FR3136777A1 - Use of an epoxy-silicone copolymer, crosslinkable fluid composition containing it and banknote coated with this composition - Google Patents

Abstract

The present invention relates in particular to the use of an epoxy-silicone copolymer, that is to say a polyorganosiloxane provided with branches comprising epoxy functions, for the manufacture of an anti-writing surface coating of 'a banknote.

Description

Use of an epoxy-silicone copolymer, crosslinkable fluid composition containing it and banknote coated with this composition FIELD OF THE INVENTION

The present invention lies in the field of security documents. Its main subject is the use of an epoxy-silicone copolymer, a crosslinkable fluid composition containing it and a bank note coated with this composition.

STATE OF THE ART

In the field of security documents and more particularly bank notes, one of the causes of the withdrawal by central banks of some of them is the presence of parasitic inscriptions, generally handwritten, made on the surface of these notes by users, using pens, pencils, felt-tip pens or other writing instruments.

More than a simple aesthetic cause for withdrawal, the fact of writing or making drawings on a banknote on which is present the portrait of a living or deceased person (such as a king, a queen, an emir etc. ), the representation of a national symbol or a sacred entity, can be perceived in certain countries as a real offense.

Current protective varnishes which are applied to the surface of banknotes provide barrier properties, namely that they oppose the adhesion of dry dirt particles (evaluated by the Fritsch test), the penetration of aqueous substances (resistance to water or hydrophobia – assessed by the Cobb test) or greasy (resistance to fatty substances, grease or oleophobia – assessed by the Kit Test) on the surface and inside the banknote.

An example is given in document WO2013/045496 which describes a high-performance varnish in terms of barrier properties.

To achieve these high barrier properties, those skilled in the art can choose, as mentioned in the example above, to test macroscopic characteristics intended to reflect the attacks encountered by the notes in circulation. But he can also choose to directly measure a physico-chemical quantity which will be able to characterize in advance the repulsive effects or the ability of a surface to be wet through, in particular, the measurement of inter-facial tension. or surface energy.

Thus in document WO2014/067715, a high-efficiency security document varnishing solution is proposed and its performance is evaluated only by surface tension measurements, the most effective solution having a value less than or equal to 25 mN/ mr.

Even if the surface energy of such coatings is very low, which generally reflects the difficulty in adhering to the surface of the security document, the present applicant has curiously observed that such varnishes do not sufficiently prevent or limit the possibility of write on the tickets.

In other words, we see that it is possible to write relatively easily on the note. Despite this low surface energy and as long as the substance (ink or similar) used to write is not dry, it may be possible to erase what has been written with certain pens, highlighters or pencils. On the other hand, this is more difficult with a Bic brand ballpoint pen or a marker for example. Furthermore, after drying, we note that it is particularly difficult to erase correctly without leaving traces.

Furthermore, it is easy to understand that a procedure implemented by central banks, consisting of attempting to systematically erase the inscriptions on banknotes, is very difficult, if not impossible, to implement, unless cleaning machines are developed. the banknotes without damaging them, which would greatly increase the time and costs associated with sorting the banknotes before putting them back into circulation.

In a completely different field, it is known to apply anti-graffiti treatments to surfaces such as concrete, wood, masonry, metal, etc.

Again, such treatments make it possible to obtain low surface energy. But the term “anti-graffiti” is confusing. Indeed, writing or applying paint with a brush or aerosol spray (tag) on the surface remains possible but the said treatment implemented allows more or less easy erasure a posteriori . In this way, the graffiti can be completely or largely removed.

It follows from the above that there is an unresolved need for a surface coating formulation, that is to say a varnish applicable to security documents and more particularly to bank notes, which not only presents the barrier properties mentioned above (resistance to dry dirt, water and grease), but also anti-writing properties which reflect the impossibility, or at least the difficulty, of writing on the previously varnished support, thus dissuading the man in the street to use notes as "Post-it" (registered trademark), reminder or "release" towards a personality or a symbol of power.

By the expression “anti-writing” properties is meant the ability of the coating applied to a substrate made of paper or plastic material for bank notes, to resist writing. In other words, the pen inks used during writing attempts tend to remain on the tips of the pens, to form droplets on the surface of the substrate (non-continuous line, water repellency) or to adhere with difficulty (continuous line but with low intensity and which can “drool” easily).

