APPAERATUS AND METHOD FOR DECORATING TEXTILE MATERIALS Technical Field

The present invention relates to an apparatus and method for decorating, with ornamental patterns, textile materials of any kind, whether untreated, dyed and/or printed with any type of dyes and pigments. State of the Art

At present, the decoration of textile materials may be carried out in various ways, mostly by weaving, printing, or by the application of dyes in most different ways.

Decolorization processes are also known which use oxidizing agents (such as sodium hypochlorite, hydrogen dioxide, potassium permanganate) added directly to the bath in which the textile material is held for the decolorization thereof. In this case, the decolorizing action is diffused at random over the whole material in contact with the oxidant, with various intensity in one region and the other, mostly due to material's creases and overlapping which alter the uniform distribution of the oxidant onto the textile.

Oxidizing agents (potassium permanganate, for example) are also applied onto the suitably masked textile. Also known from EP1094148 are decoration processes by decolorization, in which a dyed textile is put in contact with a substance whose formulation includes active oxidizing agents and which is distributed according to selected lines and regions of the textile.

Because of the presence of such oxidizing agents, the appearance of the textile results locally modified by decolorization.

These known processes, however, exhibit one or all of the following drawbacks: requiring a lengthy application, exhibiting a poor repeatability or no repeatability at all, and not allowing an efficient control of the decolorization process.

Description of the Invention

It is therefore in great demand a method and apparatus, for the decoration of any textile material, able to overcome the drawbacks of the above mentioned techniques. The technical task and the specified objects are substantially obtained by providing a process and an apparatus for decorating a textile material comprising the technical characteristics set forth in one or more of the appended claims. Further characteristics and advantages of the present invention will appear more clearly from the following indicative, and thus non-limiting, description of a preferred, but non-exclusive, embodiment of the invention, as illustrated in the accompanying drawings, in which: - Fig. 1 shows a first embodiment of an apparatus according to the invention in successive steps for the treatment of a textile material;

- Fig. 2 shows a second application of the apparatus of Fig. 1 in successive steps for the treatment of a textile material;

- Fig. 3 shows an embodiment of an apparatus according to the invention for decorating finished and/or semifinished articles;

- Fig. 4 shows an embodiment of an apparatus according to the invention;

Fig. 5 shows a further embodiment of an apparatus according to the invention;

- Fig. 6 shows a shaped electrode in an apparatus according to the invention; - Fig. 7 shows a first embodiment for continual decolorization;

Fig. 8 shows an embodiment of an apparatus for the treatment of finished and/or semifinished articles;

Fig. 9 shows a preferred embodiment of an apparatus according to the invention, in successive steps for the

treatment of a textile material;

Fig. 10 shows a further application of the apparatus of

Fig. 9 in successive steps for the treatment of a textile material; Fig. 11 shows a preferred embodiment of an apparatus according to the invention for decolorizing finished and semifinished articles;

Fig. 12 shows a first preferred embodiment of the apparatus of Fig. 4; Fig. 13 shows a second preferred embodiment of the apparatus of Fig. 5;

Fig. 14 shows a first embodiment of a shaped electrode in an apparatus according to the invention;

Fig. 15 shows a second embodiment of a shaped electrode in an apparatus according to the invention;

Fig. 16 shows the use of a first type of mask in an apparatus according to the invention;

Fig. 17 shows the use of a second type of mask in an apparatus according to the invention; Fig. 18 shows a second embodiment for continual decoration;

Fig. 19 shows a further embodiment for the treatment of finished and semifinished articles;

Fig. 20 shows an embodiment of the anode-cathode coupling by means of a pressing pad; Fig. 21 shows an embodiment of the anode-cathode coupling by means of a cathode having sharp and/or rounded relieves;

Fig. 22 shows an embodiment of the anode-cathode coupling by means of an anode having sharp and/or rounded relieves;

Fig. 23 shows an embodiment of the anode-cathode coupling by means of a cathode having variable geometry;

Fig. 24 shows an embodiment of the anode-cathode coupling by means of an inflatable shape;

Fig. 25 shows a configuration in which the anode is made from a fabric of insulating fibres and of electrically conductive fibres which define a pattern to be reproduced;

Fig. 26 shows the successive steps of a method according to the present invention; and

Fig. 27 is a schematic view from above of a machine provided with operating stations for carrying out the steps of Fig. 26.

