Abstract:
Systems, methods, and devices are described that dispense microdroplets of dye onto individual filaments or fibers and infuse them into the interior of such filaments and/or fibers in a highly controlled manner. Control of dye dispensing permits changing the dye applied to a fiber during a dyeing operation, and supports the generation of patterns in woven products via the dyeing process. The resulting systems and methods require much less water and generate much less waste than conventional dyeing processes.

Description:
[0001]    This application claims the benefit of U.S. Provisional Patent Application No. 62/063,858, filed Oct. 14, 2014, which is hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The field of the invention is fabric and fiber dyeing. 
       BACKGROUND 
       [0003]    Traditionally, application of dyes to fibers is performed by contacting a mass of fiber, yarn, thread, or similar filamentous materials with a solution of a dye or colorant. This is generally performed at elevated temperatures, with the dye in an aqueous solution. In this process the amount of dye that is utilized is far in excess of the capacity of the yarn or thread, so following application and fixing the excess dye is removed, generally by extensive washing or rinsing in water. This process is inefficient and wasteful in terms of expensive dyestuffs and in terms of fresh water (which is in increasingly short supply). 
         [0004]    In conventional processes, dying fiber typically requires the performance of multiple color test cycles in order to optimize mixing, application, and cleaning before the final produced color of the dyed fiber can be approved. Once proper conditions are determined large quantities of colorant, chemicals and water are transferred to a dye vessel. This dye vessel must be carefully cleaned of previous colorants and chemicals prior to use in order to prevent contamination. Such pre-process and post-process steps consume significant time, during which dyeing operations. As a result dye houses are forced to compensate for this lost time by requiring a certain minimum volume for production runs of dyed fibers and typically need to charge significant premiums for short runs. 
         [0005]    Once dyed, the fiber, yarn, thread or other filamentous material is typically wound on a reel or spool. These spools or reels are stored until they are needed, then supplied to knitting machines or similar devices to be incorporated into clothing and other textiles. This process is similarly wasteful, due to shipping of the dyed materials from the dyeing facility to the linen fabrication facility (thereby generating greenhouse gases), utilization of large amounts of space for storage, inevitable losses during storage, incurring significant labor costs to supply and resupply the reels or spools as they are needed, and the need to use elaborate inventory control and monitoring systems to track the supply and usage of each type of dyed material. 
         [0006]    Thus, there is still a need for rapid and efficient systems and methods for dyeing filamentous materials with minimal environmental impact, and that can do so on an on-demand basis that is relatively independent of run volume. 
       SUMMARY OF THE INVENTION 
       [0007]    Embodiments of the inventive concept include systems, methods, and devices that dispense microdroplets of dye onto individual filaments or fibers and infuse them into the interior of such filaments and/or fibers in a highly controlled manner. Control of dye dispensing permits changing the dye applied to a fiber during a dyeing operation, and supports the generation of patterns in woven products via the dyeing process. 
         [0008]    One embodiment of the inventive concept is a system for producing a colored filament that includes a source of a filament (which can include a polymer, a colorant application unit that receives the filament and includes a print head, wherein the print head that is in fluid communication with a dye or colorant, a colorant infusion unit that receives a coated filament from the colorant application unit and includes a source of infrared radiation and is in connected to one or more vacuum source (which reduces the pressure within the colorant application unit to less than ambient air pressure) and a drive unit that moves the filament through the colorant infusion unit and the colorant infusion unit. In some embodiment the print head is in fluid communication with a second dye or colorant, and the print head can be instructed to dispense a first colorant a second colorant over different time intervals. Suitable colorants or dyes include disperse dyes or reactive dyes. In some embodiments the polymer of the filament includes a crystalline phase, and amorphous phase, and an intermediate phase interposed between the crystalline phase and the amorphous phase. The source of infrared radiation emits a wavelength of infrared radiation at an energy that corresponds to a boson peak in the infrared energy absorbance profile of the polymer. The system of one claim  1  wherein the primary colorant is a disperse dye. After dyeing, the fiber can be collected on a take up reel or can be supplied directly to a fabrication unit (such as a knitting machine). In some embodiments a preheating module is placed between the colorant application unit and the colorant infusion unit. 
