Patent Description:
The writing ink composition of the invention preferably has a low viscosity, preferably a viscosity ranging from <NUM> to <NUM> mPa. s, more preferably ranging from <NUM> to <NUM> mPa. s, (the viscosity being measured at <NUM> with a Shell Cup # <NUM> marketed by NORCROSS® Corporation) and as a result is particularly suitable for use with standard felt-tip markers that rely on a capillary feed system to draw ink from a reservoir. Thus, the writing ink composition of the invention is suitable for use in felt-pens, highlighters, markers, which typically use colored pigments. When the viscosity is less than <NUM> mPa. s, the pigment particles may settle more rapidly in the writing ink composition with a risk of ink leakage. Furthermore, when the viscosity is higher than <NUM> mPa. s, the flow rate of the writing ink composition is too low and any line was not written.

Furthermore, the writing ink composition of the invention can be included in one single writing instrument. This allows having multiple color options within the same color mark, for example when the user takes notes, journal or draws to emphasize information or to make things stand out, which allows the user not to use multiple writing instruments.

Color-changing writing ink compositions capable of changing the color of the ink by an eraser are known in the art such as in <CIT>. Said color-changing ink compositions contain a water-soluble resin, as well as pigment and dye. However, with this kind of color-changing ink compositions, peelability may be difficult after a long period of time, and is thus sometimes not satisfactory. Furthermore, the peelability of the ink compositions of the prior art requires significantly high pressure to obtain a good color-changing. In addition, the colors obtained with the ink compositions of the prior art are generally not very vivid.

<CIT> also discloses a color-changing ink composition capable of changing the color of the ink by an eraser. The ink composition described contains acrylonitrile butadiene rubber (NBR) and/or hydrogenated acrylonitrile butadiene rubber (HNBR) as the film-forming agent and polyoxyethylene sorbitan ester. However surprisingly the inventors have found that the use of polyether-modified polysiloxane such as Bis-PEG <NUM>-Methyl Ether Dimethicone (INCI name) in particular sold under the tradename Belsil® DMC <NUM> by Wacker improves the quality of erasing and acts as a release agent. There are indeed less traces after erasing after its introduction in the composition when compared to the composition of the prior art.

<CIT> describes a color changeable writing ink composition comprising an urethan resin, a pigment, a dye and water. It is mentioned in this document, that it is possible to add a silicone-based surfactant to improve the ink penetration. Hence, the skilled person in the art is encouraged to use a silicone raw material in order to facilitate the penetration of the ink into porous substrates. In contrary, according to the invention, polyether modified polysiloxane is used as release agent. That means that polyether modified polysiloxane migrates to the surface on the porous substrate and decreases the adhesion of the ink composition on porous substrate.

Therefore, there is a need to find a new color-changing writing ink composition enabling to obtain a good deposit which has, in particular, a satisfactory color intensity (vivid), a good color-changing capacity (in particular such as easiness and efficiency of the color-changing) particularly when used on writing porous substrates, preferably while avoiding an unwanted color return and/or color change or color loss due to a change in temperature.

The inventors have surprisingly found that the use of a polyether-modified polysiloxane, in combination with an homopolymer or copolymer of polyurethane, in presence of pigment and dye dispersed in water, can lead to a writing color-changing ink composition resolving the above-mentioned problems. The writing ink composition of the invention also presents the advantage of being peelable, for example with fingers, in particular by applying a low pressure (by the user), thus using less waste than with conventional erasers. Furthermore, the writing ink composition of the invention also presents the advantage of enabling a change of color. In particular, the deposit made with the writing ink composition on writing porous substrate can be easily and/or efficiently removed (peeled or rubbed), in particular the deposit can be easily removed when an intentional friction force is applied (in particular the deposit is not unintentionally removed).

In addition, the writing ink composition of the invention enables obtaining vivid colors of written marks once applied, especially on writing porous substrates, in particular the initial first color as well as the second color (after peeling) are vivid.

