US-20260125571-A1 - PRINTING INK

US20260125571A1US 20260125571 A1US20260125571 A1US 20260125571A1US-20260125571-A1

Abstract

The present invention relates to an inkjet ink comprising: a continuous aqueous phase; a dispersed encapsulated pigment comprising pigment particles encapsulated by a cross-linked polymer coating having pendant hydrophilic groups including hydroxyl groups; and a cross-linking agent having two or more protected reactive groups, wherein the two or more protected reactive groups, when deprotected, are reactive to hydroxyl groups. The present invention also relates to a method of inkjet printing, a dispersion and a printed substrate.

Inventors

Iris Coe
Brodyck Royles
Joanna Swiecicka-Fichou

Assignees

FUJIFILM SPECIALITY INK SYSTEMS LIMITED
FUJIFILM IMAGING COLORANTS LIMITED

Dates

Publication Date: 20260507
Application Date: 20230926
Priority Date: 20220926

Claims (15)

1 . An inkjet ink comprising: a continuous aqueous phase; a dispersed encapsulated pigment comprising pigment particles encapsulated by a cross-linked polymer coating having pendant hydrophilic groups including hydroxyl groups; a cross-linking agent having two or more protected reactive groups, wherein the two or more protected reactive groups, when deprotected, are reactive to hydroxyl groups; wherein the ink contains less than 5% by weight of a binder resin, based on the total weight of the ink; and wherein the dispersed encapsulated pigment is present in an amount of 3 to 20% by weight, based on the total weight of the ink.
2 . The inkjet ink as claimed in claim 1 , wherein the dispersed encapsulated pigment consists of pigment particles encapsulated by a cross-linked polymer coating having pendant hydrophilic groups including hydroxyl groups.
3 . The inkjet ink as claimed in claim 1 , wherein the pendant hydrophilic groups further include carboxyl groups.
4 . The inkjet ink as claimed in claim 1 , wherein the cross-linking agent having two or more protected reactive groups is a blocked di- and/or poly-isocyanate where the two or more isocyanate groups are protected.
5 . (canceled)
6 . The inkjet ink as claimed in claim 1 , wherein the two or more protected reactive groups, when deprotected, are present in the ink in an amount of 0.01 to 1.00%, preferably 0.02 to 0.80%, more preferably 0.03 to 0.60% by weight, based on the total weight of the ink.
7 . (canceled)
8 . A method of inkjet printing comprising the following steps in order: (i) providing an inkjet ink as claimed in claim 1 ; (ii) inkjet printing the inkjet ink onto a substrate to provide a printed substrate; (iii) drying the printed substrate to remove water; and (iv) deprotecting the two or more protected reactive groups.
9 . The method of inkjet printing as claimed in claim 8 , wherein the two or more protected reactive groups are reactive to hydroxyl groups when thermally deprotected, and wherein deprotecting the two or more protected reactive groups is by heating the printed substrate to a temperature sufficient to deprotect the two or more protected reactive groups.
10 . The method of inkjet printing as claimed in claim 8 , wherein the substrate is a textile substrate, and wherein the textile substrate is composed of a polymeric material having reactive groups which are available to react with the two or more protected reactive groups of the cross-linking agent, when deprotected, preferably wherein the textile substrate comprises a cellulosic material.
11 . The method of inkjet printing as claimed in claim 8 , wherein drying the printed substrate to remove water comprises heating the printed substrate to a temperature of less than 100° C.
12 . The method of inkjet printing as claimed in claim 9 , wherein the temperature sufficient to deprotect the two or more protected reactive groups is 100° C. or higher, preferably 120° C. or higher, more preferably 135° C. or higher.
13 . A dispersion comprising: a continuous aqueous phase; a dispersed encapsulated pigment comprising pigment particles encapsulated by a cross-linked polymer coating having pendant hydrophilic groups including hydroxyl groups; a cross-linking agent having two or more protected reactive groups, wherein the two or more protected reactive groups, when deprotected, are reactive to hydroxyl groups; wherein the dispersion contains less than 5% by weight of a binder resin, based on the total weight of the dispersion; and wherein the dispersed encapsulated pigment is present in an amount of 3 to 20% by weight, based on the total weight of the dispersion.
14 . The printed substrate having the inkjet ink as claimed in claim 1 printed thereon.
15 . The printed substrate obtainable by the method of claim 8 .

