EP3771754A1 - Method for modifying the color-hue of colored synthetic yarns and filaments, and system for carrying it out - Google Patents

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.

Description

Field of the invention
• The present invention pertains to the field of colored synthetic-fiber production, mainly for the textile industry and relates to the correction of the color hue of such colored synthetic yarn and fibers in a conventional fusion spinning procedure.
• Particularly, the present invention relates to a method for modifying the color hue of colored synthetic yarn and filaments during the extrusion in the fusion spinning procedure as well as to a system for carrying it out in order to correct color-hue deviations beyond tolerances that usually appear during production of colored synthetic yarns and filaments.
• The present invention also relates to the use, in the method for modifying the color hue, of a correcting liquid-masterbatch composition for carrying out the correction of the color hue during the extrusion in the fusion spinning procedure by the manufacturers themselves.
Background of the invention
• A polymer support or main polymer is the medium in which a concentrate of color pigments and/or other additives, known as "masterbatch", is dispersed in order to mainly modify the properties of the fibers and filaments in the fusion spinning procedure, creating products with different technical characteristics and specific improvements for the applications they have been designed for. In the art, a "masterbatch" is also named an "additive/color concentrate". The masterbatch can be a color concentrate, an additive concentrate, or a concentrate of both additive(s) and color(s) according to the needs of the manufacturer of the fusion spinning procedure.
• There is a wide range of "masterbatches" on the market, liquid and solid, the composition of which depends on what they are to be used for.
• In this sense, EP0242754 discloses the use of a concentrated polymeric composition as solid-masterbatch for coloring thermoplastic resins in a melt-spinning process, the concentrated composition being added into the molten fiber and filament-forming polyester polymers.
• For the same purpose, in US4879335 and US5106905 , carbon black is used with a liquid carrier made of polyester to form a liquid coloring agent as a liquid masterbatch for polyester spinning process. However, the use of such liquid coloring agent will decrease the viscosity of the spinning polyester and it does not have the required thermal stability at the spinning temperature, which usually is between 280°C-300°C, whereby the liquid coloring agent will degrade into gas with smaller molecular weight. Moreover, the polyester itself will change to be yellow in color and the filament breakage rate will increase. Furthermore, it causes an unacceptable influence on the strength, stretch ability, and heat resistance of the fiber.
• On the other hand, JP49-87792 and US4208318 suggest the addition of a small amount of chemically modified metal phthalocyanine to make the color concentrate have a slight bluish tone. However, the chemically modified metal phthalocyanine is too expensive to use at industrial scale.
• Although, it has been reported liquid-masterbatch compositions for coloring thermoplastic resins, such formulations have limited suitability for inorganic pigments or carbon black; also, the spinning temperature condition often degrade the liquid-masterbatch and the physical properties of the obtained yarns and filaments can be adversely affected. Moreover, the amount of liquid-masterbatch that can be added in the polymer support is very limited in percentage in order to do not adversely affect the physical and/or chemical properties in the manufactured synthetic yarns and/or filaments.
• At this time, for example, there is not in the art a competitive method for obtaining synthetic yarns and filaments with different shades of gray without one of the problems posed in the art. This is especially of great importance in the automotive field, where the demands on a specific shade within tolerances of a color are very high. The demand for fibers having a specific color hue is increasing and, thus, there is a need to provide a method from which a color hue can be corrected to a specific color hue, and also within its tolerances during the fusion spinning procedure by the manufacturers themselves.
• Many factors adversely can affect the color hues in melt-spinning processes. Such factors can be differences in the raw materials including the polymer support; different suppliers for the same raw material including the polymer support; unpredictable changes in the solid-masterbatch used to coloring the polymer support; changes in the yarn structure itself or even changes in the line of melt spinning production, among others.
• Nowadays, once a change in the color hue of yarns and filaments is detected, there is no other remedy to correct it than to replace all the raw material including the polymer support with the solid-masterbatch dispersed therein, and often further to clean the screw of the extruder before adding a new batch with the corrected-color hue.
• Hence, it is necessary to provide a color-hue modifying method capable during production of colored synthetic yarns and/or filament of correcting deviations beyond tolerances in the color hue of those colored synthetic yarns and/or filaments. It is desirable that the method overcomes at least one of the drawbacks described above. It is desirable preventing and/or reducing rejections of the raw material, particularly present in the extruder, and/or the substitution of all the current raw material by a new batch having the color shade within the tolerances established by the manufacturer.
• Moreover, it is still desirable in the art that the manufacturer can do such correction in the color hue themselves. There is the need that the manufacturer of yarns and/or filaments themselves can correct the color hue of colored yarns and/or filaments during extrusion without generating high amounts of residues or even without the need for returning to the suppliers the raw material.
• Hence, it is also desirable in the art a method for color hue correction suitable for performing in the line melt-spinning production itself, without adversely affecting the yarns and filaments properties.
Description of the invention
• The present invention was made in view of the prior art described above.
• Therefore, in a first aspect, the invention provides a method for modifying the color hue of colored synthetic yarns and/or filaments, wherein such modification of the color hue is simultaneously a correction of the color hue of at least one of the colorants present in the colored synthetic yarns and/or filaments, such modification and/or correction being performed during the extrusion in a conventional melt-spinning procedure. Herein, synthetic yarns and/or filaments encompass yarns and/or filaments already made by synthetic polymers in a melt-spinning procedure, and molten fiber- and filament-forming synthetic polymers present in the extrusion line of the melt-spinning procedure.
• Herein, raw material includes thermoplastic resins as a polymer support in which a solid-masterbatch is dispersed. The raw material can optionally further include a liquid-masterbatch dispersed therein. These masterbatches are responsible, among others, for the coloration of the synthetic yarns and/or filaments.
• The method of correction of the color hue of colored synthetic yarns and/or filaments according to the present invention allows modifying the hue or shade of actual colored yarns and/or filaments to a target color hue when it is required. The "target" color hue is intended to mean a hue or shade value that is within the tolerances established by the manufacturer of the colored yarns and/or filaments. Therefore, the correction method of this invention is intended to return, when it deviates beyond tolerances, the "actual" color hue of the colored synthetic polymeric yarns and/or filaments to within the limits of the target color-hue tolerances. The actual color hue can be measured by using the most popular color spaces, chromaticity coordinates, defined by CIE Lab. According to the CIE Lab, the chromaticity coordinates are expressed as a* and b*.
• According to the present invention:
• a* and/or b* refer to the actual color-coordinate values measured in colored synthetic yarns and/or filaments, those values should be within the target color-hue tolerances; however, for at least one of the reasons explained above in the art, the actual color hue deviates beyond the tolerances, so the raw material should be replaced by a new batch having the "corrected" color hue to return the actual color hue to within the target color hue tolerance;
• a_t* and/or b_t* refer to color-coordinate values that are within the limits of tolerances, that is, the target color-coordinate values that give the target color hue in the colored synthetic yarns and/or filaments, or the ones that provide a color hue within the limits of tolerances in the colored synthetic yarns and/or filaments;
• am* and/or bm* refer to color-coordinate values measured once the colored synthetic yarns and/or filaments have been modified with the aim to correct the color hue.
• The method for modifying and/or correcting the color hue of colored synthetic yarns and/or filaments to a target hue in a conventional melt-spinning procedure is 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 the 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 is selected to be the same as present in the colored synthetic yarns and/or filaments those color hue is to be corrected;
• 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 during the extrusion of 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; and optionally
• verifying the corrected color hue in the corrected and colored synthetic yarns and/or filaments by taking new measurements of color coordinates a_m* and/or b_m* 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.
• The method of the invention is directed to correct the actual color hue of a colored synthetic yarns and/or filament, the correction comprising the modification of the actual color hue to a target color hue within the limits of target color hue tolerances established by the manufacturers themselves. Particularly, the method of the invention is directed to correct small deviations outside of the target color hue tolerances. Usually, the tolerances are a range, within which a variation of the color hue results imperceptible for a healthy human eye. Therefore, the range defining such tolerances does not form part of the invention. Usually, deviations outside the limits of the range of tolerances are perceptible to a healthy human eye. The method of the present invention corrects for deviations in yarns and/or filaments having an actual color hue that is beyond the limits of the target color hue tolerances range.
• The skilled person in the art would understand that the tolerances can be different depending on the requirements established by the manufacturer and/or depending on the particular technical field in which the colored synthetic yarns and/or filaments are to be used.
• In an embodiment, the method of the present invention is suitable for correcting deviations in the color hue outside the limits of tolerances, expressed as Δa and/or Δb, within a value of |3|, preferable within a value lower than |1|.
• Advantageously, the method of the present invention is capable of correcting deviations in the color hue with a high sensitivity, expressed as Δa and/or Δb.
• In an embodiment, the method is capable of correcting deviations in the color hue, expressed as Δa and/or Δb, as low as |0.1|, indeed as low as |0.08|, or as low as |0.05|.
• Therefore, it is provided a method of high sensitivity, which is suitable for correcting very low deviations outside of the tolerances of a color hue.
• The present invention does not intend to protect a melt spinning process, but a method for modifying the color hue of already colored synthetic yarns and/or filaments toward the target color hue during extrusion in a conventional melt-spinning process.
• In the state of the art, a correction in the color hue usually results in metameric problems in the yarns and/or filaments. Therefore, such corrections do not solve the main problem of manufacturers so they need a replacement of all raw material including the solid masterbatch, which is present in the yarns and/or filaments for coloring them, by a new batch with the corrected color hue.
