Patent Description:
The state of the art includes examples of compositions intended for depositing conductive materials on textiles. In this sense, patent application <CIT> describes a screen printing ink formulation for printing electrically conductive traces on flexible fabrics which comprises an elastomer, a liquid vehicle mixed with the elastomer, such that the liquid vehicle is capable of swelling the elastomer and has a boiling point of <NUM> or more at <NUM> atmospheric pressure, and a plurality of non-spherical, electrically conductive particles. The conductive particles are selected from the group comprising particles in a percentage comprised between <NUM>% and <NUM>% by mass of the ink. These particles can be flake-like, needle-like and/or nanotubular, and they can be comprised of silver and/or carbon. However, the flake-like, needle-like and nanotubular particles are unfeasible in the inkjet ink formulation because they block the holes in the injection heads and, therefore, they prevent the ink from being printed on the fabric. In addition, this application does not provide any information about fundamental aspects in the formulation of an ink such as viscosity. Nevertheless, by indicating that it is intended for screen printing, it follows that the viscosity values are inherently much higher than those values for inkjet and, therefore, unfeasible for its application using this technology. Moreover, it does not provide information about the additives required for the formulation of an inkjet ink such as dispersants and wetting agents, among others. It should also be noted that patent application <CIT> does not provide information about conductivity based on the concentration of conductive particles, a fundamental aspect for evaluating effectiveness in antistatic applications.

The state of the art also includes coloured fabrics with antistatic properties. Thus, patent application <CIT> describes a coloured garment that comprises a conductive acrylic fibre based on conductive carbon microparticles, as a material that provides the antistatic property, which is coloured with a cationic soluble dye. However, this application has the limitation that it requires prior preparation of the thread or fibre, since it is necessary to incorporate the conductive acrylic fibre based on conductive carbon microparticles and subsequently carry out the weaving process to obtain the conductive textile material. Moreover, patent application <CIT> does not provide any information about the dispersion and stabilisation of said conductive carbon microparticles in a liquid medium. Additionally, it is important to indicate that, since the fabric is completely coloured, motifs with different colours, such as images, cannot be printed, nor can each textile piece be personalised with a different decoration.

Finally, it should be noted that the state of the art does not include inks capable of simultaneously stabilising organic and inorganic particles due to their different nature. In this sense, the present invention provides for the formulation of an ink composition that is capable of imparting a good colour effect while maintaining the antistatic property when it is deposited on any type of fabric without the need for prior preparation thereof. For this, the ink composition according to the present invention allows for the simultaneous stabilisation of organic pigments, responsible for the chromatic function, and inorganic particles of SnO<NUM> doped with Sb<NUM>O<NUM>, responsible for the antistatic function.

Throughout the description and the claims, the word "comprises" and its variants do not intend to exclude other technical features, additives, components or steps. Moreover, the word "comprises" includes the case of "consists of". For those skilled in the art, other objects, advantages and features of the invention may be partially deduced from both the description and the embodiment of the invention.

The present invention is an antistatic hybrid ink applicable by inkjet drop-on-demand (DoD) technology which simultaneously imparts colour effects and antistatic properties when printed on textiles.

The term "textile" as used in the present invention refers to any natural or synthetic material that has been made from threads, filaments or fibres, of any size, including micro and nanofibres, joined by mechanical, thermal or chemical processes. Examples of materials with which textiles can be made, by way of example, but not limitation, are cotton, hemp, wood, wool, linen, polyester, nylon, polyethylene, polypropylene, elastomers, silk and Lycra, in a pure state or combined therebetween.