With reference to the attached figures, an apparatus according to the invention comprises a path 1 for the advancement of a textile material 2, preferably in the form of an endless belt. By way of example, the textile material 2 can be made to advance along the path 1, in one or both the directions shown by the arrows in Fig. 1, 9 ^' and 2, 10, by feeding means known per se, such as pairs of rollers 3 _f 4, or the like, located respectively upstream and downstream of a region 5 for the decolorizing treatment of the textile material, the said region being preferably delimited by two rollers 6, 7 for driving out the textile therebetween. The path of the textile material 2 is completed in the described example by further transmission rollers 8, 9, 10, 11, 12 between the pairs of feed rollers 3, 4.

According to the invention, upstream of the decolorization region 5 there is provided a tank 13 holding an aqueous solution 14, and inside which, by means of a transmission roller 9 disposed therein, the textile material 2 is made to pass for the impregnation thereof. Alternatively, any other impregnation system may be used, for example with the use of spraying means or inking rollers.

By way of example, the solution 14 could be made up of demineralized water, treated with electrolyte additives (sodium chloride, sodium sulphate, or others) , surfactants having inhibiting and deaerating action to optimize the solution-textile contact - the amount and nature of the additives being possibly preset according to the decolorization process to be obtained for a given textile material.

Provision is made for controlling the degree of impregnation through a pressing system (not shown in the figures) operated after said impregnation, and for controlling the temperature of the solution as well, at least in the treatment/decolorization region.

As shown in Figs. 1, 9 and 2, 10, the decolorization region 5 includes two electrodes (anode 15 and cathode 16) powered by direct current and carrying out an electrochemical process with production, at the anode 15, of oxidants such as chlorine, chlorine dioxide, hydroxylic radicals, nascent oxygen, ozone and others, which cause the local, selective decolorization of the textile material 2 thereby producing the desired decorative effect. At least one of the two electrodes is shaped according to the patterns to be reproduced ^' on the textile material.

With reference to Figs. 6, 7, 9-15, it is the anode 15 which is preferably shaped, but it is also possible to shape the cathode 16 or even both of them (Fig. 8, 21 and 23) . The patterns to be reproduced on the textile material 2 may be in relief, each being formed on supports or plates 21, 22, preferably of isolating material, connected to the respective pole (positive for the anode 15 and negative for the cathode 16) of the d.c. supply. Advantageously, and as shown in Figs. 16, 17 and 19, the patterns to be reproduced on the textile material 2 may be formed also through an isolating masking of anode 15 or cathode 16 (or of both) ; the mask 25 being possibly made up of a film disposed on one or both the electrodes, or of electrodes deposited directly on one or both the electrodes .

The mask 25 may be made from any isolating material resisting both to the action of the oxidants developed locally by the electrochemical process, and to the operating conditions (pH, temperature, salinity, etc.) of

the same process.

The production at the anode 15 of oxidants which are cause for the decolorization and, thus, the decoration, takes place in correspondence of the unmasked shaped surface (whether of the anode 15, cathode 16 or of both) .

By way of example, the surface of anode 15 may be formed by any material able to produce the wanted oxidants in the electrolytic process; to this end, use can be made of titanium, tantalum, zirconium, covered with metals such as iridium, ruthenium, tin, lead, antimony, platinum.

Other suited materials may be graphite, diamond doped with boron, and carbon fibres in the form of fabric or knit. It is stressed that the use of carbon fibres 33 to form the anode 15, besides implying a relatively limited cost, allows making the pattern by weaving it with the said carbon fibres, while using a base of non-conductive fibres 34 which resist to the operating conditions of the process, as schematically shown in Fig. 25. The cathode 16 will be made also from the same material used for the anode or from a different metallic material (steel, stainless steel, copper, aluminium, or alloys of said metals) .

