Method for modifying the color-hue of colored synthetic yarns and filaments, and system for carrying it out

Abstract

The invention provides a method for modifying the color hue of already colored synthetic yarns and/or filaments in a conventional melt-spinning process, which allows correcting deviations from tolerances in the color hue by the manufacturers themselves. The method comprises storing color coordinates of a target hue; measuring color coordinates of colored yarns and filaments to be corrected; comparing the data to provide deviations beyond tolerances; preparing a correcting-liquid-masterbatch composition; converting the deviations beyond tolerances into a dose of the correcting liquid-masterbatch composition; and adding such dose to molten mass of the synthetic yarns and filaments.The invention is also directed to a system suitable for performing the method of color hue modification and/or correction.

1 - 15 . (canceled) 
     
     
         16 . A method for modifying color hue of colored synthetic yarns and/or filaments to a target color hue during a conventional melt-spinning process, characterized in that the method comprises the following steps:
 storing color coordinates a t * and/or b t * of the target color-hue including limits of tolerances;   taking measurements of color coordinates a* and/or b* in the colored synthetic yarns and/or filaments to identify the actual color hue;   comparing stored target color hue coordinates with the actual color hue coordinates measured, that is Δa and/or Δb, to determine if the differences, if any, are beyond limits of the target color hue tolerances;   preparing at least one correcting liquid-masterbatch composition comprising a liquid polymer carrier and at least one colorant dispersed therein, with the proviso that one of the colorants included in the correcting liquid-masterbatch composition is selected to be the same as present in the colored synthetic yarns and/or filaments, wherein the colorant concentration is between 1% and 40% by weight to the weight of the correcting liquid-masterbatch composition;   converting the observed differences in the color coordinates, i.e. Δa and/or Δb, into a dose of the prepared correcting-liquid-masterbatch composition;   adding such dose of the correcting-liquid-masterbatch composition during the extrusion of the colored synthetic yarns and/or filaments to correct the actual color hue toward the target color hue, thus resulting in a corrected color hue modifying the actual color hue to be within the target color hue tolerances, wherein the dose is equal to or lower than 3% by weight with respect to the weight of the colored synthetic yarns and/or filaments; and optionally   verifying the corrected color hue in the corrected and colored synthetic fibers and/or filaments by taking new measurements of color coordinates am* and/or bm* in the newly obtained colored synthetic yarns and/or filaments in order to assure that the corrected color hue is within limits of target color hue tolerances.   
     
     
         17 . The method according to  claim 16 , wherein the differences in the color coordinates, that is Δa and/or Δb, are converted into a dose of the correcting-liquid-masterbatch composition by a relationship that is substantially linear. 
     
     
         18 . The method according to  claim 16 , wherein the preparation of the correcting-liquid-masterbatch composition comprises:
 preparing a dispersion of at least one colorant in a liquid polymer carrier, with the proviso that at least one of the colorants included in the correcting liquid-masterbatch composition is selected to be the same as present in the colored synthetic yarns and/or filaments whose color-hue is desired to be corrected.   
     
     
         19 . The method according to  claim 16 , wherein the correcting-liquid-masterbatch composition comprises a colorant concentration between 1 and 30% by weight to the weight of the correcting-liquid-masterbatch composition. 
     
     
         20 . The method according to  claim 19 , wherein the correcting-liquid-masterbatch composition comprises a colorant concentration between 5 and 10% by weight to the weight of the correcting-liquid-masterbatch composition. 
     
     
         21 . The method according to  claim 16 , wherein the colorant included in the correcting-liquid-masterbatch composition is selected from an organic pigment, an inorganic pigment or solvent dyes, and it is further selected having the same color index value than one of the colorants that is present in the colored synthetic yarns and/or filaments. 
     
     
         22 . The method according to  claim 16 , wherein the correcting-liquid-masterbatch composition is added in a concentration equal to or lower than 1% by weight with respect to the weight of the colored synthetic yarns and/or filaments. 
     
     
         23 . The method of  claim 22 , wherein the correcting-liquid-masterbatch composition is added between 0.1 and 0.6% by weight with respect to the weight of the colored synthetic yarns and/or filaments. 
     
     
         24 . The method according to  claim 16 , wherein the differences beyond limits of tolerances, that is Δa and/or Δb, are within a value of |3|. 
     
     
         25 . The method according to  claim 24 , wherein the differences beyond limits of tolerances, that is Δa and/or Δb, are within a value of |1|. 
     
     
         26 . The method according to  claim 16 , wherein the synthetic polymer for forming yarns and/or filaments is selected from polyester, co-polyester, polyamide, polyethylene, polypropylene, polyethyleneterephthalate (PET), polybutyleneterephthalate (PBT), polytrimethyleneterephthalate (PTT), polylactic acid (PLA) or a mixture thereof.