CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from Indian Patent Application Serial No. 767/DEL/201 1 , filed March 18, 201 1 , the contents of which are incorporated herein by reference.

BACKGROUND

[0002] The following description is provided to assist the understanding of the reader. None of the information provided or references cited is admitted to be prior art.

[0003] Dye houses are known to generate a large amount of pollution. The nature of pollution that accompanies the dyeing industry is primarily due to the nonbiodegradable nature of the dyes along with the trace presence of toxic materials in the effluents used to rinse dyed materials. More than 1,000 types of aromatic or conjugated structure dyes are available, and these dyes have varying toxicity levels. Current dyeing techniques utilize a large amount of dye, which increases the amount of pollution generated by dye houses. Dye can be lost due to incomplete exhaustion and incomplete fixation of the dye to a material. In addition, these problems can be intensified by the tendency of reactive dyes to hydrolyze during the dyeing process.

[0004] As most dyes are aqueous based, dye houses also use a significant amount of water for rinsing. Current processes include dye rinsing procedures which produce large amounts of toxic effluent. To reduce the amount of water used for rinsing the dye, pretreatment agents and adhesion promoters have been used. These pretreatment agents and adhesion promoters, however, must be washed from the dyed material, which increases the use of water. Spraying dyes using compressed air as the carrier has also been used to reduce the amount of water used in the dyeing process.

Spraying dyes, however, creates turbulence at the interface between two different atomizing cones, which creates an uneven coating of the dye on a material. Turbulence can also be formed within an atomizing cone directly on the outlet edge of a spray nozzle, which may lead to uneven distribution of the sprayed dye within the atomizing cone.

SUMMARY [0005] An illustrative process includes charging a material with a first charge using a material charging device. A charged dye is applied to the charged material such that an amount of the charged dye is deposited onto the charged material. The charged dye is charged with a second charge that is opposite of the first charge.

[0006] An illustrative apparatus includes a material charging device configured to charge a material with a first charge. The apparatus further includes an applicator configured to receive the charged material and a charged dye and apply the charged dye to the charged material such that an amount of the charged dye is deposited on the charged material. The charged dye is charged with a second charge that is opposite of the first charge. [0007] Another illustrative apparatus includes means for charging a material with a first charge, and means for applying a charged dye to the charged material such that an amount of the charged dye is deposited onto the charged material. The charged dye is charged with a second charge that is opposite of the first charge.

[0008] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the following drawings and the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. These drawings depict only several embodiments in accordance with the disclosure and are, therefore, not to be considered limiting of its scope. The disclosure will be described with additional specificity and detail through use of the accompanying drawings.

[0010] FIG. 1 is a perspective view of an illustrative embodiment of a dyeing apparatus.

[0011] FIG. 2 is a circuit diagram of an illustrative embodiment of a high voltage device used to charge a material.

[0012] FIG. 3 is a flow diagram depicting operations performed in an illustrative embodiment.

[0013] FIG. 4 is a graph illustrating effects of varying a voltage on dye uptake used to charge 30 count cotton yarn at 20 milliamps (mA) in an illustrative embodiment.

[0014] FIG. 5 is a graph illustrating effects of varying current on dye uptake used to charge 30 count cotton yarn at 4,000 volts in an illustrative embodiment.

[0015] FIG. 6 is a graph illustrating effects of varying current on dye uptake used to charge 30 count cotton yarn at 2,000 volts in an illustrative embodiment.

[0016] FIG. 7 is a graph illustrating a comparison of varying current on dye uptake between 30 count cotton yarn and 40 count cotton yarn charged at 4,000 volts in an illustrative embodiment.

[0017] FIG. 8a depicts undyed cotton yarn under a scanning electron microscope in accordance with an illustrative embodiment.

[0018] FIG. 8b depicts dye deposited cotton yarn prior to fixation under a scanning electron microscope in accordance with an illustrative embodiment.

[0019] FIG. 8c depicts dyed cotton yarn after fixation under a scanning electron microscope in accordance with an illustrative embodiment.

DETAILED DESCRIPTION

[0020] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.