The anode 15 and cathode 16 may be made in the form of a plate, a net or, when possible, in the form of fabric or knit, according to the decorative motifs to be made or to the type of machine.

The oxidants causing the decolorization process are always produced on the anodic surface and, therefore, act on the surface of the textile material 2 in contact with said anode 15.

In the embodiment of Figs. 1, 9 and 2, 10, the anode 15 and cathode 16 are solid to the respective plates 21, 22 that can be moved as required close to or away from each other

^■ by conventional driving means (not shown) known per se, such as clamp devices connected on the sides of both plates

to operate the movement thereof close to and away from each other.

Also schematically depicted in the figures are the connections of the electrodes to poles (+ / -) of an electric d.c. supply able to apply the desired voltage to the electrodes.

In particular, upon the application of the voltage, provision is made for controlling the application time and the current intensity which accounts for the type of ^■ textile being treated, the decolorizing substance produced and the desired degree of decolorization.

In order to extend the range of possible effects, provision is also made for dividing the electrodes into separate parts 36, each being possibly electrically powered at different voltages and times. Besides, the direct current for powering the electrodes may be applied continually or by pulses.

A schematic example of this embodiment is depicted in Figs. 9 to 13. Illustrated in Figs. 1 and 9 is a first example of application of the apparatus, showing a decolorization region 5 provided with a tank 17 filled with an aqueous solution 18, preferably of the same type as the solution 14 held in the tank 13. The tank 17 shall have a depth sufficient to receive the textile material 2 and electrodes 15, 16 - as necessary for the electrochemical process to take place - and to perform the treatment under conditions of complete immersion into the solution 18. In Fig. 2, the region 5 takes up a "dry" length of path 1. In this case, the electrochemical process takes place inasmuch as the electrical circuit between the electrodes is closed by the aqueous solution 14 by which the textile material 2 has been soaked within the upstream tank 13. Again with reference to figures 1, 9 and 2, 10, there is

illustrated the succession of steps in a preferred embodiment of a method according to the invention. In the step (a) , the textile material 2 has already passed through the tank 13 and has been impregnated with the electrolytic solution. In this stage (a) , the length of textile material 2 to be decolorized is stopped in the region 5, the same material being preferably taken under tensile condition by the pairs of rollers 3, 4 and with the electrodes 15, 16 spaced out. In the step (b) , the electrodes are moved close to each other so as to move both the anode 15 and the cathode 16 close to the respective surfaces 19, 20 of the textile material 2 in the region 5. Once the textile material 2 has been positioned and possibly pressed between the electrodes 15, 16, direct current is applied according to preset modes (voltage, times, etc.) which depend on the conductivity of the electrodes and of the impregnating solution, on the rate at which it is desired to form the oxidants, on the nature of the textile support, and on the degree and type of decolorization wanted.

In this step (b) , during the application of current, the regions of textile material between the electrodes, that is, the regions corresponding to the shaped surface of one of the electrodes (or of both) , or corresponding to the unmasked regions of anode 15 and/or cathode 16, are run into by the oxidants (chlorine, hydroxylic radicals, nascent oxygen and ozone) that are released from the anode 15 and are cause for the local, selective decolorization of the textile material producing the desired decorative effect .

In the step (c) , the voltage is relieved, the electrodes 15, 16 are moved away from each other and, in. the next step 4, a fresh stretch of textile material 2 is fed to the region 5 to carry out a novel decolorization.

In the step (d) , the stretch previously treated, now downstream of region 5, is instead subjected, when necessary, to a neutralization-washing-drying process. Figs. 3 and 11 illustrate two embodiments of the apparatus of the invention for the treatment of finished and semifinished articles.

In this case, the material 2 is fed not in a continual manner, but in succession, one item after the other. The steps of the process and the corresponding parts of the apparatus are numbered as in the previous figures 1, 9 and 2, 10.