In the context of the present invention, this “anti-writing” property has been the subject of an instrumental and visual characterization based both on the ASTM D6578 standard entitled “Determination of Graffiti Resistance”, which is adapted to the particularity security documents, and also on a specific test developed on this occasion to reflect the difficulty of writing on the media and therefore deter registration attempts. More precisely, the “anti-write” property is the subject of an anti-write note described below.

This objective is achieved in accordance with the present invention.

For this purpose, the present invention relates firstly to the use of an epoxy-silicone copolymer, that is to say a polyorganosiloxane provided with branches comprising epoxy functions, for the manufacture of a coating anti-write surface of a bank note.

Preferred, but non-limiting, aspects of such use are the following:

• said polyorganosiloxane corresponds to one of the following formulas:

(formula a)

or : (formula b),

formulas in which:

• R represent hydrocarbon groups that are identical or different from each other,
• R ¹ represent hydrogen atoms or hydrocarbon groups identical or different from each other,
• R ² represents a hydrocarbon group with at least one carbon atom, a group which can also contain an oxygen atom,
• n ≥ 1 and m ≥ 1 and n > m, n and m being integers,
• R ³ represents a hydrocarbon group with at least one carbon atom;
• X is a carbon atom and its index o is greater than or equal to 0,

• said polyorganosiloxane corresponds to one of the following formulas:
• [chem 3]

or : (formula c'),

formulas in which:

• R ⁴ is a methyl substituent or a methylene bridging inside cyclohexyl and chemically stable,

the combination of formula (b) and formula (c’) being excluded,

• said polyorganosiloxane corresponds to formula (c).

Secondly, the invention relates to a fluid composition crosslinkable under ultraviolet radiation, characterized in that it comprises a matrix with cationic crosslinking, as well as an epoxy-silicone copolymer, that is to say of a polyorganosiloxane provided with branches comprising epoxy functions.

Preferred, but non-limiting, aspects of such a composition are the following:

• said polyorganosiloxane corresponds to one of the following formulas:

(formula a)

or : (formula b),

formulas in which:

• R represent hydrocarbon groups that are identical or different from each other,
• R ¹ represent hydrogen atoms or hydrocarbon groups identical or different from each other,
• R ² represents a hydrocarbon group with at least one carbon atom, a group which can also contain an oxygen atom,
• n ≥ 1 and m ≥ 1 and n > m, n and m being integers,
• R ³ represents a hydrocarbon group with at least one carbon atom;
• X is a one-carbon atom and its index o is greater than or equal to 0,

• said polyorganosiloxane corresponds to one of the following formulas:

(formula c)

or : (formula c'),

formulas in which:

• R ⁴ is a methyl substituent or a methylene bridging inside cyclohexyl and chemically stable,

the combination of formula (b) and formula (c’) being excluded,

• the cationically crosslinked matrix comprises a cycloaliphatic di-epoxide, preferably in an amount of at least 50% by weight,
• said polyorganosiloxane is present in an amount of at least 5% by weight, preferably between 5 and 15% and even more preferably between 8 and 12%,
• the composition also comprises a PFPE-tetra urethane acrylate mixed with ethyl acetate and butyl acetate,
• said PFPE-tetra urethane acrylate is present in an amount of at least 0.5% by weight, preferably between 0.5 and 5%, and even more preferably between 2 and 4%.

Finally, the present invention relates to a banknote, of which at least one of its opposite faces carries an anti-writing surface coating formed of a composition according to at least one of the aspects explained above, and which has underwent crosslinking under ultraviolet radiation.

A preferred, but non-limiting, aspect of such a banknote is the following:

• said anti-write surface coating has an anti-write rating

• greater than 8.5 if said at least one side is printed intaglio or calendered, or 4.5 otherwise,
• preferably greater than 10 if said at least one side is printed intaglio or calendered, or 6 otherwise,
• and more preferably greater than 13 if said at least one side is printed intaglio or calendered, or 9 otherwise.

DETAILED DESCRIPTION OF THE INVENTION

1. EVALUATION OF THE ANTI-WRITE PROPERTY OF A SAMPLE OF VARNISHED NOTES.

Two evaluations were carried out to characterize:

• the ease of erasing a mark on a sample according to the ASTM D6578 “Determination of Graffiti Resistance” standard;
• the difficulty of writing on the sample using a method specially developed to respond to the problem posed.

