US20070056118A1

US20070056118A1 - Fabric pretreatment for inkjet printing

Info

Publication number: US20070056118A1
Application number: US11/521,693
Authority: US
Inventors: Scott Ellis
Original assignee: Individual
Current assignee: EIDP Inc
Priority date: 2005-09-15
Filing date: 2006-09-15
Publication date: 2007-03-15
Also published as: WO2007035509A1; JP4969578B2; EP1924738A1; WO2007035508A1; US20070067928A1; JP2009508717A; JP2009509057A; US8784508B2; EP1924738B1; EP1924737A1

Abstract

This invention pertains to inkjet printing on fabric and to a pretreatment solution for the fabric that allows high quality printing thereon. The preferred digitally printed inks are pigmented inks.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119 from U.S. Provisional Application Ser. No. 60/717,439, filed Sep. 15, 2005.

BACKGROUND OF THE INVENTION

This invention pertains to inkjet printing on a pretreated fabric with pigmented inkjet inks, and to a pretreatment solution for the fabric that allows high quality printing thereon.
Digital printing methods such as inkjet printing are becoming increasingly important for the printing of textiles and offer a number of potential benefits over conventional printing methods such as screen printing. Digital printing eliminates the set up expense associated with screen preparation and can potentially enable cost effective short run production. Inkjet printing furthermore allows visual effects such as tonal gradients and infinite pattern repeat sizes that cannot be practically achieved with a screen printing process.
While digital printing provides a breadth of available printing conditions for almost any fabric, there is often a need for achieving a higher color on the fabric. It is an object of this invention to enable higher color, high quality inkjet printing of fabrics, such as cotton and cotton blends, with pigmented inkjet inks.

