US3528129A - Apparatus for producing nonwoven fleeces - Google Patents

Description

Sept. 15, 1970 HARTMANN APPARATUS FOR PRODUCING NONWOVEN FLEECES Filed Nov. 7, 1966 INVENTOR LUDWIG HARTMANN BY @w.

ATTORNEYS. 6

United States Patent 3,528,129 APPARATUS FOR PRODUCING NONWOVEN FLEECES Ludwig Hartmann, Oberflockenbach, Germany, assignor to Carl Freudenberg Kommanditgesellschaft, Weinheim, Bergstrasse, Germany, a corporation of Germany Continuation-impart of application Ser. No. 495,929, Oct. 14, 1965. This application Nov. 7, 1966, Ser. No. 592,545 Claims priority, application Germany, Oct. 24, 1964, 1,435,466; Nov. 11, 1965, 1,660,297 Int. Cl. B28b 21/54 US. Cl. 18-8 2 Claims ABSTRACT OF THE DISCLOSURE Apparatus for producing a nonwoven fabric having filaments of noncircular cross section by melt spinning filament-forming material through spinneret holes having noncircular cross-sections, which filament holes are linearly aligned to form at least one row of melt spun filaments, the axes of which are substantially parallel, air-drawing all of these filaments substantially simultaneously directly out of the spinneret holes, passing these filaments and the drawn air through channel means, and then laying down these drawn filaments on a suit able substrate While still in the tacky condition, whereby to cause these filaments to bond together predominantly at their crossing points.

The present invention relates to apparatus for the manufacture of textile fiber products from a fused mass of fiber-forming high polymers and has as an object the manufacture of nonwoven textile products of substantially improved properties.

This application is a continuation-in-part of application Ser. No. 495,929, filed Oct. 14, 1965, now abandoned.

In the fusion spinning process for the manufacture of fibers, spinnerets are generally used which have concentric circles of holes. (See Hill, Fasern aus Synthetischen Polymeren, 1956, pp. 378 et seq.) The fibers which Hill discloses are introduced, at a distance from the spinneret, into a passageway into which air currents of certain temperature and humidity are injected at low velocity contrary to the direction of movement or crosswise thereto. (See also German Pat. 916,458, drawings.) These endless fibers are then brought together in' the manner of a cable or string, and the string is wound into a roll. In U.S. Pat. 3,117,055, it is proposed, for the manufacture of nonwoven fleeces, not to wind the filaments, but to guide the filaments together at a distance from the spinneret, accelerate them with air by means of an annular jet, and also charge them electrically. See FIG. 1 of US. 3,117,055. The charging causes the fibers as they fall to a fleece form, to repel one another, and separate for collection in random array on the form. It has developed, however, that it is difficult to effect suitable separation for the production of thin sheets with a uniform structure.

It has furthermore been proposed, for the manufacture of filter material, to extrude plastic masses from fiat nozzles having adjacent slots. The nozzles are formed of two Wedges compressed together, which contain grooves running lengthwise, which when passed together, form a sort of row of holes (Wente, Ind. and Eng. Chemistry, vol. 48, p. 8, August 1956). On each side of the row of holes there is located an air slit parallel therewith, from which air currents are driven. The air currents seize the extruded fibrous masses and carry them forward. It

3,528,129 Patented Sept. 15,, 1970 has not been possible by this process to produce fiber batts of high strength, because due to the excessive turbulence of the air currents, especially when they combine with the outside air, it is not possible to achieve a high orientation of the chain molecules within the fibers. Furthermore, the nozzle wedges do not fit together in a suitable manner to permit uniform fiber formation over relatively large production widths.

As is disclosed in application Ser. No. 341,489, filed Jan. 27, 1964, it has now been found that these diificulties can be overcome by extruding spinnable melts from nozzles which contain the spinning holes in the form of a straight row (see FIG. 1a hereof) and by guiding the rank of endless fibers emerging from the row by means of air currents within a filament drawing passageway in such a manner that they remain separate from one another up to the moment when they are collected on a screen belt (see FIG. 2), or other fleece forming support.

It has now been found that improved results can be obtained if the spinneret head holes are nonround in cross-section, especially if the holes have a branched cross-section. Desirably, the fused polymer mass issuing in a filament form from the nonround holes is drawn into a filament and cooled to provide the filament in solid state wherein the solid filament retains impressions corresponding to the branched cross-section. The drawing can be by means of air currents as is described in said Ser. No. 341,489. The filaments are collected as mono-filaments on a fleece form. The nonround monofilaments are characterized in that they have improved adhesion for binders. Accordingly, the invention particularly contemplates that a binder will be applied to the randomly arrayed mono-filaments collected on the fleece form.