1. MARK ERASURE TEST ACCORDING TO ASTM D6578 MODIFIED

1. Equipment associated with the mark erasure test according to modified ASTM D6578

Microfiber cloths;

Spectrocolorimeter marketed by the company DATACOLOR model DC45IR;

Glossmeter (or Glossmeter) marketed by the company BYK model 4450 Micro TRI gloss;

Tester pencils:

• PentelPEN black indelible marker N 50 from PENTEL CO. LTD. (hereinafter MIN);
• BIC brand SOFTfeel MED blue ballpoint pen (hereinafter SBB);
• PILOT brand V Ball 0.5 Pure Liquid Ink red microball pen (hereinafter SMR);
• BIC brand WHITEBOARD MARKER VELLEDA green erasable marker (hereinafter MEV);
• Pink fluorescent highlighter Art. No. 70/56 rechargeable original STABILO BOSS brand (hereinafter SFR).

The choice of tester pencils as well as the associated references/brands are not completely specified in the ASTM D6578 standard. In fact, it is indicated: indelible marker / erasable marker / microballpoint pen / spray paint / grease pencil for coloring.

The choice was made to replace the last two examples with a blue ballpoint pen and a pink fluorescent highlighter, as it is unlikely that spray paint or a grease pencil could be used to write on tickets unless you want them. divert into a work of art but this is outside the scope investigated in this application. Furthermore, the colors were generally chosen to cover a wide spectral range.

Cleaning agents:

• MEK (Methyl Ethyl Ketone or Methyl Ethyl Ketone);
• Xylene;
• Gasoline (mixture of C6-C7 alkanes whose proportion of n-hexane is less than 5%);
• IPA (Isopropyl Alcohol or Isopropyl Alcohol);
• 5% aqueous sodium phosphate solution;
• Dry white cotton cloth.

The preparation of the 5% sodium phosphate solution is done in the following proportions:

• 5 g of tri-sodium phosphate dodecahydrate;
• 95 g of demineralized water.

1. Carrying out the test

A surface of at least 1cm x 0.5cm is colored with each of the writing methods listed above. The lines must dry for at least 24 hours before carrying out the erasing test (do not exceed 48 hours of drying time).

After drying, the mark removal test is carried out with each of the cleaning agents from the list indicated above with the specified cloth. The cleaning agent used is indicated next to the erased mark.

1. Instrumental evaluations

The spectrocolorimeter is used to measure the following two characteristics for each mark made (i.e. a total of 30 measurement zones – 5 eraser pencil marks multiplied by 6 different cleaning agents (5 liquid + 1 dry):

• The ΔE (colorimetric difference): between the area of the sample chosen before making the mark and the residual mark after cleaning. Three measurements are taken at different points of the residual mark and the average is calculated. A mark is considered completely erased if the ΔE ≤ 2.
• The gloss ratio ΔBrillance (measured at 60°): between the area of the sample chosen before making the mark and the residual mark after cleaning. Three measurements are taken at different points of the residual mark and the average is calculated. The ratio must be ≥ 0.9 to consider that the varnish film has not been altered.

1. Rating scale

The following ratings are assigned based on the measured ΔE and ΔBrightness results (mark erased if ΔE ≤ 2 and gloss ratio ≥ 0.9):

10 Dry erase 9 Erasable with 5% sodium phosphate solution 8 Erasable with IPA 7 Erasable with Essence 6 Erasable with Xylene 5 Erasable with MEK 4 Erasable with MEK but loss of gloss (ΔE ≤ 2 but gloss ratio ≤ 0.9). 3.5 Not erasable with MEK but very significant removal of the mark (ΔE: 2 < ΔE ≤ 4) 3 Not erasable with MEK but significant removal of the mark (ΔE: 4< ΔE ≤6) 2 Not erasable with MEK but low removal of the mark visible to the naked eye 1 Not erasable with MEK but low mark removal and loss of shine (ratio ≤ 0.9) 0 Not erasable with MEK, no modification of appearance

When half points are applied on grades 4 and above, it means that the ΔE with the less aggressive cleaning agent (in descending order of aggressiveness: MEK, Xylene, gasoline, IPA and 5% phosphate solution sodium) is close to 2 (2 ≤ ΔE ≤ 4). For example if ΔE ≤ 2 with Xylene and 2 ≤ ΔE ≤ 4 with gasoline, then the score awarded will be 6.5.

Although this test arises from an existing standard, the present applicant was able to note in preliminary tests that the latter was however not sufficient to perfectly characterize the anti-writing property sought.

