Patent ID: 12202988

DETAILED DESCRIPTION OF THE DISCLOSURE

In the sense of the disclosure, the term “in situ” means that the metallic nanoparticles present in the aqueous gel ink of the disclosure are synthetized directly in the gel-based matrix of the aqueous ink.

In the sense of the disclosure, the term “fixed color” means that the color of the aqueous gel ink of the disclosure is the same, by visual observation, before and after application on a media, in particular over a period of seven calendar days (one week).

According to a preferred embodiment of the disclosure, the media is an absorbing support wherein the absorbing support is a porous substrate, and more specifically an absorbing support chosen in the group consisting of paper, cardboard and textiles.

For the purposes of the present disclosure, the term “ink” is intended to mean a “writing ink” which is intended to be used in a writing instrument, and in particular in a pen. A writing ink should not be confused with a “printing ink” which is used in printing machines and which does not have the same technical constraints and thus the same specifications. Indeed, a writing ink must not contain solid particles of which the size is greater than the channels of the writing instrument, in order to avoid blocking them, which would inevitably lead to writing being irreversibly stopped. In addition, it must allow an ink flow rate suitable for the writing instrument used, in particular a flow rate of between 100 and 500 mg/200 m of writing, and advantageously between 150 and 400 mg/200 m of writing. It must also dry sufficiently rapidly to avoid smudging the writing medium. It must also avoid the problems of migration (bleeding) over time. Thus, the ink according to the present disclosure will be suitable for the writing instrument for which it is intended, in particular for a pen.

In addition, a “writing ink” must not be too fluid, so as to avoid leaks during writing. However, it must be sufficiently fluid to facilitate the flow of the writing action.

In the particular case of the disclosure, the writing ink being a “gel ink” (which corresponds therefore to a thixotropic ink), the viscosity measured at rest (at a shear rate of 0.01 s−1) at 20° C. is different and in particular higher than the viscosity measured with a shear rate of 100 s−1at 20° C. using the same rheometer such as a cone-and-plate rheometer for example Malvern KINEXUS with a cone of 60 mm and an angle of 1°. In a particular embodiment, the viscosity of the gel ink according to the present disclosure measured under these conditions ranges from 1,000 to 7,000 mPa·s, advantageously from 2,000 to 5,000 mPa·s, and more advantageously from 2,500 to 3,500 mPa·s, with a shear rate of 1 s−1, and advantageously from 5 to 50 mPa·s, more advantageously from 7 to 40 mPa·s, and still more advantageously from 10 to 20 mPa·s with a shear rate of 5,000 s−1. Advantageously, such a viscosity is stable during storage for at least three months at 40° C. and 20% relative humidity, in particular the viscosity will not have a more than 50% decrease. More advantageously, the return to viscosity at rest after shear is very quick, advantageously at most a few minutes, in order to avoid the static leakage in the minutes after writing.

In the present disclosure, the gel-based matrix of aqueous ink prepared in step (i) may comprise from 50 to 95%, more specifically from 60 to 90%, and even more specifically from 70 to 85%, by weight of water.

The gel-based matrix of aqueous ink prepared in step (i) may also comprise classic gel ink ingredients such as solvents, antimicrobial agents, corrosion inhibitors, antifoam agents, rheology modifiers, etc. The gel ink ingredients used to prepare the gel-based matrix of aqueous ink of step (i) will be largely described below, in relation with the subject-matter of the aqueous gel ink with fixed color of the disclosure.

The reducing agent 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid may be added in the form of a solution or in the form of powder. The reducing agent reduces the metallic salts to elemental metal (i.e. oxidation state: 0).

In a preferred embodiment, the concentration of the reducing agent 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid in the gel-based matrix of aqueous ink of step (i) ranges from 0.1 to 2 mol·L−1, more specifically from 0.2 to 1 mol·L−1, and even more specifically 0.3 to 0.8 mol·L−1.

In the present disclosure, the solution of metallic salts is advantageously a solution of gold salts (Au3+), which is more advantageously a solution of gold (III) chloride trihydrate HAuCl4.3H2O. Metallic nanoparticles are formed when contacting the metallic salts with the reducing agent.

In a preferred embodiment, the concentration of metallic salts in the gel-based matrix of aqueous ink of step (ii) ranges from 0.0001 to 0.5 mol·L−1, more specifically 0.001 to 0.1 mol·L−1, and even more specifically 0.002 to 0.08 mol·L−1.