SUMMARY OF THE INVENTION

In one aspect, the present invention relates to a method of digitally printing a textile comprising the steps of:
(a) pretreating the textile with a pretreatment solution comprising an aqueous multivalent cationic salt solution,
(b) drying the pretreated textile,
(c) digitally printing the dried, pretreated textile with a pigmented ink jet ink.
The present invention pertains, in another aspect, to a fabric that has been pretreated with an aqueous multivalent cationic salt solution, wherein the multivalent cationic salt is a calcium salt selected from the group consisting of calcium nitrate, calcium nitrate hydrate and mixtures thereof.
These and other features and advantages of the present invention will be more readily understood by those of ordinary skill in the art from a reading of the following detailed description. It is to be appreciated that certain features of the invention which are, for clarity, described above and below in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any subcombination. In addition, references to in the singular may also include the plural (for example, “a” and “an” may refer to one, or one or more) unless the context specifically states otherwise.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Pretreatment Solution
The pretreatment solution used in the method of the present invention is an aqueous multivalent cationic salt solution. More preferably, the preteatment solution comprises a solution of a multivalent cationic salt in water. Optionally, other ingredients can be added. Ingredient percentages mentioned herein after are weight percent based on the total weight of the final solution, unless otherwise indicated.
Multivalent Cation
The pretreatments of this invention comprise one or more multivalent cations. The effective amounts needed in a particular situation can vary, and some adjustment, as provided for herein, will generally be necessary.
“Multivalent” indicates an oxidation state of two or more and, for an element “Z”, are typically described as Z²⁺, Z³⁺, Z⁴⁺ and so forth. For brevity, multivalent cations may be referred to herein as Z^x. The multivalent cations are substantially soluble in the aqueous pretreatment solution and preferably exist (in solution) in a substantially ionized state so that they are in a form where they are free and available to interact with textile when the textile is exposed to the pretreatment solution.
Z^xincludes, but is not limited to multivalent cations of the following elements: Mg, Ca, Sr, Ba, Sc, Y, La, Ti, Zr, V, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pd, Pt, Cu, Au, Zn, Al, Ga, In, Sb, Bi, Ge, Sn, Pb. In another embodiment, the multivalent cation comprises at least one of Ca, Ba, Ru, Co, Zn and Ga. In yet another embodiment, the multivalent cation comprises at least one of Ca, Ba, Ru, Co, Zn and Ga. Preferably the multivalent cation is Ca.
Z^xcan be incorporated into pretreatment solution by addition in a salt form or by addition in an alkaline form and used as a base in the adjustment of the pretreatment solution pH.
The associated anionic material can be chosen from any common anionic material, especially halides, nitrates and sulfates. The anionic form is chosen so that the multivalent cation is soluble in the aqueous pretreatment solution. The multivalent cationic salts can be used in their hydrated form.
For Ca, the preferred multivalent cation salts are calcium chloride, calcium nitrate, calcium nitrate hydrate and mixtures thereof. Particularly preferred are calcium nitrate, calcium nitrate hydrate and mixtures thereof.
Other optional ingredients in the pretreatment solution may include, but are not limited to, humectants and biocides. Biocides prevent microbial degradation—their selection and use is generally well known in the art. Suitable humectants are the same as those suitable for use in pigmented inkjet inks, as discussed in further detail below.
The balance of the pretreatment solution is water. A pretreatment solution consisting essentially of a solution of a multivalent cationic salt in water is particularly suitable.
The solution should comprise sufficient multivalent cation content and other ingredients to provide adequate infusion and/or coating of the textile with the multivalent cation. Typically, the pretreatment will comprise at least about 0.5 wt % of the multivalent cation salt, and amounts can be used up to the solubility limits of the particularly multivalent cation salt or salts utilized. Preferably, the pretreatment will comprise from about 1.0 wt % to about 30 wt % of the multivalent cation salt.
Fabric
The fabric to be pretreated can be any fabric suitable for printing with pigmented inkjet inks, and is preferably a fabric comprising cotton and/or cotton blends.
Pretreatment of the Fabric
Application of the pretreatment to the fabric can be any convenient method and such methods are generally well-known in the art. One example is an application method referred to as padding. In padding, a fabric is dipped in the pretreatment solution, then the saturated fabric is passed through nip rollers that squeeze out the excess solution. The amount of solution retained in the fabric can be regulated by the nip pressure applied by the rollers. Other pretreatment techniques include spray application wherein the solution is applied by spraying on the face or face and back of the fabric. Spraying can be limited to the digitally printed area of the printed fabric. An example of where this limited spraying would be particularly applicable is in the digital printing of an image on preformed textile articles such as, for example, a T-shirts, caps, undergarments and like clothing articles.
Preferably, the pretreatment solution is applied to the fabric in a wet pick-up of from about 0.20 to about 7.5 grams of multivalent cationic (calcium) salt per 100 grams of fabric, more preferably from about 0.60 to about 6.0 grams of multivalent cationic (calcium) salt per 100 grams of fabric, and still more preferably from about 0.75 to about 5.0 grams of multivalent cationic (calcium) salt per 100 grams of fabric.
After application of pretreatment, the fabric may be dried in any convenient manner. The fabric is preferably substantially dry at the time of printing, such that the final percent moisture is (approximately) equal to the equilibrium moisture of the pretreated fabric at ambient temperature. The absolute amount of moisture in the fabric, of course, can vary somewhat depending on the relative humidity of the surrounding air.
