a polymer to be melt drawn and oriented in order to give filaments of high strength in the present process can be investigated in the laboratory. By melting the polymer and measuring the recrystallization-temperature a good indication is obtained whether the specific material might be useful. If the recrystallization temperature is within 50 C. of the spinning temperature of the melt it is a good indication that this polymer is very useful for the process of the invention. It seems that the filament which leaves the spinning hole and which is drawn for instance from a diameter of 400 microns to 16 microns within about 5 ;mm. from leaving the hole is composed in this melt drawn stage to a large extent of molecularly oriented molecules. This can also be seen in curve 9. This orientation of chain molecules is evidently caused by the very large draw ratio of the molten filament. This drawing is helped by the high temperature of the primary air streams which envelope the filament at the moment it leaves the spinning orifice. As explained before, the drawing takes place within a very short distance (5 mm.)
from the spinning nozzle. The orientation of polymer molecules has to be frozen in" as soon as possible, therefor cool secondary air streams are added at this stage at the entrance of the air channels which guide the filaments and help in this drawing and orientation step. By the use of polymers or polymer mixtures, which when melted and consequently cooled down start quickly to crystallize, orientation retention can be very successfully performed.
The recrystallization temperature can very easily be measured by placing a substance on a microscope. (Fa. Reichert Wien: Kofier Heiztisch RCH), where the specimen can be heated and cooled down. By first heating the specimen to the temperature where the melt is normally spun and observing through crossed Nicols prisms the field of observation is dark, since crystals are no longer present. Then the specimen is cooled down until first light appears in the microscope indicating the presence of crystals. This temperature is observed and gives the recrystallization temperature. The crystallization time can be judged by keeping the specimen at this temperature and measuring the time until it is completely crystallized, which can easily be observed under the microscope. Values of short crystallization time combined with a re crystallization temperature near the melting temperature indicate usefulness for the present process. Following are values obtained with this method:
It can be seen that the nylon 6 and the polyester-specimen tested had a temperature difference between spinning temperature and recrystallization-temperature of only about 50 C. while the polypropylene sample tested had more than 120 C. difference. This indicates that the latter sample is not as well suited for use in the production of strong oriented filaments in the present process. A difference of not more than C. between spinning temperature and recrystallization temperature should preferably be maintained, while a difference of not more than 50 C. gives optimum results. It must be understood that this rule applies to the production of strong filaments with low elongation. For special non-Wovens, for instance the iron-on fabrics mentioned above or certain filler materials, this rule is unimportant, since they do not need to consist of filaments with high strength properties.
The fact, that the spinning nozzles are placed in parallel rows over an endless screen which collects these rows of filaments after their travel through the air channels is of significance for the formation of the non-woven fabrics made according to the invention. Each single orifice within a spinning row can be projected downwards onto the collecting screen. The position of the spinning orifice within the row as well as the position of the row within the parallel arrangement of neighbor rows governs the arrangement and position of the filament leaving this particular spinning orifice within the final assembly of filaments. Since with the help of the primary and secondary air streams and the longitudinal air channels the filament rows are guided down to the collecting screen in the same order as the spinning orifices are placed, it is possible to achieve a certain order of placement of filaments within the non-woven fabric. This order of placement within the non-woven fabric is determined by the order of placement of the spinning nozzles as well as spinning orifices. Thereby it is possible to arrange groups of filaments within the spinning rows and by the parallel guidance of these filaments to the collecting screen these groups can be found in the non-woven fabrics formed. In order to visualize this method, FIGURE 18 shows the arrangement in groups. The spinning rows are arranged in ranks 101. The spinning nozzles are placed over the collecting screen 102, which travels in the direction 103. The arrangement of air guidance systems, etc. are not shown in the figure to simplify it. They are arranged similar to FIGURE 8. It can be seen that the spinning rows are arranged at an angle to the direction of the collecting screen. The angle at is so chosen that the filaments spun out at one end 104 of a nozzle are met by the forward movement of the collecting screen by the filaments spun out at 105, which is at the other end of the neighboring nozzle. As can be seen, the filament rows consist of groups of three spinning orifices, whereby two of the orifices in each group are of smaller diameter than the third orifice of the group. By spinning different polymers out of different groups non-Wovens can be made with tailored properties. For instance, the first three groups 106 of all nozzles and the last three groups 107 of all nozzles should spin polyester filaments While the middle groups spin polyamide filaments 108. By the forward movement 103 of the collecting screen, a non-woven is prepared according to FIGURE 19, where the bottom layer is composed of polyester filaments 107, the middle layer is composed of polyamide filaments 108 while the,
top layer contains polyester filaments 106. It should be understood that different polymers can be spun in different orders and sequences so as to construct non-woven fabrics with specific properties. It is also possible to vary the form of the spinning within the groups so that, for instance, star-shaped spinning orifices are arranged together with Y-shaped to form certain groups. It is thereby possible to spin filaments with different cross-sections and different chemical composition and place them in the non-woven structure in predetermined positions.