The addition of a solution of metallic salts to the gel-based matrix of aqueous ink prepared in step (i) can be made:by continuous injection, to obtain lighter colored aqueous gel inks, ordrop-by-drop, to obtain darker colored aqueous gel inks.

In a preferred embodiment, the metallic nanoparticles obtained in step (ii) are gold nanoparticles. In another preferred embodiment, the metallic nanoparticles have the shape of spheres or polyhedral shape, more specifically polyhedral shape, and even more specifically triangular, square, rectangular shapes.

In a preferred embodiment, the molar ratio between the metallic salts and the reducing agent 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid ranges from 0.1 to 20%, and more specifically from 1 to 15%.

The present disclosure also concerns an aqueous gel ink with fixed color obtained according to the process of the disclosure, the aqueous gel comprising 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid as reducing agent and metallic nanoparticles.

The 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid and the metallic nanoparticles are as defined above in relation with the subject-matter of the process of the disclosure.

In the aqueous gel ink with fixed color of the disclosure, the amount of reducing agent 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid advantageously ranges from 10 to 30%, and more advantageously from 12 to 25%, by weight relative to the total weight of the aqueous gel ink.

In the aqueous gel ink with fixed color of the disclosure, the metallic nanoparticles are advantageously gold nanoparticles. The metallic nanoparticles present in the aqueous gel ink with fixed color of the disclosure have more specifically the shape of spheres or polyhedral shape, even more specifically polyhedral shape, and even more specifically triangular, square, rectangular shapes.

In the aqueous gel ink with fixed color of the disclosure, the metallic nanoparticles of the disclosure have more specifically an average particle size ranging from 1 to 100 nm, and even more specifically from 10 to 60 nm. This average particle size is determined by analysis of 2D images (microscope: JEOL ARM 200), according to the standard ISO9001:2015.

According to a preferred embodiment, the distance between the metallic nanoparticles within the aqueous gel ink of the disclosure is lower than 100 nm, more specifically varies from 10 to 50 nm, and even more specifically varies from 15 to 30 nm.

In the aqueous gel ink with fixed color of the disclosure, the amount of metallic nanoparticles advantageously ranges from 0.001 to 0.1%, and more advantageously from 0.005 to 0.008%, by weight relative to the total weight of the aqueous gel ink.

In the aqueous gel ink with fixed color of the disclosure, the amount of water advantageously ranges from 50 to 95%, more advantageously from 60 to 90%, and even more advantageously from 70 to 85%, by weight relative to the total weight of the aqueous gel ink.

The aqueous gel ink with fixed color of the disclosure may also comprise classic gel ink ingredients such as solvents, antimicrobial agents, corrosion inhibitors, antifoam agents, rheology modifiers, as described below. These gel ink ingredients are added to the gel-based matrix of aqueous ink in step (i) of the process of the disclosure.

The aqueous gel ink of the disclosure may comprise a solvent. Among the solvents that can be used, mention may be made of polar solvents miscible in water such as:glycol ethers such as triethylene glycol, polyethylene glycol, diethylene glycol monoethyl ether, diethylene-glycol-mono butyl ether, dipropyleneglycol monobutyl ether, tripropylene glycol monomethyl ether, phenoxyethanol, phenoxypropanol,alcohols: linear or branched alcohol in C1-C15such as isopropanol, butanol, isobutanol, pentanol, benzyl alcohol, glycerin, diglycerin, polyglycerin,esters such as ethyl acetate or propyl acetate,carbonate esters such as propylene carbonate or ethylene carbonate,ketones such as methylisobutylketone (MIBK), acetone or cyclohexanone, andmixtures thereof.

In a preferred embodiment, the solvent is chosen in the group consisting of glycol ethers, and more specifically is chosen in the group consisting of triethylene glycol, polyethylene glycol, diethylene glycol monoethyl ether, diethylene-glycol-mono butyl ether, dipropyleneglycol monobutyl ether, tripropylene glycol monomethyl ether, phenoxyethanol, phenoxypropanol, and mixture thereof. In a further advantageous embodiment the solvent is chosen in the group consisting of triethylene glycol, polyethylene glycol, and mixture thereof.

