Patent Description:
Supercritical fluid based textile dyeing process is environment friendly, green process that minimizes environmental, water pollution issues faced by the conventional textile dyeing industry. In a typical supercritical fluid based dyeing process, a dye material is first dissolved in the supercritical fluid. The supercritical fluid along with the dissolved dye molecules is then passed over the textile material in the supercritical dyeing vessel. The dye from supercritical fluid thus comes in contact with textile material to achieve dying operation. One of the primary reasons for the limited success for the typical supercritical dyeing process being its slow rate of action due to low solubility of dye materials in supercritical fluids. Further, limitation being that only part of the dye material, which is dissolved in the supercritical fluid, actually comes in contact with a surface of the textile material to contribute in dyeing process and the rest of the dye material just passes through the empty spaces present in and between the textile materials, without actually coming in contact with the surface of the textile material for achieving dyeing operation. Further, even out of the dissolved dye material, which actually comes in contact with the surface of the textile material, only a small amount of the dye material penetrates inside the surface, pores, capillaries etc. of the textile material. This may be mainly due to shorter residence time of the dynamic supercritical fluid, flowing through the supercritical dyeing vessel. This limits a quantity of dye molecules that diffuses inside the textile material. The unused dissolved dye material in supercritical fluid coming out of dyeing vessel is then flows to a separator vessel, where the pressure and temperature of the supercritical fluid is reduced to subcritical state to reduce the solubility of dye molecules, resulting in precipitation and recovery of the unused dye material.

Therefore, the above mentioned supercritical dyeing process has the limitations of: (i) low solubility of the dye material in the supercritical fluid giving low concentration of dye in supercritical fluid being used as dyeing medium, (ii) Further, only a fraction of the dissolved dye material is able to come in contact with the surface of the textile material, and (iii) Low residence time (i.e. a time available for dye molecule between entry into and exit out of dyeing vessel) limits the contact, interaction between textile material surface and the dye molecules. The aforementioned limitations collectively result in a situation that only a part of the dissolved dye in the supercritical fluid gets a chance to penetrate inside textile material matrix to achieve desired colour intensity and fastness. This also makes the existing supercritical dyeing process less versatile, slow and inefficient. Hence, there remains a need for an improved dyeing process that effectively facilitates interaction of the dye molecules with the surface of the textile material, to increase the rate and efficiency of dyeing process using supercritical fluids. Further, the existing supercritical dyeing process that involves pre-dissolution of dye molecules in the supercritical fluid, has a major limitation of being able to apply only a single color shade at a time on the textile material. The above said existing supercritical dyeing process limits the possibility of applying multiple colors simultaneously or of applying controlled variations of shade along the width of the textile material or formation of desired design patterns on the textile material. The market also has demand for textiles with multiple colors, shades, patterns etc. Hence, there is also a need for applying multiple colors, shades, patterns etc. on the textile material in single operation of supercritical fluid based dyeing process.

Accordingly, there remains a need for an improved supercritical fluid based dyeing process for efficient dyeing of the textile materials with single or multi-colors in various shades, patterns, designs etc., preferably in a single dyeing step.

<CIT> describes a method for static dyeing by adopting supercritical fluid. Step (<NUM>) dyeing: placing an object to be dyed in an uptake dyeing system for uptake dyeing. Step (<NUM>) static developing and color fixing with the supercritical fluid: placing the dyed object to be dyed in the step (<NUM>) in a supercritical fluid developing and color fixing kettle, and adding the supercritical fluid in the supercritical fluid developing and color fixing kettle for the developing and color fixing of the object to be dyed in the static supercritical fluid. Step (<NUM>): after the developing and color fixing are completed, eliminating system pressure to recover the supercritical fluid, and opening the supercritical fluid developing and color fixing kettle for taking out the object to be dyed. In the method for static dyeing by adopting supercritical fluid, the supercritical fluid is in a stationary state in the developing and color fixing process, so that the phenomenon of dye migration cannot occur, the dyeing quality is easy to control, and the dyeing system does not need to be cleaned in the replacement of the dyeing color. A device is described for realizing the method for static dyeing by adopting the supercritical fluid.

<CIT> describes a way of producing a printed matter having excellent weather-resistant fastness, antifriction fastness and washing resistance. A printed matter producing method is described that includes a print step to print ink comprising dye on a fiber, and a color developing step to develop a color of the fiber in a supercritical fluid after the print step.

