Method and device for digitally upgrading textile

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DESCRIPTION

Procedure and device for digitally coating a textile product and digitally coated textile product

The present invention relates to a device for digitally coating a textile product. In particular, it relates to a device for coating a textile product using a continuous flow inkjet technique to provide precise coating characteristics. It also relates to a process for coating textile products using said technique and to the textile product produced in this way.

Coating is one of the operations frequently performed during the production of textile products. Approximately, five phases can be distinguished in said production; fiber production; spinning of fibers; manufacture of cloth (for example, woven fabrics or knitted fabrics, plush or felt material, and non-woven materials); fabric improvement; and production or manufacture of finished products. The improvement of textile products covers a number of operations such as preparation, bleaching, optical whitening, coloring (painting and / or printing), coating and finishing. In general, these operations are for the purpose of giving the textile product the appearance and physical characteristics that are desired by the user. Coating the textile product is one of the most important improvement techniques and can be used to impart various specific characteristics to the resulting product. It can be used to manufacture the non-wrinkle, non-shrink, non-rotting, non-slip, crease-preserving and / or anti-static substrate that is flame retardant or non-flammable, water repellent and / or oleophobic.

Conventional procedures for improving the textile product are composed of (Figure 1) a number of procedures in parts and improvement stages, i.e. pretreating the textile article (also referred to as a substrate), painting the substrate, coating the substrate, finishing the substrate and post-treatment of the substrate. Common techniques for applying a solvent- or water-based coating are so-called knife-over-roll, dip, and reverse roll coating machines. Typically a dispersion of a polymeric substance in water is applied to the fabric and then the excess coating is scraped off with a scraper. Certain characteristics are difficult to achieve using these conventional coating techniques and must be achieved by other techniques. To provide full color to the article, painting can take place by immersing the textile article in a paint bath, so that a colored substance is provided to the textile product on both sides. For other effects, a technique with a Foulard machine (impregnation and pressing) can be used.

Each of the improvement stages shown in Figure 1 consists of a series of operations. Different treatments are required with different types of chemicals, depending on the nature of the substrate and the desired end result. For the stages of improvement of printing, painting, coating and finishing, in general four recurring stages can be distinguished that often take place in the same order. These treatments are called in the professional field as unit operations. These are impregnation treatments (i.e. application or introduction of chemicals), reaction / fixation (i.e. bonding of chemicals to substrate), washing (i.e. removing excess chemicals and secondary chemicals) and drying. These unit operations also need to be repeated a number of times for each enhancement step, eg, repeated wash cycles. In general, large amounts of chemical reagents and water are used which implies a relatively high environmental impact, a long production time and relatively high production costs.

Furthermore, it is customary today to carry out the different stages of improvement of the textile product in separate devices. This means that, for example, painting is carried out in a series of paint baths especially suitable for this purpose, printing and coating are carried out on separate printing devices and coating machines, while finishing is carried out out by another device. Because the different operations are carried out individually in separate devices, the treatment of the textile product requires a relatively large area, usually it is distributed in different room areas.

Thus, it is desirable to provide methods for improving, ie painting, coating and finishing, a textile product substrate in which the above-noted drawbacks and other drawbacks associated with conventional procedures are reduced.

Various attempts have been made to use inkjet printing techniques to perform improvement steps. In particular, the use of ink jet printers has been suggested to print an image on a textile product. However, known conventional inkjet techniques for printing on paper media have been found to be difficult to apply for textile production where textile measurements over 1 meter are standard and where production speeds are required. 20 meters per minute or more for the process to be effective. In particular, conventional ink jet printers comprise a print head that moves back and forth through the medium. The print head has a number of nozzles through which streams of ink droplets can be launched. These print heads work according to the principle of dot-on-demand, that is, they are electronically controlled to deposit or not a drop of ink according to the image to be printed. Media is fed forward intermittently after each print head pass. Both intermittent feeding and drop-on-demand control make the procedure too slow for practical use. Feeding speeds of 2 meters per minute can now be achieved using these procedures for

ES 2 393 486 T3 printing of textile products. A method is known from US Patent No. US 4,702,742 in which a conventional printing device is used on sheets of white cloth. Another procedure is suggested in German Patent Application No. DE 199 30 866 in which both the ink and the fixing solution are applied to a textile product using a conventional ink jet head. A method disclosed in US 4,650,694 proposes a random droplet forming procedure using an electrostatic liquid injection applicator to achieve a uniform application.