Advantageously, the solvent is present in the aqueous gel ink of the disclosure in an amount ranging from 5 to 35%, more advantageously from 9 to 30%, and even more advantageously from 11 to 25%, by weight relative to the total weight of the aqueous gel ink.

The aqueous gel ink of the disclosure may comprise an antimicrobial agent such as isothiazolinone (ACTICIDE® from Thor), more specifically chosen in the group consisting of 1,2-benzisothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, and mixture thereof.

Advantageously, the antimicrobial agent is present in the aqueous gel ink of the disclosure in an amount ranging from 0.01 to 0.5%, and more advantageously from 0.1 to 0.2%, by weight relative to the total weight of the aqueous gel ink.

The aqueous gel ink of the disclosure may comprise a corrosion inhibitor, more specifically chosen in the group consisting of tolytriazole, benzotriazole, and mixture thereof.

Advantageously, the corrosion inhibitor is present in the aqueous gel ink of the disclosure in an amount ranging from 0.05 to 1%, more advantageously from 0.07 to 0.5%, and even more specifically from 0.08 to 0.15%, by weight relative to the total weight of the aqueous gel ink.

The aqueous gel ink of the disclosure may comprise an antifoam agent, more specifically a polysiloxane-based antifoam agent, and even more specifically an aqueous emulsion of modified polysiloxane (such as MOUSSEX® from Synthron, TEGO® Foamex from Evonik).

Advantageously, the antifoam agent is present in the aqueous gel ink of the disclosure in an amount ranging from 0.05 to 1%, more advantageously from 0.1 to 0.5%, and even more advantageously from 0.2 to 0.4%, by weight relative to the total weight of the aqueous gel ink.

The aqueous gel ink of the disclosure may comprise a rheology modifier capable of generating a gelling effect, more specifically chosen in the group consisting of xanthan gum, gum arabic, and mixture thereof.

Advantageously, the rheology modifier is present in an amount ranging from 0.08 to 2%, more specifically from 0.2 to 0.8%, and even more specifically from 0.3 to 0.6%, by weight relative to the total weight of the aqueous gel ink.

The aqueous gel ink with fixed color of the disclosure may also comprise other additives such as:pH regulators like sodium hydroxide and triethanolamine,lubricants,coalescing agents,crosslinking agents,wetting agents,plasticizers,antioxidants, andUV stabilizers.

When present, these additives are added to the gel-based matrix of aqueous ink in step (i) of the process of the disclosure.

The present disclosure also concerns a method of writing with an aqueous gel ink of fixed color comprising the step of writing onto a media, more specifically on an absorbing support wherein the absorbing support is a porous substrate, and more specifically on paper, cardboard, or textiles, with an aqueous gel ink with fixed color according to the disclosure.

After writing onto a media, more specifically onto an absorbing support wherein the absorbing support is a porous substrate, and more specifically onto paper, cardboard, or textiles, with the aqueous gel ink of fixed color of the disclosure, the distance between the metallic nanoparticles in the aqueous gel ink applied on the media is lower than 1 μm, more specifically varies from 1 nm to 500 nm, and even more specifically varies from 100 to 200 nm.

Finally, the present disclosure concerns a writing instrument comprising:an axial barrel containing the aqueous gel ink according to the disclosure, anda pen body which delivers the aqueous gel ink stored in the axial barrel.

The writing instrument of the disclosure may be chosen in the group consisting of gel pens, felt pens, correction fluid, markers, and more specifically gel pens.

In addition to the foregoing, the disclosure also comprises other provisions which will emerge from the additional description which follows, which relates to the preparation of aqueous gel inks with fixed color according to the process of the disclosure and comparative examples, as well as toFIGS.1to6which show Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) images of gold nanoparticles dispersed in the gel-based matrix of aqueous ink containing 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid or other reducing agents, prepared according to examples 1 and 2 and to comparative examples 1 and 2.