• Surprisingly, the method of the first aspect of the present invention is suitable for performing such correction in the line melt-spinning production itself without adversely affecting the yarns and filaments properties thus corrected, and without generating metameric problems after correction.
• Advantageously, the method of the invention allows correcting the actual color hue deviations by the manufacturers themselves without requiring the replacement of the raw material (main polymer), nor the masterbatch (liquid or solid) responsible for coloring the yarns and/or filaments.
• A general explanation of a conventional melt-spinning process would be that polymer granules (main polymer) are melted, then, extruded through a spin head. The metering pump controls the flow of molten liquid to the spin head, where it is filtered before extrusion to ensure any unmelted granules are removed, which may cause weak points. The quench air cools the fibers as they emerge. A lubricant can be added then to spin the cooled filament and fibers, as the synthetic fibers are not conductive and therefore static can be problematic. The winding speed is a critical element to the alignment of the polymers in the fiber, which will influence the strength of the resultant fiber. The melt spun has a variety of benefits; at high scale, the molten polymer is sent directly to the extruder taking out the steps of granule production and melting. The temperatures required to form a melt solution of the desired viscosity are preferably those do not cause thermal degradation of the polymers during the fusion method. The melt-spinning process can be comprise of coloring the synthetic polymer yarns and/or filaments by adding masterbatch granules (solid) into the main polymer and, optionally, by further adding a liquid-masterbatch together with the solid-masterbatch.
• Advantageously, the method of the first aspect of the invention is capable of correcting the color hue of already colored synthetic yarns and/or filaments to different grades of hues directly by the manufacturers themselves.
• Unexpectedly, the authors of the present invention have found that the observed differences in the color coordinates, expressed as Δa and/or Δb, can be linked to a predesigned dose of a correcting liquid-masterbatch composition, the relationship being substantially linear, see Figures 1 and 2. The substantially linear relationship allows scaling the method at industrial scale and most importantly allows correcting the color hue by the manufacturers themselves.
• Therefore, the authors of the present invention have also designed a correcting liquid-masterbatch composition to be used during the extrusion of colored synthetic polymers forming yarns and/or filaments for correcting deviations outside of tolerances of the actual color hue to return to within the target color hue tolerances. The correcting liquid-masterbatch composition should comprise at least one colorant substantially the same as present in the raw material, which includes the main polymer, and a solid- and/or a liquid-masterbatch composition responsible for coloring the yarns and/or filaments.
• The fact that the correcting liquid-masterbatch composition comprises at least one colorant that is preferably as much as possible the same colorant responsible for coloring the synthetic yarns and/or filaments, allows overcoming the particular metameric problems of the prior art.
• As used herein the "same colorant responsible for coloring the colored synthetic yarns and/or filaments" means a colorant having the same Color Index (C.I.). The Color Index is defined as the Color Index International. Color Index International is a reference database jointly maintained by the Society of Dyers and Colorists and the American Association of Textile Chemists and Colorists. It currently contains over 27,000 individual products listed under 13,000 Color Index Generic Names. It is published solely on the World-Wide Web. The index serves as a common reference database of manufactured color products and is used by manufacturers and consumers, such as artists and decorators. Preferably, the same colorant means a colorant having equal C.I. values.
• Colorants (both dyes and pigments) are listed using a dual classification, which use the Color Index Generic Name (the prime identifier), and Color Index Constitution Numbers. These numbers are prefixed in Brazil and various other countries with C.I. or CI. This abbreviation is sometimes thought to be CL, due to the font used to display the information. A detailed record of products available on the market is presented under each Color Index reference. For each product name, Color Index International lists the manufacturer, physical form, and principal uses, with comments supplied by the manufacturer to guide prospective customers.
• Once an actual color hue deviation beyond the target color hue tolerances is identified, then, measurements of color coordinates, that is a* and/or b*, are taken in the colored synthetic yarns and/or filaments already prepared in a fusion spinning procedure. In this step, the colored synthetic yarns and/or filaments are the synthetic yarns and/or filaments after leaving the spinneret (see Fig 3).
• Thus, measurements of color coordinates can be performed in the synthetic yarns and/or filament texturized or not texturized. Measurements are taken by using means for taking a readout of the color hue coordinates (a* and/or b*). Preferable means of measurement is a spectrophotometer. The preferable spectrophotometer is the Datacolor 650 Spectrophotometer. The major features and functions of spectrophotometer are Illuminant conditions, Background and size differences, Fixed illumination/viewing angles, Spectral sensor, Color spaces, Color-difference measurement, Spectral reflectance graph display, Data communication, and Data memory among others.
• With the method of the first aspect, the need of the manufacturer to replace or to return to the suppliers the raw material responsible for the color and/or to clean the screw of the extruder is solved, whereby substantially reducing residues of waste material and providing a method more versatile for the manufacturers themselves.
• Moreover, the fact that the correction of the actual color hue can be performed with a dose having a linear relationship with the needed hue correction provides a practical and reliable method suitable for manufacturers.
• The correcting liquid-masterbatch composition, to result in the yarn and/or filament having a corrected color hue within the target color hue tolerances, can be prepared by dispersing at least one colorant in a liquid polymer carrier.
• The colorant can be any one with the proviso that at least one of the colorants included in the correcting liquid-masterbatch composition is selected to be the same as the colorant responsible for coloring the already colored yarns and/or filaments. In a preferable embodiment, at least one of the colorants included in the correcting liquid-masterbatch composition has the same color index value (C.I.) that one of the colorants included in the colored yarns and/or filaments.
• The liquid polymer carrier is selected to be compatible with the raw material used for preparing the fibers of yarns and filaments, that is, polymerically compatible with the main polymer and/or the carrier polymer of the masterbatch used for coloring the fibers in melt spinning. Polymerically compatible means that the polymers can be homogeneously mixed..
• Preferably, the liquid polymer carrier is stable at the temperatures employed in the extrusion line of the fusion spinning procedure. Preferable liquid polymer carrier is a liquid paraffin, heat resistant, more preferable of saturated hydrocarbon composition, still more preferably a mixture of inert oils of high heat resistant. A preferable oil has a liquid yellow appearance, an active content of 99.5 ± 0.5 %, a viscosity (40 °C) of 45 ± 10 mm²/s, and a density (20 °C) of 0.915 ± 0.01 g/ml or the like.
• The correcting liquid-masterbatch composition can be comprise of a dispersant. The dispersant agent can be sorbitan trioleate or polyoxyethylene/PEG (20) sorbitan monoestearate or the like.
• The correcting liquid-masterbatch composition can be comprise of an anti-caking agent. The anti-caking agent can be selected from the group consisting of tricalcium phosphate, powdered cellulose, magnesium stearate, sodium bicarbonate, sodium ferrocyanide, calcium phosphate, sodium silicate, silicon dioxide, talcum powder, stearic acid, or the like.
• Advantageously, the correction of the color hue by using the method defined in the first aspect of the invention minimizes the problems of metamerism that would appear if corrections are made in situ during extrusion in the melt spinning processes in the art. The correction allows returning the actual color hue of the colored yarns and/or filaments within the target color hue tolerances, so the corrected color hue of the newly colored yarn and/or filament cannot be distinguished by a healthy human eye from the target color hue.
• Therefore, the method of the invention is further suitable for solving metameric problems in fibers, particularly for automotive field.
• The correcting liquid-masterbatch composition can be supplied in one or several correcting liquid-masterbatch compositions.
• In an embodiment, the correcting liquid-masterbatch composition includes one colorant, also known as a single colorant dispersion.
• In another embodiment, the correcting liquid-masterbatch composition includes a mixture of colorants.
• In a still another embodiment, the correcting liquid-masterbatch composition can be a mixture of several correcting liquid-masterbatch compositions in which each one includes only one colorant, the mixture being the correcting composition suitable for correcting the deviations outside of tolerances of the color hue.
• In order to manage the degree of hue with high accuracy, it is preferable to have a dosage mixture of several dosages of individual correcting liquid-masterbatch compositions.
• The correcting-liquid-masterbatch composition can be added to the molten polymeric mass of colored synthetic yarns and/or filaments during the extrusion in an amount equal to or lower than 3% by weigh to the total weight of yarns and/or filaments. Preferably, the correcting liquid-masterbatch composition is added in an amount equal to or lower than 1% by weight, still more preferable between 0.1 to 0.6% by weight to the total weight of yarns and/or filaments. The correcting-liquid-masterbatch composition is added in the extrusion area where the main polymer and the masterbatch dispersed there are a molten mass of viscous fluid. The low percentage used achieves the goal that the physical properties of synthetic yarns and filaments are not adversely affected by the addition of the correcting liquid-masterbatch composition.
• In an embodiment, 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 the at least one of the colorants is selected to be the same as present in the colored synthetic yarns and/or filaments those color hue is desired to correct.
• The colorant included in the correcting-liquid-masterbatch composition can be selected from an organic pigment, an inorganic pigment or a solvent dye, 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.
• Preferable colorants are pigments having a structure of ftalocianine, antraquinone, quinacridone, ftalocianine, blue ultramar, carbon black, titanium dioxide. Examples of such pigments include a color index (C.I.) of pigment green 7 (organic), pigment yellow 147 (organic), pigment red 202 (organic), pigment blue 15:3 (organic), pigment blue 29 (inorganic), pigment black 7 (inorganic), or pigment white 6 (inorganic) or the like.
• The liquid polymer carrier concentration can be between 60 and 99% by weight to the total weight of the correcting liquid-masterbatch composition, preferably between 70 and 99% by weight, more preferably between 90 and 95% by weight.
• Preferable liquid polymer carrier is selected to have very low lubrication, high thermal stability, and no generation of gases in the melt spinning conditions.
• The colorant concentration can be between 1 and 40% by weight to the total weight of the correcting liquid-masterbatch composition, preferably between 1 and 30% by weight, more preferably between 5 and 10% by weight.
• In an embodiment, the correcting liquid-masterbatch composition can be prepared by using conventional Cowles stirrer and ball-mills. Thus, for example, in a Cowles stirrer the liquid polymer carrier can be added, then, the colorant(s); and the resultant mixture be stirred for a period between 30 min and 1 hour. The obtained dispersion can be moved to a ball-mill and stirred again for a period between 20 min and 5 hours.