In particular, conventional inkjet printing devices have been found to be unsuitable for the purpose of coating textile products. In particular, this is the case when they are used on fibrous textiles where there are gaps between adjacent fibers, especially for knitted or coarsely woven textiles. Typical nozzle diameters used in conventional inkjet devices are relatively small to provide fine pixel definition. It has been found that the droplets produced by these nozzles tend to pass into or even through the gaps providing a less than adequate surface finish. It has also been found that despite the advantages of printing on textiles using inkjet techniques, the pixel definition of images produced on thick textiles is often poor due to the thickness of the fiber structure and other effects such as capillary action, which may not be homogeneous in all respects. A device that proposes coating application for fabrics using capillary injectors is shown in GB2187419. The device has electromechanical valves controlled to open and close rapidly so that liquid is released from the injectors in a succession of short pulses.

In accordance with the invention, there is provided a method of digitally forming a coating on a fibrous textile having mesh openings between adjacent fibers, wherein the method comprises continuously feeding the textile along a treatment path having a row of static coating nozzles generally arranged transversely along the path, the coating nozzles having outlet diameters greater than about 70 microns, supplying the nozzles with a supply of coating substance, individually controlling the nozzles to provide a substantially continuous stream of coating substance droplets and selectively directing the individual droplets to strike the textile to form a coating of pixels that are generally located on the textile surface , each pixel covering at least four mesh apertures and having a diameter of more than 100 microns. In this way, by using a larger nozzle and producing a droplet of sufficient size to cover four mesh openings, the droplet is adequately supported and sprayed or flattened across the surface of the textile product. In the present context, it is considered that the pixel formed by the drop falls, generally on the surface but can also enter the gaps between the fibers and can also partially surround the fiber at least on the side of one of the surfaces to form a suitable link to it. The method can be applied in particular to woven or knitted textile products.

According to an important feature of the present invention, the treatment path comprises a conveyor belt and the textile product is fixed to the conveyor belt, so that the position of the textile product relative to the conveyor belt can be maintained. In this way, when the precise location of each pixel is important, a displacement of the textile can be prevented. This is particularly important when the treatment includes printing using different colors applied by different rows of nozzles. The textile product can be attached to the conveyor belt by means of an adhesive or the like.

Preferably, the method further comprises feeding the textile product along a second row of static nozzles also generally arranged transversely along the path, supplying the second row of nozzles with a supply of a second substance and individually controlling the nozzles to provide a substantially continuous stream of droplets of the second substance to the textile. The second row of nozzles can be used for a different upgrade stage. In particular, they can be used to print, paint or dry the fabric. In particular, the second row may comprise nozzles having outlet diameters of less than 50 microns to produce finer pixel definition. In an exemplary embodiment, high definition inkjet printing can be performed on the coating after the textile has passed the first row of nozzles. Alternatively, the second substance can be applied before the coating substance. In this case, for example, it can be received and absorbed into the fibrous structure and the coating can form a protective layer on it.

In another embodiment of the invention, the second row of nozzles can be provided on the opposite side of the treatment path from the first row of nozzles. In this case, the second row can be substantially similar to the first row and the process can comprise applying the coating to both surfaces of the textile product. Alternatively, the second line can be used to apply a different substance to the second surface of the textile so that the finished textile has different characteristics on each surface. Additional nozzle rows can be provided according to required treatments.

