METHOD FOR DYEING A TORN FIBER BUNDLE AND APPARATUS FOR CARRYING OUT THE METHOD

Abstract: The invention relates to a method of dyeing a torn fiber bundle, and an apparatus implementing the method. The method is characterized in that the bundle of syn­ thetic fibers, after being torn and packed in an autoclave to a packed doughnut shape is directly immersed in a dye tank, wherein it undergoes the action of a bath flowing through the doughnut in a radial direction. Thus, containers and related apparatus may be used having larger diameters than conventional approaches.

Description: This invention relates to a method for dyeing synthetic fibers (i.e. acrylic, polyamide, and the like fibers) as collected into a bundle of fibers. This type-of product is normally dyed on the same apparatus used for dyeing wool fibers. In order to make the dyeing apparatus suitable for use with synthetic fibers, the latter are subjected to a series of treatments resulting in a product volume intended for accommodation in dyeing tanks of practically standard size, that is having diameters on the order of 400 mm and unit loads per dyeing tank not exceeding 60 to 80 kg with unit packages of 8-12 kg being pressed in the tanks. In order to achieve that "compatibility" of the product to be treated with existing apparatus, the preparation of the combed bundles or top of synthetic fibers for dyeing is usually effected through a set of practically standardized operations: - after the initial treatment of the fiber bundle which results progressively first in the stretching and then chopping thereof (hence the term "torn bundle") the pieces of the originally continuous bundle are collected in a container which is then introduced into an autoclave. The treatment undergone by the fibers in this autoclave has the effect of causing a consistent shrinkage thereof, made necessary to eliminate the retracting capability of the frhors springing from the tearing operation. Said shrinkage also brings about a thickening which reduces its volume. Thereafter,-the fiber is subjected to a first pass through a plucker machine which has the purpose of restoring softness in the fibers, resetting them as far as possible one parallel to the other (condition, this one, to be observed in order for the material to be suitable for subsequent spinning). Upon leaving this plucking treatment, the bundle is received into cylindrical containers, wherein it arranges itself into stacked coils around a center core. These stacked coils, of a diameter by now reduced to standard (that is lower than 400 mm) are still soft. At this point they are compressed vertically, packing themselves to an appreciably smaller height (for a given diameter) resulting in an intermediate product called "bumps". These bumps are at this point inserted (with their center bores), serially one above the other, onto a perforated rod and undergo a renovated axial compression which further reduces their height. Finally, the "pack" of several bumps pressed in stacked relationship is introduced into a cylindrical dyeing tank whereinto the dyeing bath is introduced by a pump starting from the bottom; then it flows up all around the fibers, penetrates them radially, and comes out thereof at the perforated rod carrying them, which rod is in turn connected, at the tank bottom, to the pump return line. Since the scrubbing tank, and related pump, have, as mentioned, standard characteristics,that is suitable in particular for dyeing wool, the pump head is low, and accordingly the capability of the dyeing bath to penetrate the interior of the fiber bundle is relatively moderate, and implies as a consequence that the degree of thickening of the fibers themselves be not excessive, and accordingly also the amount in weight of fibers being treated in each tank be limited within the 60 to 80 kg range. Thus the task of the invention is to overcome the limitations of the prior methods for dyeing a torn bundle of synthetic fibers. Within this task it is a primary object of this invention to provide a method whereby zone umber crf qperating steps provided for completing the dyeing cycle is lowered, thus shortening its duration and reducing costs. Another object of the invention is to enable the dyeing of larger amounts of fiber, for the same operating conditions. A further object is to provide a more uniform dyeing of the fibers, notwithstanding the presence of appreciably higher unit masses to be dyed. According to one aspect of the invention, the above task and objects as well as yet other objects which will be more apparent thereinafter, are achieved by a method of dyeing a bundle of torn fibers comprising a preliminary step wherein the fiber bundle is torn in accordance with a characteristic fibrous diagram and the thus chopped fibers are collected into a cylindrical container adapted for fixing in an autoclave wherein they are sLii- jected to a shrinkage and thickening treatment, characterized in that the thus thickened fibers are transferred, upon leaving the autoclave, directly into a dyeing tank wherein they are subjected to the action of a bath flowing radially therethrough. According to another aspect of the invention an apparatus is provided for carrying out the method comprising, as the fiber container introduced into the autoclave, a basket element having means for raising and direct transporting into said dyeing tank interior. Further features and advantages will become more apparent from the description of a preferred but not limitative embodiment of the method according to the invention, with reference to the accompanying drawings, where: Figure 1 illustrates diagramatically the preliminary fiber stretching step, known per se; Figure 1A being an enlarged view of the terminating area of Figllre 1; Figure 2 is adetail view of the basket or containing element whereinto the torn fibers are collected and which is provided for being accommodated within the autoclave; Figures 3 and 4 illustrate the procedure for extracting the fibers from the basket; Figure 5 illustrates the insertion of the fiber mass into the dyeing tank; Figure 6 shows that same fiber mass within the dyeing tank, during the dyeing itself; ; Figure 7 illustrates the step of inserting the dyed mass into a centrifugation apparatus; and Figure 8 shows schematically a final step of the method, wherein the dyed and centrifuged fibers are subjected to a single plucking pass prior to -be coiled into a storage package. Figure 1 shows the initial step, known per se, of the method, whereby the synthetic fibers collected into a web 1 are caused to pass through successive roller stations 2,3 and 4, whereat the web is wound around drive and return rollers. The roller sets of the stations 2,3 and 4 have progressively increasing speeds, so that the fiber is gradually '1stretched" to reach the final zone 5 where further rollers at further progressive by increasing speeds cause the bundle to be torn into fiber pieces extending more or less parallel; these fibers, when leaving this first zone of the apparatus, are schematically indicated at 6 and are usually collected in a basket or container 7. According to a peculiar feature of the invention, better shown in Figure 1A to an enlarged scale, on the interior ofthecontainer 7, there is arranged the fiber collecting element 6, in the form of a washer or Mk 8 from the center whereof there extends an upwardly oriented core 9. Fitted upon this core 9, is provided a further disk 10 to the periphery whereof there are attached, at intervals, small chains II which are provided with hooks 12 at the upper portion thereof. These hooks are so arranged as to remain suspended from the rim of the tank 7. Thus, the torn fibers 6 are collected inside the container 7 around the core 9, as illustrated by the cited Figure 1A, to form a "toroid" or pack of fibers or doughnuts. Upon completion of the container 7 filling operation, a bell 13 is lowered onto the container which seals the assembly to form an autoclave (Figure 2). After treating the material in torn fibers or top for an appropriate time period, the bell 13 is raised and the whole assembly comprising the bundle of treated fibers and disk 10 carrying it is extracted, e.g. with a hoisting means 14 which hooks, e.g. through small chains 15, to the hooks 12 of the cited small chains 11. The hoisting operation (Figure 4) is carried out while maintaining in the material doughnut the channel 16 created by the core 9. At this point, the fiber doughnut is transferred (Figure 5) into a dyeing tank 17 which is fed through an inlet conduit 18 by a high head pump 19. The return 20 of the pump is connected to a perforated tube 21 the diameter and height whereof are such as to allow the fiber mass to be slipped onto the tube 21 itself, thanks to the channel 16 left within the fiber mass. As may be observed in Figure 6, after the dyeing tank has been closed by means of the top lid 22, there is established within the tank itself a dyeing bath circulation which flows radially through the doughnut from the periphery thereof and returns through the axial perforated tube 21. moreover, owing to the effect of a disk 23 overlying the doughnut, a downwardly directed pressure is also applied (as indicated by the arrows 24) which tends to hold the doughnut compacted. Also during this step, the doughnut being treated is carried on the base disk 10 whilst the chains 11 are suspended with the hooks 12 from the edge of an inner frame 25 which does not hinder an ample circulation of the dyeing bath. The further step of the cycle provides for the removal of the dyed doughnut, again through the possibility of hoisting the assembly including the base washer and chains with a conventional means (Figure 7) and the introduction of this dyed doughnut directly into a centrifuge 26 having a concave bottom 27 which arranges for the centrifugal ejection of the water contained in the dyed material. The cycle is terminated (Figure 8) with a final plucking operation. Several doughnuts are inserted into the inlet end of a line where the fibers are conveyed through successive return rollers 28, being steam heated for the purpose of drying the pack which still contains residual water (the bundle being at this stage open, the water vaporization occurs more easily than with a drying process carried out on the wholetoroidor doughnut). Then, there follow stretching rollers 29 and pairs of plucking rollers 30. At the end of the line the thusly dyed and plucked bundle is collected into the container 31. As a result of the foregoing cycle procedure, it will be appreciated that at each pass large amounts of synthetic fiber top may be treated, up to 100 kg and above, per pack or doughnut and accordingly of 200 kg and above per tank load, thus exceeding the limits inherent to the solutions hitherto employed, and that during the dyeing step there can be created conditions for an improved and more uniform distribution of the dye through the use, among others, of higher head pumps which, however, cannot entangle the fibers because the latter have been compacted by the shrinking treatment carried out in the surge tank. With the method just described, the traditional practice of pressing the fibers with a mechanical action under a press has been replaced with the notion of accomplishing said compression by utilizing the inherent capability of the fiber to shrink when subjected to a thermal treatment, thus achieving a higher uniformity in the compactness throughout its volume, since all of the fibers will shrink in a substantially uniform manner. The invention as described is susceptible to many modifications and variations, as will readily occur to the expert in the art. The container has preferably a diameter in the range from 50 to 200 Cm.