         [0009]    Another embodiment of the inventive concept is a system in which two or more systems as described above are arranged to work in parallel, such that two or more filaments or fibers are dyed simultaneously. In such embodiments the colorant infusion units can be connected to one or more common vacuum sources (for example, using a manifold). In such embodiments two or more of the dyed filaments or fibers produced can be supplied to a single reel or to a single fabrication device (for example, a knitting machine). 
         [0010]    Yet another embodiment of the inventive concept is a method of providing a colored filament comprising in which a filament is moved through a colorant application unit and a colorant infusion unit. A a primary colorant is dispensed onto a first portion of the filament as it is moves through a colorant application unit by a print head to generate a first segment of a coated filament. This is transferred to the colorant infusion unit where a first infrared irradiation is applied to the coated filament at a pressure below that of ambient air pressure. This disperses the primary colorant within the coated filament to generate a first segment of a colored filament. In some embodiments a secondary colorant is dispensed onto a second segment of the filament as it moves through the colorant application unit by the same print head to generate a second segment of the coated filament, and a second infrared irradiation is applied to the coated filament at a pressure below that of ambient air pressure as it moves through the colorant infusion unit. This disperses the secondary colorant within the coated filament to generate a second segment of the colored filament. In preferred embodiments the gap between the first segment of colored filament and the second segment of colored filament is equal to or less than 2 cm. Suitable dyes include disperse dyes and reactive dyes, and in some embodiments the primary colorant is a disperse dye and the secondary colorant is a reactive dye. Following infusion of the colorant, the filament can be transferred to either a take up reel or a fabricator 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  schematically depicts an embodiment of a system of the inventive concept, in which multiple fibers are dyed simultaneously. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    The inventive subject matter provides apparatus, systems and methods in which a one or more filaments (i.e. thread, yarn, fiber, ribbon, or similar materials that can be woven to form a fabric, web, and/or mesh) have colorant dispensed on their surface in the form of microdroplets, which dry rapidly to form a colorant-coated filament. The dispensed colorant can be changed during processing, permitting more than one colorant to be added to a given filament. The colorant-coated filament moves to a colorant infusion unit, in which the colorant is drawn into the fiber. In a preferred embodiment the colorant infusion unit applies infrared radiation at reduced pressure, thereby permitting the colorant to move to the interior of the filament. The colored filament can be collected on a take up reel or can be supplied directly to a knitting machine or similar device without the need for a rinsing or washing step, resulting in a drastic reduction in water consumption and elimination of the need for shipping from a dyeing facility. In preferred systems, two or more sets of colorant application units and colorant infusion units work to process a corresponding number of filaments in parallel. 
         [0013]    The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art. 
         [0014]    In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements. 
         [0015]    As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise. 
         [0016]    The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention. 
         [0017]    Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims. 
         [0018]    Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components. 
         [0019]    One should appreciate that the disclosed techniques provide many advantageous technical effects including a dramatic reduction in the consumption of fresh water and in the production of greenhouse gases generated by shipping operations. Similarly, storage and inventory control are simplified. 
         [0020]    The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed. 
         [0021]    In embodiments of the inventive concept the filament to which the colorant is applied can be a thread, yarn, twine, ribbon, or other substantially linear and flexible component that can be woven into a fabric, mesh, or web. Such a filament can have a polymeric composition. Suitable polymers include naturally occurring polymers (for example, cellulose or silk), synthetic polymers (for example, polypropylene, polyester, or polyamide), and/or a combination of these. In some embodiments the filament is composed of two or more sub-filaments or strands that are coupled to one another, for example by winding the sub-filaments around one another, so that they move and are processed as a single filament. 