The multivalent salts remaining in the fabric after drying provide an interactive material that will interact with the inkjet inks during printing. It will be appreciated that sufficient multivalent salts must be present to effect a brighter/more colorful image. Routine optimization will reveal appropriate multivalent salt levels for a given printer and pigmented ink or ink set.
Pigmented Inkjet Inks
Pigmented inkjet inks suitable for use in the present method typically comprise a pigment dispersed in a vehicle. The vehicle can be aqueous or non-aqueous, but aqueous vehicles are preferred. Preferably, the pigment ink comprises an anionically stabilized pigment dispersed in an aqueous vehicle.
An “aqueous vehicle” refers to a vehicle comprised of water or a mixture of water and at least one water-soluble organic solvent (co-solvent) or humectant. Selection of a suitable mixture depends on requirements of the specific application, such as desired surface tension and viscosity, the selected colorant, and compatibility with substrate onto which the ink will be printed.
Examples of water-soluble organic solvents and humectants include: alcohols, ketones, keto-alcohols, ethers and others, such as thiodiglycol, sulfolane, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and caprolactam; glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, trimethylene glycol, butylene glycol and hexylene glycol; addition polymers of oxyethylene or oxypropylene such as polyethylene glycol, polypropylene glycol and the like; triols such as glycerol and 1,2,6-hexanetriol; lower alkyl ethers of polyhydric alcohols, such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl, diethylene glycol monoethyl ether; lower dialkyl ethers of polyhydric alcohols, such as diethylene glycol dimethyl or diethyl ether; urea and substituted ureas.
An aqueous vehicle will typically contain about 30% to about 95% water with the balance (i.e., about 70% to about 5%) being the water-soluble solvent. Ink compositions typically contain about 60% to about 95% water, based on the total weight of the aqueous vehicle.
Pigments suitable for being used with the multivalent pretreatment of the textile are those generally well-known in the art for aqueous inkjet inks. Traditionally, pigments are stabilized by dispersing agents, such as polymeric dispersants or surfactants, to produce a stable dispersion of the pigment in the vehicle. More recently though, so-called “self-dispersible” or “self-dispersing” pigments (hereafter “SDP”) have been developed. As the name would imply, SDPs are dispersible in water without dispersants. Dispersed dyes are also considered pigments as they are insoluble in the aqueous inks used herein.
The dispersant or surface treatment applied to the pigment creates an anionic surface charge (“anionic pigment dispersion”). Preferably, that surface charge is imparted predominately by ionizable carboxylic acid (carboxylate) groups.
The pigments which are stabilized by added dispersing agents may be prepared by methods known in the art. It is generally desirable to make the stabilized pigment in a concentrated form. The stabilized pigment is first prepared by premixing the selected pigment(s) and polymeric dispersant(s) in an aqueous carrier medium (such as water and, optionally, a water-miscible solvent), and then dispersing or deflocculating the pigment. The dispersing step may be accomplished in a 2-roll mill, media mill, a horizontal mini mill, a ball mill, an attritor, or by passing the mixture through a plurality of nozzles within a liquid jet interaction chamber at a liquid pressure of at least 5,000 psi to produce a uniform dispersion of the pigment particles in the aqueous carrier medium (microfluidizer). Alternatively, the concentrates may be prepared by dry milling the polymeric dispersant and the pigment under pressure. The media for the media mill is chosen from commonly available media, including zirconia, YTZ and nylon. These various dispersion processes are in a general sense well known in the art, as exemplified by U.S. Pat. No. 5,022,592, U.S. Pat. No. 5,026,427, U.S. Pat. No. 5,310,778, U.S. Pat. No. 5,891,231, U.S. Pat. No. 5,976,232 and US20030089277. The disclosures of each of these publications are incorporated by reference herein for all purposes as if fully set forth. Preferred are 2-roll mill, media mill, and by passing the mixture through a plurality of nozzles within a liquid jet interaction chamber at a liquid pressure of at least 5,000 psi.
After the milling process is complete the pigment concentrate may be “let down” into an aqueous system. “Let down” refers to the dilution of the concentrate with mixing or dispersing, the intensity of the mixing/dispersing normally being determined by trial and error using routine methodology, and often being dependent on the combination of the polymeric dispersant, solvent and pigment.
The dispersant used to stabilize the pigment is preferably a polymeric dispersant. Either structured or random polymers may be used, although structured polymers are preferred for use as dispersants for reasons well known in the art. The term “structured polymer” means polymers having a block, branched or graft structure. Examples of structured polymers include AB or BAB block copolymers such as disclosed in U.S. Pat. No. 5,085,698; ABC block copolymers such as disclosed in EP-A-0556649; and graft polymers such as disclosed in U.S. Pat. No. 5,231,131. Other polymeric dispersants that can be used are described, for example, in U.S. Pat. No. 6,117,921, U.S. Pat. No. 6,262,152, U.S. Pat. No. 6,306,994 and U.S. Pat. No. 6,433,117. The disclosure of each of these publications is incorporated herein by reference for all purposes as if fully set forth.
Polymer dispersants suitable for use in the present invention comprise both hydrophobic and hydrophilic monomers. Some examples of hydrophobic monomers used in random polymers are methyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, benzyl methacrylate, 2-phenylethyl methacrylate and the corresponding acrylates. Examples of hydrophilic monomers are methacrylic acid, acrylic acid, dimethylaminoethyl(meth)acrylate and salts thereof. Also quaternary salts of dimethylaminoethyl(meth)acrylate may be employed.