In Figs. 3 and 11, plane electrodes 15, 16 are shown for the sake of simplicity, but it will be appreciated that, especially in the treatment of finished and semifinished articles, it is also possible making use, in addition to plane electrodes, of suitably rounded electrodes able to follow the spatial development of the article (leg portions, sleeves, etc.). Some examples of configuration of electrodes are shown in Figs. 20 to 24.

In particular, Fig. 20 shows a preferred solution in which the cathode 16a is made from a metal net and is kept pressed onto the material 2 to be decorated by means of an elastic pad 26. Advantageously, this configuration provides for the use of a mask 25 interposed between the textile material 2 to be treated and the anode 15, in order to limit the decoration only to certain regions of the textile 2. Figs. 21 and 22 show instead a possible second and third configurations of the electrodes in which the cathode 16b or anode 15b, respectively, exhibits one or more relieves, with sharp 32 or rounded 31 edges on the surface in contact with the textile material 2, again in order to limit the decoration only to certain regions of the textile 2. A further configuration of the electrodes is shown in Fig.

23 in which a shaded decorative effect is obtained on the textile 2 by using a cathode 16c having variable geometry, for example, of elliptical cross-section.

In the illustrated examples of Figs. 21, 22 reference is made to relieves with sharp edges allowing the reproduction of likewise sharp patterns.

Advantageously, a use can also be made of relieves with rounded edges to reproduce patterns with shaded contours.

The shading can be obtained, besides by rounding off the sharp edges of the relieves, also by using anodes or cathodes (or both) which are flexible and with variable geometry, as shown in Fig. 23.

Fig. 24 shows in particular a configuration in which the textile material 2, after having being soaked with electrolytic solution, as necessary for the process to be activated, is positioned over a shape 27 preferably of rubber material.

The shape 27 is partially covered by the cathode 16a constructed in such a way as to result perfectly flexible (for example, made from metal net, conductive fabric or other material suited for use) . The flexible cathode 16a is made to adhere to the shape 27 by a tensioning system consisting, for example, of an elastic element 29.

Thereafter, the shape 27 is inflated until the textile material 2 is put in tension and, thereby, in close contact with the cathode lβa.

The anode 15a is moved closer to the textile material 2 and pressed thereagainst . In this configuration, the anode 15a carries the decorative motifs to be reproduced according to one of the modes above described with reference to Figs. 20 to 23. Also in this configuration, a mask 25 may be interposed between the anode 15a and the textile material

2.

Advantageously, the anode 15a can be shaped to follow the development of the shape 27, that is, it can be plane and,

by virtue of the deformability of the same shape 27 is able to cause the contact between the electrodes and the textile

2.

Figs. 4 and 12 illustrate further embodiments of the apparatus wherein the same numerals already used are associated with functionally equivalent parts.

In these embodiments, the electrodes, anode 15 and cathode

16, are disposed on a pair of counter-rotating rollers 23,

24 between which the textile material 2 is able to slide within a region of decolorization 5 which, in this case, consists of the region of contact between the anode 15 and cathode 16.

Also in this case, the region 5 may be within a tank 17 holding or not the impregnating aqueous solution 18. The pattern may be made by shaping at least one of the electrodes, or by masking at least one of the electrodes as previously illustrated.

With reference to Figs. 5 and 13 there are illustrated two other embodiments of the apparatus, in which one of the electrodes is shaped like a roller 24 whose outer surface makes up the cathode 16, whereas the other electrode, the anode 15, is in the shape of a bandaging which envelops, at least partially, the roller 24.

In the described example, the bandaging is formed by an anode 15 of ribbon shape rotating over rollers 23a-23c so as to result in contact, through the textile 2 impregnated with the solution 14, with the surface of the cathode 16.

Also feasible is a solution with roller-wise anode 15 and wrapping cathode 16. Shown in Figs. 7 and 18 is the case of a cathode 16 (Fig.

7) and of an anode (Fig. 18) shaped in relief on the outer surface of a preferably cylindrical support 30, respectively with single and double strip.

In this configuration, the region 5 of decolorization is in correspondence of the region of contact between the strips,

forming the cathode 16 or the anode 15, and the cylinder making up, respectively, the anode or the facing cathode. In this configuration, the decolorization region 5 is in correspondence of the region of contact between the strips making up the anode 15 and the cylinder making up the cathode 16.