Description

The present invention relates to a printing ink and, in particular, an inkjet ink for printing onto textiles. The present invention also relates to a method of printing said ink. Digital inkjet printing is commonly used in the textile industry as it offers many advantages over analogue printing such as a rapid and facile print process, print flexibility and much shorter preparation times. Digital inkjet printing is also more environmentally friendly than analogue printing as it offers substantial reductions in energy consumption and chemical, water and carbon dioxide waste. There are two inkjet inks typically used in the textile industry, dye-based inkjet inks and pigmented inkjet inks. Dye-based inkjet inks provide printed textiles with brilliant colours, good handle and wash- and rub-fastness. However, the textile substrate dictates the particular dye used. Reactive dyes are used for cellulosic and protein fibres, acid dyes are limited to protein fibres and dispersed and sublimation dyes can only be applied to polyester substrates. Printing processes involving dye-based inkjet inks also tend to be multi-step and complex. For example, reactive dyes necessitate pre-treating the textile followed by printing, steaming and then washing the textile. All of these steps are energy and water intensive. Sublimation dyes require printing onto a transfer medium and applying heat and pressure to transfer the print to the substrate. Pigmented inkjet inks offer a significant advantage in terms of universal applicability to textile substrates. Printing using pigmented inkjet inks is also simpler, quicker and more environmentally friendly than using dye-based inkjet inks as the ink can just be printed on the textile and heat treated. Pigmented inkjet inks typically contain a binder resin to enable the pigment to bind to the textile substrate. However, the binder resin tends to provide printed substrates with a poor handle that feel very stiff to the touch, and sub-optimal optical density, print wash, rub and perspiration fastness. There is therefore a need in the art for a pigmented inkjet ink for printing onto textiles that provides a printed substrate with a good handle and optical density, without compromising the wash-fastness and adhesion. Accordingly, the present invention provides an inkjet ink comprising: a continuous aqueous phase;a dispersed encapsulated pigment comprising pigment particles encapsulated by a cross-linked polymer coating having pendant hydrophilic groups including hydroxyl groups; anda cross-linking agent having two or more protected reactive groups, wherein the two or more protected reactive groups, when deprotected, are reactive to hydroxyl groups. The present invention also provides a method of inkjet printing comprising the following steps in order: (i) providing an inkjet ink of the present invention;(ii) inkjet printing the inkjet ink onto a substrate to provide a printed substrate;(iii) drying the printed substrate to remove water; and(iv) deprotecting the two or more protected reactive groups. The present invention will now be described with reference to the accompanying drawings, in which: FIG. 1 shows the handle/softness of substrates, to which inks have been drawn down upon, using inks of the invention (left-hand side and middle) and a comparative ink (right-hand side); FIG. 2 shows the L′ values per wash of printed substrates at a range of print densities using an ink of the invention (line with circles) and a comparative ink (line with squares); FIG. 3 shows optical density values per wash of printed substrates at a range of print densities using an ink of the invention (line with circles) and a comparative ink (line with squares); FIG. 4 shows photographs of substrates, to which inks have been drawn down upon, after no washes (left-hand side), one wash (position X), five washes (position Y) and ten washes (position Z) using inks of the invention (Inks E.1 and E.2) and comparative inks (Inks A and C); FIG. 5 shows optical density values of printed substrates at a range of print densities using an ink of the invention (line with circles) and a comparative ink (line with squares); FIG. 6A shows a micrograph of a printed substrate using a comparative ink at ×90 magnification; FIG. 6B shows a micrograph of a printed substrate using an ink of the invention at ×90 magnification; FIG. 7A shows a micrograph of a printed substrate using a comparative ink at ×150 magnification; FIG. 7B shows a micrograph of a printed substrate using an ink of the invention at ×150 magnification; FIG. 8A shows the wash-fastness deviation of Ink F of the invention from comparative Ink A; FIG. 8B shows the wash-fastness deviation of Ink G of the invention from comparative Ink A; FIG. 9 shows the wash-fastness deviation of Ink I of the invention from comparative Ink A; FIG. 10A shows the crock deviation of Ink F of the invention from comparative Ink A; FIG. 10B shows the crock deviation of Ink G of the invention f