A wide variety of organic and inorganic pigments, alone or in combination, may be selected to make the ink. The term “pigment” as used herein means an insoluble colorant. The pigment particles are sufficiently small to permit free flow of the ink through the inkjet printing device, especially at the ejecting nozzles that usually have a diameter ranging from about 10 micron to about 50 micron. The particle size also has an influence on the pigment dispersion stability, which is critical throughout the life of the ink. Brownian motion of minute particles will help prevent the particles from flocculation. It is also desirable to use small particles for maximum color strength and gloss. The range of useful particle size is typically about 0.005 micron to about 15 micron. Preferably, the pigment particle size should range from about 0.005 to about 5 micron and, most preferably, from about 0.005 to about 1 micron. The average particle size as measured by dynamic light scattering is less than about 500 nm, preferably less than about 300 nm.
The selected pigment(s) may be used in dry or wet form. For example, pigments are usually manufactured in aqueous media and the resulting pigment is obtained as water-wet presscake. In presscake form, the pigment is not agglomerated to the extent that it is in dry form. Thus, pigments in water-wet presscake form do not require as much deflocculation in the process of preparing the inks as pigments in dry form. Representative commercial dry pigments are listed in previously incorporated U.S. Pat. No. 5,085,698.
In the case of organic pigments, the ink may contain up to approximately 30%, preferably about 0.1 to about 25%, and more preferably about 0.25 to about 10%, pigment by weight based on the total ink weight. If an inorganic pigment is selected, the ink will tend to contain higher weight percentages of pigment than with comparable inks employing organic pigment, and may be as high as about 75% in some cases, since inorganic pigments generally have higher specific gravities than organic pigments.
Self-dispersed pigments can be used and are often advantageous over traditional dispersant stabilized pigments from the standpoint of greater stability and lower viscosity at the same pigment loading. This can provide greater formulation latitude in final ink.
SDPs, and particularly self-dispersing carbon black pigments, are disclosed in, for example, U.S. Pat. No. 2,439,442, U.S. Pat. No. 3,023,118, U.S. Pat. No. 3,279,935 and U.S. Pat. No. 3,347,632. Additional disclosures of SDPs, methods of making SDPs and/or aqueous inkjet inks formulated with SDP's can be found in, for example, U.S. Pat. No. 5,554,739, U.S. Pat. No. 5,571,311, U.S. Pat. No. 5,609,671, U.S. Pat. No. 5,672,198, U.S. Pat. No. 5,698,016, U.S. Pat. No. 5,707,432, U.S. Pat. No. 5,718,746, U.S. Pat. No. 5,747,562, U.S. Pat. No. 5,749,950, U.S. Pat. No. 5,803,959, U.S. Pat. No. 5,837,045, U.S. Pat. No. ,5,846,307, U.S. Pat. No. 5,851,280, U.S. Pat. No. 5,861,447, U.S. Pat. No. 5,885,335, U.S. Pat. No. 5,895,522, U.S. Pat. No. 5,922,118, U.S. Pat. No. 5,928,419, U.S. Pat. No. 5,976,233, U.S. Pat. No. 6,057,384, U.S. Pat. No. 6,099,632, U.S. Pat. No. 6,123,759, U.S. Pat. No. 6,153,001, U.S. Pat. No. ,6,221,141, U.S. Pat. No. 6,221,142, U.S. Pat. No. 6,221,143, U.S. Pat. No. 6,281,267, U.S. Pat. No. 6,329,446, US2001/0035110, EP-A-1114851, EP-A-1158030, WO01/10963, WO01/25340 and WO01/94476.
Titanium dioxide is also an example of a pigment that can be used, and is potentially advantageous because it is white in color. Titanium dioxide can be difficult to disperse in an ink vehicle that is compatible with an ink jet printer system. Those dispersions and/or ink vehicles that provide inkjet stable titanium dioxide can be used with the multivalent cation pretreated textile.
In a preferred embodiment, a combination of a graft and block copolymers are used as co-dispersants for the titanium dioxide pigment, such as described in U.S. application Ser. No. 10/872,856 (filed Jun. 21, 2004), the disclosure of which is incorporated by reference herein for all purposes as if fully set forth. This combination of dispersants is effective in stabilizing titanium dioxide pigment slurries and, furthermore, provides enhanced stability in the ink formulations. Other preferred titanium dioxide ink jet inks are described in commonly owned US Provisional Appln. Ser. No. 60/717,483, entitled “Aqueous Inkjet Ink” (Internal Reference # IJ0132 USPRV) and filed concurrently herewith, the disclosure of which is incorporated by reference herein for all purposes as if fully set forth.
Additives
Other ingredients (additives) may be formulated into the inkjet ink, to the extent that such other ingredients do not interfere with the stability and jetablity of the finished ink, which may be readily determined by routine experimentation. Such other ingredients are in a general sense well known in the art.
Commonly, surfactants are added to the ink to adjust surface tension and wetting properties. Suitable surfactants include ethoxylated acetylene diols (e.g. Surfynols® series from Air Products), ethoxylated primary (e.g. Neodol® series from Shell and Tomadol® series from Tomah Products) and secondary (e.g. Tergitol® series from Union Carbide) alcohols, sulfosuccinates (e.g. Aerosol(® series from Cytec), organosilicones (e.g. Silwet® series from GE Silicons) and fluoro surfactants (e.g. Zonyl® series from DuPont). Surfactants are typically used in the amount of about 0.01 to about 5% and preferably about 0.2 to about 2%, based on the total weight of the ink.
Polymers may be added to the ink to improve durability. The polymers can be soluble in the vehicle or dispersed (e.g. “emulsion polymer” or “latex”), and can be ionic or nonionic. Useful classes of polymers include acrylics, styrene-acrylics and polyurethanes. A particularly preferred binder additive is a crosslinked polyurethane as described in US20050182154, the disclosure of which is incorporated by reference herein for all purposes as if fully set forth.
Biocides may be used to inhibit growth of microorganisms. Buffers may be used to maintain pH. Buffers include, for example, tris(hydroxymethyl)-aminomethane (“Trizma” or “Tris”).
Inclusion of sequestering (or chelating) agents such as ethylenediaminetetraacetic acid (EDTA), iminodiacetic acid (IDA), ethylenediamine-di(o-hydroxyphenylacetic acid) (EDDHA), nitrilotriacetic acid (NTA), dihydroxyethylglycine (DHEG), trans-1,2-cyclohexanediaminetetraacetic acid (CyDTA), dethylenetriamine-N,N,N′,N″, N″-pentaacetic acid (DTPA), and glycoletherdiamine-N,N,N′,N′-tetraacetic acid (GEDTA), and salts thereof, may be advantageous, for example, to eliminate deleterious effects of heavy metal impurities.