An additional advantage of the invention is the possibility to obtain a writing ink composition with color-changing having a good cap-off time. The term "cap-off" designated the ability of the writing ink composition of the invention with color-changing of not drying up in the writing instrument, which means in particular that the writing instrument can be left open for longer period of time, preferably one hour or even several hours, in particular with removed cap, without drying up.

The present invention therefore concerns a writing ink composition comprising:.

Hereinafter, a detailed description of the present invention will be given. The specific embodiments are meant to better illustrate the present invention, however, it should be understood that the present invention is not limited to these specific embodiments.

In the sense of the present invention, the expression "comprising a" should be understood as being synonymous with "comprising at least one".

In the sense of the present invention, the expressions "between. " or "ranging from. " should be understood as including the values of the limits.

The writing ink composition according to the present invention is advantageously a color changing writing ink.

For the purposes of the present invention, the term "color-changing writing ink" is intended to mean any writing ink which can change color after writing.

After writing, in particular on a writing substrate, the written mark made with the ink can change from a first initial color to second color. In particular, the term "color-changing writing ink" is intended to mean that the initial first color of the writing ink is changed into another (second) color. In particular, this second color is not colorless (in this sense, the writing ink according to this disclosure is not erasable). Hence, the initial color (first color) of the writing ink composition after writing on a substrate can be changed into a second color by removing part of the written mark, in particular by peeling (or rubbing). In particular, the first and second colors are different which mean that they can distinguished from each other by human eye.

The first (initial) color of the written mark before the color change will depend on the color of the dye(s) and pigment(s) contained in the writing ink composition.

By peeling the written mark, the pigment(s) is(are) removed, and therefore after peeling, the second color of the written mark will depend on the dye(s) comprised in the writing ink composition. Therefore, part of the written mark (deposit) has been removed.

The written mark obtained, in particular on cellulosic fiber paper such as paper (printer paper for example) and cardboard paper, by this writing ink can therefore change color just after writing and also even a few days after writing.

The writing ink composition according to the present invention is advantageously a peelable writing ink.

For the purposes of the present disclosure, the term "peelable" writing ink is intended to mean that the written mark made with the writing ink can be peeled (or rubbed) after writing by removing part of the written mark, such as by mechanical friction, preferably by the use of a finger or a friction body wherein the friction body can be an eraser or a tissue. For example, the eraser can be a rubber which can be made of a blend of ethylene-propylene-diene monomer rubber and polypropylene. In particular, the writing ink can be peeled (or at least partly peeled) from a writing substrate, in particular for some period of time after formation of the writing mark, without damaging the substrate. The written mark obtained, in particular on cellulosic fibers papers, by this writing ink can therefore be peeled just after writing such as less than <NUM> second after writing, even a few days after writing, and also even one month after writing, to change the initial (ie first) color of the writing mark in another color (second color).

More specifically, the present disclosure concerns a peelable color-changing writing ink comprising: (a) at least one film forming elastomeric polymer wherein the film-forming elastomeric polymer (a) is an homopolymer or copolymer of polyurethane, (b) at least one polyether-modified polysiloxane, (c) at least one dye, (d) at least one pigment, and (e) water, wherein the color changing , in particular from a first color into a second color; is essentially obtained by removing the pigment by peeling.

Hence, once applied, the first color of the written mark made with the writing ink composition according to the invention, can be changed by peeling off the written mark into a second color.

The writing ink composition according to the present invention is advantageously irreversibly peeled. It is therefore an irreversible peelable color-changing writing ink composition. More specifically, once the color has changed, it is not possible to change it again, and in particular it is not possible to go back to the initial color (first color).