It has also been found that the nonround filament form issuing from the spinneret can readily be formed into a crimped fiber. This is done by utilizing gas streams to elongate the filament form issuing from the spinneret. Variation in the influence of the gas stream on different portions about the circumference of the filaments affects the crimping. Crimping is further facilitated by utilization of gas streams of different temperature.

The invention is further described in reference to the accompanying drawing, wherein:

FIG. 1 is a perspective view of a spinneret head according to the invention;

FIG. 2 is a perspective view of apparatus for forming a fleece by the method of the invention; and

FIG. 3 is a cross-sectional view of a filament immediately following issuance from a spinneret hole as is shown for the spinneret head in FIG. 1, and after cooling of the same filament to the solid state.

The spinneret 1 is outfitted with a spinneret head 2 having a plurality of spinneret holes 3 for receiving molten filament forming material from the spinneret and issuing it in a plurality of molten filament forms. The holes 3 are nonround in cross-section, and preferably are branched, for example, T-shaped, or Y-shaped, as is shown in FIG. 1. Elongated air outlet passageways 4 are positioned on either side of the row of spinneret holes 3. Also, a guide passageway 5 is disposed to receive filament forms issuing from the spinneret and to guide them in parallel relation to the screen 6 which serves as a fleece form. Air passageways 7 are provided in the guide passageways, for the introduction of air into the guide passageways to assist in the treatment of the filament forms. A plurality of spinnerets and guide passageways can be utilized. The apparatus involving the combination of spinnerets, guide passageways, and fleece collecting form is more fully described in said Ser. No. 341,489. The fleece form 6 re- 3 ceives the filaments from the filament form 5 and collects the filaments disposed on the form in random crossing relation to form a felted fleece 8.

The apparatus and the method of the invention are particularly effective when the spinneret head is of the type shown in FIG. 1, wherein the head is elongated and the spinneret head holes are disposed along a line extending longitudinally of the head, while at the same time the head includes the gas passageways 4 for directing streams of gas along the path of the filament forms issuing from the holes 3.

The cross-section of the filament forms issuing from the spinneret holes 3 is as shown in FIG. 3.

Any suitable binder can be applied to the fleece 8 on the form 6 via the spray conduit 9. The binder can then be distributed through the fiee'ce by the calender rolls 10.

It will be observed that the outlet opening of the air passageways 4 are asymmetrical with respect to the outlet openings of the holes 3. This facilitates crimp1ng. The spinnerets here used preferably have the splnmng orifices spaced very close together (1.5 to 2 mm. apart). Furthermore, they are all shaped very uniformly, and the spinning orifices are parallel and equal to one another, so as to assure that the endless fibers, after they emerge from the spinning orifices, do not touch one another for a distance of at least 500 mm. or even more, and remain on parallel courses. Now, it is important that a filament drawing passageway 5 be associated with each row of spinning orifices, and that pairs of high velocity air jets are directed into the passageway in the direction of the flight of the fibers, in such a manner that the endless ranks of fibers emerging from the spinnerets are struck on both sides by jets of air from slits (a-l and a2, through passageways 4, and b-l and l2-2, through passageways 7). 1n the embodiment shown in FIG. 2, two pairs of air jets are represented, pair a1-a2 directly at the spinneret, and pair b-1-b-2 at a distance therefrom in the drawing passageway. To increase the draft of the fibers and hence the strength of the fiber batts, additional pairs of air jets can also be used. To obtain other fiber properties, e.g., to achieve a shorter elongation, the first pair of air jets, (1-1 and a-Z, can be very greatly throttled in comparison with 11-1 and 17-2, and in the extreme case, it can be shut off. 'In order to demonstrate the influence of the drawing passageways, experiments were performed first without drawing passageways and with air jets a-l and a2 alone, and then with drawing passageways and with the addition of air jets b-l and b2, at increasing velocities. The results obtained are shown by the following table:

Substance spun: Nylon 6 Throughput: 0.1 g. per spinning orifice It is apparent that, by arranging the conditions appropriately, e.g., drawing passageway operated at high air velocity, high strengths are obtained in the fibers and hence in the batting made therewith. It is furthermore apparent that the ultimate tensile strength, which to some extent reflects the molecular orientation, can be varied over a very wide range.

