US3781393A

US3781393A - Process for the continuous production of a random-filament fleece

Info

Publication number: US3781393A
Application number: US00165779A
Authority: US
Inventors: K Feltgen; G Espanion
Original assignee: Bayer AG
Current assignee: Bayer AG
Priority date: 1968-09-07
Filing date: 1971-07-15
Publication date: 1973-12-25
Anticipated expiration: 1990-12-25
Also published as: CH1113369A4; BE738511A; FR2017575A1; GB1215679A; CH540372A; US3621531A; CH532148A; SE352671B; DE1785302B2; DE1785302C3; DE1785302A1; NL6913595A

Abstract

Process for forming a random-filament fleece by supplying filaments to a trumpet-shaped aerodynamic takeoff which throws the filaments against a collecting means where the filaments adhere to form a tubular fleece.

Description

KARL'HEINZ FELTGEN L PROCESS FOR Dec. 25, 1973 3,781,393 THE CONTINUOUS PRODUCTION 01 A RANDOM'FIIJAMENT FLEECE- 2 Shaets-Sheet 1 Original Filed Sept.

Dec. 25, 1973 KARL'HEINZ FELTGEN ETAL 3,781,393

PROCESS FOR THE CONTINUOUS PRODUCTION OF A RANDOM-FILAMENT ELEEcE Original Filed Sent. '7, 1968 2 Sheets-Sheet 2 FIG. 2

30 FIG. 3

United States Patent US. Cl. 264-89 6 Claims ABSTRACT OF THE DISCLOSURE Process for forming a random-filament fleece by supplying filaments to a trumpet-shaped aerodynamic takeoff which throws the filaments against a collecting means where the filaments adhere to form a tubular fleece.

This application is a division of US. Ser. No. 848,138, filed Sept. 7, 1968, now US. Pat. 3,621,531.

A process for the continuous production of a randomfilament fleece.

There are numerous processes for producing randomfilament fleeces from endless filaments arranged at random, for example from synthetic high polymers. In all these processes, a bunch of endless filaments is continuously run off either directly from a 'meltor dry-spinning machine for the corresponding polymer or from an element used for the after-treatment of filaments such as these, for instance rollers or cylinders, and is deposited in a random arrangement, but with as uniform a density as possible, for example onto a porous revolving conveyor belt. The take-off forces required are applied mechanically, for example by means of a pair of rollers, or aerodynamically to the filaments, and their irregular random distribution can be obtained either aerodynamically by utilizing turbulence or even electrostatically by the repulsion of similarly charged filaments, thus preventing them from bunching, or by a combination of both measures.

If they are to be economically further processed, random-filament fleeces such as these, for instance textile sheet structures, must in practice have a minimum width of approximately 1 metre. Some applications require widths of up to 3 metres and more. One difiiculty common to all manufacturing techniques lies in the difi'iculty of achieving economic production of these widths coupled with uniform density over the entire width and the absence of seams. Seams are obtained when the fleece web is formed from several narrow bands simultaneously deposited alongside one another, or when a relatively narrow random-filament band is deposited in a zig-zag or meandering arrangement from an element, for example a slot die, reciprocating perpendicularly to the direction of movement of the fleece web in the course of formation, the length of stroke corresponding to the required width of the fleece.

On account of the necessity for consistency of speed over the length of the stroke, all reciprocating movements require mechanisms that are not only complicated but also prone to wear. Depending on the kinematics involved in traversing, more or less wide zones of high or low density are always formed along the edges of the fleece web. These zones have to be cut off and are discarded as waste. Compared, however, with all the possible obvious alternatives for making the width of the bundle of filaments to be deposited equal to the required width of "Ice the fleece from the outset, the traversing method has certain advantages. As will readily be appreciated, a marked anisotropy of the physical properties such as strength, elongation and shrinkage is peculiar to a fleece prepared by the first method on account of the preferential orientation of the filaments in the longitudinal direction, i.e. in the direction of travel of the fleece web produced. Both in aerodynamic and in electrostatic processes for the production of random-filament fleeces, allowance must always be made for the possibility of the deposition length not being uniformly covered by filaments. Differences in density such as these would result in elongated streaks in the final fleece if no precautions were taken i.e. by traversing across the fleece as it is being formed, to ensure that every part of the depositing mechanism passes over every part of the fleece being formed.

In order, therefore, to avoid the aforementioned disadvantages, all conventional processes for the production of random-filament fleeces tolerate the difliculties of traversing mechanisms referred to earlier on.

The object of the present invention is to provide a process and an apparatus not employing any of these traversing mechanisms. The process according to the invention not only makes it possible to obviate the aforementioned disadvantages without any need for complicated mechanisms, it also embodies some important modifications which simplify the apparatus as compared with conventional apparatus for the production of randomfilament fleeces.