Further aspects are also described.

In view of foregoing, an embodiment herein provides a process for dyeing of textile material using supercritical fluid. The process includes the steps of: (a) mixing at least one dye material in at least one suitable solvent to obtain at least one dye solution; (b) pre-treating a surface of the textile material with an optimum quantity of the at least one dye solution to obtain a dye coated textile material; (c) placing the dye coated textile material in a supercritical fluid dyeing vessel; (d) adding a supercritical fluid into the supercritical fluid dyeing vessel at controlled temperature and pressure, wherein the supercritical fluid solubilizes the at least one dye material which is present on the surface of the dye coated textile material and further diffuses the solubilized at least one dye material inside the surface, pores and capillaries of the textile material; and (f) depressurizing the supercritical fluid dyeing vessel to precipitate and entrap the at least one dye material in the textile material.

According to the invention, the dye materials are mixed with at least one suitable solvent to obtain at least one dye solution. In an embodiment, the additives are at least one of dispersing agents, emulsifiers, surface active agents etc..

In an embodiment, the controlled temperature ranges from <NUM> to <NUM>. In another embodiment, the controlled pressure ranges from <NUM> Bar to <NUM> Bar.

In another embodiment, the process further includes the steps of: treating the dye coated textile material using a suitable process to control at least one of (i) moisture and/or (ii) solvent content of the dye coated textile material.

According to the invention, the surface of the textile material is pre-treated with more than one dye solution to obtain a multi-color, multi shade dyed textile material with desired design patterns as required.

In yet another embodiment, the surface of the textile material is pre-treated with the at least one dye solution using a method similar to ink jet printing.

In yet another embodiment, the method similar to ink jet printing is performed using a single jet printing and/or a multi-jet printing.

According to the invention, the surface of the textile material is pretreated with the at least one dye solution using any desired coating process to obtain a desired thickness and concentration of the at least one dye material on the surface of the textile material.

In yet another embodiment, the process comprising maintaining the controlled temperature and pressure of the supercritical fluid at optimum level to have desirable solubility for coated dye molecules in the supercritical fluid, to help in swelling of pores and capillaries of the dye coated textile material, and to contribute in reducing glass transition temperature of the textile material. The optimum value or the optimum level for temperature and pressure may vary with nature and solubility of dye molecule, type of the textile material and their interaction with the supercritical fluid used for the dyeing process.

In yet another embodiment, at least one type of dye molecules penetrates inside the surface, the pores and capillaries of the textile material along with the supercritical fluid which acts as solvent.

A method for dyeing of a textile material using supercritical fluid may include the following steps of: (A) mixing at least one dye molecule in a suitable solvent along with additives to obtain at least one dye solution; (B) pre-treating the surface of the textile material with an optimum quantity of the at least one dye solution to obtain a dye coated textile material; (C) treating the coated textile material using a suitable process to control (i) moisture and/or (ii) solvent content of the dye coated textile material; (D) placing the coated textile material in a supercritical fluid dyeing vessel; (E) adding a supercritical fluid into the supercritical fluid dyeing vessel at controlled temperature and pressure, wherein the supercritical fluid (i) solubilizes the at least one dye molecule which is present on the surface of the dye coated textile material and (ii) diffuses the at least one dye molecule inside the surface, pores and capillaries of the textile material; and (F) depressurizing the supercritical fluid dyeing vessel to precipitate and entrap the at least one dye molecule in the textile material.

This process of dyeing of textile materials with supercritical fluid provides the textile material dyed with multi-color and with desired design patterns in an efficient way. The process of dyeing of textile materials with the supercritical fluid by pre-treating the textile material with the one or more dye solutions using any suitable method (e.g. ink jet printing, multi jet printing, coating, spraying etc.) reduces the wastage of the one or more dye materials. Further, this process of dyeing of textile materials with supercritical fluid enables in achieving desired uniform color or color pattern, design on the textile material in a single step. This process of dyeing of textile materials with supercritical fluid is simpler, versatile and efficient. This process also makes scale up of the dyeing process easier as the dye molecules are already present on the entire surface of the textile material that needs to be dyed and therefore the dye molecules are not required to be transported to the textile material surface, along with supercritical fluid to reach uniformly at each part of the material that needs to be dyed.