The writing ink according to the present invention is a non-thermochromic ink. For the purposes of the present invention, the term "non-thermochromic ink" is intended to mean any ink which will not be erased or will not change its color due to a change in temperature such as an increase or a decrease. For the purposes of the present disclosure, the term "writing porous substrate" is intended to mean writing substrate that contains pores. The writing porous substrates have empty spaces or pores that allow external matter, like writing ink, to penetrate into the substrate. In particular, writing surfaces such as white board or enamel board are not considered as writing porous substrate. In particular, the writing porous substrates are fibrous. In particular, the "writing porous substrate" can be cellulosic fiber paper such as paper (printer paper for example) and cardboard paper. Advantageously, the average size of the pores of writing porous substrate ranges from <NUM> nanometer to <NUM> micrometers, in particular when measured by inverse size-exclusion chromatography.

Advantageously, the roughness of the writing substrate can be defined by its air permeability and measured by the standard ISO <NUM>-<NUM>:<NUM> (unit: mL. min-<NUM>). In a preferred embodiment, the air permeability of the writing porous substrate of the invention ranges from <NUM> to <NUM>,<NUM>. min-<NUM>, preferably from <NUM> to <NUM>. min-<NUM>, and more preferably from <NUM> to <NUM>.

In particular, the writing porous substrate is chosen among writing porous substrate comprising cellulosic fibers such as paper, printer paper, or cardboard.

The writing ink composition according to the present invention is more specifically an aqueous writing ink. For the purposes of the present invention, the term "writing ink" is intended to mean any ink which is intended to be used in a writing instrument, and in particular in a felt-pen, a highlighter, a marker. 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. 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 writing ink composition according to the present invention will be suitable for the writing instrument for which it is intended, in particular for handheld writing instrument.

In the sense of the invention, "film-forming" means a polymer capable of forming, by itself a macroscopically continuous film on a writing substrate, in particular on a writing porous substrate, and preferably a cohesive film.

In the sense of the invention, "elastomeric" means a polymer that displays rubber-like elasticity, i.e. a deformable, flexible polymer which has viscoelastic properties.

In the sense of the invention, a "polymer" is a compound (in particular a large molecule or a macromolecule) corresponding to the repetition of one or more units (these units being derived from compounds called monomers), and in particular the repetition of at least two repeating units, and preferably at least ten repeating units.

The film-forming elastomeric polymer (a) allows the fixation of the writing ink composition of the invention on the paper, and therefore avoids the written mark (deposit) of the writing ink to be peeled (i.e. removed) by simply brushing it with another sheet of paper while being able to change its initial first color to another one by peeling with a finger or a friction body. The at least one film-forming elastomeric polymer (a) of the invention is an homopolymer or copolymer of polyurethane, advantageously selected in the group consisting of amphoteric polyurethanes, anionic polyurethanes, cationic polyurethanes, non-ionic polyurethanes, polyester-polyurethanes, polyether-polyurethanes and mixtures thereof, more specifically the polyurethane (a) is an anionic polyurethane homopolymer or copolymer, even more specifically the polyurethane (a) is an anionic polyurethane homopolymer, in particular the polyurethane (a) is an aliphatic polyurethane. More particularly it can be a polyester-polyurethane such as an anionic aliphatic polyester-polyurethane for example commercially available under the name Impranil® DLE, Impranil® DL1069 or Bahydrol® UH240 (Covestro AG), a polyether diol polyurethane such as an anionic aliphatic polyurethane based on polyester diols for example commercially available under the name Esacote PU78 (Lamberti) or an anionic aliphatic polyurethane for example commercially available under the name Esacote SW3 (Lamberti). More advantageously, the polyurethane (a) is a polyether diol polyurethane such as an anionic aliphatic polyurethane based on polyester diols for example commercially available under the name Esacote PU78 (Lamberti) or an aliphatic polyurethane for example commercially available under the name Esacote SW3 (Lamberti), still more advantageously it is an aliphatic polyurethane for example commercially available under the name Esacote SW3 (Lamberti).

In an advantageous manner, the polyurethane (a) is in the form of an aqueous dispersion.

Advantageously, the writing ink composition of the invention does not comprise a water-soluble resin. Advantageously, the writing ink composition of the invention, does not comprise a water-soluble resin and the polyurethane (a) is in the form of an aqueous dispersion.

