FIELD AND BACKGROUND OF THE INVENTION

The present invention, in some embodiments thereof, relates to inkjet printing technology and, more particularly, but not exclusively, to processes and compositions for direct inkjet printing on untreated dyed synthetic fabrics.

Inkjet printing on fabrics typically involves forming a film on the surface of the substrate such that the colorant (pigment and/or dye) is embedded in the film and the film is affixed to the substrate, giving the finished product wash-fastness and durability. Adherence of the film is typically achieved by forming bonds between functional groups in the substrate and corresponding functional groups in the material of the film; the film comprises binders and adhesion promoting agents, collectively referred to herein as film-forming agents, which form the film with when crosslinked with a crosslinking agent upon exposing the mixture to heat or other forms of energy; a step of the printing process referred to curing.

Problems associated with inkjet printing liquid inks directly on absorptive substrates, such as textile and garments, have been mitigated in U.S. Patent Application Publication No. 20150152274, and PCT Application Nos. WO 2005/115089 and WO 2005/115761, by the present assignee, and which are incorporated by reference as if fully set forth herein. These documents teach a process, a composition and an apparatus for printing an image on an absorptive surface, such as an untreated (a substrate that has not been pre-treated chemically) textile piece, that includes applying a wetting composition on the surface which is capable of interfering with the engagement of a liquid ink composition with the binding sites of the surface. According to the processes taught in these patent applications, once the wetting composition is applied, the liquid ink composition is applied while the surface is still wet. Using this process, a vivid color image is formed on the absorptive surface. These patent applications, however, fail to address printing a color image on an absorptive dark surface.

Multi-part ink compositions, which are based on contacting an immobilizing composition and a colored ink composition on the surface of an untreated substrate, so as to congeal the colored ink composition on the substrate, thereby minimizing feathering and soaking thereof into absorptive substrates, are also taught in U.S. patent application Ser. No. 11/588,277 (U.S. Patent Application Publication No. 20070104899), and U.S. patent application Ser. No. 11/606,242 (U.S. Patent Application Publication No. 20070103529), all of which are incorporated by reference as if fully set forth herein.

Problems associated with inkjet printing transparent liquid inks directly on dark substrates, such as dyed textile and garments, have been mitigated in U.S. Pat. No. 7,134,749, by the present assignee, which is incorporated by reference as if fully set forth herein. This document teaches a method and an apparatus for color printing on an untreated dark textile piece which includes digitally printing, by means of an inkjet printer head, an opaque white ink layer directly onto the untreated dark textile piece, and digitally printing a colored image on the white ink layer.

U.S. Pat. No. 8,540,358, by the present assignee, which is incorporated by reference as if fully set forth herein, teaches an inkjet ink compositions for forming an image in a form of an elastic film attached to a surface of an untreated stretchable and/or flexible substrate and processes utilizing same for inkjet printing color images on various substrates such as colored and absorptive or impregnable stretchable materials, which are characterized by heightened efficiency in process time, ink and energy consumption, as well as products having durable, wash-fast and abrasion-fast images printed thereon by the process, are disclosed.

Direct inkjet printing of pigments on untreated fabrics has enjoyed the improvements provided by the aforementioned technologies, since the emulsified and suspended pigment particles are required to be bound to the substrate by means of film-forming agents (adhesion agents and/or binders), forming a transparent film that encapsulates the pigment particles while adhering to the substrate, and in cases where the substrate is not white, the process is supplemented by an opaque white base layer. The aforementioned technologies employed the presence of emulsified film-forming adhesion agents and film-forming binders and/or dispersants of the suspended pigment particles, by utilizing property-sensitive variants of these ingredients, wherein these ingredients tend to lose their solubility in the ink's medium, and thereby cause coagulation of the ink composition when contacting with a property-adjusting agent (e.g., an acid) on the surface of the substrate. In addition, the aforementioned technologies are based on the ability to crosslink the various ingredients of the film amongst themselves and with the substrate, which is obtained by using a crosslinking agent which cures the film at elevated temperatures.