Another considerable possibility of variation in the process is provided by variation of the temperatures of the air jets. For example, 11-1 and a-2 can have a higher temperature than b-1 and 11-2, or the temperature may be equal. If the temperature of jets 11-1 and [1-2 are increased, it is possible to sustain the plasticity of the endless filaments coming in the melted state from the spinneret and thus achieve an improvement in properties, depending upon the end product. An especially advantageous effect is achieved when the temperatures of the individual jets of a pair are different, i.e., a-l different from a-2 or b-1 different from b2. In this manner it is possible, for example, in the case of a branched crosssection, e. g., Y-shaped cross-section, in the spinning orifice, to produce a tension variation within the fiber, since the air jets both stretch the fibers and cool them, and thus create different orientation conditions about the circumference of the fibers. It has developed that improved crimping can be produced within the fibers in this manner, and that this crimping has a very great effect on the properties of the fiber batts that are formed from them. It makes the fiber batts bulkier and gives them a softer feel. Further, the Y-shaped or branched cross-section of the filaments improves the adhesion of the fibers for binding substances, which can be any suitable binding substance.

The ranks of endless fibers emerging from the drawing passageways are caught on a screen felt having an aspirating means beneath it similar to the indication in FIG. 2 of Ser. No. 341,489. The screen belt can furthermore be arranged either athiwart the row of spinning orifices (as represented) or in line therewith, or at any desired angle thereto, depending on the end products desired. The high uniformity of the fiber batt is achieved by the fact that the individual fibers, from the moment of their formation to their deposition on the form, remain substantially unaffected by the other fibers, and primarily by the fact that they are not brought together in the manner of a cable or string. The high degree of mutual entanglement is achieved by the fact that the spinning orifices are very close to one another (e.g., 2 mm. apart), and the spinning speed is several times greater than the belt speed. For example, a spinning speed of about 2000 m./min. is used with a screen belt speed of about 20 m./min. Now, since the spacing of the spinning orifice is very small in comparison with the diameter of the fiber loops that form and are deposited on the screen belt, a mutual felting occurs. This can be effected by rocking the drawing passageways as disclosed in Ser. No. 341,489. The entanglement of the fibers is further augmented by the use of the branched, e.g., Y-shaped cross-section, and in the case in which an increase in crimping is produced by air jets of different temperature.

EXAMPLE 1 Polycaprolactam granules (reduced viscosity-2.28) were melted in a worm press and fed to a spinning pump at a temperature of 260 C. The spinning pump proportioned the melt to a spinneret heated to 228 C. The spinneret consisted of a rectilinear row of spinning orifices, these orifices being Y-shaped and spaced 2 mm. apart. An air slit 0.3 mm. wide was disposed on each side of the row of orifices, at a distance of 0.4 mm. Air currents at 230 C. were ejected from both air slits at a pressure of 0.1 atmosphere overpressure. These paired air streams seized the row of filaments emerging from the Y-shaped cross-sections and carried them forward. The filaments along with the air streams enveloping them on both sides were introduced into an air passageway 5 which had been mounted at a distance of 40 mm. from the nozzle (FIG. 2 The distance between the plates of the rectangular air passageway was 20 mm. At the entry of the air passageway there was arranged another pair of air slits 7, as shown in FIG. 2, from which air at room temperature was ejected at 1.5 cu. m. per minute. The second pair of air jets produced an additional pulling effect on the rank of filaments, so that an additional force was exerted and took effect in the zone where the drawing was being done. Furthermore, these air streams produced a cooling of the filaments and a freezing of the molecular orientation obtained. As a result of the guiding passageway surrounding the rank of filaments on all sides, turbulence was prevented, so that the filaments remained on a parallel course and did not entangle or come together into cables. At the bottom end of the 40-centimeter-long guiding passage 5, the air velocity was 1500 meters per minute.

The filaments were built into a coherent batting by aspiration. They had a titre of 0.81 denier, a tensile strength of 4 grams per denier and an elongation at rupture of 140%. The filament cross-section was triangular with indented sides, i.e., retained impressions corresponding to the shape of the branched spinneret holes, and the fibers were highly crimped.

EXAMPLE 2 Example 1 is repeated with the modification that the air temperature of the air issuing from one of the passageways 4 is 230" C., while the air temperature of the air issuing from the other of the passageways is 150 0., and the air temperature of the air issuing from one of the air passageways 7 is room temperature, while the temperature of the air issuing from the other of the passageways 7 is 75 C. More crimping of the fibers is obtained due to this variation.