In an advantageous manner, the film-forming elastomeric polymer (a) is not in the form of spherical particles such as beads, more specifically the homopolymer or copolymer of polyurethane (a) is not in the form of spherical particles such as beads.

Advantageously, the total solid content of the polyurethane (a) ranges from <NUM> to <NUM>%, more specifically from <NUM> to <NUM>%, by weight relative to the total weight of the writing ink composition.

The writing ink composition of the invention also comprises at least one polyether-modified polysiloxane. In the sense of the present invention the term "polyether-modified polysiloxane" is intended to mean any polysiloxane, in particular any alkylpolysiloxane, more particularly any poly((C<NUM>-C<NUM>)alkyl)siloxane, which is modified by a polyether, advantageously a poly ((C<NUM>-C<NUM>)alkyloxy. More specifically, the polyether-modified polysiloxane is a polyalkyloxy-polysiloxane. In an advantageous manner, the polyether-modified polysiloxane (b) is non-ionic, more advantageously it is water soluble or dispersible in water. In an advantageous manner, the polyether-modified polysiloxane (b) is a polyether-modified poly((C<NUM>-C<NUM>)alkyl)siloxane, in particular a polyalkyloxy-poly((C<NUM>-C<NUM>)alkyl)siloxane, in particular a polyether-modified polydimethylsiloxane, more specifically a poly((C<NUM>-C<NUM>)alkyloxy polydimethylsiloxane, more particularly a polyoxyethylenated polydimethylsiloxane, and in a particular manner it is a Bis-PEG <NUM>-Methyl Ether Dimethicone (INCI name), in particular having the following formula (<NUM>):
<CHM>
for example commercially available under the name BELSIL® DMC <NUM> (Wacker).

Advantageously, the total amount of the at least one polyether-modified polysiloxane (b) in the writing ink composition of the invention ranges from <NUM> to <NUM> % by weight, more specifically from <NUM> to <NUM>% by weight, relative to the total weight of the writing ink composition.

The writing ink composition of the invention also comprises at least one dye (c), in particular a mixture of dyes, solubilized in water. The term "dyes" should be understood as meaning colored, mineral or organic particles of any form, which are soluble in the medium in which they are solubilized, and which are intended to color the writing ink composition once applied on a writing porous substrate after peeling. Thanks to the presence of a dye in the writing ink composition of the invention, the initial (first) color of the writing mark can change in another color (second color) by peeling with a finger or a friction body. The at least one dye (c) may be selected in the group consisting of direct dyes (for example C. I direct black <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>; C. I direct yellow <NUM>, <NUM>, <NUM>, <NUM>; C. I direct red <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>; C. I direct blue <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and the like), acid dyes (for example C. I acid black <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>; C. I acid yellow <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>; C. I acid red <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>; C. I acid violet <NUM>, <NUM>, <NUM>; C. I acid blue <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>; C. I acid green <NUM>, <NUM>, <NUM>, <NUM>, <NUM>; C. I acid orange <NUM>, and the like), food dyes (such as C. food yellow <NUM>, and the like), Malachite green (C. I <NUM>) Victoria blue FB (C. <NUM>) methyl violet FN (C. <NUM>), rhodamine F4G (C. <NUM>), and rhodamine 6GCP (C. I <NUM>), and mixtures thereof.

The content of the at least one dye (c) in the writing ink composition according to the invention ranges from <NUM> to <NUM>% by weight, advantageously from <NUM> to <NUM>% by weight, and more advantageously from <NUM> to <NUM>% by weight, by weight relative to the total weight of the writing ink composition.