What is claimed is:
1. A non-woven fabric comprising substantially geometrically randomly oriented and disarrayed, substantially molecularly oriented continuous organic filaments having a softening temperature of at least about 110 C., which filaments have varying degrees of molecular orientation with respect to other of said filaments.
2. A fabric as claimed in claim 1 comprising filaments having a softening point of about 110 to 180 C.
3. A composite fabric comprising the non-woven fabric claimed in claim 2, bonded to a second, distinct fabric.
4. A composite fabric as claimed in claim 3, wherein said fabrics are thermally bonded together.
5. A composite fabric claimed in claim 3 having a multiplicity of second fabrics.
6. A composite fabric claimed in claim 5 having a multiplicity of said non-woven fabrics.
7. A fabric as claimed in claim 1, wherein said filaments have been axially drawn to reduce the diameter thereof at least about 30 to 1.
8. A fabric as claimed in claim 1, wherein said filaments comprise at least one member of the group consisting of polyethylene, polyamide, plasticized polyamide, and plasticized cellulosic material.
9. A fabric as claimed in claim 1, wherein said filaments are bonded together at their intersections.
10. A fabric claimed in claim 1, wherein at least some of the filament cross-sections are non-circular.
11. A fabric claimed in claim 1, wherein the filaments thereof are of at least two different compositions.
12. A fabric as claimed in claim 11, wherein the filaments thereof have at least two different cross-sections.
13. An ordered fiber repeating-pattern fabric having warp and weft yarns, wherein each of said yarns is itself a non-woven fabric as claimed in claim 1.
14. A fabric as claimed in claim 13, wherein said pattern is a woven pattern.
15. An ordered fiber repeating pattern fabric wherein each of the yarns is itself a non-woven fabric as claimed in claim 1 and wherein said repeating pattern is a knit pattern.
16. A garment comprising a fabric as claimed in claim 1 having substantially no sewn seams in said fabric.
17. A cigarette filter comprising a fabric as claimed in claim 1.
18. A fabric as claimed in claim 1 having an embossed design on at least one surface thereof.
19. A fabric as claimed in claim 1 comprising at least some heterogeneous filaments.
References Cited UNITED STATES PATENTS 1,786,669 12/1930 Manning 146-67 2,188,332 1/1940 Carothers 161-82 2,336,743 12/1943 Manning 156-74 2,336,745 12/1945 Manning 264-10 2,411,660 11/1946 Manning 156-167 2,522,527 9/1950 Manning 156-167 2,688,380 9/1954 MacHenry -514 2,810,426 3/1962 Till et al. 51-295 2,861,319 11/1958 Breen 161-175 3,314,840 4/1967 Lloyd et a1. 156-167 ROBERT F. BURNETT, Primary Examiner R. L. MAY, Assistant Examiner US. Cl. X.R.