Abstract:
An article comprising a fabric wherein said fabric comprises a cationic dyeable polyurethane elastic yarn and an acid dyeable yarn.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    Included are fabrics prepared from polyurethane elastic yarn having a cationic dyeable functionality and an acid dyeable yarn. The fabrics can have a uniform color when prepared with separate dye systems. 
         [0003]    2. Description of Related Art 
         [0004]    A fabric that contains elastane (a segmented polyurethane also referred to as spandex) has recognized benefits of comfort, fit, and shape retention. Additionally, it is obvious that consumers value fabrics with a professional looking appearance, which can include having a uniform color. One issue that the fabric industry has failed to address lies in combining the benefits of elastane with uniform color, specifically, the ability to dye the elastane to a shade of similar depth of a companion fiber such as polyamide (nylon). This issue increases with increasing elastane content in the fabric, and in knitted fabrics, including those that have been molded in an extended state. In both cases for knitted fabrics, the inherent stretch in the knitted construction allows for higher fabric stretch and higher yarn movement which exposes the spandex. In the trade the issue of elastane becoming visible in an undesirable manner in a section of fabric that has been stretched is commonly referred to as “grin through”. 
         [0005]    The inability to dye the elastane a common shade as the companion yarn, especially polyamide, is related to several factors that are common to shade matching any two chemically distinct fibers that dye with the same class of dyes. As an example, acid dyes are used to dye polyamide, silk, and wool, and yet they also are able to stain elastane, thus both fibers dye “together.” In addition to differences in affinity and chemical reaction rates between dye molecules and two or more distinct fiber types, depth of shade is widely recognized to also be affected by yarn properties such as decitex, decitex-per-filament in a yarn bundle, and the thermal behavior of the fiber during dye processing conditions. 
         [0006]    Previous attempts to combine the benefits of elastane functionality with uniform coloration have attempted to improve the affinity and depth of shade of the elastane with the acid dye types commonly used with polyamide such as U.S. Patent Application Publication No. 2005/0165200 A1 by Selle et al. These efforts are affected by the same difficulties with shade match that resulting from physical and dye uptake differences between the elastane and companion yarns (See for example “Dyeing and Chemical Technology of Textile Fibers” 5th ed. By E. R. Trotman). 
         [0007]    Therefore, a need exists for improved stretch fabrics including an elastane yarn and a polyamide yarns and/or proteinaceous yarns that have a more uniform color. 
       SUMMARY OF THE INVENTION 
       [0008]    In some embodiments is an article including a fabric, where the fabric includes a cationic dyeable polyurethane elastic yarn and an acid dyeable yarn. The cationic dyeable yarn is selected from those disclosed in WO 2008/075605 to OPELONTEX CO., LTD of Japan., which is included herein by reference in its entirety. 
         [0009]    In some embodiments is an article including a fabric, where the fabric has a uniform color. The fabric includes a cationic dyeable polyurethane elastic yarn, an acid dyeable yarn, a cationic dye, and an acid dye, wherein the acid dyeable yarn is selected from the group consisting of polyamide, proteinaceous, and combinations thereof. 
         [0010]    In another embodiment is a method for preparing a fabric including:
       (a) providing a fabric including a cationic dyeable polyurethane yarn and an acid dyeable yarn,   (b) contacting the fabric with a cationic dye, and   (c) contacting the fabric with an acid dye,
 
wherein the fabric has uniform color.
       
 
     