• The total masterbatch amount that can be present in the colored synthetic yarns and/or filaments is desired to be equal to or lower than 10% by weight, preferable lower than 6% by weight. As explained herein, this total amount can be the sum of the concentration of the correcting liquid-masterbatch composition plus the concentration of a solid- and/or a liquid-masterbatch previously added and present in the colored synthetic yarns and/or filaments for polymer support coloring purposes in a melt spinning process.
• A skilled person would understand by the content of the invention that the solid- or liquid-masterbatch present in the colored synthetic yarns and/or filaments itself do not form part of the present invention. The skilled person is aware that these solid- or liquid-masterbatches can include more than one colorant and/or additives dispersed in a solid polymer carrier. The solid polymer carrier can be a polybutyleneterephthalate (PBT), polyethyleneterephthalate (PET), polytrimethyleneterephthalate (PTT), polylactic acid (PLA), polyethylene, polyamide, polypropylene or co-polyester (COPET). The additives usually are lubricants, anti-static, plasticizers, stabilizers, antioxidants, compatibilizing agents, flame-retardants as well as mixtures thereof.
• The polymer support or main polymer can be a thermoplastic resin, which is selected from polyester, polyamide, polypropylene, polyethyleneterephthalate (PET), polybutyleneterephthalate (PBT), polytrimethyleneterephthalate (PTT), or polylactic acid (PLA), polyethylene, preferably polyester or polyamide. The skill person in the art is also aware that many others synthetic polymers are suitable for forming synthetic yarns and/or filaments.
• In a second aspect, the present invention provides a system suitable for performing the method defined in the first aspect of the invention.
• Thus, according to the second aspect, the invention provides a system for modifying the color hue of colored synthetic yarns and/or filaments to a target color hue including limits of tolerances during extrusion in a conventional fusion spinning process by using the method and correcting-liquid-masterbatch composition defined in the first aspect, the system comprising:
• extrusion means adapted and configured for producing colored synthetic yarns and/or filaments in fusion spinning process, which comprises:
  • ∘ an extruder configured and adapted to receive, in use, a polymer support and a solid and/or a liquid masterbatch composition responsible for coloring the polymer support;
  • ∘ polymer supplying means configured and adapted for supplying, in use, the polymer support to the extruder to which it is coupled;
  • ∘ masterbatch supplying means configured and adapted for suppling, in use, the solid and/or a liquid masterbatch composition to the extruder to which it is coupled;
and is characterized in that the system further comprises:
• a portable equipment, which comprises:
  • ∘ housing means configured and adapted for housing a correcting liquid-masterbatch composition;
  • ∘ correction supplying means associated to the housing means, and configured for supplying, in use, a dose of the correcting liquid-masterbatch composition to the extruder to which they are coupled;
• colorimetric readout means associated to the extruder for taking of a readout of actual color-hue-coordinates, that is a*, b*, of the synthetic colored yarns and/or filaments to compare them with the stored target-color-hue-coordinates, that is a_t*, b_t*, in order to determine differences, if any, in the color-hue-coordinates, that is Δa and/or Δb, beyond limits of target color hue tolerances, and
• electronic processor means associated to such differences beyond limits of tolerances in the color-hue-coordinates, that is Δa, Δb, by means of the colorimetric readout means for generating a dose-indicative signal of the correcting liquid-masterbatch composition housed in the portable equipment, and further operatively connected to the correction supplying means for supplying, in use, a dose of the correcting liquid-masterbatch composition during extrusion of the colored synthetic yarns and/or filaments to the extrusion means;
and in that, the extrusion means are further configured and adapted for receiving, in use, the dose of the correcting liquid-masterbatch composition for modifying the actual color hue of the colored synthetic yarns and/or filaments to the target color hue within limits of tolerances, resulting in an acceptable corrected color hue.
• Advantageously, the differences in the color-hue-coordinates (Δa, Δb) can be easily converted into a dose of the correcting liquid masterbatch composition due to a substantially linear relationship between them (as seen in Figures 1 and 2), thereby providing a system for correcting actual color hue during the melt spinning process by the manufacturers themselves. Without undue experimentation, a person skilled in the art of authoring technology software can write one or more computer programs to facilitate the selecting and dosing of the correcting liquid-masterbatch composition to alter the actual color hue yarns and/or filaments into the corrected color hue yarns and filaments.
• In an embodiment, the system comprises:
• an extruder assembly adapted and configured to produce colored synthetic yarns and/or filaments in fusion spinning process, which comprises:
  • ∘ an extruder configured and adapted to receive, in use, a polymer support and a solid and/or a liquid masterbatch composition responsible for coloring the polymer support;
  • ∘ polymer supplying apparatus configured and adapted to supply, in use, the polymer support to the extruder to which it is coupled;
  • ∘ masterbatch supplying apparatus configured and adapted to supply, in use, the solid and/or a liquid masterbatch composition to the extruder to which it is coupled;
wherein the system further comprises:
• a portable equipment comprising:
  • ∘ housing apparatus configured and adapted to house a correcting liquid-masterbatch composition;
  • ∘ correction supplying apparatus associated to the housing means, and configured to supply, in use, a dose of the correcting liquid-masterbatch composition to the extruder to which they are coupled;
• a colorimetric readout apparatus to take of a readout of actual color-hue-coordinates, that is a*, b*, of the synthetic colored yarns and/or filaments to compare them with the stored target-color-hue-coordinates, that is a_t*, b_t*, in order to determine differences, if any, in the color-hue-coordinates, that is Δa, Δb, beyond limits of target color hue tolerances, and
• an electronic processor apparatus associated to such differences beyond limits of tolerances in the color-hue-coordinates, that is Δa, Δb, by means of the colorimetric readout apparatus to generate a dose-indicative signal of the correcting liquid-masterbatch composition housed in the portable equipment, and further operatively connected to the correction supplying apparatus to supply, in use, a dose of the correcting liquid-masterbatch composition during extrusion of the colored synthetic yarns and/or filaments to the extrusion means;
• And wherein, the extrusion assembly is further configured and adapted to receive, in use, the dose of the correcting liquid-masterbatch composition for modifying the actual color hue of the colored synthetic yarns and/or filaments to the target color hue within limits of tolerances, resulting in an acceptable corrected color hue.
• The correction supplying means, which can be a correction supplying apparatus, are configured for supplying, in use, to the extruder one or several dosages of correcting liquid-masterbatch composition/s.
• The correction supplying means or the correction supplying apparatus can be a hopper or the like.
• In an embodiment, the correction supplying means or the correction supplying apparatus are positioned at a position proximal to the spinneret plate. As closest to the spinneret plate is the position of the correction supplying means or apparatus more preferable is the use of a pump capable of exceeding the pressure at this position. In an embodiment, the correction supplying means or apparatus can be a pump capable to exceed the required pressure at the position in the extruder where the correction supplying means or apparatus is coupled.
• In another embodiment, the correction supplying means or correction supplying apparatus, are positioned at a position proximal to the masterbatch or polymer supplying means or polymer supplying apparatus.
• In the embodiment seen in Fig. 4.2, the portable equipment comprises several housing means or several housing apparatus, each one independently configured and adapted for housing therein one correcting liquid-masterbatch composition. Preferably, each of these correcting-liquid-masterbatch compositions comprises only one colorant dispersed in the liquid polymer carrier. The portable equipment further comprises masterbatch-mixing means, which can be a masterbatch-mixing apparatus,configured and adapted for mixing the several doses in order to supply a mixture of the doses to the extruder to which is coupled. In this embodiment, the electronic processor means, which can be an electronic processor apparatus, are further operatively connected to the masterbatch mixing means for generating a dose-indicative signal of the mixture, in use, to be supplied to the extruder to which it is coupled.
• In a further aspect, the present invention also relates to the use of a correcting-liquid-masterbatch composition during the extrusion in a conventional melt-spinning process, the composition being as defined in the first aspect of the invention for correction of the color-hue of colored synthetic yarns and/or filaments within limits of tolerances.
• The method and system of the present invention provide at least one of the following advantages:
• reproducibility batch to batch, that is, the differences batch to batch are imperceptible to the healthy human eye;
• maximum flexibility for the manufacturer for correction of deviations beyond tolerances in situ, and optionally for adding a liquid masterbatch composition to the extruder in an accurate way;
• simple and low cost technology;
• technology can be applicable to medium and small productions;
• refinement for color changes;
• maximal absence of off-spec color;
• maximal color fastness;
• maximal mechanical properties.
Definitions
• According to the scope of the present invention, the terms "hue" or "hue color" is intended to mean one of the three-color attributes known in the field of colors, in addition to lightness and saturation. The three elements put together create the known three-dimensional solid. Hues form the outer rim of the solid, with lightness as the center axis and saturation as the horizontal spokes. Hue is the term used in the world of color for the classifications of red, yellow, blue, etc. Also, although yellow and red are two completely different hues, mixing yellow and red together results in orange, which in sometimes referred to as yellow-red, mixing yellow and green results in yellow-green, mixing blue and green results in blue-green, and so on. The continuum of these hues results in the color wheel.
• According to the scope of the present invention, the L* a* b* color space (also referred to as CIE Lab) is presently one of the most popular color spaces for measuring object color and is widely used in virtually all fields. It is one of the uniform color spaces defined by CIE. In this color space, L* indicates lightness and the terms "a*" and "b*" are the chromaticity coordinates. The "a*" and "b*" are represented in the chromaticity diagram, known by a person with general knowledge in this field. In the diagram, the a* and b* indicate color directions: +a* is the red direction, -a* is the green direction, +b* is the yellow direction, and -b* is the blue direction. The center is achromatic; as the a* and b* values increase and the point moves out from the center, the saturation of the color increases. In the L*a*b* color space, color difference can be expressed as a single numerical value, ΔE*ab, which indicates the size of the color difference but not in what way the colors are different.
• The ΔE*ab is defined by the following equation: $$\mathrm{\Delta E}\ast \mathit{ab}=\sqrt{{\left(\mathrm{\Delta L}\ast \right)}^2+{\left(\mathrm{\Delta a}\ast \right)}^2+{\left(\mathrm{\Delta b}\ast \right)}^2}$$