The components described above can be combined to make an ink in various proportions and combinations in order to achieve desired ink properties, as generally described above, and as generally recognized by those of ordinary skill in the art. Some experimentation may be necessary to optimize inks for a particular end use, but such optimization is generally within the ordinary skill in the art.
The amount of vehicle in an ink is typically in the range of about 70% to about 99.8%, and more typically about 80% to about 99%. Colorant is generally present in amounts up to about 10%. Percentages are weight percent of the total weight of ink.
Other ingredients (additives), when present, generally comprise less than about 15% by weight, based on the total weight of the ink. Surfactants, when added, are generally in the range of about 0.2 to about 3% by weight based on the total weight of the ink. Polymers can be added as needed, but will generally be less than about 15% by weight based on the total weight of the ink.
Drop velocity, separation length of the droplets, drop size and stream stability are greatly affected by the surface tension and the viscosity of the ink. Ink jet inks typically have a surface tension in the range of about 20 dyne/cm to about 70 dyne/cm at 25° C. Viscosity can be as high as 30 cP at 25° C., but is typically somewhat lower. The ink has physical properties are adjusted to the ejecting conditions and printhead design. The inks should have excellent storage stability for long periods so as not clog to a significant extent in an ink jet apparatus. Further, the ink should not corrode parts of the ink jet printing device it comes in contact with, and it should be essentially odorless and non-toxic. Preferred pH for the ink is in the range of from about 6.5 to about 8.
Ink Sets
The term “ink set” refers to all the individual inks or other fluids an inkjet printer is equipped to jet.
In one preferred embodiment, the ink set comprises at least two differently colored pigmented inkjet inks, at least one of which is a white pigmented inkjet ink as described above.
In another preferred embodiment, the ink set comprises at least three differently colored pigmented inkjet inks, wherein at least one is a cyan pigmented inkjet ink, at least one is a magenta pigmented inkjet ink, and at least one is a yellow pigmented inkjet ink.
In addition to the colored inkjet inks just mentioned, it is also preferable to include a black pigmented inkjet ink in the ink set.
In addition to the CMYKW inks mentioned above, the ink sets may contain additional differently colored inks, as well as different strength versions of the CMYKW and other inks.
For example, the inks sets of the present invention can comprise full-strength versions of one or more of the inks in the ink set, as well as “light” versions thereof.
Additional colors for the inkjet ink set include, for example, orange, violet, green, red and/or blue.
Printing Method
The present method relates to digitally printing a pretreated textile substrate. Typically, this involves the following steps:
(1) providing an inkjet printer that is responsive to digital data signals;
(2) loading the printer with the textile substrate to be printed, in this case the pretreated textile substrate;
(3) loading the printer with the above-mentioned inks or inkjet ink sets; and
(4) printing onto the substrate using the inkjet ink or inkjet ink set in response to the digital data signals.
Printing can be accomplished by any inkjet printer equipped for handling and printing fabric. Commercial printers include, for example, the Dupont® Artistri® 3210 and 2020 printers, and the Mimaki TX series of printers.
As indicated above, a variety of inks and ink sets are available for use with these printers. Commercially available ink sets include, for example, DuPont® Artistri® P700 and P5000 series inks.
The amount of ink laid down on the fabric can vary by printer model, by print mode (resolution) within a given printer and by the percent coverage need to achieve a given color. The combined effect of all these considerations is grams of ink per unit area of fabric for each color. In one embodiment, ink coverage is preferably from about 5 to about 17 grams of ink per square meter of fabric for colored inks (including black and white inks).
If, however, a white ink is used as a background for the digitally printed image, up to about six times more white ink (generally from about 5 to about 100 grams of ink per square meter of fabric) may be used to obtain an enhanced final image. In such case, the white ink is initially printed onto the substrate in at least a portion of the area to be covered by the final image (the underprint portion), then the final image is printed at least over the underprint portion.
The white ink can also be printed outside the boundaries of the final image (either as part of the initial background printing or subsequently as part of the image printing), for example, to generate a small, imperceptible boundary to the image, making the image appear to have a distinct boundary.
The use of the white ink for printing a background for an image is particularly useful when printed onto colored (non-white) textiles.
Post Treatment of Fabric
Fabric printed with pigmented inks will typically be post-treated according to procedures well-known in the textile printing art.
The printed textiles may optionally be post processed with heat and/or pressure, such as disclosed in US20030160851 (the disclosure of which is incorporated by reference herein for all purposes as if fully set forth). Upper temperature is dictated by the tolerance of the particular textile being printed. Lower temperature is determined by the amount of heat needed to achieve the desired level of durability. Generally, fusion temperatures will be at least about 80° C. and preferably at least about 140° C., more preferably at least about 160° C. and most preferably at least about 180° C.
Fusion pressures required to achieve improved durability can be very modest. Thus, pressures can be about 3 psig, preferably at least about 5 psig, more preferrable at least about 8 psig and most preferably at least about 10 psig. Fusion pressures of about 30 psi and above seem to provide no additional benefit to durability, but such pressures are not excluded.
The duration of fusion (amount of time the printed textile is under pressure at the desired temperature) is not believed to be particularly critical. Most of the time in the fusion operation generally involves bringing the print up to the desired temperature. Once the print is fully up to temperature, the time under pressure can be brief (seconds).