The hybrid ink object of the invention comprises particles of SnO<NUM> doped with Sb<NUM>O<NUM>, in a percentage by weight of the ink comprised between <NUM>% and <NUM>%, with a particle size (D90) less than <NUM>, and they are responsible for providing the printed fabric with the antistatic property. The content of Sb<NUM>O<NUM> in SnO<NUM> is comprised between <NUM>% and <NUM>% by weight with respect to the total weight of the particles, preferably between <NUM>% and <NUM>%. The term "particles of SnO<NUM> doped with Sb<NUM>O<NUM>" as used in the present invention refers to particles whose main component is SnO<NUM> to which a certain amount of Sb<NUM>O<NUM> has been added by physical or chemical methods, resulting in a new indivisible material. By way of example, <NUM> grams of particles of SnO<NUM> doped with <NUM>% by weight of Sb<NUM>O<NUM> means that the content of SnO<NUM> in the particles is <NUM> grams and that of Sb<NUM>O<NUM> is <NUM> grams, wherein the particles are a material formed by both components that cannot be separated.

In addition, according to the present invention, the particles of SnO<NUM> doped with Sb<NUM>O<NUM> are obtained by the synthesis method selected from the group comprising solid state reaction at a maximum temperature comprised between <NUM> and <NUM>, sol-gel, hydrothermal synthesis and coprecipitation.

The present invention also comprises at least one organic pigment, in a percentage by weight of the ink comprised between <NUM>% and <NUM>% and which is selected from the group comprising cyan, cobalt blue, turquoise blue, violet, magenta, red, yellow, orange, black, white, green, grey or a mixture thereof.

The term "organic pigment" as used in the present invention refers to any insoluble material in the ink medium, of natural or synthetic origin and characterised in that it comprises double bonds, triple bonds and/or organic chemical groups (amine, sulphone, chlorine, hydroxyl, carboxyl, bromine, etc.) responsible for changing the colour of reflected or transmitted light as a result of wavelength selective absorption, giving rise to a certain colour. Examples of organic pigments, by way of example, but not limitation, are monoazo pigments (yellow <NUM> pigment, red <NUM> pigment, red <NUM> pigment, orange <NUM> pigment, etc.), diazo pigments (yellow <NUM> pigment, yellow <NUM> pigment, red <NUM> pigment, etc.), phthalocyanine-based pigments (blue <NUM> pigment, blue <NUM>:<NUM> pigment, green <NUM> pigment, green <NUM> pigment), isoindolinone-based pigments, dioxazine-based pigments, anthraquinone pigments, quinacridone-based pigments, perylene pigments or a mixture thereof.

To fix the organic pigments and particles to the textile, it is necessary to include a resin in the formulation of the hybrid ink. In this sense, the present invention comprises at least one resin that is dispersible in water and heat-curable at a temperature below <NUM>, in a percentage by weight of the ink comprised between <NUM>% and <NUM>%. The resin is selected from the group comprising urethane resin with polyether groups, urethane resin with polyester groups, urethane resin with polycarbonate groups, acrylic resin or a mixture thereof.

The water-dispersible and heat-curable resins can be formulated directly or commercial resins can be used. Examples of commercial resins, by way of example, but not limitation, are Joncryl HPD, Joncryl <NUM>, Cromoelastic SE, Cromoelastic NI, Edolan SN and Edolan SE.

The antistatic hybrid ink object of the invention also comprises water in a percentage by weight of the ink comprised between <NUM>% and <NUM>%. In addition, the hybrid ink comprises a solvent, soluble in water, from the glycol family, in a percentage by weight of the ink comprised between <NUM>% and <NUM>%. The water-soluble solvent is selected from the group comprising monoethylene glycol, monopropylene glycol, ethylene glycol propyl ether, <NUM>,<NUM>,<NUM>-propanetriol, ethylene glycol n-butyl ether, diethylene glycol, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol n-butyl ether, triethylene glycol, triethylene glycol methyl ether, triethylene glycol ethyl ether, triethylene glycol n-butyl ether, tripropylene glycol methyl ether, polyethylene glycol, <NUM>,<NUM>-butanediol and <NUM>,<NUM>-pentanediol or a mixture thereof.

The water-soluble solvent can be formulated directly or commercial products can be used. Examples of commercial solvents, by way of example, but not limitation, are Butyl Carbitol, Dipropylene Glycol, Dowanol DPnB Glycol Ether, Dowanol PPH Glycol Ether, Hexyl Carbitol and Butyl Cellosolve.