  
• Taking a measurement with a spectrophotometer and displaying the results on a spectral reflectance graph, it can be seen the nature and location in color space of a yarn and filament's color.
• According to the scope of the present invention, the term "metamerism" is intended to mean when two colors appear the same under one light source but different under another. For metameric objects, the spectral reflectance characteristics of the colors of the two objects are different, but the resulting tri-stimuli values are the same under one light source and different from each other under another. If a person looks at the spectral reflectance curves for the two specimens, he can immediately see that they are different. However, the L*a*b* values for measurements under Standard Illuminant A are different from each other. This shows that even though the two specimens have different spectral reflectance characteristics, they would appear to be the same color under daylight (Standard Illuminant D65). To evaluate metamerism, it is necessary to measure the specimens under two or more illuminants with very different spectral power distributions, such as Standard Illuminant D65, Standard Illuminant A, and Standard Illuminant F11.
• In the present invention, the metamerism will exist when differences in the color coordinates Δa and/or Δb are perceptible to the healthy human eye.
Brief Description of the Drawings
• Figure 1 is a graph showing the variation of the color coordinate a* according to Example 1 with respect to a colorant percentage increase of 0.03, 0.06, 0.12 and 0.20% by weight to the weight of a colored yarn. This figure shows the substantially linear relationship between the variation of the color coordinate a* with respect to the dosages of correcting-liquid-masterbatch compositions containing the colorant percentage. See Tables 4 to 7, wherein the correspondence of the colorant percentage to the correcting-liquid masterbatch dosage is included.
• Figure 2 is a graph showing the variation of the color coordinate b* according to Example 1 with respect to a colorant percentage increase of 0.03, 0.06, 0.12 and 0.20% by weight to the weight of a colored yarn. This figure shows the substantially linear relationship between the variation of the color coordinate b* with respect to the dosages of correcting liquid-masterbatch compositions containing the colorant percentage. See Tables 4 to 7, wherein the correspondence of the colorant percentage to the correcting-liquid masterbatch dosage is included.
• Figure 3 depicts a schematic view of a fusion spinning system, wherein the extrusion means 1 is configured and adapted to receive, in use, a dose of the correcting liquid-masterbatch composition of a portable equipment 2 during the extrusion of the synthetic yarns and/or filaments in the extruder 10 to which it is coupled. In this embodiment, the portable equipment 2 is positioned at a position proximal to the spinneret plate. However, the portable equipment 2 can be positioned in any other position along the extruder 10.
• Figure 4 . 1 depicts a detailed view of an embodiment of the portable equipment 2 of the invention, showing one reservoir as housing means 20 configured and adapted to house therein a correcting-liquid-masterbatch composition. The portable equipment 2 comprises correction-supplying means 21 coupled to the housing means 20 for supplying, in use, a dose of the correcting-composition to the extrusion means 1.
• Figure 4 . 2 depicts a detailed view of another embodiment of the portable equipment 2 of the invention, showing three reservoirs as housing means 20, each one independently, configured and adapted to house therein a correcting liquid-masterbatch composition. The portable equipment 2 comprises correction-supplying means 21 coupled to the housing means 20. In this embodiment, the portable equipment 2 further comprises a static mixer as masterbatch-mixing means 22 coupled to the correction supplying means 21 for mixing several dosages of the correcting liquid-masterbatch compositions housed in the reservoirs for supplying, in use, a mixture of dosages to the extrusion means 1.
• Figure 5 is a processor-operating scheme showing the electronic processor means 4, which are operatively connected to the colorimetric readout means 3 to generate a dose-indicative signal of the correcting liquid-masterbatch composition contained in the portable equipment 2. The electronic processor means 4 are associated to the colorimetric readout means 3 for supplying, in use, a dose thereof to the extrusion means 1.
Detailed Description of the Invention
• Hereinafter, the best mode for carrying out the present invention is described in detail making reference to Figure 3-5.
• A variety of extrusion equipment exists and choosing which to use will depend on the characteristics and properties of the product to be extruded. The preferable equipment is a corotating twin-screw extruder, characterized by the fact that its screws rotate in the same direction. This extrusion equipment transfers a large amount of mechanical energy (called shear force) to the material, enabling large amounts of colorants and/or additives to be dispersed. The configuration of the screws is essential in order to guarantee good productivity and optimum product quality. The screws are composed of different assembled elements, which according to their geometry and position, distribute, disperse or transport the material.
• The starting point for melt spinning are the thermoplastic polymers (referred to also as synthetic polymer, main polymer or polymer support) in the form of chips, granulate or pellets, which are added through the polymer supplying apparatus 11 such a feeder or similar to the extruder 10, wherein they are melted forming a viscous fluid mass. The viscous mass is dosed by means of a volumetric pump to a filtration system and a plate with holes called spinneret (Fig. 3). The molten polymer is forced through spinneret holes at high pressure, obtaining a series of filaments that together will form the yarn. The cooling of the viscose mass at the outlet of the spinneret plate is carried out by a controlled flow of air, the filaments are then lubricated with a sizing oil emulsion and are finally wound on a bobbin.
• Usually, the thermoplastic polymer comprises a solid- and/or a liquid-masterbatch dispersed therein, which is added by means of a gravimetric system, or in viscose form by means of lateral extruder, in the extrusion area for forming the fiber with the desired properties. Masterbatch supplying apparatus 12 such a hopper (Fig. 3), or a lateral extruder (not represented) or similar can be coupled to the extruder assembly 1 for such purpose.
• Profile of temperatures in the extruder 10 can be modified according to the dimensions of the extruder 10, the time the molten mass is there or the particularities of the type of the used extrusion equipment, as utilized and determined by the skilled person.
• In this embodiment, the correcting-liquid-masterbatch composition is added by means of the portable equipment 2 in a proximal position to the spinneret (Fig. 3). At this position, the correcting-liquid-masterbatch composition is added under pressure to the extruder 10. Preferably, the correction-supplying apparatus 21 includes a variable frequency drive, and a dosing pump (not shown) configured and adapted to supply under pressure the dose of the correcting liquid-masterbatch composition from the reservoir 20 to the extruder 10 to which it is coupled (Figs. 4.1 and 4.2).
• Fig. 4.2 shows the portable equipment 2, which further comprises more than one housing apparatus 20 (reservoir), each one independently, configured and adapted to house therein a correcting-liquid-masterbatch composition; the liquid-masterbatch mixing apparatus 22 is configured and adapted to mix several dosages of the correcting-liquid-masterbatch compositions housed in the housing apparatus 20 and to supply, in use, the mixture to the extrusion assembly 1 to which it is coupled. Preferable liquid-masterbatch mixing apparatus 22 is a static mixer.
• The colorimetric readout apparatus 3 is used for taking of a readout of the actual color-hue-coordinates (a*, b*) in the colored synthetic yarns and/or filaments obtained in melt-spinning process.
• These measurements are compared, preferably using computer software programs for speed and reliability, with the stored target-color-hue-coordinates (a_t*, b_t*) in order to determine deviations in the color-hue-coordinates (Δa, Δb) beyond limits of target color hue tolerances. These deviations have a linear relationship with the dose of the correcting liquid-masterbatch composition for correcting the color hue deviations and return the actual color hue to the target color hue tolerance value (Figs 1 and 2).
• The electronic processor apparatus 4 associated to these deviations by a linear relationship with the dose of the correcting liquid-masterbatch composition, preferably using computer software programs for speed and reliability, generates a dose-indicative signal of the dose, in use, to be supplied to the extrusion assembly 1. The extrusion assembly 1 configured and adapted to receive, in use, the dose of the correcting liquid-masterbatch composition of the portable equipment 2 allows adding the dose for correcting the actual color hue of the colored synthetic yarns and/or filaments to the extruder 10 during the extrusion of the colored synthetic polymer for forming fiber and/or filaments. The resulting corrected color hue of the yarns and/or filaments is within the target color hue tolerances.
• Preferable colorimetric readout apparatus 3 is a spectrophotometer. The spectrophotometer takes measure differences in the yarn's color. The yarn and/or filament can be texturized or not. A preferable spectrophotometer is the Datacolor 650 Spectrophotometer those main features are included below: Datacolor 650/600/400 Instrument Specifications