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    Surprisingly, it has been found that one may overcome the deficiencies of a stretch fabric having an elastane yarn and an acid dyeable yarn, by preparing a fabric that includes a unique combination of polyurethane elastic yarn with cationic dye-able functionality as disclosed in WO 2008/075605 and a companion yarn with acid dye functionality. 
         [0015]    As used herein, the terms spandex, elastane, and polyurethane elastic yarn are used interchangeably and refer to a segmented polyurethane elastic yarn. 
         [0016]    The cationic dyeable polyurethane elastic yarn and the acid dyeable companion yarn can be combined either in the same yarn, or in separately combined into the fabric. The fabric can be prepared into any suitable construction including circular knit, warp knit, and woven. After the fabric is prepared, the fabric is separately treated with cationic dyes and acid dyes. Either the cationic dye or the acid dye may be applied first depending on the desired properties of the fabric. The cationic dyeable elastane may be used in a fabric in any suitable amount to provide the desired stretch-recovery property to the fabric. For example, the fabric may include greater than zero and up to about  60 % by weight of the cationic dyeable elastane. 
         [0017]    Another suitable method for obtaining a uniformly colored fabric is to prepare a knitted or woven fabric with the cationic dyeable elastane and an acid dyeable companion yarn. The fabric is first contacted with an acid dye to the achieve the desired shade for the companion yarn using dyes that either do not dye at all or only slightly dye or stain the cationic dyeable elastane. Then the fabric is contacted with a cationic dye to dye the elastane. Dyeing of the elastane yarn of the fabric may occur in a separate step or in the same dye bath where the acid dyeable companion yarn is dyed. When one dye bath is used, the acid dye bath is combined with an alternative dye recipe (such cationic dyes) that have been specifically adjusted for the elastane&#39;s unique chemistry and fiber diameter to match the shade of the companion yarn. 
         [0018]    Additionally, given that elastane yarns stretch up to 500%, and that shade appearance is dependent on fiber diameter, the elastane color depth can be optimized to match the companion yarn in the relaxed state in a fabric or at a specifically targeted level of extension. 
         [0019]    The companion yarn may include any acid dyeable yarn. Examples of fibers that are dyeable with acid dyes include polyamides and proteinaceous fibers. Polyamide polymers are well known in the art. They are generally prepared by the condensation polymerization of a dicarboxylic acid and a diamine or the condensation of a monoaminomonocarboxylic acid which is normally derived from its internal lactam. Examples of such polyamides are nylon 6,6 or nylon-6 which are respectively prepared from hexamethylene diamine—adipic acid mixtures and ε-caprolactam. Examples of other fiber-forming polyamides are nylon-6/6,6 copolymers, nylon-11, nylon-12. Examples of proteinaceous fibers include silk, wool, mohair, angora, and alpaca. Combinations of these fibers may be used in the same yarn or single component yarns may be combined into fabric. 
         [0020]    Examples of useful acid dyes include Color Index (C.I.) dyes: Acid Yellows 24, 40, 59, 159, 184, 204 and 246, Acid Oranges 142 and 156, Acid Reds 50, 51, 52, 138, 151, 299, 361, 362, Acid Greens 104 and 108, Acid Blues 113, 171, 185, 193, 277 and 324, Acid Violet 90, Acid Brown 298, Acid Blacks 52, 131:1, 132:1, 172, 187 and 194. Examples of useful non-Color Index dyes include: Lanaset Blue 2R, Lanaset Navy R, Lanaset Red G, Lanaset Red 2GA, Lanaset Violet B, Lanaset Brown B, Burconyl Brick Red AF-3b, Burconyl Rubine AF-GR, Burconyl Orange AF-3R, Burconyl Green AF-B, Burconyl Brilliant Blue AF-R, Burconyl Royal Blue AF-R, Burconyl Brilliant Yellow AF-4G, Erionyl Red A-3G, Erionyl Blue RL 200, and Nylanthrene Brilliant Blue 2RFF. 
         [0021]    Other useful dyes, including cationic dyes are known in the art and are disclosed in WO 2008/075605. 
         [0022]    Color measurements are made on fabrics with a Datacolor Spectraflash Model SF-300 colorimeter (Datacolor International, Lawrenceville, N.J.) using a D65/10 degree illuminant. Measurements are reported using the international standard color measurement method promulgated by “Commission Internationale de L&#39;Eclairage” (Paris, France), (International Society for Illumination/Lighting), (“CIE”) using standard color coordinates of the CIELAB L*a*b* color space: “L” designates the lightness coordinate; “a” designates the red/green coordinate (+a indicating red and −a indicating green); and “b” designates the yellow/blue coordinate (+b indicating yellow and −b indicating blue). The total color difference between two samples, ΔE, is obtained by taking the difference between the L*, a*, and b* coordinates. The uniform color of the fabrics include where color of the fabric as measured by a-color, b-color, and L-value is within 10% of the values that are obtained by removing the cationic dyeable elastic yarn from the fabric. 
         [0023]    General Processing Conditions 
         [0024]    Preparation 
         [0025]    Hose or garment pre-steamed at autoclave temperatures ranging from 85-115 C can be used to stabilise garment sizing and to minimise creasing in subsequent wet processing. 
         [0026]    Open Width Fabric Stabilisation, particularly for LYCRA® fibre blends can be achieved in dry heat stenter setting at 160-200 C for 60-45 seconds, Depending on fabric quality an Anti-oxidant protection may be used in the pad to protect the amine end groups/dye sites of the polyamide during pre-setting (commercial example 2-3% owf Spanscour Spark Tanatex) 
         [0027]    Scouring 
         [0028]    1-2 g/l non-ionic detergent 
         [0029]    1-2 g/l Soda at 70-80 C for 20 minutes 
         [0030]    Single Bath 2 stage Method 
         [0031]    Since the solid shade colour effects are based on a combination of anionic and cationic dyes it is important to modify single bath dyeings to facilitate separate exhaustion of the two dye types. 
         [0032]    Cationic dyes strike faster than anionic dyes and should be applied to the dye bath first at the lowest possible temperature, with a cationic levelling agent. subsequent treatment at 40-70 C for 10-30 minutes will achieve substantial exhaustion&gt;Application of the acid dyes, after cooling back to 40 C, can then be more safely managed raise at 1 c/ minute to 98 c dye 30-60 minutes. 
         [0033]    Two Bath Method 
         [0034]    Apply the cationic dyes to the spandex as described in the single bath method cool back and rinse then apply the acid dyes on to the polyamide in a second bath, this will be preferred for very dark shades where there might risk of dye precipitation ie cationic dyes that have not exhausted on to the fibre remaining in the dye bath resulting in precipitation of the dyes when the acid dyes are added. 
       Dyeing Process Control 
       [0035]    Dyeing by constant pH will ensure the best balance in shade and colour reproducibility although acid donors can be used. 
         [0036]    A constant pH6.5-7.0 will be optimum but sometimes downward adjustment to pH4.5-5.5 will be required to achieve dye exhaustion. It is important to set the pH before the addition of the cationic dyes to avoid rapid strike on to the spandex from residual scour alkali 
         [0037]    Improved levelling and migration of the cationic dyes on spandex can be achieved by the simultaneous addition to the dyebath of 0.1% Tinegal MR (Huntsman). This product can foam more easily and so additional application 0.5 ml/per litre Aphrogene NS (non silicone anti-foam from Uniqema) can be helpful. 
         [0038]    Glaubers salt retards cationic dyes on spandex and also improves levelling. 
         [0039]    Non-ionic anti-precipitants Uniperol KA (BASF) at 0.25% level can reduce precipitation risks in single bath dyeing applications. Amphoteric-Albegal A (Huntsman) can be used where foaming is a problem.