By means of the apparatus previously described, the decolorization method proceeds likewise what has been previously described, but with continual advancement of the textile material 2 along the path 1 and with a voltage being applied to the electrodes.

There will be therefore a first step of impregnation of the textile material 2 in the tank 13 containing the solution 14, the moving of the same material through the electrodes 15, 16, with decolorization of the textile regions in correspondence of the shaped or unmasked surface, and then, as necessary, a neutralization-washing-drying treatment of the textile material 2 already decolorized. For a successful result of the treatment, it is generally required that the adhesion textile-electrodes be as much as possible uniform, and this can be attained by means of a rigid anode coupled to a very elastic cathode (made from metal net, thin sheet possibly slotted to increase the flexibility, metal fabric, fabric in carbon fibres 33, fabric made conductive by metallization, and the like) being pressed onto the anode with an elastic material (rubber, resilient pad) 26.

The anode may be flexible as well (for example, made from a fabric of carbon fibres as shown in Fig. 25) which is pressed on a rigid or flexible cathode.

The method allows making patterns of sharp or shaded contours. For sharp-edge designs, it is necessary that the pattern of anode 15 has sharp edges 32 or the mask pattern be sharp; for patterns with shaded edges, anodes can be constructed with rounded edges 31.

Illustrated in Fig. 26 are the steps included in the method for decorating finished or semifinished textiles according to the present invention:

F.I: positioning the textile material on the cathode 16 or anode 15 in a firm way;

F.2: wetting the textile material 2, preferably by spraying or immersion with an aqueous solution 14 of electrolytes which, once subjected to an electrochemical process, develop oxidizing agents with decolorizing action and/or able to activate the molecules making up the textile material 2 in order to modify their behaviour upon successive operations;

F.3: decolorizing the textile material 2 by keeping pressed the same material 2 between the pair of electrodes, anode 15 and cathode 16, at least one of which is shaped or masked and to which electrodes d.c. power is applied to locally generate oxidizing agents and selectively treat certain regions of the textile material 2; F.4: drying the treated textile material 2 for example by moving close to it a plate heated by electric resistances. In a preferred embodiment of the method, the steps making up the above method correspond to as many operating stations in a machine M, shown diagrammatically in Fig. 27. The machine M is preferably provided with article's supply/removal units, rotatively engaged to a central shaft 35 so as to allow the operators in charge to make the textile transit through operating stations S1-S4 and optimize the processing thereof. More in particular, the first step F.I is carried out by a unit Sl for the positioning of the textile material 2 in correspondence of one of the two electrodes. The second step F.2 provides for the use of a wetting unit S2, preferably by spraying, to impregnate the textile material with an aqueous solution 14 which, when subjected to an electrochemical process, develops the wanted

oxidizing agents.

The decolorization step F.3 is performed on the decolorization unit S3 by moving the textile material close to the two electrodes, between which the electric current is made to flow, and keeping the same material in contact with said electrodes for a predetermined time. The step F.4 consists in drying the textile material 2 by means of a drying unit S4. The last step F.5 is the removal of the article from the operating stations to make it pass to the successive treatments such as ironing and packaging.

The method has been described with particular reference to the case in which a coloured textile material is treated, wherein the treatment mainly consists in the decolorization of the dyeing molecules of the same material 2.

The inventive method is however efficient also in case of non coloured or raw materials.

In this case the treatment according to the invention consists in the modification of the molecules making up the material which are activated in preparation to successive decorative operations by printing and/or dyeing, during which there will be a preferential, or anyway, differential deposition of decorative substances in the treated regions, with respect to regions unaffected by the electrochemical process.

The invention thus devised may also be subjected to several modifications and variants without departing from the scope of the inventive principle; moreover, all the parts may be replaced by technically equivalent elements. By way of example, the treated material may also be formed by natural or synthetic leather, provided it is able to absorb the aqueous solution 14 necessary for the decoloration of the same material.