  ITEM	DESCRIPTION
  Instrument Type	Dual beam integrating sphere with xenon flash lamp.
  Measuring Geometry	Diffuse illumination, 8º viewing in conformance with CIE publication No. 15.2 Colorimetry.
  Illumination Source	Pulsed xenon, filtered to approximate D65.
  Sphere Diameter	152 mm / 6.0 inches
  Specular Port	Automated specular included or specular excluded
  Spectral Analyzer	Proprietary SP 2000 analyzer with dual 256-diode array and
  	high-resolution holographic grating.
  Wavelength Range	360 - 700nm
  Photometric Range	0 to 200%
  Black Trap	High performance
  Aperture Configuration	Large Area View. 30mm illuminated/ 26mm viewed
  	Medium Area View. 20mm illuminated/ 16mm viewed
  	Small Area View. 9mm illuminated/ 5mm viewed
  	Ultra-Small Area View. 6.5mm illuminated/ 2.5mm viewed
  	X-Ultra Small Area View. 3mm illuminated/ 2.5mm viewed
  Power	85 to 264 VAC, 47 to 63 Hz, 80 VA peak, 35 VA typical
  Absolute Operating Environment	5º to 40º C, 5% to-85% RH, non-condensing
  Interface	Serial: RS232, 9600/115200 baud (shipped as 19200)
  	USB: 1.1 or higher