The process according to the invention for the continuous production of a random-filament fleece employs the method whereby a plurality of filaments is drawn of aerodynamically by means of a gas jet. The inventive feature is that, by using at least one annular jet which, after engaging the bundle of filaments, is deflected axially symmetrically, the filaments are blown in one plane on to the wall of a collecting unit, randomly to all sides, but in a uniform density, and form a tube which is continuously drawn off.

In this way, a tubular random-filament fleece is formed which is uniform in density over its entire periphery, and the uniform density is also constant over its entire length providing the manufacturing conditions remain constant.

Preferably, the gas is removed through gas-permeable walls in the collecting unit. This is of particular advantage in the production of random-filament fleeces of fairly high density, because this measure prevents the tubular structure formed from fluttering.

In one particularly advantageous embodiment of the process, the bundle of filaments sucked in and the tubular fleece formed are privoted or rotated with respect to one another. In this way, a further improvement relating isotrophy of the fleece generated is being achieved.

In another particular embodiment of the process according to the invention, the tubular fleece formed is moistened, for example with steam or a liquid, thus increasing cohesion of the fleece during draw-off.

According to another embodiment of the process, the tubular fleece formed is preferably cut up in order to obtain a single-layer fleece Web. In another embodiment of the process, the tubular fleece is cut into a plurality of webs in order to obtain suitable processing widths.

The main advantage of the process according to the invention does not, however, lie only in the homogeneous density of the fleece webs, but also in the possibility of using all the material produced without any waste because no irregular, useless marginal zones are formed.

In terms of known features, the apparatus for carrying out the process according to the invention comprises a filament or yarn dispenser, preferably in the form of a spinning head or a frame with supply rollers and takeoff cylinders, an aerodynamic take-off means and means for collecting the random-filament fleece.

The inventive feature is that the aerodynamic take-off means comprise a tube into whose wall opens at least one annular slot die arranged concentrically to the axis of the tube, the outlet end of the tube being widened like a trumpet and surrounded at a distance by the collecting means.

In one advantageous embodiment, the outlets for the filaments paid out by the dispenser are uniformly distributed over an annular surface, thus ensuring uniform density of filaments along the inlet circumference of the aerodynamic take-off jet-device.

In order to further enhance this uniformity, a distributor element is arranged above the inlet end of the take-off means. This distributor element comprises, for example, a disc surrounded externally by the filament, or a ring being touched by the running filaments either from inside or from outside. The distributor element may also be provided with guide grooves for each individual filament. Preferably, it is arranged at a variable distance from the take-01f means.

The distributor element is alternatively provided around its periphery with an encircling blow nozzle connected to a source for pressurized preferably heated, gas. This ensures that the filaments are guided in the total absence of friction. The object of heating the filaments with a heated gas issuing from the nozzle is to increase the temperature of the filaments traveling past to such an extent that, under filament tension produced by the resistance to drafting in the melting zone just beneath the spinneret an additional molecular orientation going beyond the quick draft is obtained by heat-stretching.

A displacement means is preferably arranged in the trumpet-like widening of the tube of the take-oft means. It is possible in this way more effectively to deflect the gas stream, axisymmetrically together with the filaments, and to minimize energy losses.

In another particular embodiment of the apparatus, the collecting means comprises a perforated jacket arranged concentrically to the central axis of the take-olf means. The carrier gas can penetrate through this perforated jacket. Preferably, the perforated jacket is removably attached so that perforated jackets of different diameter can be selective used for the production of tubular randomfilament fleeces of corresponding diameter. In one embodiment, the perforated jacket is in the form of a contractible sleeve. In this embodiment, however, the join in the perforated jacket adversely affects formation of the fleece, and additional precautions have to be taken to cover this join.

In another preferred embodiment, the collecting means is coupled with a moistening means, for example in the form of spray nozzles for steam or liquid.

At least one cutter unit is preferably arranged, on or behind the collecting means, for cutting up the tubular fleece into one or more single-layer webs.

In another advantageous embodiment, the collecting means is heatable to enable the filaments to weld together.

Preferably, the take-off means is, with advantage mounted in such a way that it can be pivoted or rotated. Alternatively to or in combination with this, the collecting means is pivotally or rotatably mounted. The pivoting range and speed or the rotational speed are Preferably variable.

The random-filament fleece according to the invention is distinguished by the fact that it is in the form of a seamless tube. In a particular embodiment, the randomfilament fleece comprises a web cut from a seamless tube.

The process according to the invention and the apparatus according to the invention are diagrammatically illustrated by way of example in the accompanying drawings, wherein:

FIG. 1 is a longtiudinal section through the apparatus,

FIG. 2, which is drawn on a larger scale, shows a particular embodiment of the distributor element in the form of a blow nozzle with a take-off means, and

FIG. 3 is a plan view of the collecting means with rotary drive.