Suitable binders are disclosed in Nottebohm, Pat. 2,719,806, Oct. 4, 1955.

By crimping is meant that the fibers are distorted so that when disposed longitudinally, with no tension applied thereto, the application of tension will initially effect an elongation, without any corresponding reduction in cross-section.

While good results are obtained by practicing the process of this invention in the apparatus hereof, it has been found that under some spinning and drawing conditions, the filaments are not treated exactly uniformly with respect to all surfaces thereof. Under some conditions, the resultant fiber nonuniformities produce a nonuniform crimping of the individual fibers. This in itself is not too bad since the fibers are intended for use in a relatively random nonwoven fibrous batt or fleece.

However, it has been found that, if all of the fibers are spun from noncircular spinning nozzles which are parallelly oriented, the resulting fibers may cool nonuniformly, but similarly, and thus the nonwoven fabric may have an overall slant pattern as opposed to the random array of fibers which is usually desired. It has been found that this overall slant pattern of the resultant fabric can be simply avoided by spinning the noncircular filaments from spinning nozzles which are randomly oriented with respect to each other. In this way, the potentially irregular cooling and crimping will not uniformly affect all filaments and there will again be produced a random oriented fleece product. In this regard, it is preferred that every other spinning nozzle be oriented at 180 degrees from its adjacent nozzles. For example, every other Y-nozzle will be upside down with respect to its adjacent nozzles.

While the invention has been described with respect to particular embodiments thereof, these embodiments are merely representative and do not serve to set forth the limits of the invention.

What is claimed is:

1. In an apparatus for the continuous production of substantially endless filament nonwoven fabrics which comprises spinneret means having at least one substan tially linearly aligned row of spinning nozzles, gas Outlet means adjacent to and on opposite sides of said row of spinning nozzles for impinging a gas stream onto two opposite sides of the rank of filaments spun from said row of nozzles; channel means adjacent to and spaced longitudinally from said spinneret and from said gas opening means adapted to be associated with (a) said single row of substantially endless filaments and adapted to receive said filaments and at least a portion of said gas stream therein and to pass such therethrough, said channel means having an inlet substantially aligned with, adjacent to, and spaced from said spinning nozzles and from said gas outlet means; and continuously moving fleece-form filament receiving means spaced from the end of said channel means opposite to the end thereof adjacent to said spinneret and disposed at an angle to said filaments adapted to receive said substantially endless filaments upon emergence thereof from said channels; the improvement which comprises said spinning nozzles being Y-shaped and adjacent nozzles are positioned out of phase with each other.

2. In an apparatus for the continuous production of substantially endless filament nonwoven fabrics which comprises spinneret means having at least one substantially linearly aligned row of spinning nozzles, gas outlet means adjacent to and on opposite sides of said opposite sides of said row of spinning nozzles for impinging a gas stream onto two opposite sides of the rank of filaments spun from said row of nozzles; channel means adjacent to and spaced longitudinally from said spinneret and from said gas opening means adapted to be associated with (a) said single row of substantially endless filaments and adapted to receive said filaments and at least a portion of said gas stream therein and to pass such therethrough, said channel means having an inlet substantially aligned with, adjacent to, and spaced from said spinning nozzles and from said gas outlet means; and continuously moving fleece-form filament receiving means spaced from the end of said channel means opposite to the end thereof adjacent to said spinneret and disposed at an angle to said filaments adapted to receive said substantially endless filaments upon emergence thereof from said channels; the improvement which comprises said spinning nozzles each having cross-sections which are substantially the same and wherein said nozzles are randomly oriented with respect to each other.

References Cited UNITED STATES PATENTS 2,121,802 6/1938 [Kleist et al. 2,331,945 10/ 1943 Pazsiczky et al. 2,411,660 11/1946 Manning. 2,437,263 3/1948 Manning. 2,604,667 7/1952 Hebler 264-68 2,644,779 7/ 1953 Manning. 3,028,623 4/ 1962 Labino 18-2.5 3,154,836 11/1964 Hoag et al. 3,219,739 11/1965 Breen et al. 214168 3,297,807 1/ 1967 Settele. 3,303,169 2/1967 Pitzl 161-172 X 3,366,722 1/1968 Tessier. 2,508,462 5/1950 Marshall 18--8 3,266,969 8/1966 Makansi. 3,379,811 4/ 1968 Hartmann et al.

FOREIGN PATENTS 296,015 5/ 1965 Netherlands.

JULIUS FROME, Primary Examiner I. H. WOO, Assistant Examiner U.S. Cl. X.R.

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