Indeed, it was noted that certain brands of tester pencils, once the ink had dried, could be particularly difficult to erase while paradoxically, it was particularly difficult to write on the treated banknotes which would result in dissuading a person from any insistent attempt. A second assessment was thus created to visually characterize the difficulty in writing on a sample.

1. WRITING DIFFICULTY ASSESSMENT TEST

1. Carrying out the test and evaluation

Lines are made in several places on the sheet with each of the tester pencils, exactly as in the ASTM D6578 standard previously described and adapted to the safety document but in this evaluation it is the behavior of the "fresh" line (that is- i.e. which has just been carried out) which is evaluated.

Thus this evaluation is done visually and a score is applied according to the rating scale detailed in the following paragraph.

1. Rating scale

The score is awarded on the quality of the “fresh” route, in particular on its continuity, its water repellency and its intensity, according to the following scenarios:

0 Continuous and intense line 1 Continuous line but low intensity 2 Light water repellency 3 Average water repellency 4 Light/medium water repellency + low intensity or high water repellency 5 High water repellency + low intensity or very high water repellency

1. WRITING DIFFICULTY ASSESSMENT TEST

Given that the deterrent to writing is based on the ease of being able to remove or erase the inscriptions made and to a greater extent on the fact of being able to make the medium difficult to write, the choice was made to weight the second criterion with a coefficient of 2 so as to be able to constitute a rating out of 20, that is to say:

Anti-Writing Rating = (Modified ASTM D6578 Mark Erasure Test Score) + 2 x (Writing Difficulty Assessment Test Score).

1. ASSESSMENT TESTS OF BARRIER PROPERTIES

1. FRITSCH TEST

The dirt resistance was tested according to the Fritsch test well known in the world of banknote printing. This test uses a vibrating device where small glass beads spread and encrust on a paper test tube a dirty composition based on sand, peat, activated carbon, flour, and glycerin mono-oleate (fat present in particular in the sebum).

The test lasts 15 minutes. The luminance of an initially white area is measured several times before and after exposure to the dirty composition. The difference obtained, or ΔL, makes it possible to characterize the adhesion of the dirt to the banknote: the smaller it is, the better the resistance to dry dirt.

1. COBB TEST ACCORDING TO ISO 535:2014

Hydrophobicity is described as resistance to the penetration of water but also its ability to repel it on the surface called water repellency. Resistance to water penetration is therefore measured using the Cobb test at 60 s. This is the quantity of water absorbed by the support in g/m² thanks to a cylindrical impregnation template during a period of 60 seconds. This is a test that is also common in the paper industry to characterize the absorption of paper.

1. TEST KIT ACCORDING TO TAPPI T559 STANDARD

Oleophobia or resistance to fats is measured using exposure tests to fatty substances. The “Kit Test” method uses a mixture of castor oil (fatty substance) and high-boiling point solvents, namely toluene (aromatic solvent) and n-heptane (aliphatic solvent).

Depending on the different proportions of the above-mentioned products, a composition is obtained whose viscosity and surface tension vary inversely with its aggressiveness, that is to say its impregnation capacity.

A composition rich in castor oil is at the bottom of the scale, while a composition rich in heavy solvents is at the top of the same scale.

There are 12 compositions. A score of 0 corresponds to no oleophobia and a score of 12 to maximum oleophobia.

1. PRINTING PROTOCOL

All samples are overprinted with protective varnishes tested on 100% cotton vellum paper, white but calendered paper with a soft white size (without ink) on the front to reflect the classic surface condition of a note printed once. intaglio side. The barrier properties of varnishes are generally increased on the side which has been calendered in intaglio (closer paper).

The samples are varnished in flexography with a 6 cm ³ /m ² anilox (front/back) and dried under HÖNLE UV lamps with mercury spectrum 200 W/cm at 65% of their power.

1. PRELIMINARY WORKS

The present applicant already had a high-performance varnishing solution dedicated to banknotes, in an attempt to resolve the technical problem posed.

The varnish in question, known under the brand ULTRA, was therefore tested and compared with a reference known in the fiduciary market and widely used on banknotes, namely the SICPAPROTECT varnish (registered trademark) reference 889368 marketed by the company SICPA.

These two varnishes will hereinafter be referred to as “ULTRA varnish” and “reference varnish”.