The writing ink composition of the present invention also comprises at least one pigment (d). The term "pigment" should be understood as meaning white or colored, mineral or organic particles of any form, which are insoluble in the medium in which they are solubilized, and which are intended to color the writing ink composition once applied on a writing porous substrate before peeling. The pigments (d) are also generally contained in a dispersion, where the grinding down or particle size reduction is accompanied by appropriate dispersants to achieve stable dispersions. The at least one pigment (d) is preferably in the form of a pigment dispersion, more preferably selected in the group consisting of pigment black <NUM> (such as Flexiverse III black <NUM> by SunChemical®), pigment blue <NUM>:<NUM> (such as APE FREE BL <NUM>:<NUM> DISP by SunChemical®), pigment red <NUM> (such as Sunsperse®Red 210by SunChemical®), pigment green <NUM> (such as Sunsperse Eco green, Flexiverse FD Green, Flexiverse Green <NUM>, Flexiverse HC GRN <NUM> by SunChemical®), and mixtures thereof. In a preferred embodiment, the at least one pigment (b) is selected in the group consisting of pigment black <NUM> (such as Flexiverse III black <NUM> by SunChemical®), pigment blue <NUM>:<NUM> (such as APE FREE BL <NUM>:<NUM> DISP by SunChemical®), and mixtures thereof.

According to a preferred embodiment, the diameter of the pigment in the pigment dispersion is less than <NUM>, and preferably less than <NUM>.

Advantageously, the total amount of pigment (d) ranges from <NUM> to <NUM>% by weight, relative to the total weight of the pigment dispersion.

The total amount of pigment (d) in the writing ink composition according to the invention ranges from <NUM> to <NUM>% by weight, and preferably from <NUM> to <NUM>% by weight, relative to the total weight of the writing ink composition.

The writing ink composition of the invention also contains water (e) as the solvent.

Advantageously, the total amount of water (e) in the writing ink composition of the invention ranges from <NUM> to <NUM>% by weight, more specifically from <NUM> to <NUM>% by weight, and even more specifically from <NUM> to <NUM>% by weight, relative to the total weight of the writing ink composition.

Advantageously, the total amount of water (e) in the writing ink composition of the invention ranges from <NUM> to <NUM>% by weight, more specifically from <NUM> to <NUM>% by weight, and in particular from <NUM> to <NUM>% by weight, relative to the total weight of the writing ink composition.

More specifically, writing ink composition of the invention are water-based inks compositions. Advantageously, water (e) is the main solvent of the writing ink composition of the invention.

The writing ink composition of the invention may further contain at least one plasticizer. The plasticizer of the invention is chosen in the group consisting of alcohols, preferably glycerin, benzoate esters, diisobutyrate esters such as trimethyl pentanyl diisobutyrate, and mixtures thereof, and more preferably glycerin, benzoate esters, and mixtures thereof, in particular glycerin. According to a preferred embodiment, the writing ink composition of the invention comprises as plasticizer a mixture of at least one ester and at least one alcohol, wherein the at least one alcohol preferably has a boiling point higher than <NUM>, and more preferably is glycerin (boiling point: <NUM>).

Advantageously, the content of plasticizer in the writing ink composition of the invention ranges from <NUM> to <NUM>% by weight, and more advantageously from <NUM> to <NUM>% by weight, relative to the total weight of the writing ink composition. The writing ink composition according to the present invention may further comprise additional additive(s) known by the skilled person to be usable in writing ink compositions, in particular in aqueous writing ink compositions, advantageously selected in the group consisting of antimicrobial agents, antifungal agents, dispersing agents, wetting agents, pH regulators, and mixtures thereof.

Advantageously, the content of additional additive(s) in the writing ink composition of the invention ranges from <NUM> to <NUM>% by weight, more advantageously from <NUM> to <NUM>% by weight, and even more advantageously from <NUM> to <NUM>% by weight, relative to the total weight of the writing ink composition.

The writing ink composition of the invention may advantageously contain at least one antimicrobial agent such as methyl paraben, phenoxyethanol, isothiazolinone, <NUM>,<NUM>-benzoisothiazolin-<NUM>-one, <NUM>-methyl-<NUM>-isothiazolin-<NUM>-one, and mixtures thereof.