EXAMPLES

Printing Conditions
The examples described below were done using an Epson 3000 ink jet printer, a Fast T-Jet™ from US Screen Printing Institute (Tempe, Ariz.), the and prints were made on various substrates. The textile substrates used were Hanes Beefy T 100% cotton t-shirts, Hanes Heavy weight 100% cotton t-shirts, Hanes 50/50 polycotton cotton t-shirts, and a black fabric from Joann's Fabric (woven 100% cotton tweed). All test prints were fused at about 170° C. for about 1 minute.
Colorimetric measurements were done using a Minolta Spectrophotometer CM-3600d using Spectra Match software.
Where indicated the printed textile was tested for washfastness according to methods developed by the American Association of Textile Chemists and Colorists, (AATCC), Research Triangle Park, N.C. The AATCC Test Method 61-1996, “Colorfastness to Laundering, Home and Commercial: Accelerated”, was used. In that test, colorfastness is described as “the resistance of a material to change in any of its color characteristics, to transfer of its colorant(s) to adjacent materials or both as a result of the exposure of the material to any environment that might be encountered during the processing, testing, storage or use of the material.” Tests 2A and 3A were done and the color washfastness and stain rating were recorded. The ratings for these tests are from 1-5 with 5 being the best result, that is, little or no loss of color and little or no transfer of color to another material, respectively.
Pretreatment Solutions
Reagent grade calcium nitrate tetrahydrate (Aldrich) was mixed with deionized water until the calcium nitrate was completely in solution. Four pretreatment solutions were prepared, and a comparative solution without a multivalent cation present was also prepared.

TABLE 1

Pretreatment Solutions 1-4

Component (Wt %)

as Calcium Nitrate as Calcium

Tetrahydrate Nitrate

Pretreatment Solution 1 2 1.39

Pretreatment Solution 2 5 3.47

Pretreatment Solution 3 10 6.95

Pretreatment Solution 4 20 13.9

Comparative Solution 0.0 0.0

Pigmented Inks
Pigmented Inks were used for testing the multivalent pretreatment solution.

Ink Example 1 has the following formulation shown in Table 1. This ink is a white ink that can be printed prior to printing other pigmented ink or at the same time.

TABLE 1


Ink Example 1

		Wt %
		(based on total
Component	Source	weight of Ink)

Titanium Dioxide Slurry	R-746	10.0
		(solids)
Polymeric Binder	Crosslinked	8.0
	polyurethane	(solids)
	PUD EX2 in
	US20050182154
Surfactant	Byk-348	0.25
	(BykChemie)
Solvent	Ethylene	25.0
	Glycol
Solvent	Glycerol	12.0
Biocide	Proxel ® GXL	0.2
	(Avecia)
Water		Bal. to 100%

R-746 is a commercially available titanium dioxide dispersion (E.I. DuPont de Nemours, Wilmington Del.), which is described as a 76.5 wt % (solids) titanium dioxide slurry with a hydrophilic acrylic copolymer as the dispersant. The titanium dioxide used in this slurry is described as being coated with 3% hydrous silica and 1.5-2.0% hydrous alumina, with a mean particle size of about 280 nm.
Where all of the weights are the net weights in the ink. For example, the polymeric binder is available as an emulsion in about a 33% weight percent solution in water. Thus about 24 grams of the polymeric binder emulsion is added to the ink formulation so that 8% polymeric binder is in the final ink.

Ink example 2 is a magenta ink and is based on pigment R122. The formulation is listed in Table 2.

TABLE 2


Magenta Ink Formulation

	Component	Wt %

	R122
	Glycerol	15.00
	Ethylene Glycol	8.00
	Dowanol ® DPM (Dow Chemical)	3.00
	Surfynol ® 440	1.25
	2-Pyrrolidone
	Proxel ® GXL (Avecia)	0.10
	Polymeric Binder	7.00 (solids)
	Water	Bal. to 100%

The polymeric binder was a crosslinked polyurethane (PUD EX2) in previously incorporated US20050182154.
Printing Performance
Ink Example 1 was printed with and without Pretreatment Solution 4. The Pretreatment solution was sprayed on the T-shirt in an area about the same as the intended image to be printed. The estimated amount of calcium nitrate on the T-shirt prior to printing was about 5 grams/square meter.