Firstly, the barrier properties were evaluated:

The average double-sided results for the barrier properties of ULTRA varnish are as follows:

Fritsch test (absolute value of ΔL) Cobb test (g/m²) Test Kit (note) Front Back Front Back Front Back ULTRA varnish <5 <10 <5 <15 6 5 Reference varnish <5 < 12 < 11 <50 2 2

Then, the tests described above were carried out and were supplemented by surface energy measurements (see last line of the table below).

Reference varnish ULTRA varnish Front Back Front Back Average score on the erasure test (/10) 4.7 2.8 6.2 3.0 Average rating on difficulty of writing (/5) 0.4 0 0.5 0.3 Score /20 (difficulty writing x2) 5.5 2.8 7.2 3.5 Surface energy (mN/m) 32.7 32.0 18.7 13.7

Surprisingly, despite high and very present barrier properties compared to the reference varnish for a varnish weight of approximately 2 g/m² per side, the ULTRA varnish does not show the expected anti-writing properties.

In any case, the ULTRA varnish has an anti-writing property superior to that of the reference varnish, but this improvement is very limited and therefore needs to be reinforced.

To try to explain these results, additional measurements were carried out, in particular to evaluate the surface tension. As expected, that of the ULTRA varnish is approximately 2 times lower than that of the reference varnish but, still surprisingly, this does not translate into significantly better results with regard to the desired anti-writing property.

The present applicant has therefore undertaken work to understand and test new formulations capable of presenting the desired anti-writing property and of providing a solution to the problem posed.

Cationic polymerization varnishes offer generally effective protective coatings on banknotes (such as the reference varnish already mentioned above).

In addition, the barrier properties of cationic varnishes can be increased by choosing reaction additives in suitable dosages.

Thus, perfluoropolyether type compounds (characteristics of ULTRA varnish) are very useful for significantly improving the barrier properties as mentioned previously but are not very effective in terms of anti-writing.

A possible alternative would be to use silicon-based additives such as siloxanes, some members of which have anti-adhesive properties. These additives were not chosen at random. Indeed, in addition to their chemical properties, they present economic and ecological advantages and also in terms of safety of implementation, namely:

• they are classified as non-dangerous,
• their flash point is high, notably above 94°C,
• their transport by road does not require the Agreement for the Transport of Dangerous Goods by Road (or ADR),
• they do not produce Volatile Organic Compounds (or VOCs), and
• their cost is generally lower than that of perfluoropolyether type compounds.

In order to carry out comparative tests on different silicon-based additives, a pre-test with a discriminative aim was carried out on a sampling of siloxane-based additives.

The table below summarizes the chemical information obtained from Technical Data Sheets (TDS) and Safety Data Sheets (SDS). Several different products obtained from different suppliers were evaluated at different percentages.

Company DOW Sartomer BYK Commercial name Dowsil AP8041 Xiameter
ACP-1000 CN 9800 CN 9801 3760 3505 3576 Below AP8041 ACP-1000 CN 9800 CN9801 BYK3760 BYK3505 BYK3576 Technical data sheet Amino-functional siloxane polymer for textile finishing softener 100% active anti-foam silicone compound Difunctional aliphatic silicon acrylate oligomer for UV curing applications Hexafunctional aliphatic silicon acrylate oligomer for UV curing applications Polyether modified polydimethylsiloxane (PDMS) Solution of a multi-functionalized acrylic modified polydimethylsiloxane Solution of a multi-functionalized acrylic modified polydimethylsiloxane Safety Data Sheet Dimethyl, methyl aminoethylaminoisobutyl siloxane with methoxyl and hydroxyl termination Dimethyl siloxane, hydroxyl terminated reaction with silica (7 to 8%) / / Polyether modified polysiloxane Acrylic Function Dimethylpolysiloxane in Tripropylene Glycol Diacrylate Acrylic Function Dimethylpolysiloxane in Tripropylene Glycol Diacrylate

The pre-test carried out here and presented below is based, in this upstream stage, on the sole difficulty of writing and with only two pencils, namely the red microballpoint pen and the pink fluorescent highlighter because the results with these pencils are discriminating between the different varnishes tested. The reference varnish is the SICPAPROTECT 889368 cationic polymerization varnish. The ULTRA varnish is the second reference and incorporates a reactive perfluoropolyether urethane compound with acrylate endings, namely Fluorolink AD1700 (registered trademark, hereinafter AD1700) marketed by the company SOLVAY.