         [0022]    Embodiments of the inventive concept include a device for processing of a single fiber. Other embodiments of the inventive concept include systems that include two or more of such devices operating in parallel. As such, descriptions of the various components and operations below are applicable to the features and operation of both device and system embodiments of the inventive concept. 
         [0023]      FIG. 1  provides a schematic representation that depicts a system  100  that processes seven of such filaments simultaneously. Descriptions directed to a single filament are understood to be potentially applicable to all filaments being processed within such a system, in concert or independently, unless stated otherwise. A filament is supplied by a source  110 . Such a source can be a reel, spool, hank, or similar arrangement or reservoir capable of supplying the filament in an untangled manner. In some embodiments of the inventive concept the source can be a mechanism that produces the filament from a raw material as needed, for example a mechanism that receives cotton, spins the cotton into strands, and winds the strands into a cotton thread that is supplied to the system as a filament. 
         [0024]    From the source the filament moves through a colorant application unit  120 . The colorant application unit dispenses numerous small-volume (i.e. 0.1 to 100 pL) microdroplets of colorant onto the filament as it moves through to produce a coated filament. In a preferred embodiment of the inventive concept the volume of a colorant microdroplet is 1 to 1.5 pL. At these volumes the colorant is dry before the coated filament (or the coated portion of the filament) leaves the colorant application unit. The colorant can be dispensed by any suitable means, but is preferably dispensed using a MEMS print head that is in fluid communication with one or more sources of colorant. Such devices provide accurate and reproducible dispensing of suitably small volumes, and provide an area over which the colorant can be dispensed that is substantially larger than that of other microdispensing methods (for example, micropipettors and conventional ink jets). Such a large dispensing area supports rapid processing speeds. In preferred embodiments of the inventive concept a filament can move through a colorant application unit at a rate greater than or equal to 100 meters per minute. 
         [0025]    In a system such as shown in  FIG. 1 , a colorant application unit  120  or a set of colorant application units can be controlled using a digital color controller  130 . The digital color controller can be used to instruct a colorant application unit to change the colorant that is applied to a filament as it moves through the colorant application unit. This can be accomplished by changing the source of colorant that is supplied to a print head. Alternatively, this can be accomplished by switching from a first set of dispensing nozzles of a print head that are dispensing a first colorant to a second set of dispensing nozzles of the print head that are dispensing a second, different colorant. In a preferred embodiment of the inventive concept a colorant application unit can change the colorant that is dispensed to a filament while leaving a gap of about 10, 8, 6, 4, 2, or less than 2 cm between the portions of the filament over which the first colorant and the second colorant are dispensed. In some embodiments of the inventive concept print head (or similar device) of a colorant application unit can dispense two or more colorants to the same region of the filament, producing a blended result. In still other embodiments of the inventive concept, the digital color controller can instruct the colorant application unit to dispense different amounts of the same colorant to the filament, thereby varying the intensity of shading along the length of the filament. This can be achieved, for example, by adjusting the rate at which the microdroplets of dye are dispensed and/or adjusting the volume of the dispensed microdroplets. 
         [0026]    It should be appreciated that the use of such a colorant application unit dramatically reduces the amount and the volume of colorant that is applied to a filament relative to conventional dyeing processes. Additional features can reduce this even further. For example, the MEMS print head can be controlled such that only nozzles that are in contact with or in immediate proximity (i.e. less than 1 cm) to the filament are activated to dispense colorant. In some embodiments the colorant application unit can impart a charge to the filament and an opposing charge to the dispensed colorant, so that the dispensed droplets of colorant are impelled onto the filament. In such an embodiment interior walls of the colorant application unit can carry a charge that matches that of the dispensed colorant droplet, repelling the colorant from the walls of the colorant application unit and reducing the need for cleaning and other maintenance. Colorant application units can be provided with filter, forced air, and/or vacuum resources that serve to remove or segregate colorant that failed to adhere to the filament on colorant dispensing. 