The requirement to form a well-adhered transparent film to the substrate by crosslinking rises a problem when attempting to inkjet-print images on dyed substrates, particularly synthetic fabrics, wherein the dye in the substrate is of the typical type that becomes loose under elevated temperatures, and prone to migrate. This problem, known as dye migration, renders the colors of the image tinted with the color of the substrate, since the dye migrates during the curing step, and infiltrates the freshly printed film (image). In case where the image printing process is supplemented with an opaque white underbase later, the white underbase becomes tinted with the dye migrating from the substrate therein, skewing the colors that are printed on top of it.

Attempts to minimize the problem of dye migration into inkjet-printed and heat-cured images on dyed substrates include pretreatment of the substrate with substances that allegedly limit dye migration upon heating the substrate to effect curing of the image; however, these pretreatments pose a commercial burden and limit the scope of fabrics that can be used, and provide a marginal solution to the problem.

Attempts to block dye-migration in printing onto colored synthetic fiber included the use of activated carbon as an active ingredient of a transfer paper comprising a resin layer containing the activated carbon to block dyes in the synthetic fiber from migration.

Low-bleed inks have been designed to minimize dye migration, however, no ink can stop dye from sublimating at elevated temperatures. Low-bleed inks contain chemical-blocking agents that are selected to mitigate migration; however, since the ratio of sublimated dye to chemical-blocking agents in the ink is so great, the dye simply overpowers the ink's ability to block its migration.

Other attempts include using UV-curable inks; however, such inks are less adapted for printing on synthetic substrates, heat-migrating of dyes is most pronounced. Using other rapid-acting crosslinking agent, such as aziridine and/or isocyanate is not possible due to safety, health and stability issues.

Low-temperature curing crosslinking agent (LTCC) have been suggested for use in inkjet printing; however, these agent were chosen for their ability to disperse as colloids and latex suspensions in water and cure under alkaline conditions at about 120° C.

SUMMARY OF THE INVENTION

The present invention provides a compositions and processes for inkjet printing a color image on a dyed synthetic fabric, such that the printed ink is not soaked into the fabric during the printing step, and the dye in the substrate does not migrate into and distort the colors of the printed image during the curing step. These two feats are achieved by applying an immobilizing composition to the fabric that causes the ink composition to coagulate upon contact due to its low pH, and at the same time deliver a low-temperature curing crosslinking agent to the ink composition that affixes the image film to the substrate while avoiding heating it to dye-migration temperatures.

Thus, according to an aspect of some embodiments of the present invention there is provided an inkset that includes an immobilizing composition and at least one ink composition, the ink composition includes a dispersed pigment and/or dye, a low-temperature curing self-crosslinking resin and an aqueous carrier, and formulated to exhibit an alkaline pH higher than 7, the immobilizing composition includes an acid and an aqueous carrier, and formulated to exhibit an acidic pH lower than 7, the inkset is for digital inkjet printing color images directly on a dyed substrate.

In some embodiments of the present invention, the substrate is dyed with a migratable dye.

According to some embodiments of the invention, the acidic pH is lower than 6.5.

According to some embodiments of the invention, the immobilizing composition is essentially devoid of a crosslinking agent.

According to some embodiments of the invention, the ink composition is essentially devoid of an additional crosslinking agent other than the low-temperature curing self-crosslinking resin.

According to some embodiments of the invention, the ink composition is essentially devoid of an additional film-forming agent and/or binder other than the low-temperature curing self-crosslinking resin.

According to some embodiments of the invention, the low-temperature curing self-crosslinking resin initiates crosslinking reaction at a temperature lower than 120° C., or lower than 110° C., or lower than 90° C., or that ranges from 90° C. to 110° C.

According to some embodiments of the invention, the low-temperature curing self-crosslinking resin initiates crosslinking reaction upon contacting an acid.

According to some embodiments of the invention, the low-temperature curing self-crosslinking resin is a low-Tglow-temperature curing self-crosslinking resin.

According to some embodiments of the invention, the low-temperature curing self-crosslinking resin is a pH-sensitive low-temperature curing self-crosslinking resin.