The use of continuous ink jet multi-level diverter type nozzles has been found to be extremely advantageous. Thus, the method may comprise electrically charging or discharging the droplets, applying an electric field, and varying the electric field to deflect the droplets so that they are individually deposited at suitable locations on the textile. Thus, the precise position can be carefully controlled.

ES 2 393 486 T3 of each pixel, for example, the degree of overlap or the spacing of each other. Using these techniques, each nozzle can generate up to 100,000 drops per second. In the case of a plurality of rows of nozzles, some rows may be of the multi-level offset type while other rows may be of the binary level type.

Preferably, the nozzles are arranged substantially along the entire width of the treatment path and the coating is applied over substantially the entire width of the textile product. This width can be in excess of 1 meter, however it is common to produce textile products that have widths of up to 2.5 meters.

In a preferred embodiment, the coating is a water-repellent coating and the coating substance may comprise a fluorocarbon or silicon-based emulsion, an antifoam medium, an electrolyte, and a thickener. By applying this coating in an open structure with pores between adjacent pixels, a breathable structure can be achieved.

Preferably, the coating substance has a viscosity greater than 4 centipoise (4 mPa · s) as measured with a Brookfield viscometer. It has been observed that the use of these viscosities with nozzle diameters of 70 microns or more ensures that the droplets are formed with adequate shape stability on impact with the textile, so that the desired pixel shape is achieved.

Lower viscosities can lead to greater capillary action of the coating substance along and around the fiber structure.

The present invention also relates to a device for digitally coating a textile product, the device comprising a conveyor belt for substantially continuously feeding the textile product along the treatment path, a row of arranged static coating nozzles, in general, transversely along the route, to apply a coating substance over substantially the entire width of the textile product, wherein the coating nozzles have outlet diameters greater than 70 microns and can be individually controlled to provide a substantially continuous stream of droplets that can selectively direct to affect the textile product. The device further comprises means for fixing the textile product to the conveyor belt to substantially prevent movement relative to each other. In the present context, static is intended to indicate that the nozzles are not physically moving through the treatment path from one side to the other. Furthermore, the term continuous is intended to indicate that the stream of drops is continuous during operation of the device so that drops that are not required are diverted to a collection device. It is considered that this definition should be clearly distinguished from the so-called drop-on-demand systems.

According to an advantageous embodiment, the device may additionally comprise a second or more rows of nozzles arranged, generally, transversely along the path, to apply another substance to the textile product. To carry out a different finishing step, such as drying or printing, the second row of nozzles can have outlet diameters less than 70 microns, preferably about 50 microns. Preferably, they can also be individually controlled to provide a substantially continuous flow of droplets that can be selectively directed to impinge on the textile product.

According to a particular embodiment of the device, the rows of nozzles can be arranged on both sides of the path for coating or otherwise applying substances to both surfaces of the textile product.

To properly and accurately perform operation across the entire width of the textile product, each row of nozzles is provided on a printing bar spanning the treatment path. Preferably, each bar comprises a plurality of heads, each head comprising a number of nozzles. By using separate heads, the pressure distribution between the individual nozzles can be carefully controlled. In particular, by using approximately eight nozzles per head, proper pressure control is ensured for each nozzle. In this case, a total of between 10 and 100 heads can be provided on each bar.

According to a preferred embodiment, the nozzles are of the multi-level offset inkjet type, so that the position of a drop on the textile can be controlled. Alternatively, some or all rows of nozzles may be of the binary offset inkjet type, so that a drop exiting the nozzle can be selectively directed towards the textile or the collector. Whatever type of nozzle used, it is desirable that they can be controlled to each generate at least 100,000 drops per second to achieve the desired process speed.

Preferably, the conveyor belt is wide enough to accommodate textile products over 1 meter wide, more preferably up to about 2 meters wide. It must also be arranged to operate at a speed of more than 15 meters per minute, more preferably, more than 25 meters per minute. It can also be provided with an adhesive or the like to prevent relative movement of the textile product.