[0021] FIG. 1 is a perspective view of an illustrative embodiment of a dyeing apparatus 100 for applying a dye to a material. The dyeing apparatus includes a material charging device 1 10, dye charging device 120, an applicator 130, a residual dye collecting unit 140, a steamer 160, a dye hopper 170, an air-dye mixing device 180, and a compressed air inlet 190. These components are described in more detail below. Materials that may be dyed using the dyeing apparatus 100 include yarn (filament or spun), fabric (woven or non-woven), films, tapes, strands, and other forms of continuous substrates. The dyeing apparatus 100 is configured to electrostatically deposit dye on the material. Dyes which may be used by the dyeing apparatus 100 include dyes that are fixed in alkaline pH, acidic pH, or neutral pH.

[0022] The material to be dyed may be pretreated prior to dyeing. Pretreatment may include scouring of the material. In an illustrative embodiment, scouring of cotton includes using a 3% sodium hydroxide and 0.5% detergent solution at 100-degrees Celsius for four hours. Other methods of scouring various materials are well known to those of skill in the art. Following the scouring, the material may be given a hot wash followed by a cold wash and allowed to air dry. In conjunction with scouring or independent of scouring, the material may also be passed through a solution containing hygroscopic compounds. For example, a solution containing between 5% and 10% urea and between 1 % and 20% sodium hydroxide can be used as a pretreatment for applying reactive dyes to cellulosic materials. Such a solution helps a dyed material absorb water vapor during a steaming process, and helps in faster dissolution of the dye inside the material and its reaction with the cellulosic material. The steaming process is described in more detail below. Before being charged, the material is dried at a high temperature in a hot air oven. [0023] The dyeing apparatus 100 includes a material charging device 1 10 which charges the material as it passes through the charging device 1 10. The material charging device 1 10 charges the material using contact electrification under an electric field using between 500 and 10,000 volts and/or 1 mA to 100mA of direct current. The material can be charged by bringing the material in contact with one terminal of a high voltage circuit 200, explained in greater detail below. The other terminal, which does not come in contact with the material, is maintained near the first one in order to create an electric field. In one illustrative embodiment, the material charging device 1 10 is configured to charge a yarn. In other illustrative embodiments, the material charging device 100 is configured to charge fabric or textiles. A higher range of voltage and/or current may be used for charging materials with higher linear density or while running the dyeing apparatus 100 at higher throughput. Uncharged dye is charged using a dye charging device 120. The dye charging device 120 also uses contact electrification between 500 and 10,000 volts and/or 1 mA to 100mA of direct current. Increasing the voltage or current allows for higher speeds of deposition of a dye to a material.

[0024] FIG. 2 is a diagram of an illustrative embodiment of a high voltage circuit 200 for use in the material charging device 1 10 to charge the material or the dye charging device 120 to charge the dye. Alternatively, other circuits known in the art may be used to charge the dye and the material. In addition, the circuit used to charge the dye is not limited to being the same circuit used to charge the material. The high voltage circuit 200 converts a 220 volt and alternating current source to a variable high voltage and direct current output. For example, the circuit 200 may convert a 220 volt input into a voltage between 500 and 10,000 volts. Using variable resistance, the high voltage device 200 can independently control the high voltage and direct current outputs. The high voltage circuit 200 includes a transformer 205 used to convert an alternating current source to a different voltage. The transformer 205 may be a 220: 1000 ratio transformer. Terminals 230a and 230b are source terminals that are connected to a source, such as a 220 volt alternating current source. Capacitors 225a-225h can be 0.22 microfarads or 0.1 microfarads. Other values for the capacitors may also be used, and the values of the capacitors do not need to be the same. Diodes 220a-220d may be 1N4007 diodes or any other suitable diode. The illustrative example of a high voltage circuit 200 also includes a resistor 235 and a variable resistor 240. The resister 235 may be a 20 kilohms. Other resistors may also be used in the high voltage circuit 200. The variable resistor 240 may be a 1 megaohm variable resistor or any other suitable variable resistor. The current in the high voltage circuit 200 may be regulated by changing the value of resistor 235 or the value of the variable resistor 240. Open terminals 245a and 245b are used to charge the material or the dye. The material is charged by contacting one of the terminals 245a or 245b. The dye is charged by aerosolizing the dye, and bringing the aerosolized dye in contact with one of the terminals 245a or 245b.