EXAMPLES

Example 1

Preparation of an Aqueous Gel Ink with Fixed Color Based on 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid and Gold Nanoparticles, According to the Process of the Present Invention

In a first step (i), a gel-based matrix of aqueous ink was prepared by mixing 180 g of triethylene glycol (solvent), 48 g of polyethylene glycol (solvent), 2.3 g of Acticide® MBS (antimicrobial agent), and 1.20 g of Additin® RC8221 (corrosion inhibitor). The mixture was homogeneized with a homogeneizer mixer at a speed of 15 m·s−1during 15 minutes and heated at a temperature of 35° C. Then, 5 g of xanthan gum (rheology modifier) was added to the mixture. The mixture was homogenized with a homogenizing mixer at a speed of 15 m·s−1during 15 minutes at a temperature of 35° C. 960 g of deionized water was slowly added to the mixture. The mixture was left to stand for 2 h 30. Then, 3.60 g of Moussex® S 9092 (antifoam agent) was added. The mixture was homogenized with a homogenizing mixer at a speed of 15 m·s−1during 30 minutes at a temperature of 35° C. The gel-based matrix of aqueous ink obtained was cooled at room temperature (25° C.). Then, 1 mL of the obtained gel-based matrix of aqueous ink was mixed with 1 mL of a solution of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (83264-100ML-F HEPES Buffer Solution Sigma-Aldrich) (1 M). The mixture was homogeneized with a homogeneizer mixer at a speed of 15 m·s−1during 2 minutes.

In a second step (ii), 100 μL of a solution of gold (III) chloride trihydrate (520918-1G Sigma-Aldrich) (100 mM) was introduced into the mixture at a speed of 400 rpm during 10 minutes.

When the addition of the solution of gold (III) chloride trihydrate was made by continuous injection, the color of the aqueous gel ink was blue.

When the addition of the solution of gold (III) chloride trihydrate was made drop-by-drop (one drop every 10 seconds), the color of the aqueous gel ink was purple.

FIG.1shows TEM images (apparatus: JEOL ARM200) of the gold nanoparticles dispersed in the gel-based matrix of aqueous ink comprising 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid andFIG.2shows SEM images (apparatus: MEB Philips XL30) of the gold nanoparticles once the aqueous gel ink is applied on a cellulosic paper A4 80 g·m−2(INACOPIA Elite), when the addition was made by continuous injection. The average particle size of the gold nanoparticles is of 50 nm.

FIG.3shows TEM images (apparatus: JEOL ARM200) of the gold nanoparticles dispersed in the gel-based matrix of aqueous ink comprising 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid andFIG.4shows SEM images (apparatus: MEB Philips XL30) of the gold nanoparticles once the aqueous gel ink is applied on a cellulosic paper A4 80 g·m−2(INACOPIA Elite), when the addition was made drop-by-drop. The average particle size of the gold nanoparticles is of 30 nm.

When the obtained aqueous gel ink with fixed color was written on the cellulosic paper, the color appeared blue or purple (depending the introduction was made by continuous injection or drop-by-drop) and did not change after all.

Example 2

Preparation of an Aqueous Gel Ink with Fixed Color Based on 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid and Gold Nanoparticles, According to the Process of the Present Invention

In a first step (i), a gel-based matrix of aqueous ink was prepared by mixing 180 g of triethylene glycol (solvent), 48 g of polyethylene glycol (solvent), 2.3 g of Acticide® MBS (antimicrobial agent), and 1.20 g of Additin® RC8221 (corrosion inhibitor). The mixture was homogeneized with a homogeneizer mixer at a speed of 15 m·s−1during 15 minutes and heated at a temperature of 35° C. Then, 5 g of xanthan gum (rheology modifier) was added to the mixture. The mixture was homogenized with a homogenizing mixer at a speed of 15 m·s−1during 15 minutes at a temperature of 35° C. 960 g of deionized water was slowly added to the mixture. The mixture was left to stand for 2 h 30. Then, 3.60 g of Moussex® S 9092 (antifoam agent) was added. The mixture was homogenized with a homogenizing mixer at a speed of 15 m·5−1during 30 minutes at a temperature of 35° C. The gel-based matrix of aqueous ink obtained was cooled at room temperature (25° C.). Then, 1 mL of the obtained gel-based matrix of aqueous ink was mixed with 0.14 g of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES 1M>99.5%, Reference: H3375, from Sigma-Aldrich). The mixture was homogeneized with a homogeneizer mixer at a speed of 15 m·s−1during 2 minutes.

In a second step (ii), 450 μL of a solution of gold (III) chloride trihydrate (520918-1G Sigma-Aldrich) (200 mM) was introduced into the mixture at a speed of 400 rpm during 20 minutes.

When the addition of the solution of gold (III) chloride trihydrate was made by continuous injection, the color of the aqueous gel ink was brown.

When the addition of the solution of gold (III) chloride trihydrate was made drop-by-drop (one drop every 30 seconds), the color of the aqueous gel ink was dark.