         [0027]    Colorants of the inventive concept can be any material, either liquid or in liquid suspension, that the user wishes to incorporate into or bond to the filament. For example, a colorant can be a disperse dye or suspension of disperse dye in a suitable solvent. Alternatively, a colorant can be a reactive dye. It should be appreciated, however, that systems and methods of the inventive concept can also be used to incorporate other functional molecules into a filament, for example UV protectors, conductive materials (i.e. metals, graphites, fullerenes, nanotubes, and other carbon clusters), water repellants, insect repellants and/or insecticides, and pharmaceuticals (for example antiseptics, antibiotics, anticoagulants, tissue growth and/or trophic factors, etc.). 
         [0028]    As shown in  FIG. 1 , on exiting the colorant application unit  120  the coated filament is directed to a colorant infusion unit  150 . In doing so the coated filament can be passed through a preheating unit  140 , for example a set of heated rollers. Such heated rollers can also form part of an impelling mechanism that moves the filament through the system. A colorant infusion unit of the inventive concept includes one or more sources of infrared radiation. Such a source can be a source of electromagnetic radiation (EM radiation) that provides electromagnetic energy in the wavelength range of 700 nm to 1 mm. Alternatively, such a source can be a resistive heater. In a preferred embodiment of the inventive concept the colorant infusion unit includes both EM radiation sources and resistive heaters. In some embodiments of the inventive concept the EM radiation source can provide two or more wavelengths, for example by energizing different sets of EM radiation emitters (for example LED or laser sources) or by the use of a wavelength selector (for example, a diffraction grating or interferometer). 
         [0029]    A colorant infusion unit of the inventive concept is operated at reduced (i.e. below ambient air pressure). Towards that end such a colorant infusion unit is in communication with one or more vacuum units  160  that serve to exhaust air from the colorant infusion unit. The inventor has found, surprisingly, that reducing the pressure surrounding a coated filament greatly reduces the energy (in the form of infrared energy, heat, or a combination thereof) necessary to incorporate or draw the colorant into the filament. In preferred embodiments of the inventive concept the pressure within such reduced pressure portions of the system or device is about 759, 700, 600, 500, 400, 300, 200, 100, 30, 10, 3, 1, 0.3, 0.1, or less than about 0.1 Torr. In order to efficiently maintain a low pressure environment within the colorant infusion unit as the filament moves through, the filament can pass through an area or stage that is evacuated using a pump that is capable of moving large quantities of air but does not maintain a high vacuum (for example, a rotary pump) and then through a second area or stage that is evacuated using a pump that is capable of maintaining a high vacuum but that does not move large volumes of air (for example, a cam or a piston pump). The two vacuum stage sections can be separated by a sealing device (for example, a pair of silicone rollers) that reduce air loss between the vacuum stages as the filament moves through the sealing device. A similar set of vacuum stages can be supplied at the exit of the colorant infusion unit. In some embodiments of the inventive concept, the rollers of such a sealing device can form part of an impelling mechanism that moves the filament through the system. 