[0025] Referring again to Fig. 1 , the dye charging device 120 receives dye that has been aerosolized or fluidized. Aerosolized dye provides a way to control the movement of the dye and allow the dye to come into contact with the charged material. In one illustrative embodiment, uncharged dye from a dye hopper 170 is mixed with compressed air in an air-dye mixing device 180. The air-dye mixing device funnels compressed air from a compressed air inlet 190 to the dye charging device 120. Dye from the dye hopper 170 uses gravity to flow into the air-dye mixing device 170, where the dye is aerosolized and carried to the dye charging device 120. As the uncharged dye passes through the dye charging device 120, the dye is charged using the high voltage device 200 of FIG. 2 by coming into contact with one terminal of the high voltage device 200. The other terminal, which does not come in contact with the dye, is maintained near the first one in order to create an electric field. The dye may also be charged by any suitable alternative. The dye is charged oppositely than the material. In other words, the dye can be positively charged and the material can be negatively charged, or the dye can be negatively charged and the material can be positively charged. The charged aerosolized dye travels through the dye charging device 120 to an applicator 130 where the charged aerosolized dye comes into contact with the charged material. The flow rate of the dye particles through the dye charging device 120 and the applicator 130 can be controlled by varying the pressure and flow rate of the compress air. Any dye that is not deposited on the material may be carried to a residual dye collecting unit 140. These components are discussed in more detail below.

[0026] The applicator 130 is operatively coupled to the material charging device 1 10 and the dye charging device 120. In some embodiments, the applicator 130 is combined with the dye charging device 120, the material charging device 1 10, or both. The applicator 130 receives both the charged material and the charged dye, and is configured to bring the charged material in contact with the charged dye. In an illustrative embodiment, the material is moved through the charged aerosolized dye at an angle. FIG. 1 shows the applicator 130 bringing the dye and the material into contact at a 90 degree angle. Other angles, however, such as about 90 degrees, about 75 degrees, about 60 degrees, about 45 degrees, or about 30 degrees may also be used. Because of the opposite charges of the dye and the material, the dye is attracted to and deposited upon the charged material.

[0027] Dye that is not deposited on the material is collected in a residual dye collecting unit 140. The residual dye collecting unit 140 may be a centrifuge separator that separates the unused dye from the compressed air. The residual dye collection unit 140 may also be a filtration device that collects the unused dye. The unused dye can be recycled by circulating the dye back to the dye hopper 170. The recycled dye can then be reused in the dyeing process. Alternatively, the unused dye can be collected and either reused or disposed.

[0028] After the material has been made to come into contact with the charged dye, the material can be subject to a fixation process. In one illustrative embodiment, the dyeing apparatus 100 includes a steamer 160 configured to fix the dye connected between the applicator 130 and a heater (not shown). Dyed material enters the steamer 160 and is subject to wet steam. The steam can be a saturated steam, which lightly moistens the dyed material. In one configuration, the dyed material is subject to 100-degrees Celsius steam for a time between 5 seconds and 5 minutes. Subjecting the material to steam and heat localizes dissolution and diffusion of the deposited dye. In another configuration, the streamer 160 includes a water sprayer configured to spray the dyed material with water followed by a heater configured to heat the sprayed dyed material to produce steam. The alkaline or acidic condition of the material activates and fixes the dye to the material. The concentration of the acidic or the alkaline compound inside the material, which is dependent upon the concentration of acid or alkali in the pretreatment padding bath, affects the fixation of the dye. Depending upon the class and type of dye being used, a particular concentration of acid and alkali is needed for a higher degree of fixation, which is well known to those of skill in the art of dyeing and printing.

[0029] The heater, configured to dry the steamed material, may be optionally connected to the steamer 160. In another configuration the heater 160 may not be included in the dyeing apparatus 100. In this configuration, the dyed material can be air dried.

[0030] After the material is steamed or dried, the dyed material can be neutralized to remove any unused acid or alkali. The material can also be stripped of any un-reacted dye. A rinsing unit (not shown) rinses the dyed material in a padded bath or any other form of bath known to those of skill in the art. In one configuration, alkaline pretreated materials are rinsed in a dilute solution made of 50% acetic acid at room temperature. Alternatively, materials pretreated with an acidic solution may be rinsed with a weak base such as sodium hydroxide or sodium bicarbonate solution. During the rinsing, the dyed material is optionally washed with a small amount of water and then dried in an oven or air.