According to some embodiments of the invention, the low-Tglow-temperature curing self-crosslinking resin is a low-TgpH-sensitive low-temperature curing self-crosslinking resin.

According to some embodiments of the invention, the low-TgpH-sensitive low-temperature curing self-crosslinking resin is a polyurethane resin exhibiting self-crosslinking pendant groups and/or self-crosslinking end-capping groups.

According to some embodiments of the invention, the self-crosslinking pendant groups and/or the self-crosslinking end-capping groups includes silanol groups.

According to some embodiments of the invention, the acid is an organic acid.

According to some embodiments of the invention, the organic acid is volatile and/or decomposes at a temperature higher than 70° C.

According to some embodiments of the invention, the acid is selected form the group consisting of glycolic acid, acetic acid, lactic acid, malic acid, ascorbic acid, maleic acid and benzoic acid.

According to some embodiments of the invention, the substrate is a fabric that includes dyed synthetic fibers.

According to some embodiments of the invention, the dye in the dyed synthetic fibers migrates at a temperature higher than 120° C.

According to some embodiments of the invention, the dyed substrate is an untreated substrate.

According to an aspect of some embodiments of the present invention there is provided an inkset for digital inkjet printing color images directly on a dyed substrate; the inkset includes an immobilizing composition and at least one ink composition, the immobilizing composition includes a low-temperature curing crosslinking (LTCC) agent and a first carrier, and formulated to exhibit a pH lower than 7, whereas the ink composition includes a dispersed pigment and/or dye, an alkali-soluble agent, a high acid number film-forming agent and a second carrier. The inkset provided herein is particularly useful for digital inkjet printing color images on colored synthetic fabrics that are dyed with a migratable dye, and more particularly useful for digital inkjet printing color images on darkly colored synthetic fabrics that are dyed with a migratable dye that can sublime at high temperatures typically used for curing a digital ink composition such that the dye penetrates the printed image and distorts the colors of the image upon curing or thereafter.

According to some embodiments of the invention, the pH of the immobilizing composition is lower than 6.5.

According to some embodiments of the invention, the pH ranges from 4 to 6.5.

According to some embodiments of the invention, each of the immobilizing composition and the ink composition is substantially devoid of an aziridine and/or a small-molecule isocyanate.

According to some embodiments of the invention, the LTCC agent initiates crosslinking reaction at a temperature that ranges from 90° C. to 110° C.

According to some embodiments of the invention, the LTCC agent propagates crosslinking reaction at a temperature lower than 100° C.

According to some embodiments of the invention, the LTCC agent is a carbodiimide crosslinking agent.

According to some embodiments of the invention, the LTCC agent is a polycarbodiimide crosslinking agent.

According to some embodiments of the invention, the immobilizing composition includes an acid.

According to some embodiments of the invention, the acid is an organic acid.

According to some embodiments of the invention, the organic acid is volatile and/or decomposes at a temperature higher than 70° C.

According to some embodiments of the invention, the acid is selected form the group consisting of glycolic acid, acetic acid, lactic acid, malic acid, ascorbic acid, maleic acid and benzoic acid.

According to some embodiments of the invention, the first carrier includes water.

According to some embodiments of the invention, the first carrier includes water and a water-miscible organic solvent.

According to some embodiments of the invention, the ratio of water to organic solvent ranges from 100:1-1:1.

According to some embodiments of the invention, the water-miscible organic solvent is a glycol ether.

According to some embodiments of the invention, the glycol ether is selected from the group consisting of dipropylene glycol methyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether and diethylene glycol mono-n-butyl ether.

According to some embodiments of the invention, the alkali-soluble agent is capable of coagulating upon contacting the acid.

According to some embodiments of the invention, the alkali-soluble agent is selected from the group consisting of an alkali-soluble resin, an alkali-soluble polymer, an alkali-soluble dispersant, an alkali-soluble surfactant, an alkali-soluble coagulant and an alkali-soluble gelling agent.

According to some embodiments of the invention, the alkali-soluble agent is an alkali-soluble polymer.