The present invention further relates to a digitally coated fibrous textile product having mesh openings between adjacent fibers, the fibers having an average spacing greater than 40 microns, being

ES 2 393 486 T3 provided the textile product with a coating comprising a plurality of individually perceptible pixels of coating material substantially located on the surface of the textile product with pores formed between adjacent pixels, each pixel covering at least four apertures mesh and having a diameter greater than 100 microns. Preferably, the textile product is a woven or knitted textile product.

According to other particular embodiments of the invention, the textile product can have a width greater than 1.5 meters.

The invention will now be described in more detail with reference to a number of exemplary embodiments according to the attached figures, in which:

Figure 1 shows a schematic block diagram of the substrate enhancement procedure;

Figure 2 shows a perspective view of a textile improver including a coating device in accordance with the present invention;

Figure 3 is a schematic side view of the textile improver of Figure 2;

Figure 4 is a schematic front view of the textile improver of Figure 2;

Figure 5 is a schematic sectional view of the textile improver of Figure 2;

Figure 6 is a schematic representation of a preferred sequence for carrying out the different treatment steps;

Figure 7 is a schematic representation of an alternative preferred sequence for performing enhancement steps;

Figure 8 is a schematic representation of another preferred sequence for performing enhancement steps;

Figure 9 shows a schematic view of a part of a coated woven textile product according to the invention;

Figure 10 is a cross section through the textile of Figure 9 along line 10-10; Y

Figure 11 shows a view similar to Figure 10 through a coated textile in which smaller droplets have been used.

Figures 2-5 show a textile improver 1 according to a preferred embodiment of the invention. The textile improver 1 is constructed from an endless conveyor belt 2 driven using electric motors (not shown). On the conveyor belt 2 there can be arranged a textile product article T which can be transported in the direction of the arrow P1 along a housing 3 in which the textile product is subjected to a number of operations. The textile product is physically attached to the conveyor belt by means of an adhesive to prevent displacement of the textile during the process. Finally, the textile product is discharged in the direction of the arrow P2 by releasing the adhesive. A large number of nozzles 12 are arranged in the housing 3. The nozzles are arranged in parallel bars 14 placed successively. Thus, a first row 4, a second row 5, a third row 6 and so on are formed. The number of rows can vary (indicated in figure 5 with a broken line) and depends, for example, on the desired number and on the nature of the operations. The number of nozzles per row is also variable and depends, among other things, on the desired resolution of the designs to be applied to the textile product. In the illustrated embodiment, the effective width of the bars is approximately 1 m, and the bars are provided with approximately 29 fixedly arranged spray heads, each having approximately eight nozzles per head. Each of the nozzles 12 generates a stream of substance droplets.

In the preferred continuous ink jet method, the pumps draw a constant flow of ink or other medium through one or more very small orifices in the nozzles. In the following, although reference will be made to ink and inkjet, it is understood that this is not limiting and that other substances may be expelled from the nozzles. One or more ink nozzles, ink jets, are expelled through these holes. Under the influence of an excitation mechanism, this inkjet splits into a constant stream of droplets of the same size. The most widely used exciter is a piezo crystal although other forms of excitation or cavitation can be used. From the constant flow of drops of the same size that are now generated, the drops that are to be applied to the substrate of the textile product and those that should not be applied must be selected. For this purpose, the drops are electrically charged or discharged. There are two variations for arranging the drops on the textile product. According to one method, an applied electric field deflects the charged drops, in which the charged drops come to rest on the substrate. This procedure is also called binary deviation. According to another preferred method, also known as the multilevel method, the electrically charged drops are typically directed at the textile and the uncharged drops are deflected. Herein, the drops are subjected to an electric field that is varied between a plurality of levels so that the final position in which the different drops come to be positioned on the substrate can be adjusted in this way.

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In figure 5 it is indicated with broken lines that the different nozzles 12 are connected (electrically or wirelessly) by means of a network 15 to a central control unit 16, comprising, for example, a microcontroller or a computer. The drive mechanism of the conveyor belt 2 is also connected to the control unit by means of the network 15 '. The control unit can now actuate the drive mechanism and individual nozzles as required.