  Dimensions	Metric
  Height	325 mm
  Width	312 mm
  Depth	471 mm
  Weight	14.97 mm

  Features by Model 650

  FEATURE	Model 650
  Reporting Interval	5 or 10nm**
  Effective Bandwidth	5 or 10nm**
  20 Read Repeatability on WhiteTile Using Dual Flash (CIELAB)	0.015 (max)
  Inter-instrument Agreement-Reflectance	0.15 (max)
  Measurements* (CIEL*a*b*)	0.08 (avg)
  Transmittance Measurements	Yes***
  Inter-instrument Agreement for Regular Transmittance	±0.20% at 85%T
  (550 nm)*	±0.10% at 32% T
  Inter-instrument Agreement for Diffuse Transmittance (550 nm)*	±.40% at 42% T
  Inter-instrument Agreement for Transmission Haze Measurements*	±0.15% at 10% TH
  Lens	4 position auto-zoom
  Aperture Plates	4 standard
  	LAV
  	SAV
  	USAV
  	MAV barium coated
  	2 optional
  	MAV
  	XUSAV
  Aperture Detection	Yes
  Automated, adjustable UV Calibration	Yes
  UV Cutoff Filters	400 nm
  	420 nm
  	460nm
  Remote Measurement Button	Yes
  Vertical Mount****	No

  * Measurements made at 23º C +/- 1º C. ** Software must be capable of 5nm reporting *** Capable of measuring regular, total and diffuse transmission **** Includes sample viewer assembly

• Standard Illuminants have been used to determinate the color coordinates.
• The Standard Illuminants to determinate the color coordinates (a*, b*), the target color coordinates (a_t*, b_t*), the modified color coordinates (a_m*, b_m*), or the differences in the color coordinates (Δa, Δb) have been the Standard Illuminant D65, the Standard Illuminant A, and Standard Illuminant F11.
• According to the common general knowledge, "Standard Illuminant D65" is defined as the average daylight (including ultraviolet wavelength region) with a correlated color temperature of 6504K; should be used for measuring specimens, which will be illuminated by daylight including ultraviolet radiation.
• According to the common general knowledge, "Standard Illuminant A" is defined as the incandescent light with a correlated color temperature of 2856K; should be used for measuring specimens, which will be illuminated by incandescent lamps.
• According to the common general knowledge, "Standard Illuminant F11" represents a narrow tri-band fluorescent of 4000° Kelvin color temperature, CRI 83. TL84 represents a Philips narrow tri-band fluorescent lamp (4000° Kelvin, similar to CIE illuminant F11) typically found in Marks & Spencer stores in Europe. In practice, CIE F11 and Philips TL84 illuminants are similar. The difference in color values calculated using F11 and TL84 should be very close in absolute values and would agree in differences.
Examples
• Hereinafter, the present invention is disclosed in more detail and specifically with reference to the Examples and Figures, which however are not intended to limit the present invention.
Examples Example 1: Modification system by using a correcting liquid-masterbatch composition in a fusion spinning process with the method of the present invention
• The polymer support was polyester having a solid-masterbatch dispersed therein.
• Spinning a gray polyester yarn was carried out by dosing a solid masterbatch. The solid masterbatch was developed for the mass coloring of threads for the manufacture of fabrics for upholstering car seats. The demands of color in this automotive sector are extremely high and deviations between batches are not tolerated.
• The solid-masterbatch (solid-M) was prepared with the following pigments: PIGMENT BLACK 7, PIGMENT BLUE 29, PIGMENT GREEN 7, PIGMENT WHITE 6, PIGMENT RED 202. The solid-M contained 16.4% by weight of pigment in total. To obtain the final color, the dosage of this solid-M on the total weight of polyester is 2.5%. This implies that "on fiber" the amount of colorant contributed will be 0.41% (16.4 x 2.5/100).
• The extruded yarn was textured by air. Then, a fabric was knitted from this yarn. This fabric was placed in the sample holder of a Datacolor 650 spectrophotometer. Averaged readings were made in the spectrophotometer to determine the coordinates L*, a* and b*. The results for each of the three illuminants used were the following seen in Table 1:

  Table 1
  Polyester polymer with 2.5% wt. of the above prepared solid-M
  Ilum./Obs.	L*	a*	b*
  D65 10 Deg	32.56	0.35	0.98
  A 10 Deg	32.67	0.64	1.11
  F11 10 Deg	36.65	0.33	1.16

• As liquid masterbatches (liquid-M) ready for color correction, the compositions shown below in Table 2 were prepared and ready for use.

  Table 2
  Liquid Masterbatch (L-M)	Yellow-pigment	Red-pigment	Green-pigment	Blue-pigment
  Color index (C.I.)	P. Y. 147	P. R. 202	P. G. 7	P. BI. 15:3
  % PIGMENT	50 %	35%	38 %	44 %

• Four different corrections in an incremental way, for each pigment, were performed to demonstrate the correction capacity of the method of the invention.
• The following dosages of liquid-masterbatches (L-M) were added to the colored yarn during extrusion, as seen in Table 3:

  Table 3
  Assay	solid-M contained in the yarn	Yellow-L-M	Red-L-M	Green-L-M	Blue-L-M
  1	2.5 %	0.060%	0.086%	0.079%	0.068%
  2	2.5 %	0.120%	0.171%	0.158%	0.136%
  3	2.5 %	0.240%	0.343%	0.316%	0.273%
  4	2.5 %	0.400%	0.571%	0.526%	0.455%

• The total pigment percentage on the yarn as well as the pigment percentage of the correcting-liquid-M added to correct the color hue, and of the solid-M already contained in the colored yarn are included below for each of the colors, as seen in Tables 4-7:

  Table 4
  Assay	solid-M contained in the yarn		Yellow-L-M		% total pigment on the yarn
  	Dosage	% pigment on the yarn	Dosage	% pigment on the yarn
  1	2.5 %	0.41 %	0.060%	0.03 %	0.44%
  2	2.5 %	0.41 %	0.120%	0.06 %	0.47%
  3	2.5 %	0.41 %	0.240%	0.12 %	0.53%
  4	2.5 %	0.41 %	0.400%	0.20 %	0.61%

  Table 5
  Assay	solid-M contained in the yarn		Red-L-M		% total pigment on the yarn
  	Dosage	% pigment on the yarn	Dosage	% pigment on the yarn
  1	2.5 %	0.41 %	0.086%	0.03 %	0.44%
  2	2.5 %	0.41 %	0.171%	0.06 %	0.47%
  3	2.5 %	0.41 %	0.343%	0.12 %	0.53%
  4	2.5 %	0.41 %	0.571%	0.20 %	0.61%

  Table 6
  Assay	solid-M contained in the yarn		Green-L-M		% total pigment on the yarn
  	Dosage	% pigment on the yarn	Dosage	% pigment on the yarn
  1	2.5 %	0.41 %	0.079%	0.03 %	0.44%
  2	2.5 %	0.41 %	0.158%	0.06 %	0.47%
  3	2.5 %	0.41 %	0.316%	0.12 %	0.53%
  4	2.5 %	0.41 %	0.526%	0.20 %	0.61%

  Table 7
  Assay	solid-M contained in the yarn		Blue-L-M		% total pigment on the yarn
  	Dosage	% pigment on the yarn	Dosage	% pigment on the yarn
  1	2.5 %	0.41 %	0.068%	0.03 %	0.44%
  2	2.5 %	0.41 %	0.136%	0.06 %	0.47%
  3	2.5 %	0.41 %	0.273%	0.12 %	0.53%
  4	2.5 %	0.41 %	0.455%	0.20 %	0.61%

• After each dosage, the corresponding yarn was collected and knitted fabrics equivalent in structure to the first one made were prepared. Each of the fabrics was placed in the sample holder of the spectrophotometer and readings were made.
• The results of the color difference obtained by comparison with the initial sample of colored yarn (made of polyester polymer and 2.5% by weight of solid-M) were as follows in Tables 8 - 11 for yellow, red, green, and blue, respectively. In each Table, the first measurements are of the composition with only solid masterbatch, followed by the composition also including liquid masterbatch, followed by color difference between the two compositions (assessed under three different illuminants).