The fact that the hybrid ink contains water provides an environmental advantage over other formulations based on hydrocarbons and non-polar solvents. However, this highly polar liquid medium in DoD inkjet formulations also poses an added difficulty when it comes to simultaneously stabilising the particles of SnO<NUM> doped with Sb<NUM>O<NUM>, which are inorganic in nature, and the organic pigments, of an organic nature. After performing numerous experimental assays, it has been discovered that the required simultaneous stabilisation is achieved by means of optimally selecting the concentration of the dispersants for both types of materials. To that end, the hybrid ink composition comprises:.

The dispersants for organic pigments can be formulated directly or commercial products can be used such as Disperbyk <NUM>, Disperbyk <NUM>, Solsperse <NUM>, Solsperse <NUM>, Solsperse <NUM> and Solsperse <NUM>.

Additionally, in its formulation the hybrid ink object of the invention also comprises at least one wetting agent in a percentage by weight of the ink comprised between <NUM>% and <NUM>%. The wetting agent is selected from the group comprising a mixture of ethers with polyethylene-polypropylene glycol with monobenzyl ether and C8-C10 alcohols, polyether-polysiloxane copolymer, anionic surfactants, non-ionic surfactants or a mixture thereof.

In addition, the antistatic hybrid ink comprises at least one anti-foaming agent to prevent the formation of bubbles when in the printing circuit and when printing occurs. The content of anti-foaming agent is comprised between <NUM>% and <NUM>% of the weight of the ink, and is selected from the group comprising modified silicones, polydimethylsiloxanes, mineral oil derivatives, fatty acid derivatives or a mixture thereof.

In a preferred embodiment of the present invention, the antistatic hybrid ink comprises:.

In the formulation of inks for DoD inkjet technology, it is essential to define a series of properties that ensure their correct behaviour. In this sense, it is worth noting the value of the viscosity based on the shear rate or derived from the transverse deformation with respect to time, both when the water-based ink is practically at rest (shear rate at <NUM>-<NUM>) and when it is in motion in the printing equipment circuit (shear rate comprised between <NUM>-<NUM> and <NUM>-<NUM>). The shear rate was measured with an Anton Paar model MCR102 cone-plate rheometer. The method for measurement consists of placing the water-based ink on a horizontal heated plate. Subsequently, the cone lowers and begins to rotate, measuring the torque. From the torque value, the viscosity value is calculated at a given temperature and shear rate. In this sense, the water-based ink object of the present invention is characterised in that it has the following viscosity values at <NUM> based on the shear rate:.

In the field of inkjet inks, the use of the centipoise unit (cP) is common, where <NUM> cP is equivalent to <NUM> Pa s in the International System of Units.

Another fundamental property of ink in the field of DoD inkjet is surface tension, since it ensures that the drop exits the print head correctly and is deposited on the textile without expanding, which would cause a loss of definition of the printed motif. In this sense, the antistatic hybrid ink object of the invention is characterised in that it has a surface tension value comprised between <NUM> mN/m and <NUM> mN/m.

A common method of measuring the antistatic property in the textile sector is standard EN1149-<NUM>:<NUM>. In this sense, the antistatic hybrid ink composition object of the invention is characterised in that it provides the printed fabric with a half decay time (t<NUM>) of less than <NUM> seconds, when the amount of ink deposited on said fabric is equal to or greater than <NUM>/m<NUM>. The half decay time (t<NUM>) is defined as the time it takes for the intensity of the electric field induced in the tested textile material to be reduced by half. The method consists of charging the textile material to be tested by inductive effect. To that end, a field electrode is placed immediately below the test sample, which remains horizontal, and it does not make contact with the same.

