Patent Publication Number: US-2006000034-A1

Title: Textile ink composition

Description:
BACKGROUND OF THE INVENTION  
      The present invention relates to textile ink compositions that are capable of durably dyeing two or more types of fabric. A method of preparing such a composition is also disclosed.  
      A simple application of a dye solution onto cotton or polyester fabrics usually fails to durably dye the fabric, and the dye is simply washed out upon laundering of the fabric. This is due to the absence of any specific interaction mechanisms or covalent attachment between the fibers and the dye molecules.  
      Only a few commercially available dyes can be used to form washfast textile inks in this manner, and these inks are generally specific to only one type of fabric. For example, fiber reactive dyes are able to durably dye cotton, but not polyester.  
      Most dyes require some form of pre- or post-dye treatment of the fabric in order to durably dye the fabric. Thus, developed dyes require the fabric to be first treated with a direct dye, then treated with an acid and further treated with a developer solution; naphthol dyes are applied by impregnation of the fabric with a caustic solution of beta-naphthol and the fabric is then immersed in a second dye solution; and vat dyes are applied to fabrics in a reduced, soluble form and are then re-oxidized to their original, insoluble form.  
      Cationically charged dyes tend to bind tightly to some negatively charged fiber surfaces to form durable washfast complexes. However, these dyes are generally not lightfast or washfast on polyester textiles. Washfastness is a measure of the resistance of a dye to washing out of the textile fiber. There is not necessarily any relationship between washfastness and lightfastness, which is a measure of how resistant a dye is to fading due to exposure to light.  
      Covalent attachment of dyes to a cationic polymer on a laboratory scale is also known, but it is not economically feasible to scale up this reaction for commercial production.  
      As there is no universal dye for textiles, a printer cartridge containing a textile ink composition for printing on one type of fabric cannot be used for printing on another type of fabric. Thus, where a printer is used in printing a number of types of fabrics, different cartridges for the same color ink are required.  
      There is therefore a need for textile ink compositions that can durably dye two or more types of fabric and that are economically feasible to produce on a commercial scale.  
     SUMMARY OF THE INVENTION  
      In response to the discussed difficulties and problems encountered in the prior art, a new textile ink composition that is capable of durably dyeing two or more, and preferably at least three, fabrics has been discovered. The textile ink composition includes an irreversible polymeric cationic dye complex formed between a cationically charged metal oxide and a dye.  
      The metal oxide may be any cationic metal oxide, but is typically an alumina oligomer, such as oligomeric aluminum chlorohydrate (also known as aluminum chlorohydrol).  
      The dye typically contains anthraquinone, catechol, hydroxyazo or salicylic acid groups. Such dyes include Carminic Acid, Alizarin Red, Acid Blue 45, Acid Green 41, Hematoxylin, Chromoxane Cyanine R, Calconcarboxylic Acid, Plasmocorinth B, Pyrocatechol and Acid Alizarin Violet N. Mordant dyes known to form highly colored complexes with chromium, such as Mordant Yellow 12 and Mordant Blue 9, are also suitable dyes.  
      The textile ink composition is capable of durably dyeing a number of both natural and synthetic fabrics, such as cotton, silk, linen, rayon, nylon, polyester and so forth.  
      In general, the ratio of alumina oligomer:dye molecule is in the range of from about 0.1:10 to 10:1, more particularly from about 0.5:1 to 5:1 and most particularly about one alumina oligomer per dye molecule.  
      The textile ink composition may be used for inkjet printing, silk screening, gravure printing, dip and nip methods and the like.  
      The composition may further include one or more additives such as known polyols, viscosity modifiers, non-ionic surfactants to reduce surface tension, drying preventing agents, penetration accelerators, ultraviolet light absorbers, antioxidants, antifungal agents, pH adjusters, anti-foaming agents, dispersion aids, dispersion stabilizers, anti-rusting agents, chelating agents and the like. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      The invention provides textile ink compositions that are capable of durably dyeing more than one type of fabric, and preferably more than two types of fabric. The composition may be capable of dyeing both natural and synthetic fabrics, such as cotton, silk, silk charmeuse, linen, nylon, rayon and polyester.  
      The compositions require no pre- or post-treatment, can be prepared in a single step and are shelf-stable at room temperature without precipitation.  