According to some embodiments of the invention, the alkali-soluble polymer is selected from the group consisting of an alkali-soluble acrylic polymer, an alkali-soluble co-acrylic polymer, poly(styrene/acrylic acid) polymer, an emulsified polyurethane, a polyurethane polymer, a polyether polymer, a polyester polymer, a polyacrylate polymer, a polyvinyl chloride polymer, a polyvinyl acetate polymer, a polyvinyl butyral polymer, an aminosilicon polymer and any salt, co-polymer or combination thereof.

According to some embodiments of the invention, the acid number of the high acid number film-forming agent is greater than 5, 7, 10, 15, 20 or 30 mg KOH/gram.

According to some embodiments of the invention, the high acid number film-forming agent includes a plurality of carboxylic groups.

According to some embodiments of the invention, the high acid number film-forming agent is selected from the group consisting of polyacrylic acid, acidic alkoxylated polymer, poly(2-acrylamido-2-methylpropanesulphonic acid), poly(acrylic acid-co-maleic acid), poly(butadiene-co-maleic acid), poly(ethylene-co-acrylic acid), polymaleic acid, poly(methacrylic acid), poly(4-styrenesulfonic acid-co-maleic acid), and any salt thereof, any mixture thereof, any co-polymer and/or combination thereof.

According to some embodiments of the invention, the second carrier is an aqueous carrier.

According to some embodiments of the invention, the dyed substrate is a fabric that includes dyed synthetic fibers.

According to some embodiments of the invention, the synthetic fibers are selected from the group consisting of polyester fibers, polyurethane fibers, polyamide fibers, polyacryl fibers, polyolefin fibers, polybenzimidazole fibers, and any co-polymer thereof, Nylon fibers, polyacrylonitrile (Modacryl) fibers, Rayon fibers, Vinyon fibers, Saran fibers, Spandex fibers, Vinalon fibers, Aramid fibers, Modal® fibers, Dyneema® fibers and Spectra® fibers, and combination thereof with cellulosic fibers and/or animal fibers, and combination of the foregoing.

According to some embodiments of the invention, the dyed substrate includes a sublimable and/or migratable dye.

According to some embodiments of the invention, the sublimable and/or migratable dye migrates at a temperature higher than 120° C.

According to some embodiments of the invention, the dyed substrate is an untreated dyed substrate; namely not pre-treated off-line of the printing process, to limit dye migration.

According to some embodiments of the invention, the dispersed pigment is selected from the group consisting of a white pigment, a black pigment, a yellow pigment, a cyan pigment, a magenta pigment, a blue pigment, a green pigment, a red pigment, and any combination thereof.

According to an aspect of some embodiments of the present invention there is provided a process for digital inkjet printing color images directly on a dyed substrate using the inkset presented herein, the process includes:

contacting at least a portion of the substrate with the immobilizing composition;

printing the ink composition directly on the portion of the substrate; and

heating the substrate to a temperature lower than 110±5° C. to thereby initiate a crosslinking reaction and form the image in the form of a film on the surface of the substrate.

According to some embodiments of the invention, the process further includes, subsequent to heating, maintaining the substrate having the printed thereon at a temperature lower than 100° C. for a time period that ranges from 1 hour to 1 week to thereby effect propagation of the crosslinking reaction. In some embodiments, the time period is shorted than one hour or longer than one week, or can be any length between 0 to 7 days.

According to some embodiments of the invention, the temperature lower than 100° C. is room temperature.

According to an aspect of some embodiments of the present invention, there is provided a dyed substrate having an image printed thereon in a form of a cured film, wherein the image is afforded by inkjet printing the inkset provided herein on the surface of the substrate.

According to an aspect of some embodiments of the present invention, there is provided an image in a form of a cured film applied on a dyed substrate, wherein the image is afforded by the process provided herein.

According to some embodiments of the invention, the dyed substrate is dyed with a migratable dye, and the cured film is essentially devoid of the migratable dye.

According to some embodiments of the invention, the cured film is essentially devoid of a residue of a crosslinking agent other than the pH-sensitive low-temperature curing self-crosslinking resin, or the low-temperature curing crosslinking agent.

Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