The field electrode is suddenly subjected to a high voltage. If the sample is conductive or contains conductive elements, a charge with a sign opposite to that of the field electrode is induced on it. The electric field of the field electrode impinging on the conductive elements does not pass through the test sample, and the resulting electric field is reduced in a way that is characteristic of the material tested. This effect is measured and recorded behind the sample, using a suitable field measuring probe. The resulting electric field measured by the measuring probe decreases as the charge induced on the sample increases. This electric field reduction is used to determine the half decay time (t<NUM>).

Since the antistatic hybrid ink object of the invention contains water, it may be necessary to incorporate preservatives that prevent bacteria and other types of microorganisms that degrade the composition from developing. Therefore, the water-based ink of the present invention may comprise a preservative in a percentage by weight of the ink comprised between <NUM>% and <NUM>%, which is selected from the group comprising a mixture of <NUM>,<NUM>-benzisothiazol-<NUM>-one and <NUM>,<NUM>-benzisothiazol-<NUM>(<NUM>)-one, <NUM>-methyl-<NUM>-isothiazol-<NUM>-one, bronopol, sodium pyrithione, tetramethyl acetylene diurea or a mixture thereof.

The following examples are provided for illustrative purposes and are not intended to limit the present invention. Moreover, the present invention covers all possible combinations of particular and preferred embodiments indicated herein.

The following antistatic hybrid ink compositions were prepared:.

The properties in terms of viscosity and surface tension of each of the antistatic hybrid inks are indicated below.

The antistatic hybrid inks <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> were applied with DoD inkjet equipment on three types of fabrics, one <NUM>% cotton fabric, another <NUM>% cotton and <NUM>% polyester fabric and a third <NUM>% polyester fabric. In each type of fabric, each ink was printed on three specimens measuring <NUM> per side. In all cases, the amount of ink deposited on the specimen was <NUM>/m<NUM>. Subsequently, each printed specimen was subjected to a heat treatment at <NUM> for <NUM> minutes.

The printed and heat-treated specimens were evaluated both from the point of view of colorimetric performance and antistatic property. The colorimetric study focused on determining the CieLa*b* colorimetric coordinates using a spectrophotometer (Minolta or similar), with D65 lighting and detection conditions of <NUM>°. As for the measurement of the electrostatic property, the half decay time t<NUM> was measured according to standard EN1149-<NUM>:<NUM>.

Next, the mean value of L, a* and b* obtained from the three specimens of each type of fabric and with each ink is shown.

The following table indicates the mean value of the half decay time (t<NUM>) obtained from the three specimens of each type of fabric and with each ink.

Claim 1:
An antistatic hybrid ink composition applicable using inkjet drop-on-demand (DoD) technology of the type that simultaneously imparts a colour effect and antistatic properties on textiles, and comprising:
a. Particles of SnO<NUM> doped with Sb<NUM>O<NUM>, in a percentage by weight of the ink comprised between <NUM>% and <NUM>% and with a particle size (D90) smaller than <NUM>.
b. At least one organic pigment in a percentage by weight of the ink comprised between <NUM>% and <NUM>% and which is selected from the group comprising cyan, cobalt blue, turquoise blue, violet, magenta, red, yellow, orange, black, white, green, grey or a mixture thereof.
c. At least one resin that is dispersible in water and heat-curable at temperatures below <NUM> in a percentage by weight of the ink comprised between <NUM>% and <NUM>%.
d. Water in a percentage by weight of the ink comprised between <NUM>% and <NUM>%.
e. A water-soluble solvent from the glycol family in a percentage by weight of the ink comprised between <NUM>% and <NUM>%.
f. At least one dispersant for inorganic particles of SnO<NUM> doped with Sb<NUM>O<NUM> in a percentage by weight of the ink comprised between <NUM>% and <NUM>%.
g. At least one dispersant for organic pigments in a percentage by weight of the ink comprised between <NUM>% and <NUM>%.
h. At least one wetting agent in a percentage by weight of the ink comprised between <NUM>% and <NUM>%.
i. At least one anti-foaming agent in a percentage by weight of the ink comprised between <NUM>% and <NUM>%.