SFR MBR Front Back Front Back Reference varnish None None None None Added compounds: 8% AD1700 (ULTRA varnish) Average Light to medium Lightweight None to slight 1% BYK3576 None None None None 0.5% BYK3760 None None None None 0.3% BYK3505 None None None None 5% of CN 9800 None None Lightweight Lightweight 2% of CN 9801 None None Lightweight Very light 1% of AP8041 None None None None 0.1% ACP-1000 None None None None

This pre-test confirms the previous results on the reference varnish SICPAPROTECT 889368 and on the ULTRA varnish (reference varnish + 8% of AD1700), the latter presenting an certainly interesting result on the pink fluorescent highlighter (SFR) but too fair with the Red Microbead (MBR).

If the reference varnish has a predominantly cationic polymerization, it also includes compounds capable of reacting in radical mode for optimal three-dimensional crosslinking in particular. This is the reaction mode which is implemented with the perfluoropolyether-urethane acrylate additive which gives excellent barrier properties, but not the expected anti-writing property, or at least not in a truly significant dimension.

For the silicone products tested here, and surprisingly despite the acrylate functions present on some of them, none provide the desired anti-writing property either.

Polymerization by epoxy ring opening via cationic initiation is the main mode of polymerization used in the reference varnish. Cationic initiation is obtained by means of a cationic photoinitiator with for example salts of triarylsulfonium hexafluorophosphate (for example reference Speedcure 992 from the company Lambson) or diphenyl (4-phenylthio)phenylsulfonium haxefluoroantimonate (for example reference DC 1176 from the company Comexim) which are irradiated under ultraviolet radiation. The majority basic reactive compound is a cycloaliphatic di-epoxide with CAS number 2386-87-0 and full name 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate. This compound is available in particular from Cytec (under the brand UVACURE 1500), or from Comexim (under the name DOUBLEMER 420 P).

The present applicant sought a “twin” compound in terms of chemical functionality, that is to say possessing reactive epoxy functions and always with a siloxane structure. Thus, polyorganosiloxane compounds functionalized with epoxides were tested.

Usually these compounds are used to form hydrophobic and non-stick film-forming coatings, for example on paper or synthetic plastic supports to promote the removal of adhesive materials attached to these supports, in particular in a reversible manner, such as labels, ribbons. adhesives, etc.

Despite the expected chemical compatibility, it is entirely possible that the addition of these compounds does not allow the expected anti-writing property to be developed, as has already been shown above. The fact of using an additive with a reactive chemical function identical to that of the majority cationic reagent at more than 50% by mass in the formulation, the cycloaliphatic di-epoxide with CAS number 2386-87-0, could entirely be without effect because it is drowned in the mass, or need to be added in too large a quantity to be economically interesting, or at worst destabilize the formula leading to deleterious or unsuspected effects.

The same simplified protocol was used with epoxy-silicone additives from the Silcolease (registered trademark) Solventless UV range from ELKEM and reference POLY 204, RCA 200 and POLY 215.

SFR MBR Front Back Front Back Reference varnish None None None None Added compounds: 8% AD1700 (ULTRA varnish) Average Light to medium Lightweight None to slight 10% POLY 204 Strong Average Strong Average 10% of RCA 200 Average Lightweight Medium to Strong Average 20% POLY 215 Strong Average Strong Average

Encouraging preliminary results were obtained in anti-writing on this simplified test with the compounds mentioned above, which pushed the applicant to carry out complete tests. The varnishes were applied with a weight of approximately 1.6 g/m² on the front and 2.3 g/m² on the reverse. The results are presented below:

Writing method:
MIN SBB MBR MEV SFR Varnish Face
* Eff
⁽¹⁾ Dif
⁽²⁾ Eff
⁽¹⁾ Dif
⁽²⁾ Eff
⁽¹⁾ Dif
⁽²⁾ Eff
⁽¹⁾ Dif
⁽²⁾ Eff
⁽¹⁾ Dif
⁽²⁾ Reference varnish (VR) R 3.5 0 3.5 0 2 1.5 9 0 5.5 0 V 3 0 1 0 2 0 3.5 0 4.5 0 ULTRA varnish R 6.5 0 5 0 2 2 9 0 8.5 3 V 3.5 0 2 0 1 0 3.5 1 5 2 VR + 10% POLY 204 R 8 5 8 1 2 5 10 4 9 5 V 6.5 2 8 1 2 4 5 2 3.5 2 VR + 15% POLY 204 R 8 3 8 1 2 5 10 1 9.5 5 V 6.5 2 8 1 2 4 7.5 2 6 2 VR + 10% POLY 204 + 3% AD1700 R 8 5 5 1 2 5 10 2.5 9 5 V 8 2 5 1 2 5 5.5 2 5 2.5 VR + 10% RCA 200 R 3 5 3 1 2 5 5.5 5 5.5 5 V 3 1 2 1 2 5 3 0 5 2 VR + 20% POLY 255 R 3 2 3.5 1 2 5 8 1 5.5 5 V 2 0 2 1 2 5 3 0 2 2