      The textile ink composition is obtained by mixing a cationically charged metal oxide, such as an alumina oligomer or polymer, and a dye, which react to form an irreversible metal oxide-dye complex.  
      A suitable alumina oligomer is aluminum chlorohydrate (also known as aluminum chlorohydrol), which is available from Reheis of Berkeley, N.J. Aluminum chlorohydrol is formed from the reaction: 2Al(OH)3+nHCl  2Al 2 (OH) n Cl 6-n +nH 2 O. It is soluble in water and is sold as a 50 weight percent solution. Aluminum chlorohydrol has a high cationic charge, is inexpensive and is readily available in large quantities.  
      Other suitable aluminum oxides having particles ranging from nanometer to micrometer in size are also suitable, for example SNOWTEX AK® from Nissan Chemical and LUDOX® from Grace of Columbia, M.D.  
      Suitable dyes are those dye containing anthraquinone, catechol, hydroxyazo or salicylic acid groups. Such dyes include Carminic Acid, Alizarin Red, Acid Blue 45, Acid Green 41, Hematoxylin, Chromoxane Cyanine R, Calconcarboxylic Acid, Plasmocorinth B, Pyrocatechol and Acid Alizarin Violet N. Mordant dyes known to form highly colored complexes with chromium, such as Mordant Yellow 12 and Mordant Blue 9, can also be used to produce an ink composition according to the invention. The dyes are obtainable from Aldrich Chemical Corporation of Milwaukee, Wis.  
      In general, the ratio of metal oxide oligomer:dye molecule is in the range of from about 1:10 to 10:1, more particularly from about 5:1 to 5:1 and most particularly about one metal oxide oligomer per dye molecule.  
      It will be apparent to a skilled person, however, that as the purity of the dye is often not provided, and it is known that impurities in dyes can range from 10 to 70 percent (and sometimes higher), it is difficult to achieve a precise ratio in practice.  
      Typically, the ink compositions were formed by mixing 1 ml of a 1 weight percent dye solution with from 1 to 200, more preferably from 10 to 100, and even more preferably with about 25 microliters of a 50 weight percent alumina oligomer. The dye may be a 20 mM solution.  
      The composition can be formed at room temperature, optionally with stirring of the mixture for about two to sixty minutes, and typically for about 30 minutes, so as to ensure that the reaction proceeds to completion.  
      The composition may further include one or more known additives such as polyols, viscosity modifiers, non-ionic surfactants to reduce surface tension, drying preventing agents, penetration accelerators, ultraviolet light absorbers, antioxidants, anti-fungal agents, pH adjusters, anti-foaming agents, dispersion aids, dispersion stabilizers, anti-rusting agents, chelating agents and the like.  
      The textile ink composition is suitable for inkjet printing, silk screening, gravure printing, dip and nip methods and so forth.  
      Textile ink compositions prepared according to the invention were spotted onto various fabrics, which were then briefly heated so as to bind the dye to the fabric. Alternatively, the fabrics could be ironed for the same period. The washfastness of the ink compositions on the fabrics was determined using the American Association of Textile Chemists and Colorists (AATCC) (http://www.aatcc.org/technical/test_methods/topic_list.htm) Washfast Test Method 61-2003, which used detergent (TIDE® from Procter &amp; Gamble, USA) and hot water (about 90 degrees Celsius), and ball bearings for abrasiveness. In another test, the washfastness was determined by subjecting the dyed fabrics to a standard domestic laundry washing cycle. The washfastness may be determined by any method known to those skilled in the art as long as the inventive and non-inventive samples are tested in the same manner.  
      Color measurements were performed on the fabrics prior to and after washing to determine the amount of fading, if any. Color measurement refers to the interpretation of the visual sensation of color in terms of three numbers that can be used to objectively assess and quantify differences in color between objects. Instruments are available that measure the spectrum of light reflected from the surface of an object and translate this spectrum into a series of numbers that pertain to visual color sensations. For instance, the subjective term ‘brightness’ may be quantified using the objective quantity ‘luminance’ obtained using a color measuring instrument.  
      L*a*b* color values measurements (CIE 1976 Commission Internationale de I&#39;Eclairage) and optical density were made of the printed textile fabrics using a handheld spectrophotometer, in accordance with the operator&#39;s manual. The spectrophotometer was manufactured by Minolta Co. Ltd of Osaka, Japan (Model #M2600d). The spectrophotometer was calibrated against a pure white material that had been provided with the spectrophotometer.  
      Average optical densities were taken as the sum of the average of three measurements using each filter. Delta E (DE or ΔE) is calculated in accordance with the following equation: 
 