Advantageously, the antimicrobial agent is present in the writing ink composition of the invention in a content ranging from <NUM> to <NUM>% by weight, and more advantageously from <NUM> to <NUM>% by weight, relative to the total weight of the writing ink composition.

The writing ink composition according to the present invention may also contain a pH regulator, preferably chosen in the group consisting of ammonia, urea, monoethanolamine, diethanolamine, triethanolamine, alkali metal salts of phosphoric acid such as tripolyphosphate, sodium carbonate and hydroxides of alkali metals such as sodium hydroxide.

The writing ink composition according to the present invention is advantageously peelable, more advantageously it is a peelable color-changing writing ink, still more advantageously the writing ink composition is changing from a first initial color in a second color by peeling, in particular by peeling such as by mechanical friction, more particularly by the use of a finger or a friction body wherein the friction body is an eraser or a tissue, in particular an eraser. The writing ink composition of the invention is therefore not peelable or color-changing by the use of the heat generated by the friction of the finger or the eraser.

Advantageously, the eraser used as a friction body may be chosen in the group consisting of ethylene-propylene-diene monomer (EPDM) rubber, Vulcanized Thermoplastic Elastomer (TPV) which is a blend of ethylene-propylene-diene monomer (EPDM) rubber and polypropylene (PP), ethylene-propylene rubber (EPR), poly(styrene-butadiene-styrene) (SBS), styrene ethylene butylene styrene (SEBS), natural rubber (NR), polyisoprene (IR), polyvinyl chloride, styrene-based thermoplastic elastomers including styrene-butadiene-styrene (SBS), styrene-ethylene-butylene-styrene (SEBS), styrene-ethylene-propylene-styrene (SEPS), styrene-ethylene-ethylene-propylene-styrene (SEEPS), polyether based polyurethane (PTU) , and mixtures thereof.

Advantageously, the tissue used as a friction body may be chosen in the group consisting of cotton fabric, synthetic fabric and leather fabric, and more advantageously cotton fabric.

The writing ink composition according to the present invention has advantageously a viscosity of <NUM> to <NUM> mPa. s, and more advantageously of <NUM> to <NUM> mPa. s, measured at <NUM> with a Shell Cup # <NUM> marketed by NORCROSS® Corporation. When the viscosity is less than <NUM> mPa. s, the pigment particles may settle more rapidly in the writing ink composition with a risk of ink leakage. Furthermore, when the viscosity is higher than <NUM> mPa. s, the flow rate of the writing ink composition is too low and any line was not written.

In an advantageous embodiment the writing ink composition according to the invention is intended for writing porous substrate (also named porous surfaces), more specifically writing fibrous substrate, in particular made, basically, of pressed, matted fibers, preferably comprising cellulose fibers, advantageously selected in the group consisting of paper, printer paper and cardboard.

The present invention also concerns a method for preparing a writing ink composition according to the invention, comprising the steps of:.

The film-forming elastomeric polymer (a), polyether-modified polysiloxane (b), dye(s) (c), pigment (d), water (e), as well as the optional plasticizer and additive(s), are as defined above for the writing ink composition according to the invention.

During steps (i), (ii), (iii), and (iv), the ink ingredients are mixed under stirring at room temperature (<NUM>), advantageously at a stirring speed ranging from <NUM> to <NUM> rpm, and more advantageously at a stirring speed of <NUM> rpm.

The writing ink composition obtained in steps (i), (ii), (iii), and (iv), can be homogenized during a certain period of time ranging from <NUM> to <NUM> minutes, and preferably from <NUM> to <NUM> minutes.

The present invention also concerns a writing instrument, more specifically a handheld writing instrument, in particular a pen such as a felt-pen, a highlighter, a marker, and more advantageously it is a writing felt-pen, a coloring felt-pen, a highlighter, containing a writing ink composition according to the invention. Advantageously the writing instrument is not a ball pen.