[0031] One such material that may be dyed using the dyeing apparatus 100 is cotton. Wool and silk may also be dyed using the dyeing apparatus 100. Cotton is a hydrophilic material having a very high moisture regain value of 7% at 65% relative humidity and 25-degrees Celsius. As such, it is possible that any charge deposited on cotton may be dissipated quickly due to the presence of excess moisture in the fiber. To combat this, one embodiment of the dyeing apparatus includes a dryer, which uses high temperatures to dry the material to be dyed before the material is charged. In one configuration, a tube type dryer with forced air convection may be used. The temperature used to dry the material can vary based upon the type of material being dried and the rate of drying used. In one configuration, temperatures between 80 and 150 degrees Celsius can be used to dry the material prior to charging. [0032] FIG. 3 is a flow diagram depicting illustrative operations performed for an electrodeposition dyeing technique using the dyeing apparatus 100. Additional, fewer, or different operations may be performed depending on the particular embodiment. In an operation 315, a material is charged using contact electrification, which uses high voltage and direct current. The material may be optionally pretreated, in an operation 310, as described above, prior to being charged. In an operation 320, a dye is charged with a charge that is opposite of the charge of the material. The charged material is brought into contact with the charged dye in an operation 330. In an operation 340, the dye is fixed. In one illustrative embodiment, steam is used to fix the dye to the material. When using steam, the dye may be fixed by steaming the dyed material at about 100-degrees Celsius for between 5 seconds and 5 minutes. In an operation 350, the dyed material is neutralized. In one illustrative embodiment, rinsing the dyed material with a 50% acetic acid solution at room temperature neutralizes the alkaline pH of the material. Alternatively, the dyed material may be rinsed with a weak base such as dilute sodium hydroxide or sodium bicarbonate solution, if the material is pretreated with acidic compounds. After the dyed material is neutralized the material is dried at ambient conditions or dried using a dryer.

[0033] Uncharged materials may physically entrap dye particles based solely upon a material's physical properties. For example, dye may be entrapped between fibers of the material. Such entrapment reduces the ability to control the amount of dye that is deposited on the material, since the entrapped dye depends upon the physical properties of the material and not the amount of charge or current used to charge the material. Experiments have shown that the amount of entrapped dye particles in cotton yarn was limited. The experiments involved passing cotton yarn through the dyeing apparatus without applying a charge to either the cotton yarn or the dye. FIG. 4 illustrates a low surface color strength (K/S) value of cotton yarn when the cotton yarn was not charged, where voltage was equal to zero. K is a coefficient of absorption and S is a coefficient of scatter. The K/S value is proportional to the concentration of the dye molecules, and is used to measure the coloration of a material. The K/S values of FIG. 4 were derived by varying the voltage applied to 30 count yarn and applying a 20 mA current to the yarn. Before charging, the yarn had been pretreated with 3% sodium hydroxide and 10% urea. After dyeing, the yarn was also steamed for 5 minutes and subsequently was air dried. The dye used was CI Reactive Red 198. In addition, K/S values were determined by wrapping dyed yarn in multiple layers on a white paper board for reflective color value measurement.

Surface strength was determined using a Jaypak 4800 reflectance spectrophotometer interfaced with a color matching computer. K/S values were taken at the wavelength of maximum absorption of the dye, which was determined to be 530nm for the particular dye used.

[0034] The material charging device 1 10 charges the material using a non-zero voltage between 0 and 4,000 volts. As shown in FIG. 4, voltages of 2,000 through 4,000 volts were effective in dyeing 30 count cotton yarn. Regulating the amount of dye that is deposited on a material is accomplished by varying the voltage used to charge the material and hence the charge density of the material. Precise shade variations can therefore be achieved by regulation of the voltage used to charge the material. Increasing the voltage used to charge a material generates more charge trap sites in the material. More charge trap sites allow more dye to be deposited onto the material, thus, allowing for deeper shades of a color. Optimization of the voltage for a particular combination of dye and material can be easily performed.