  Table 8
  Dose of Yellow-L-M (Yellow-liquid-masterbatch)
  Sample Colored synthetic yarn composition: Polyester polymer + 2.5% wt. of solid-M	Ilum./Obs.	L*	a*	b*
  	D65 10 Deg	32.73	0.36	1.01

  Sample + dose of correcting liquid-M, expressed in wt. (dose of Yellow-L-M)	Ilum./Obs.	L*	a*	b*
  0.06%	D65	10 Deg	32.75	-0.09	2.63
  0.12%	D65	10 Deg	32.68	-0.45	4.19
  0.24%	D65	10 Deg	32.46	-1.04	7.02
  0.40%	D65	10 Deg	32.21	-1.59	9.91

  Color Difference CIE LAB Sample + dose of correcting liquid-M, expressed in wt. (dose of Yellow-L-M)	Ilum./Obs.	ΔL*/SL	Δa*	Δb*	CIE ΔE
  0.06%	D65	10 Deg	0,02	-0.46	1.61	1.82
  0.06%	A	10 Deg	0,08	-0.08	1.62	1.75
  0.06%	F11	10 Deg	0,09	-0.34	1.78	1.93
  0.12%	D65	10 Deg	-0.05	-0.81	3.17	3.27
  0.12%	A	10 Deg	0.07	-0.1	3.19	3.19
  0.12%	F11	10 Deg	0.03	-0.54	3.43	3.48
  0.24%	D65	10 Deg	-0.27	-1.41	6.01	6.19
  0.24%	A	10 Deg	0.05	-0.12	6.05	6.06
  0.24%	F11	10 Deg	-0.01	-0.94	6.51	6.59
  0.40%	D65	10 Deg	-0.52	-1.95	8.9	9.11
  0.40%	A	10 Deg	-0.3	-0.14	8.94	8.95
  0.40%	F11	10 Deg	-0.34	-1.29	9.63	9.72

  Table 9
  Dose of Red-L-M (Red-liquid-masterbatch)
  Sample--Colored synthetic yarn composition: Polyester polymer + 2.5% wt. of solid-M	Ilum./Obs.	L*	a*	b*
  	D65 10 Deg	32.56	0.35	0.98

  Sample + dose of correcting liquid-M, expressed in wt. (dose of Red-L-M)	Ilum./Obs.	L*	a*	b*
  0.09%	D65	10 Deg	30.81	0.91	0.18
  0.17%	D65	10 Deg	30.16	1.47	-0.44
  0.34%	D65	10 Deg	29.41	2.68	-1.6
  0.57%	D65	10 Deg	27.77	3.9	-2.6

  Color Difference CIE LAB Sample + dose of correcting liquid-M, expressed in wt. (dose of Red-L-M)	Ilum./Obs.	ΔL*/SL	Δa*	Δb*	CIE ΔE
  0.09%	D65	10 Deg	-1.75	0.57	-0.79	2
  0.09%	A	10 Deg	-1.74	0.65	-0.73	2
  0.09%	F11	10 Deg	-1.67	0.7	-0.67	1.93
  0.17%	D65	10 Deg	-2.4	1.12	-1.42	3.01
  0.17%	A	10 Deg	-2.38	1.27	-1.29	2.99
  0.17%	F11	10 Deg	-2.23	1.33	-1.18	2.85
  0.34%	D65	10 Deg	-3.15	2.33	-2.57	4.68
  0.34%	A	10 Deg	-3.07	2.58	-2.28	4.61
  0.34%	F11	10 Deg	-2.89	2.75	-2.23	4.57
  0.57%	D65	10 Deg	-4.79	3.55	-3.57	9.11
  0.57%	A	10 Deg	-4.65	3.83	-3.08	8.95
  0.57%	F11	10 Deg	-4.44	4.14	-3.14	9.72

  Table 10
  Dose of Green-L-M (Green-liquid-masterbatch)
  Sample Colored synthetic yarn composition: Polyester polymer + 2.5% wt. of solid-M	Ilum./Obs.	L*	a*	b*
  	D65 10 Deg	32.22	0.34	0.99

  Sample + dose of correcting liquid-M, expressed in wt. (dose of Green-L-M)	Ilum./Obs.	L*	a*	b*
  0.08%	D65	10 Deg	31.98	-0.59	0.82
  0.16%	D65	10 Deg	31.84	-1.5	0.66
  0.32%	D65	10 Deg	31.37	-3.05	0.45
  0.53%	D65	10 Deg	30.66	-4.68	0.21

  Color Difference CIE LAB Sample + dose of correcting liquid-M, expressed in wt. (dose of Green-L-M)	Ilum./Obs.	ΔL*/SL	Δa*	Δb*	CIE ΔE
  0.08%	D65	10 Deg	-0.23	-0.93	-0.17	0.97
  0.08%	A	10 Deg	-0.35	-1.01	-0.41	1.14
  0.08%	F11	10 Deg	-0.29	-0.99	-0.25	1.06
  0.16%	D65	10 Deg	-0.37	-1.84	-0.33	1.91
  0.16%	A	10 Deg	-0.6	-2	-0.8	2.24
  0.16%	F11	10 Deg	-0.49	-1.98	-0.48	2.1
  0.32%	D65	10 Deg	-0.84	-3.39	-0.54	3.53
  0.32%	A	10 Deg	-1.26	-3.66	-1.41	4.12
  0.32%	F11	10 Deg	-1.08	-3.6	-0.82	3.85
  0.53%	D65	10 Deg	-1.56	-5.01	-0.78	5.31
  0.53%	A	10 Deg	-2.17	-5.41	-2.07	6.18
  0.53%	F11	10 Deg	-1.9	-5.32	-1.18	5.77

  Table 11
  Dose of Blue-L-M (Blue-liquid-masterbatch)
  Sample Colored synthetic yarn composition: Polyester polymer + 2.5% wt. of solid-M	Ilum./Obs.	L*	a*	b*
  	D65 10 Deg	32.6	0.32	0.91

  Sample + dose of correcting liquid-M, expressed in wt. (dose of Blue-L-M)	Ilum./Obs.	L*	a*	b*
  0.07%	D65	10 Deg	31.54	-1.95	-0.25
  0.14%	D65	10 Deg	30.81	-3.41	-1.5
  0.27%	D65	10 Deg	28.83	-5.07	-3.15
  0.46%	D65	10 Deg	27.84	-6.85	-4.92

  Color Difference CIE LAB Sample + dose of correcting liquid-M, expressed in wt. (dose of Blue-L-M)	Ilum./Obs.	ΔL*/SL	Δa*	Δb*	CIE ΔE
  0.07%	D65	10 Deg	-1.05	-2.27	-1.16	2.76
  0.07%	A	10 Deg	-1.4	-2.78	-1.77	3.58
  0.07%	F11	10 Deg	-1.23	-2.38	-1.46	3.05
  0.14%	D65	10 Deg	-1.78	-3.73	-2.41	4.79
  0.14%	A	10 Deg	-2.39	-4.49	-3.46	6.15
  0.14%	F11	10 Deg	-2.07	-3.92	-2.89	5.29
  0.27%	D65	10 Deg	-3.76	-5.39	-4.06	7.72
  0.27%	A	10 Deg	-4.68	-6.47	-5.65	9.78
  0.27%	F11	10 Deg	-4.19	-5.58	-4.79	8.46
  0.46%	D65	10 Deg	-4.75	-7.17	-5.83	10.39
  0.46%	A	10 Deg	-6.01	-8.64	-8.03	13.24
  0.46%	F11	10 Deg	-5.37	-7.23	-6.87	11.33