Advantageously, the writing ink composition according to the invention is not a ball pen ink and the writing ink composition of the invention has a low viscosity, in particular a viscosity ranging from <NUM> to <NUM> mPa. s,
Advantageously, the writing instrument according to the present invention comprises an eraser, in particular located on the cap or on the non-writing end of the writing instrument. More particularly, the eraser consists of ethylene-propylene-diene monomer (EPDM) rubber, Vulcanized Thermoplastic Elastomer (TPV) which is a blend of ethylene-propylene-diene monomer (EPDM) rubber and polypropylene (PP), ethylene-propylene rubber (EPR), poly(styrene-butadiene-styrene) (SBS), styrene ethylene butylene styrene (SEBS), natural rubber (NR), polyisoprene (IR), polyvinyl chloride, styrene-based thermoplastic elastomers including styrene-butadiene-styrene (SBS), styrene-ethylene-butylene-styrene (SEBS), styrene-ethylene-propylene-styrene (SEPS), styrene-ethylene-ethylene-propylene-styrene (SEEPS), polyether based polyurethane (PTU), and mixtures thereof.

According to a preferred embodiment, the writing instrument according to the present invention comprises:.

Another object of the present invention is a method for writing on a writing porous substrate, comprising the step of applying a writing ink composition according to the invention to a writing porous substrate, preferably fibrous, preferably comprising cellulose fibers, and more preferably chosen in the group consisting of paper, printer paper or cardboard. The method for writing on a writing porous substrate may further comprise the step of changing the initial color (first color) of the writing into another color (second color) by peeling, preferably by peeling the writing mark with a finger or with a friction body wherein the friction body is an eraser or a tissue, preferably said first and second colors being different from each other.

Finally, another object of the present invention is a writing porous substrate, preferably fibrous, preferably comprising cellulose fibers, coated with a writing ink composition according to the present invention, wherein the writing substrate is preferably chosen in the group consisting of paper, printer paper or cardboard.

In addition to the foregoing, the invention also comprises other provisions which will emerge from the additional description which follows, which relates to the preparation of writing ink compositions according to the present invention and comparative examples.

A writing ink composition according to the present invention comprising the ink ingredients of Table <NUM> was prepared.

For a preparation of <NUM>, <NUM> of water was introduced at room temperature in a dissolver DISPERMAT® LC75 (dissolver disc Ø <NUM>), and <NUM> of Sanolin® Rhodamine B02 (Clariant) were added under agitation (stirring speed: <NUM> rpm). Then, <NUM> of Esacote SW3® (Lamberti) were added at the same stirring speed. The % of polyurethane in Esacote SW3® (Lamberti) represents <NUM> wt. % (dry extract), and thus the % of polyurethane in the final ink composition is of <NUM> % by weight. After <NUM> minutes, <NUM> of glycerin were introduced. After <NUM> minutes under the same stirring speed, <NUM> of Belsil®DMC6038 (Wacker) were added. After <NUM> minutes under the same stirring speed, <NUM> of a blue pigmented dispersion APE FREE BL <NUM>:<NUM> Disp BPD <NUM> (SunChemical) were added. The mixture was stirred for <NUM> minutes more. Then, <NUM> of Acticide PHE were added, and the mixture was stirred for <NUM> minutes more to obtain the final writing ink composition.

The viscosity of the writing ink composition was measured at <NUM> with a Shell Cup # <NUM> marketed by NORCROSS® Corporation, according to the following procedure:.

The viscosity of the writing ink composition of example <NUM> measured according to this procedure was: <NUM> mPa.

A comparative writing ink composition comprising the ink ingredients of Table <NUM> was prepared.