This process or method may also be used for dyeing of materials other than textiles. This process or method may also be used for controlled treatment of materials with desired chemicals by pre-coating of the treatment chemicals on material surface before exposing the material to supercritical fluid, rather than need for pre-dissolving the treatment chemicals in supercritical fluid, for other processes which require Supercritical Fluid assisted penetration of such treatment or reaction chemicals, in the desired matrix to achieve reactions, modification in properties of the matrix material etc..

Many changes and modifications may be made within the scope of the embodiments herein, and the embodiments herein include all such modifications.

The embodiments herein will be better understood from the following detailed description with reference to the drawings, in which:.

The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein.

As mentioned, there remains a need for an improved process for efficiently dyeing of textile materials using supercritical fluid. The embodiments herein achieve this by providing a process that involves pre-coating of the textile material with one or more dye materials and then exposing the dye coated textile material to the supercritical fluid, under supercritical conditions. The supercritical fluid that diffuses inside the textile material may swell the matrix and may reduce the glass transition temperature of the textile material. This helps in opening the pores and capillary structure of textile material. Simultaneously, the supercritical fluid dissolves the dye molecules present on the surface of the pre-coated textile material and further helps them to penetrate deep inside the textile material resulting in efficient dyeing with good color fastness. Referring now to the drawings, and more particularly to <FIG>, where similar reference characters denote corresponding features consistently throughout the figures, preferred embodiments are shown.

<FIG> is a flow diagram that illustrates a process of dyeing of textile materials <NUM> with supercritical fluid according to an embodiment herein. One or more dye materials <NUM> are mixed in at least one suitable solvent <NUM> (e.g. water, acetone, ethanol, hexane etc. or any other solvent depending on the suitability for the dye molecule) along with any additives (e.g. dispersing agents, emulsifiers, surface active agents etc.) (if required) to obtain one or more dye solutions <NUM>. The textile material <NUM> is then pre-treated with the one or more dye solutions <NUM> to obtain a dye coated textile material <NUM>. In one embodiment, the textile material <NUM> is pre-treated with the one or more dye solutions <NUM> to obtain the dye coated textile material <NUM> having uniform coating with desired layer thickness and desired concentration of the one or more dye materials <NUM> on the surface of the textile material <NUM>. Pre-treating the surface of the textile material <NUM> provides desired concentration of the one or more dye materials <NUM> (e.g. dye molecules) with specific and uniform intensity of color on the surface of the textile material <NUM> and reduces wastage of one or more dye materials <NUM>, and improves utilization of the one or more dye materials <NUM>.

In one embodiment, the textile material <NUM> is pre-treated with the one or more dye solutions <NUM> using any suitable technique or process that is used for coating or spreading of dye solution on the surface of textile materials with uniform and desired concentration of dye molecules. In an embodiment, the pre-coating the surface of the textile material <NUM> with the one or more dye solutions <NUM> may be achieved with an inkjet printing and/or a multi-jet printing or any suitable method to obtain the dye-coated textile material <NUM> in a single and/or multi-color with desired patterns, shades etc. as required.

In yet another embodiment, the textile material <NUM> is pre-treated with the one or more dye solutions <NUM> using ink jet printing or multi-jet printing to obtain the dye-coated textile material <NUM> with controlled, optimum quantity of dye molecules per unit textile surface to achieve desirable reproducibility of final color shade and desired color intensity. This facilitates the possibility of having multi-colour designs on the textile while dyeing using supercritical fluids. In yet another embodiment, the pre-treatment of the textile material <NUM> with the one or more dye solutions <NUM> controls concentration of the one or more dye materials <NUM> per unit area on the surface of the textile material <NUM> to obtain a specific and uniform intensity of color on the textile material <NUM>, and also improves efficient utilization of the one or more dye materials <NUM>. In yet another embodiment, the pre-treatment of the textile material <NUM> with the one or more dye solutions <NUM> helps in penetration of the one or more of dye materials <NUM> inside the pores and capillaries of the textile material <NUM>.