Claims: CLAIMS 1. A method of dyeing a bundle of torn fibers comprising a preliminary step wherein the fiber bundle is torn in accordance with a characteristic fibrous diagram and the thus chopped fibers are collected into a cylindrical container adapted for fixing in an autoclave wherein they are subjected to a shrinkage and thickening treatment, characterized in that the thaSthidmawd fibers are transferred, upon leaving the autoclave , directly into a dyeing tank wherein they are subjected to the action of a bath flowing radially therethrough. 2. An apparatus for implementing the method of Claim 1, characterized in that it comprises, as the container of the fibers introduced into the auto clay, a basket-like element (7) having a means (14)for hoisting and directly transporting the fibers into said dyeing tank (17). 3. An apparatus according to Claim 2, characterized in that said fiber container (7) comprises a central core (93 therein wherearound said fibers collect into a doughnut or toroid pack. 4. An apparatus according to Claims 2 and/or 3, characterized in that there is provided axially within the dyeing tank (17) a perforated conduit (21) adapted to nslip-thereon" the fiber pack from the autoclave and at the central area whereof an axial passage (16) has been maintained as caused by said central core (9). 5. An apparatus according to the preceding claims, characterized in that said container (7) has a diameter in the 50 to 200 em range, as likewise have the following apparatus 6. Method and an apparatus as hereinabove claimed, and described and illustrated, as well as a product obtained by means of said method.

Inventors: BERGAMASCHI, GIUSEPPE
Applicants: TINTORIA & TRASFORMAZ SPA
Application year: 1982
Main classification: D06B5
IPC codes: D06B5