         [0030]    Inside of the colorant infusion unit the coated filament is subjected to EM radiation, temperature, and vacuum conditions that either draw the dye into the interior of the fiber (in the case of disperse dyes) are permit the dye to chemically react with the filament (in the case of reactive dyes). Such conditions can be selected so that the energy (in the form of EM radiation and/or heat) lies within a boson peak characteristic of the energy absorption of a polymer of the filament. For example, polymeric filaments can have heterogeneous structures that include a highly crystalline phase in the form of inclusions within a less organized and relatively amorphous phase. An intermediate region lies between these phases. As energy (in the form of EM radiation and/or heat) is added to such materials a boson peak, or deviation from linearity, is often observed in a graph of energy added to the material versus the degrees of freedom available to molecular species of the material. The inventor has found that such a boson peak coincides with the development of tunnels or channels within the polymeric filament (generally at least partially within the intermediate regions), at least some of which extend to the exterior of the filament and can permit a colorant coating to enter the interior of the filament. The inventor has also found that application of a vacuum to such materials reduces the amount of energy that needs to be applied to reach such a boson peak, bringing it into a range that is compatible with colorant materials and polymers commonly used in filament production. A subsequent reduction in the energy applied to the filament results in the collapse of the tunnels or channels, which serves to trap the colorant within the filament and disperse it throughout the interior of the filament. In a preferred embodiment of the inventive concept, the colorant is selected to be fluidly mobile at EM radiation and temperature conditions corresponding to a boson peak of a polymer of the filament. It should be appreciated that a colorant infusion unit of the inventive concept can be controlled to provide such conditions for a wide variety of polymeric materials. In a preferred embodiment of the inventive concept, the filament, the colorant, the dispensed amount of colorant, and the conditions within the colorant infusion unit are selected so that essentially all (i.e. &gt;90%) of the colorant applied to the filament migrates to the interior of the filament. This advantageously minimizes or, preferably, eliminates the need to wash or rinse the filament following colorant infusion. 
         [0031]    Similarly, a colorant infusion unit can be controlled to provide EM radiation, temperature, and vacuum conditions that permit reactive dyes to form chemical bonds with a polymer of a filament. In a preferred embodiment of the inventive concept, the filament, the colorant, the dispensed amount of colorant, and the conditions within the colorant infusion unit are selected so that essentially all (i.e. &gt;90%) of the colorant applied to the filament migrates forms a chemical bond with a polymer of the filament. This advantageously minimizes or, preferably, eliminates the need to wash or rinse the filament following colorant infusion. In some embodiments, for example where a colorant application unit has switched from applying a disperse dye to applying a reactive dye to a given filament, a colorant infusion unit can change EM radiation, temperature, and/or vacuum conditions as a filament moves through it. 
         [0032]    On exiting the colorant infusion unit, the colored filament can pass through a polishing unit  170 . Such a polishing unit can, for example, apply a wax, polish, or other similar coating that simplifies handling and/or processing of the colored filament in subsequent steps. In some embodiments of the inventive concept the final colored filament is transferred to a take up reel  180 , where it is stored prior to use. In some embodiments of the inventive concept the take up reel can form at least part of an impelling mechanism that serves to move the filament through the system. For example, tension supplied by a rotating take up reel can serve to draw the filament from the source and through the colorant application unit and the colorant infusion unit at a desired rate (for example, 100 meters per minute or faster). Alternatively, the final colored filament can be supplied directly to a fabrication unit, for example a knitting machine or a loom, that generates a fabric, mesh, web, or similar woven product. In such embodiments a feed mechanism of the fabrication unit can form at least part of an impelling mechanism that serves to move the filament through the system. 
         [0033]    It should be appreciated that the digital color controller can configure the system to produce a multiple-dyed filament, such that the dyed segments of the filament form a desired pattern in the final fabric or mesh. Towards that end, a gap between such colored segments can serve to provide indicia to an automated knitting machine of an impending change in the colorant applied to the filament. In some embodiments of the inventive concept the digital color controller can be configured to supply indicia regarding the nature of the subsequent colorant within such a gap, for example by encoding such information using a UV-visible colorant not readily perceived by a consumer. 
         [0034]    It should also be appreciated that systems and methods of the inventive concept provide far greater flexibility in regards to the amount of dyed filament that can be processed economically relative to systems and methods of the prior art. Since the process is essentially continuous (within the limits of the supplied filament and colorant), non-productive down time is greatly minimized and the relative costs of producing smaller quantities of dyed filament are proportionately reduced. 
         [0035]    It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refers to at least one of something selected from the group consisting of A, B, C . . . . and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.