The dye-coated textile material <NUM> is then exposed to the supercritical fluid <NUM> in a supercritical fluid dyeing vessel. The dye-coated textile material <NUM> may be subjected to a suitable process like drying etc., before loading the dye-coated textile material <NUM> into the supercritical fluid dyeing vessel, to control level of residual moisture and/or solvent content of the dye-coated textile material <NUM>. The supercritical fluid <NUM> (e.g. supercritical carbon dioxide) solubilizes and diffuses the one or more dye materials <NUM> inside the surface, pores and capillaries of the dye-coated textile material <NUM> at a controlled temperature and pressure inside the supercritical fluid dyeing vessel. According to the invention, the pre-coating by the dye materials <NUM> on the surface of the textile material <NUM> results in a desired thin layer of dye material that helps in effective contact of the one or more dye materials <NUM> with the supercritical fluid <NUM>. This helps in higher solubility and concentration of dye molecules in supercritical medium, near the surface of the textile material that needs to be dyed. This also avoids inefficiencies that may be possible due to undesirable channeling of dye dissolved supercritical fluid, which result in non-uniformity in dyeing as observed in conventional supercritical fluid based dyeing processes.

The supercritical fluid dyeing vessel is then depressurized to entrap the one or more dye materials <NUM> that is diffused inside the textile material <NUM> to obtain a supercritical fluid dyed textile material <NUM>.

<FIG> is a flow diagram that illustrates a method of dyeing a textile material <NUM> under a supercritical condition according to a possible embodiment. At step <NUM>, one or more dye materials <NUM> is mixed along with additives in at least one suitable solvent <NUM> to obtain one or more dye solutions <NUM>. At step <NUM>, the textile material <NUM> is pre-treated with the one or more dye solutions <NUM> to obtain a dye-coated textile material <NUM>. Then, the dye-coated textile material <NUM> may be processed by a suitable method to control residual moisture and /or the solvent content of the dye-coated textile material <NUM>. At step <NUM>, the dye-coated textile material <NUM> is then placed in a supercritical fluid dyeing vessel. At step <NUM>, the dye-coated textile material <NUM> is exposed to the supercritical fluid, inside the supercritical fluid dyeing vessel at a controlled temperature and pressure which are above the critical temperature and pressure of the supercritical solvent. At step <NUM>, the supercritical fluid <NUM> solubilizes and diffuses the one or more dye materials <NUM> inside the surface, pores and capillaries of the textile material <NUM>. At step <NUM>, the supercritical fluid vessel is then depressurized to entrap the one or more dye materials <NUM> that is diffused in the textile material <NUM> to obtain a supercritical fluid dyed textile material <NUM>. In an embodiment, the supercritical fluid <NUM> inside the supercritical fluid dyeing vessel is maintained at the controlled temperature and pressure for achieving desired solubility for coated dye molecules in the supercritical fluid, for swelling of the pores and capillaries of the textile material <NUM>, and for reducing the glass transition temperature of the textile material <NUM>. These effects also help in efficient diffusion of the dye molecules inside the textile material <NUM> to achieve efficient dyeing. The supercritical condition is achieved by maintaining the temperature and pressure above the critical temperature and critical pressure of the said fluid.

Claim 1:
A process for dyeing of textile material (<NUM>) using supercritical fluid (<NUM>), comprising:
mixing (<NUM>) dye materials (<NUM>) in at least one suitable solvent (<NUM>) to obtain at least one dye solution (<NUM>);
pre-treating (<NUM>) a surface of said textile material (<NUM>) with an optimum quantity of said at least one dye solution (<NUM>) to obtain a dye coated textile material (<NUM>),
wherein said surface of said textile material (<NUM>) is pre-treated with more than one dye solution (<NUM>) to obtain a multi-color, multi shade coated textile material with desired design patterns as required, and
wherein said surface of said textile material (<NUM>) is pretreated with said at least one dye solution (<NUM>) using any suitable coating process to obtain a desired thickness and concentration of said dye materials (<NUM>) on said surface of said textile material (<NUM>);
placing (<NUM>) the dye coated textile material (<NUM>) in a supercritical fluid dyeing vessel;
adding (<NUM>) said supercritical fluid (<NUM>) into said supercritical fluid dyeing vessel at controlled temperature and pressure, wherein said process further comprises solubilizing (<NUM>) said dye materials (<NUM>) which are present on the surface of said dye coated textile material (<NUM>) by the supercritical fluid (<NUM>) and further diffusing said solubilized dye materials (<NUM>) inside the surface, pores and capillaries of said dye coated textile material (<NUM>); and
depressurizing (<NUM>) said supercritical fluid dyeing vessel below supercritical condition to precipitate and entrap said dye materials (<NUM>) in said dye coated textile material (<NUM>).