For a preparation of <NUM>, <NUM> of water were introduced at room temperature in a dissolver DISPERMAT® LC75 (dissolver disc Ø <NUM>), and <NUM> of Sanolin® Rhodamine B02 (Clariant) were added under agitation (stirring speed: <NUM> rpm). Then, <NUM> of Europrene Latice <NUM>® (Versalis) were added at the same stirring speed. The % of SBR in Europrene Latice <NUM>® (Versalis) represents <NUM> wt. % (dry extract), and thus the % of SBR in the final ink composition is of <NUM>% by weight. After <NUM> minutes, <NUM> of glycerin were introduced. After <NUM> minutes under the same stirring speed, <NUM> of Belsil®DMC6038 (Wacker) were added. After <NUM> minutes under the same stirring speed, <NUM> of a blue pigmented dispersion APE FREE BL <NUM>:<NUM> Disp BPD <NUM> (SunChemical) were added. The mixture was stirred for <NUM> minutes more. Then, <NUM> of Acticide PHE were added, and the mixture was stirred for <NUM> minutes more in order to obtain the final writing ink composition.

The viscosity of the writing ink composition measured at <NUM> with a Shell Cup # <NUM> marketed by NORCROSS® Corporation was <NUM> mPa.

For a preparation of <NUM>, <NUM> of water was introduced at room temperature in a dissolver DISPERMAT® LC75 (dissolver disc Ø <NUM>), and <NUM> of Sanolin® Rhodamine B02 (Clariant) were added under agitation (stirring speed: <NUM> rpm). Then, <NUM> of Esacote SW3® (Lamberti) were added at the same stirring speed. The % of polyurethane in Esacote SW3® (Lamberti) represents <NUM> wt. % (dry extract), and thus the % of polyurethane in the final ink composition is of <NUM>% by weight. After <NUM> minutes, <NUM> of glycerin were introduced. After <NUM> minutes under the same stirring speed, <NUM> of PAT®<NUM>(Wurtz) were added. After <NUM> minutes under the same stirring speed, <NUM> of a blue pigmented dispersion APE FRE BL <NUM>:<NUM> Disp BPD <NUM> (SunChemical) were added. The mixture was stirred for <NUM> minutes more. Then, <NUM> of Acticide PHE were added, and the mixture was stirred for <NUM> minutes more to obtain the final writing ink composition.

The peelability (erasing efficiency of the first color) is the ability of the eraser to peel correctly the written mark of first color applied on a writing porous substrate (calligraph notebook: Calligraphe LIGNE <NUM> (<NUM>/m<NUM>, <NUM> x <NUM>, <NUM> pages, by Clairefontaine), evaluated by visual assessment according to the following method at <NUM> and <NUM>% relative humidity. The erasability performance is part of the color-changing performances of the writing ink composition.

The color of the obtained written mark made on the writing porous substrate is called "color <NUM>" and corresponds to the initial (first) color of the written mark (here color <NUM>: blue). The written mark was then peeled (or rubbed) with an eraser, i.e. polyether based polyurethane (PTU), just after writing (around <NUM> seconds after writing), to peel the initial color of the written mark and allow it to change from initial color <NUM> (here color <NUM>: blue) into a second color <NUM> (here color <NUM>: pink). Hence, the initial color <NUM> (here color <NUM>: blue) was removed by peeling with the eraser.

The method is as follows:
Loops were drawn with a pen on the writing porous substrate, and then peeled in one time back and forth.

The scoring (i.e. the peeling efficiency of color <NUM>) is defined as follows:.

The results are indicated in Table <NUM> below.

As shown in Table <NUM>, the written marks of the writing ink composition <NUM> according to the invention (example <NUM>) exhibit good results in terms of efficiency of the erasing by peeling (the initial color of the written mark was efficiently removed).

Claim 1:
A writing ink composition comprising:
(a) at least one film-forming elastomeric polymer wherein the film-forming elastomeric polymer (a) is an homopolymer or copolymer of polyurethane,
(b) at least one polyether-modified polysiloxane,
(c) at least one dye,
(d) at least one pigment, and
(e) water
wherein the total content of the at least one dye (c) ranges from <NUM> to <NUM> % by weight, relative to the total weight of the writing ink composition and the total amount of the pigment (d) ranges from <NUM> to <NUM>% by weight, relative to the total weight of the writing ink composition.