FIG.5shows TEM images (apparatus: JEOL ARM200) of the gold nanoparticles dispersed in the gel-based matrix of aqueous ink comprising 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid andFIG.6shows SEM images (apparatus: MEB Philips XL30) of the gold nanoparticles once the aqueous gel ink is applied on a cellulosic paper A4 80 g·m−2(INACOPIA Elite), when the addition was made drop-by-drop. The average particle size of the gold nanoparticles is of 40 nm.

When the obtained aqueous gel ink with fixed color was written on the cellulosic paper, the color appeared brown or dark (depending the introduction was made by continuous injection or drop-by-drop) and did not change after all.

Comparative Example 1

Preparation of an Aqueous Gel Ink Based on Glucose as Reducing Agent and Gold Nanoparticles (Without 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid)

In a first step, a gel-based matrix of aqueous ink was prepared by mixing 180 g of triethylene glycol (solvent), 48 g of polyethylene glycol (solvent), 2.3 g of Acticide® MBS (antimicrobial agent), and 1.20 g of Additin® RC8221 (corrosion inhibitor). The mixture was homogeneized with a homogeneizer mixer at a speed of 15 m·s−1during 15 minutes and heated at a temperature of 35° C. Then, 5 g of xanthan gum (rheology modifier) was added to the mixture. The mixture was homogenized with a homogenizing mixer at a speed of 15 m·s−1during 15 minutes at a temperature of 35° C. 960 g of deionized water was slowly added to the mixture. The mixture was left to stand for 2 h 30. Then, 3.60 g of Moussex® S 9092 (antifoam agent) was added. The mixture was homogenized with a homogenizing mixer at a speed of 15 m·s−1during 30 minutes at a temperature of 35° C. The gel-based matrix of aqueous ink obtained was cooled at room temperature (25° C.). Then, 1 mL of the obtained gel-based matrix of aqueous ink was mixed with 200 μL of a solution of glucose (D(+)-GlucoseDextrose, Reference 410950010, from Acros Organics) (100 mM). The mixture was homogeneized with a homogeneizer mixer at a speed of 15 m·s−1during 2 minutes.

In a second step, 100 μL of a solution of gold (III) chloride trihydrate (520918-1G Sigma-Aldrich) (100 mM) was introduced into the mixture at a speed of 400 rpm during 10 minutes. After adding the solution of gold (III) chloride trihydrate, the color changed from transparent to yellow, and the composition gelled. The composition is too thick to be used in a pen.

Comparative Example 2

Preparation of an Aqueous Gel Ink Based on β-Cyclodextrin as Reducing Agent and Gold Nanoparticles (Without 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid)

In a first step, a gel-based matrix of aqueous ink was prepared by mixing 180 g of triethylene glycol (solvent), 48 g of polyethylene glycol (solvent), 2.3 g of Acticide® MBS (antimicrobial agent), and 1.20 g of Additin® RC8221 (corrosion inhibitor). The mixture was homogeneized with a homogeneizer mixer at a speed of 15 m·s−1during 15 minutes and heated at a temperature of 35° C. Then, 5 g of xanthan gum (rheology modifier) was added to the mixture. The mixture was homogenized with a homogenizing mixer at a speed of 15 m·s−1during 15 minutes at a temperature of 35° C. 960 g of deionized water was slowly added to the mixture. The mixture was left to stand for 2 h 30. Then, 3.60 g of Moussex® S 9092 (antifoam agent) was added. The mixture was homogenized with a homogenizing mixer at a speed of 15 m·s−1during 30 minutes at a temperature of 35° C. The gel-based matrix of aqueous ink obtained was cooled at room temperature (25° C.). Then, 1 mL of the obtained gel-based matrix of aqueous ink was mixed with 200 μL of a solution of β-cyclodextrin (C4767-25G Sigma-Aldrich) (100 mM). The mixture was homogeneized with a homogeneizer mixer at a speed of 15 m·s−1during 2 minutes.

In a second step, 100 μL of a solution of gold (III) chloride trihydrate (520918-1G Sigma-Aldrich) (100 mM) was introduced into the mixture at a speed of 400 rpm during 10 minutes. After adding the solution of gold (III) chloride trihydrate, the color changed from transparent to yellow, and the composition gelled. The composition is too thick to be used in a pen.