Also arranged per row of nozzles 4-11 is a double tank in which the substance to be applied is stored. The first row of nozzles 4 is provided with the tanks 14a, 14b, the second row 5 is provided with the tanks 15a, 15b, the third row 6 is provided with the tanks 16a, 16b and so on. The appropriate substance is arranged in at least one of the two reservoirs in a row.

The different tanks are loaded with appropriate substances and the nozzles 12 arranged in different rows are directed so that the textile product article undergoes the correct treatment. In the situation shown in Figure 6, reservoir 14a of first row 4 contains cyan ink, reservoir 15a of second row 5 contains magenta ink, reservoir 16a of third row 6 contains yellow ink. and the reservoir 17a of the fourth row 7 contains black ink. The textile product article is provided in rows 4-7 with patterns in a paint / print treatment. The nozzles in these rows have outlet diameters of approximately 50 microns. The tanks in the three rear rows 8-10 contain one or more substances with which the treated textile can be coated in three steps for the purpose of coating the textile product, the nozzles in rows 8-10 have outlet diameters of 70 micrometers. The eighth tank 11 contains a substance with which the printed and coated textile can be finished. In this embodiment, the textile article T is preferably treated at the fifth to eighth row position with infrared radiation from light sources 13 to influence the coating of the finish.

Figure 7 shows another situation in which the textile product is subjected to another sequence of treatment. First, the textile article T is painted by guiding the textile along the first row 4 and the second row 5 of nozzles. These rows 4, 5 have 70 micron nozzles and apply a relatively smooth colored coating on the textile product. In the third to fifth rows 6-8, the painted textile is then coated as before, after which the finishing step is carried out in the sixth and seventh rows 9,10.

In the embodiment shown in Fig. 8, first, the textile product article is guided along the first row 4 of nozzles. The nozzles in row 4 are approximately 70 microns and provide a completely smooth background color to the textile across the entire width. Subsequently, the textile product article is guided along the second row 5 and the third row 6 by means of the conveyor belt, in which the patterns are printed on the prepared surface. Good definition can be achieved in the printing stages in rows 5 and 6 using fine nozzles between 30 and 50 microns. Then, the textile product is guided along the fourth to sixth rows 7-9 to coat the painted and printed textile product in three steps, after which a finishing step is performed in the seventh and eighth rows 10, eleven.

It is possible to treat different articles of textile product transported successively in different ways, in some cases even without having to interrupt the transport of the textile product therein. For example, it is possible, by means of a computerized control of the nozzles 12, to provide articles of textile product supplied successively with designs that differ in each case. It is also possible to have different substances applied to the textile product through an appropriate choice of deposits. For example, the first tanks 14a, 15a, 16a are used in each case for a first type of textile product, while the second tanks 14b, 15b, 16b are used for another type of textile product.

To determine the environmental benefits of the present invention, use is made of an example of a representative improvement procedure in which a substrate goes through four cycles of unit operations for the purpose of painting, followed by four cycles for coating and finally two cycles for finishing. The quantification is based on the production of a substrate 1,800 meters long and approximately 1.6 meters wide of bleached and dried cotton weighing 100 grams per square meter of substrate. Herein, the painting, coating and finishing are each performed in a procedure run, with the necessary post-treatments and / or pre-treatments between these process runs. If the treatments can be carried out in one procedure operation, the environmental benefits will therefore be even greater.

In the traditional improvement procedure, practically every component (painting, coating and finishing) takes place in and / or with a highly aqueous solution. In the digital method according to the invention, a highly concentrated solution is sprayed directly onto the substrate with a precisely controlled dosage. In this way, less water is used. In order to rinse / wash off excess chemicals and secondary chemicals, virtually every unit operation cycle comprises a rinse cap. The number of rinsing stages can be reduced from ten in the existing procedure (four times in painting, four times in coating and twice in finishing) to three in the present digital procedure (i.e. once in painting , once in the coating and once in the finish). Therefore seven fewer rinsing stages are needed. This means that a considerable reduction in water consumption can already be achieved by reducing the rinse. The total reduction in water consumption in many cases is more than 90%.