As shown in FIG. 1, a bundle of up to several thousand individual filaments 1 issues from a spinning head acting as filament dispenser 2, the holes of the spinneret 3 being uniformly distributed over an annular surface 4. A distributor element 6 which is mounted concentrically to the annular surface 4 and which uniformly distributes the filaments 1 before they are drawn into an aerodynamic take-off means 7, is arranged on a vertical shaft 5 attached to the spinning head at a suflicient distance beneath the spinning head 2. The aerodynamic take-off means comprises an annular chamber 8 into which flows compressed air at 28 to p.s.i. atms. The annular chamber 8 surrounds a tube 9 and forms parts of the wall of this tube 9, which at its lower end is widened like a trumpet at 10. An annular slot die 11 is arranged in the tube 9, extending over its entire periphery. On leaving the slot die 11, the compressed air expands into thin high-speed jet flowing along in contact with the wall of the tube 9, taking the filaments 1 with it. The jet remains in contact with the wall even in the trumpet-like widening 10 of the tube 9 because provision is made for an adequate pressure all over the free sides of the jet so that the radial pressure gradient required for curving the flow line can be supported. This effect is enhanced by a displacement means 12 inserted into the trumpet-like widening 10 of the tube 9. In this way, the quantity of secondary air taken in from above is limited by the resulting reduction in cross-section, with the result that the partial vacuum in the tube 9 is reduced. On the other hand, the displacement means 12 ensures that any air entrained flows off in an orderly axially symmetrical manner. The flow pattern is thus similar, for example, to an axially symmetrical flow of the kind developed when a jet or stream impinges vertically on a plate. The bundle of filaments 1 follows this flow pattern and is thrown at random against a collecting means 13 comprising a perforated jacket. The take-off means 7 is rotatably mounted in the bearings 14 and is periodically pivoted back and forth by a drive 15 in conjunction with a cam 16 and crank arms 17. In this way, an extremely uniform texture is imposed upon the tubular random-filament fleece 18 which is removed at the lower end of the collecting means 13. The air penetrates through the holes in the perforated jacket 13 and in doing so presses the filaments 1 and the tubular hose 18 in the process of formation against the wall of the perforated jacket 13. The tubular hose 18 is moistened with steam or liquid, or possibly with a special preparing liquid, by means of a nozzle ring 19. Moistening promotes adhesion of the filaments although, with certain fibre polymers, it gives rise to some shrinkage so that the tubular fleece 18 readily detaches itself from the perforated jacket 13. The tubular fleece 18 is folded by means of two take-off rollers 20, behind which there is a cutter unit 21 which cuts up the tubular fleece 18 so that two

fleece webs

22 and 23 are formed, being wound up on to the

rollers

24 and 25.

The take-oif means 7 is shown on an enlarged scale in FIG. 2. The distributor element 6 is provided around its periphery with a blow nozzle 26, the shaft 5 being hollow for the delivery of gas or air. The filaments 1 are held apart by the jet of air 27 issuing from the blow nozzle 26 so that there is no friction on the distributor element 6. The filaments 1 and the propellent jet 28 take secondary air with them.

FIG. 3 shows purely diagrammatically how the collecting means 13 is rotated by the drive 30 in conjunction with belt 31, in order to impart to the tubular fleece 18 in the course of formation a spiral texture superimposed upon the meander texture imparted by the reciprocating take-01f unit 7.

What is claimed is:

1. A process for the continuous production of a random-filament fleece which comprises aerodynamical- 1y drawing off a plurality of filaments from a filament dispenser by means of a gas jet and then deflecting said filaments axially symmetrically with at least one annular gas jet and blowing said filaments in one plane on to the wall of a collecting unit at random to all sides, and in a uniform density.

2. The process of claim 1 wherein the gas is removed through the wall of the collecting unit.

3. The process of claim 1 wherein the bundle of filaments and the tubular fleece formed therefrom are rotated or pivoted with respect to one another.

4. The process of claim 1 wherein the tubular fleece formed is moistened.

5. The process of claim 1 wherein the tubular fleece formed is cut up.

6. The process of claim 1 wherein the tubular fleece is cut into a plurality of webs.

References Cited UNITED STATES PATENTS 2,931,422 4/1960 Long 65--1l R 3,015,127 1/1962 Stalego 264-Dig. 75 3,250,602 5/1966 Stalego 156167 3,254,482 6/ 1966 Stalego 264-8 3,615,998 10/1971 Kolb 156-167 3,616,030 10/ 1971 Jumenfier et a1 156285 3,650,716 3/1972 Brossard 656 JAY H. WOO, Primary Examiner U.S. Cl. X.R.