The printing was done using a Fast T-Jet® from US Screen Printing Institute with a Huffy beefy T-shirt that was used as a dark black T-shirt. The white ink of Ink Example 1 was printed out of three of the seven used printing channels (replacing the light cyan, light magenta and light black), and DuPont® Artistri® P5000 CMYK inks were printed out of the other four channels. The image printed was a picture of racing airplanes at the Reno races. The image had an area of a bright red and white nosecone. The color at these two spots was measured. Table 3 shows colorimetric measurements.

TABLE 3


Colorimetric Measurement for Ink Example 1; Black T-shirt

	Name	L*	a*	b*	C*	h°	OD	K/S

1	black t-shirt	16.3627	0.2819	−1.1899	1.2228	283.327	1.721246	25.3253
2	red nose cone control,	19.1147	1.4444	0.5092	1.5315	19.4208	1.609065	19.3375
	no pretreatment, no
	white ink background
3	red nose cone, no	21.4612	1.9184	1.5157	2.4449	38.3126	1.543634	16.4968
	pretreatment, white ink
	background
4	red nose cone,	28.2834	7.7313	7.3719	10.6826	43.6368	1.411168	11.906
	pretreatment, no white
	ink background
5	red nose cone,	40.043	24.4182	18.2712	30.4973	36.8061	1.304518	9.1054
	pretreatment and white
	ink background
6	white nose cone, no	23.9974	−0.924	−3.9734	4.0794	256.908	1.458421	13.3852
	pretreatment, no white
	background
7	white nose cone, no	28.0427	−1.3172	−4.7087	4.8894	254.372	1.341035	9.9877
	pretreatment, with
	white ink background
8	white nose cone,	70.3828	−3.1101	−1.3964	3.4092	204.179	0.613144	1.1736
	pretreatment, no white
	ink background
9	white nose cone,	77.6686	−2.4575	−2.3914	3.429	224.219	0.538501	0.8724
	pretreatment, with
	white ink background

Entry 1 was the colorimetric measurement of the unprinted T-shirt. Entries 4, 5, 8 and 9 are inventive in that they show the effect of the pretreatment. Entries 2,3, 6 and 7 show the print performance without the pretreatment with the multivalent salt. Significantly, enhanced colors are observed when the pretreatment was used.
The t-shirt of entry 9 was subject to several cycles of laundering and it was observed that the image did not fade with the washings.
A similar test was done using a white T-shirt shown in Table 4. The T-shirt was pretreated by spraying a Pretreatment Solution 4 and printed using the Fast T-Jet® US Screen Printing Institute.

TABLE 4

Colorimetric Measurement for Ink Example 1; White T-shirt

Name L* a* b* C* h° OD K/S

White T-shirt 95.18 3.36 −13.87 14.28 283.62 0.68 1.50

red nose cone 53.18 29.26 23.47 37.51 38.73 1.13 5.72

White nose cone 78.79 −1.58 −1.17 1.97 216.42 0.70 1.62
Another test was done using the Epson 3000 printer and Black 100% woven cotton tweed. The cotton was pretreated with Pretreatment Solution 4. Ink Example 1 was printed using 4 passes and the DuPont® Artistri® P5000 CK inks in one pass. Blocks of colors were printed and the color properties measured and the results are shown in Table 5.

TABLE 5

Colorimetric Measurements for Ink Example 1; Black Cotton

3A

Wash

L* a b C H° OD A05

K 28.8139 −0.1573 0.1563 0.2218 135.1751 1.29 3.5

ink

C 49.5002 −15.7895 −24.9692 29.5427 237.6924 1.08 4

ink
For comparison, K ink was printed on a 419 cotton and the OD was 1.17 and the wash fastness was 3. For comparison, C ink was printed on a 419 white cotton and the OD was 1.13 and the wash fastness was 3. The combination of the pretreatment, the white ink and the pigmented DuPont® Artistri® P5000 CK results in superior color and wash fastness.

Pretreatment Solutions 1-4 and the Comparative Solution were tested with Ink Example 1. The results are shown in Table 6.