• It can be seen that the biggest difference of Δa is with Blue-M-L, followed by Green-M-L and the one that varies least is the Yellow-M-L. And the biggest difference of Δb is with Yellow-M-L, followed by Blue-M-L and the one that varies least is Green-M-L.
• Figures 1 and 2 show with more detail the variation of the coordinate "a*" and the coordinate "b*" as result of the dosage of the liquid masterbatch composition. As can be seen in the two Figures, the behavior is practically linear. Both with the Yellow-L-M as with Green-L-M it can be seen that they are very selective in their effect: Yellow-L-M practically only affects the coordinate b, and Green-L-M practically only affects the coordinate a. In the case of Red-L-M and of Blue-L-M the color variation affects the two coordinates in a very important way. In many cases, these deviations may be desirable.
• Nevertheless, if only is required to correct one coordinate, then, it can be done by combining two correcting liquid masterbatch compositions according to the following indications: To correct coordinate "a" in the positive sense without any change in the coordinate "b", it is sufficient to dose the required red-L-M with a small proportion of yellow-L-M. Usually 1/10 of the red amount in yellow would be correct; and to correct coordinate "b" in the negative sense without any change in the coordinate "a", it is sufficient to dose the required blue-L-M with a similar amount of red-L-M.
Example 2: Correction system bv using a correcting liauid-masterbatch composition in a fusion spinning process
• The polymer support was polyester having a solid masterbatch and a liquid masterbatch dispersed therein. The solid-M was prepared as in Example 1. The liquid-M was prepared with a mixture of inert oils and 38% wt. of pigment GREEN (P.G.7).
• Spinning a polyester yarn was carried out by dosing 2.5% wt. of solid masterbatch and 0.079% wt. of liquid masterbatch. The extruded yarn was textured by air. Then, a fabric was knitted from this yarn. This fabric was placed in the sample holder of a Datacolor 650 spectrophotometer. Averaged readings were made in the spectrophotometer to determine the coordinates L, a* and b*. The results for illuminant D65 10 Deg are included in Table 12 below. These readings of the coordinates a* and b* were not within the tolerances of the desired target hue color coordinates, see target hue color row.
• To correct the actual color hue to the target color hue, a dose of 0.237% wt. of green-L-M was added as correcting-liquid-masterbatch to the molten polyester mass during the extrusion. The extruded yarn was textured by air. Then, a fabric was knitted from this yarn. This fabric was placed in the sample holder of a Datacolor 650 spectrophotometer. Averaged readings were made for the corrected sample in order to verify that the color hue is within limits of tolerances.
• After color hue correction of the sample, the corrected hue color corresponded to the target color hue (a*: -3.05 (-0.59-2.46), b*: 0.45 (0.82-0.37)). The correction did not generate metamerism, and the color hue differences, if any, were imperceptible to the healthy human eye.

  Table 12
  Comparison of Corrected Color Hue Sample to Target Color Hue
  	Ilum./Obs.	L*	a*	b*
  Sample: Colored synthetic yarn composition: Polyester polymer + 2.5% wt. of solid-M+0.079% wt. of liquid-M	D65	10 Deg	31.98	-0.59	0.82
  Target hue color	D65	10 Deg	31.37	-3.05	0.45
  Color Difference CIE Lab: Sample + dose of correcting liquid-M, expressed in wt. (Dose of Green-L-M)	Ilum./Obs.	ΔL*/SL	Δa*	Δb*	CIE ΔE
  + 0.237%	D65	10 Deg	-0.61	-2.46	-0.37	2.56
  	A 10 Deg	-0.91	-2.65	-1.00	2.97
  	F11 10 Deg	-0.79	-2.61	-0.57	2.79

• The invention is not limited to the above embodiments. The claims follow.

Claims (15)

1. A method for modifying the color hue of colored synthetic yarns and/or filaments to a target 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 is selected to be the same as present in the colored synthetic yarns and/or filaments;

   - 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 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; and optionally

   - verifying the corrected color hue in the corrected and colored synthetic fibers and/or filaments by taking new measurements of color coordinates a_m* and/or b_m* 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.
2. Method according to claim 1, wherein the differences beyond limits of tolerances in the color coordinates, that is Δa and/or Δb, have a substantially linear relationship with the dose of the correcting-liquid-masterbatch composition.
3. Method according to claim 1, 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 the at least one of the colorants is selected to be the same as present in the colored synthetic yarns and/or filaments whose color hue is desired to be corrected.
4. Method according to any one of previous claims, wherein the correcting-liquid-masterbatch composition comprises a colorant concentration between 1% and 40%, preferable between 1 and 30%, more preferable between 5 and 10% by weight to the weight of the correcting-liquid-masterbatch composition.
5. Method according to any one of previous claims, 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.
6. Method according to any one of previous claims, wherein the liquid polymer carrier is a heat resistant liquid paraffin.
7. Method according to any one of previous claims, wherein the correcting-liquid-masterbatch composition is added in a concentration equal to or lower than 3% by weight, preferably equal to or lower than 1% by weight with respect to the weight of the colored synthetic yarns and/or filaments.
8. Method of claim 7, 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.
9. Method according to any one of previous claims, wherein the differences beyond limits of tolerances, that is Δa and/or Δb, are within a value of |3|, preferable within a value of |1|.
10. Method according to any one of previous claims, 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.
11. A system for modifying the color hue of colored synthetic yarns and/or filaments to a target color hue including limits of tolerances during extrusion in a conventional fusion spinning process by using the method and the correcting-liquid-masterbatch composition defined in claims 1 to 10, the system comprising:

    - extrusion means (1) adapted and configured for producing colored synthetic yarns and/or filaments in fusion spinning process, which comprises:

    ∘ an extruder (10) configured and adapted to receive, in use, a polymer support and a solid and/or a liquid masterbatch composition responsible for coloring the polymer support;

    ∘ polymer supplying means (11) configured and adapted for suppling, in use, the polymer support to the extruder to which it is coupled;

    ∘ masterbatch supplying means (12) configured and adapted for suppling, in use, the solid and/or a liquid masterbatch composition to the extruder to which it is coupled;

    characterized in that the system further comprises:

    - a portable equipment (2), which comprises:

    ∘ housing means (20) configured and adapted for housing a correcting liquid-masterbatch composition;

    ∘ correction supplying means (21) associated to the housing means (20) and configured for suppling, in use, a dose of the correcting liquid-masterbatch composition to the extruder (10) to which they are coupled;

    - colorimetric readout means (3) associated to the extruder for taking of a readout of the color-hue-coordinates, that is a*, b*, of the colored synthetic yarns and/or filaments to compare them with the stored target-color-hue-coordinates, that is a_t*, b_t*, in order to determine differences in the color-hue-coordinates, that is Δa and/or Δb, beyond limits of target color hue tolerances, and

    - electronic processor means (4) associated to such differences beyond limits of tolerances in the color-hue-coordinates, i.e. Δa and/or Δb, by means of the colorimetric readout means (3) for generating a dose-indicative signal of the correcting liquid-masterbatch composition housed in the portable equipment (2), and further operatively connected to the correction supplying means (21) for adding, in use, a dose of the correcting liquid-masterbatch composition to the extrusion means (1) during extrusion of the colored synthetic yarns and/or filaments;

    and in that the extrusion means (1) are further configured and adapted for receiving, in use, the dose of the correcting liquid-masterbatch composition for modifying the actual color hue of the colored synthetic yarns and/or filaments to the target color hue within limits of tolerances, resulting in an acceptable corrected color hue.
12. System according to claim 11, wherein the portable equipment (2) further comprises:

    - more than one housing means (20) each one independently configured and adapted for housing a correcting-liquid-masterbatch composition;

    - masterbatch mixing means (22) configured and adapted for mixing several doses of correcting-liquid-masterbatch compositions to supply, in use, a mixture of dosages to the extruder (10) to which it is coupled.
13. Use of a correcting liquid-masterbatch composition during the extrusion in a conventional fusion spinning process for correction of the color-hue of colored synthetic yarns and/or filaments within tolerances.
14. Use according to claim 13, wherein the colorant concentration is between 1% and 40%, preferably between 1% and 30%, more preferably between 5 and 10% by weight to the weight of the correcting liquid-masterbatch composition.
15. Use according to claims 13 and 14, wherein the correcting-liquid-masterbatch composition is added to the molten mass of the colored synthetic yarns and/or filaments during extrusion in a concentration lower than 3%, preferably equal to or lower than 1%, still more preferable between 0.1 and 0.6% by weight to the weight of the synthetic yarns and/or filaments.

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