[0035] In addition to applying a voltage, the material charging device 1 10 applies a current to the material. Varying the amount of current applied to the material also affects the amount of dye that is deposited on the material. FIG. 5 illustrates the K/S value of 30 count cotton yarn charged at 4,000 volts and with varying amounts of current. The K/S values of FIG. 5 were derived by varying the current applied to 30 count yarn and applying 4,000 volts to the yarn. Before charging, the yarn had been pretreated with 3% sodium hydroxide and 10% urea. After dyeing, the yarn was also steamed for 5 minutes and subsequently was air dried. The dye used was CI Reactive Red 198. The amount of dye deposited on the cotton yarn increased significantly when more than 10mA of current was applied to the material. A saturation point was reached near 24mA. Currents greater than 24 mA did not produce significant increases in the K/S value. [0036] The number of charge sites created in a material depends upon the amount of voltage applied to the material by the material charging device 1 10. The larger the voltage the more charge sites are produced. The charge density saturates when all of these sites are filled. FIG. 6 illustrates the K/S values of a cotton yarn that is charged at 2,000 volts and with varying amounts of current applied to 30 count yarn. Before charging, the yarn had been pretreated with 3% sodium hydroxide and 10% urea. After dyeing, the yarn was also steamed for 5 minutes and subsequently was air dried. The dye used was CI Reactive Red 198. The K/S values in FIG. 6 are less when compared with the K/S values of FIG. 5 for corresponding voltages. FIG. 5 illustrates yarn that was charged with 4,000 volts, rather than 2,000 volts as illustrated in FIG. 6. The lower K/S values of FIG. 6 are a result of a smaller number of charge sites created by the 2,000 volts.

[0037] Varying the current and the voltage used to charge the material allows for very light to deep shades of color to be imparted to the material based upon the amount of dye that is deposited on the material. In addition, the voltages used in the dyeing apparatus 100 are significantly less than 20 kilo-voltages used in conventional power coating techniques.

[0038] The weight of the material also affects the amount of dye deposited on the material. FIG. 7 illustrates a comparison of K/S values for dyeing 30 count cotton yarn compared to 40 count cotton yarn. Line 710 represents the effects of varying a current on dye uptake used to charge the 30 count cotton yarn. Line 720 represents the effects of varying a current on dye uptake used to charge the 40 count cotton yarn. The two yarns were dyed using similar conditions including applying varying amounts of current and 4,000 volts to the yarn. Before charging, the yarn had been pretreated with 3% sodium hydroxide and 10% urea. After dyeing, the yarn was also steamed for 5 minutes and subsequently was air dried. The dye used was CI Reactive Red 198. The K/S values of the 40 count yarn were less compared to the K/S values of the 30 count yarn, as illustrated by lines 710 and 720. The lower K S values are based upon a lower charge density in the 40 count yarn.

[0039] FIG. 8a is a photo of pretreated cotton yarn prior to being dyed. FIG. 8b is a photo of the same cotton yarn after electrodeposition of dye using an illustrative embodiment of the dyeing apparatus 100. It can be observed from FIG. 8b that the dye particles are adhered to the surface of the cotton fibers in the yarn. These particles are distributed uniformly throughout the yarn, thus providing an even coloring. The dye particles are also high in density. FIG. 8c depicts the dyed yarn after the dye has been fixed using steam. There are no dye particles left after the fixation operation. The dye particles which were adhering due to electrostatic deposition, have successfully solubilized and diffused inside the fibers based in part on the steaming process and resulting in dyeing of the material. The diffused dye can then be fixed inside the material at the appropriate pH provided by the optional pretreatment. Figure 8c illustrates the material at the end of the dyeing operations.

[0040] One or more flow diagrams have been used herein. The use of flow diagrams is not meant to be limiting with respect to the order of operations performed. The herein-described subject matter sometimes illustrates different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures can be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively "associated" such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as "associated with" each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being "operably connected," or "operably coupled," to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being "operably couplable," to each other to achieve the desired functionality. Specific examples of "operably couplable" include but are not limited to physically mateable and/or physically interacting components and/or wirelessly interactable and/or wirelessly interacting components and/or logically interacting and/or logically interactable components. [0041] With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for the sake of clarity.

[0042] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g. , "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the

possibilities of "A" or "B" or "A and B."

[0043] The foregoing description of illustrative embodiments has been presented for purposes of illustration and of description. It is not intended to be exhaustive or limiting with respect to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the disclosed embodiments. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.