TABLE 6


Pretreatment Solutions 1-4; Print Performance

	L*	a*	b*	C*	h°	Refl.	OD	K/S

Pretreatment	57.38	−2.74	−4.77	5.50	240.17	18.29	0.74	1.83
Sol 1
Pretreatment	64.28	−2.57	−5.22	5.82	243.82	22.70	0.64	1.32
Sol 2
Pretreatment	73.82	−3.01	−3.13	4.35	226.11	27.19	0.57	0.97
Sol 3
Pretreatment	77.67	−2.46	−2.39	3.43	224.22	28.94	0.54	0.87
Sol 4
Comparative	28.04	−1.32	−4.71	4.89	254.37	4.56	1.34	9.99
Sol 1

In this test the L* is significantly higher when Pretreatment Solution 1 is compared to no pretreatment. The L* improves with increase concentration of the multivalent salt in the pretreatment solutions.

Ink Example 2 was printed with and without Pretreatment Solution 4.

TABLE 7


Pretreatment Solution 4 with Ink Example 2

						3A
						Wash-
L*	a	b	C	H°	OD	fastness

Untreated cotton	55.65	42.94	11.45	44.44	345.07	0.88	3.00
treated cotton	52.08	47.90	10.38	49.02	347.77	1.02	1.40
untreated	56.13	41.08	11.67	42.71	344.14	0.86	3.00
polycotton
treated polycotton	49.40	47.94	9.64	48.90	348.63	1.10	0.80

cotton: 419 available from Testfabrics, West Pittston, PA
polycotton: 7435 trom Testfabrics

The pretreatment significantly improves the OD for both the polycotton cotton fabrics. The washfastness of this pigmented ink is poorer with pretreatment with multivalent cations.

Claims

1. A method of digitally printing a textile comprising the steps of:

(a) pretreating the textile with a pretreatment solution comprising an aqueous multivalent cationic salt solution,

(b) drying the pretreated textile,

(c) digitally printing the dried, pretreated textile with a pigmented ink jet ink.

2. The method of claim 1, wherein the multivalent cation is selected from one or more of the group of multivalent cations of elements Mg, Ca, Sr, Ba, Sc, Y, La, Ti, Zr, V, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pd, Pt, Cu, Au, Zn, Al, Ga, In, Sb, Bi, Ge, Sn and Pb.

3. The method of claim 1, wherein the multivalent cation is calcium.

4. The method of claim 3, wherein the pretreatment solution comprises a solution of a multivalent cationic salt in water, wherein the multivalent cationic salt is selected from the group consisting of calcium nitrate, calcium nitrate hydrate and mixtures thereof.

5. The method of any one or combination of claims 1-4, wherein the textile is pretreated with the pretreatment solution in a wet pick-up of from about 0.20 to about 7.5 grams of multivalent cationic salt per 100 grams of fabric.

6. The method of any one or combination of claims 1-5, wherein the pigmented inkjet ink is a white pigmented inkjet ink.

7. The method of claim 6, wherein the textile is a colored textile, and the white pigmented inkjet ink is printed onto the colored textile as a background for an image.

8. The method of claim 7, wherein the textile is printed with the white pigmented ink to an ink coverage of between about 5 to about 100 grams of ink per square meter of textile.

9. The method of any one or combination of claims 1-5, wherein the textile is printed with a pigmented inkjet ink set comprises at least two differently colored pigmented inkjet inks.

10. The method of claim 9, wherein at least one of the pigmented inkjet inks is white.

11. The method of claim 9, wherein the ink set comprises at least three differently colored pigmented inkjet inks, wherein at least one is a cyan pigmented inkjet ink, at least one is a magenta pigmented inkjet ink, and at least one is a yellow pigmented inkjet ink.

12. The method of claim 9 or claim 10, wherein the ink set further comprises a black pigmented inkjet ink.

13. The method of any one or combination of claims 9-12, wherein the textile is printed with the at least two differently colored inkjet ink to an ink coverage of between about 5 to about 17 grams of ink per square meter of fabric.

14. The method of any one or combination of the preceding claims, wherein the pigmented inkjet ink comprises, or each the pigmented inkjet inks in the inkjet set individually comprise, an anionically stabilized pigment in an aqueous vehicle.

15. The method of any one or combination of the preceding claims, further comprising the step of post-treating the printed textile with heat and/or pressure.

16. The method of any one or combination of the preceding claims, wherein the textile is a T-shirt.

17. A pretreated fabric substrate comprising a fabric substrate having applied thereon a pretreatment solution comprises a solution of a multivalent cationic salt in water, wherein the multivalent cationic salt is selected from the group consisting of calcium nitrate, calcium nitrate hydrate and mixtures thereof, in a wet pick-up of from about 0.20 to about 7.5 grams of calcium salt per 100 grams of fabric.

18. The pretreated fabric of claim 17, wherein the fabric comprises a cotton or cotton blend.

19. The pretreated fabric of claim 17 or claim 18 which, subsequent to application of the textile pretreatment solution, has been dried to equilibrium moisture at ambient temperature.

20. The pretreated fabric of any one or combination of claims 17-19, which is a T-shirt.