 DE=SQRT [( L *standard− L *sample)2+( a *standard− a *sample)2+( b *standard− b *sample)2]
 
      The higher the Delta E, the greater the change in color intensity. Unless the color&#39;s intensity is increased by a curing step, a large increase in delta E would typically be indicative of fading. The testing was in accordance with ASTM DM 224-93 and ASTM E308-90. Where values for delta E are less than 3.0, it is generally accepted that such color change cannot be observed with the human eye. A detailed description of spectrophotometer testing is available in Color Technology in the Textile Industry, 2nd Edition, (order no. 9713) Published 1997 by AATCC.  
      The present invention is further described by the following examples. Such examples, however, are not to be construed as limiting in any way either the spirit or scope of the present invention.  
     EXAMPLE 1  
      A series of textile inks was prepared by mixing a cationically charged metal oxide with a number of dyes. The cationically charged metal oxide that was used in the example was a 50 weight percent aqueous solution of aluminum chlorohydrol obtained from Reheis. The dyes used in the example were Carminic Acid, Alizarin Red S, Acid Blue 45, Acid Green 41, Mordant Yellow 12, Hematoxylin, Mordant Blue 9, Chromoxane Cyanine R, Calcon Carboxylic Acid, Plasmocorinth B, Pyrocatechol, Acid Alizarin Violet N and Alizarin Yellow GG, obtained from Aldrich Chemical Corporation.  
      The textile ink compositions were formed by adding 25 microliters of the aluminum chlorohydrol solution to 1 ml of a 20 mM solution of each dye at room temperature, and the mixture was stirred vigorously for 30 minutes.  
      Each textile ink composition was then spotted onto separate cotton and polyester textile fabrics by applying a 10-20 microliter drop of the ink composition onto the fabric surface. The polyester fabric was then briefly heated at about 180 degrees Celsius for about 2 to 3 minutes in order to bind the dye onto the fiber surface of the fabric.  
      The washfastness of the ink compositions on the fabrics was then determined using the AATCC Washfast Test Method 61-2003. The delta E and washfast values are shown in Table 1.  
               TABLE 1                          Color loss values of alumina oligomer-dye ink compositions       applied onto cotton and polyester fabrics                         Dye complexed with                                         aluminum   Cotton fabric       Polyester fabric                                             chlorohydrol   (ΔE)   W/F   (ΔE)   W/F                                                     Carminic Acid   4.18       15.76               Alizarin Red S   2.48   2-3   11.97   2           Acid Blue 45   1.41       9.45           Acid Green 41   3.68   4   8.05   3-4           Mordant Yellow 12   12.56   2   18.56   2-3           Hematoxylin   5.45       8.17           Mordant Blue 9   3.63       9.80           Chromoxane Cyanine R   3.69   1-2   7.23   3           Calcon Carboxylic Acid   3.88   3   6.34   2           Plasmocorinth B   11.79       13.44           Pyrocatechol   4.59       5.74           Acid Alizarin Violet N   10.02       14.22           Alizarin Yellow GG       3       3                      
 
      These values indicate some color loss, which it is anticipated could be improved upon by refining the ink formulation, for example by altering the ratio of alumina oligomer:dye. As most commercially available dyes contain less than 100 percent colorant, another method would be to purify the dye, for example by using a known organic solvent extraction process.  
     EXAMPLE 2  
      Textile ink compositions were prepared as described in example 1 and were spotted onto cotton and polyester fabrics. The fabrics were then washed in a domestic washing machine on the harshest washing cycle, using the recommended dosage of a domestic laundry detergent (TIDE® from Procter &amp; Gamble, USA) and hot water (about 90 degrees Celsius) for up to 30 minutes. The color intensities and washfast values were calculated as described above, and the results that were obtained were similar to those in example 1. A skilled person will understand that this is a fairly harsh washfast test for any printed ink, and the results of this test are thus a good indication that the ink compositions are able to durably dye different fabrics.  
     EXAMPLE 3  
      Textile ink compositions prepared according to example 1 were spotted onto a silk charmeuse fabric and allowed to dry. The washfastness was tested using the AATCC Washfast Test Method 61-2003 described above, and the fabric colors prior to and after the wash test were analyzed qualitatively (results not shown). The ink compositions were shown to dye silk fabric equally well.  
      From the above examples, it can be seen that the applicant has utilized commercially available metal oxide oligomers and commercially available dyes to develop durable and washfast textile ink compositions that work equally well on silk, cotton and polyester fabrics.  
      In addition to being able to durably dye more than one type of fabric, the ink compositions of the present invention are able to incorporate more dye than many other inks, are soluble and are therefore readily incorporated into inkjet inks, and do not have lightfast issues that are associated with other inks.  
      While the invention has been described in detail with respect to specific embodiments thereof, it will be appreciated by those skilled in the art that various alterations, modifications and other changes may be made to the invention without departing from the spirit and scope of the present invention. It is therefore intended that the claims cover or encompass all such modifications, alterations and/or changes.