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Energy consumption can also be considerably reduced, since, among other things, forced drying is not necessary, or is only necessary to a very limited extent, it is not necessary to rinse with hot / lukewarm washing water, or only in a very limited measure, and the mechanical handling of the substrate is greatly reduced.

In the known improvement method, drying usually takes place between the different unit operations, and also within the operations in which a number of times has to be cycled. The substrate can contain up to several times its own weight of water. In general, drying takes place in two phases. In the first phase, most of the water is removed from the substrate mechanically. In the second phase, thermal drying is followed, in which the remaining water present on the substrate evaporates.

Because the present digital enhancement procedure is performed almost without water, virtually no water or water has to evaporate, such as, for example, by drying, between the different enhancement stages and after the last enhancement stage. . In this way a very considerable energy saving is realized. The limited drying that is necessary in some cases can be carried out, in most cases, by means of directional UV dryers. In general, as little as 70% water by weight may be required for the coating substance.

In digital procedures, due to the very limited washing of the substrate required, it will also be possible to considerably reduce the number of mechanical operations, including transporting the substrate between the different improvement operations, compared to the known improvement procedure. In this way, the consumption of electrical energy will also be considerably reduced. In total, a reduction in energy consumption of more than 90% can be realized.

With current production techniques, approximately 150 grams of wet substances (chemicals) are applied per square meter. In digital printing, due to more precise dispensing, lower pressure and less absorption in the textile product, the amount of chemicals to be applied can be reduced to about 50 grams of wet substance per square meter. Therefore, a savings of approximately 66% on chemicals is possible. The savings not only refer to the main chemicals, but also to the additives, such as salts, with which the substrate is pretreated in the digital process to facilitate the action, fixation and / or reactivity of the main chemicals. It is expected that a saving of 66% can also be obtained on these additives. Finally, wastewater production and the impact of wastewater pollution can be reduced by more than 90%.

Figure 9 shows a schematic view of a part of woven textile product 100 on which four pixels 102 of a covering material have been deposited. The textile product 100 comprises fibers 104 arranged in a mesh with mesh openings 106 between the fibers 104. The fiber spacing is approximately 40 microns and each of the pixels 102 has a diameter of approximately 100 microns. As can be seen from FIG. 9, each pixel 102 effectively covers at least four full apertures 106. Additionally, it can be seen that pixels 102 do not form a completely closed cover because a pore 108 is formed between adjacent pixels 102.

Figure 10 is a cross section through textile 100 of Figure 9 along line 10-10. It can be seen that the pixels 102 are generally located on the surface of the textile product, spanning the openings 106 between adjacent fibers 104. Due to the viscous nature of the coating substance, each pixel 102 partially maintains its shape and although the pixels 102 flow together in the overlap region, the individual pixels are still visible. Furthermore, it can be seen that the coating substance that forms the pixel 102 partially envelops the fibers 104 on the coated surface to form a good bond with them. The viscosity of the coating substance is chosen to ensure the correct degree of impregnation of the material.

Figure 11 shows a view similar to Figure 10 taken through a textile 100 in which smaller drops 110 of a coating substance have been applied. Drops 110 are similar in size to mesh aperture 106 and tend to pass into and even through the apertures. The resulting effect is less homogeneous than in the case of Figure 10 and it is also more difficult to provide a different characteristic to the opposite surfaces of the textile product.

While Figures 9 and 10 illustrate the case of a textile web of about 40 microns, it is also within the scope of the invention that even thicker structures or webs can be used. Thus, for a fiber spacing of 100 microns, a nozzle size of 200 microns could be contemplated.

The invention is not limited to the preferred embodiments described above. In particular, the rights sought are more precisely defined by the following claims, within the scope of which many modifications can be contemplated.