* Front: R for front and V for back

(1) Mark erasure test score according to ASTM D6578 modified (/10)

(2) Score on the writing difficulty assessment test (/5)

The results of the 5 tester pencils are summed and averaged to obtain the overall scores below:

Synthesis Varnish Face
* Eff
⁽¹⁾ Dif
⁽²⁾ Note
anti-writing Reference varnish (VR) R 4.7 0.3 5.3 V 2.8 0.0 2.8 ULTRA varnish R 6.2 1.0 8.2 V 3.0 0.6 4.2 VR + 10% POLY 204 R 7.4 4.0 15.4 V 5.0 2.2 9.4 VR + 15% POLY 204 R 7.5 3.0 13.5 V 6.0 2.2 10.4 VR + 10% POLY 204 + 3% AD1700 R 6.8 3.7 14.2 V 5.1 2.5 10.1 VR + 10% RCA 200 R 3.8 4.2 12.2 V 3.0 1.8 6.6 VR + 20% POLY 215 R 4.4 2.8 10.0 V 2.2 1.6 5.4

* Front: R for front and V for back

(1) Mark erasure test score according to ASTM D6578 modified (/10)

(2) Score on the writing difficulty assessment test (/5)

Among all the additives tested, POLY 204 is the one that obtains the best results added at 10%, 15% and 10% with 3% AD1700 additive in the reference varnish. With 10% POLY 204, the varnish already offers satisfactory anti-writing performance compared to the reference varnish and the ULTRA varnish.

In order to be certain that hidden deleterious effects were not introduced by the addition of POLY 204, the barrier performances according to the tests presented above were evaluated on the following varnishes: reference varnish, ULTRA varnish, varnish reference with 10% POLY 204, reference varnish with 15% POLY 204 and reference varnish with 10% POLY 204 and 3% AD1700.

Fritsch test Cobb test Test kit Varnish Face
* ΔL Standard deviation mL Standard deviation Rating (3) Reference varnish (VR) R -3.87 0.37 10.80 2.50 2 V -11.26 0.62 42.57 5.21 2 ULTRA varnish R -3.86 0.73 4.33 0.40 6 V -8.75 0.90 14.17 0.32 5 VR + 10% POLY 204 R -4.61 1.06 7.30 1.61 4 V -10.35 1.13 22.23 2.85 3-4 VR + 15% POLY 204 R -3.80 0.51 7.73 1.06 4 V -11.8 2.09 17.13 1.33 3 VR + 10% POLY 204 + 3% AD1700 R -3.62 0.41 5.97 0.42 5-6 V -7.56 0.86 13.37 0.45 4

* Front: R for front and V for back

(3) “ xy” indicates a note between notes x and y

Concerning the test of resistance to dry dirt (Fritsch), no significant difference is observed between the ULTRA varnish and the varnish incorporating 10% POLY 204. In terms of resistance to water (Cobb) and to fatty substances, It is interesting to note that the varnish with 10% POLY204 is higher than the reference but lower than the ULTRA. It is also of certain interest to note that the varnish with 10% POLY 204 and 3% FLOROLINK AD1700 sees its performance in the Cobb test equivalent to that of the ULTRA varnish, and its performance in the Kit Test just one point below those of ULTRA, which is of double interest in terms of efficiency and economy because siloxane additives are cheaper than perfluoropolyether additives.

The problem posed in the preamble was therefore solved thanks to the addition of an epoxidized polyorganosiloxane additive incorporated into a varnish cured by ultraviolet radiation, polymerizing mainly by the cationic route. The anti-writing property based both on the ease of erasing the lines made as well as on the difficulty of making fresh inscriptions on the banknotes is satisfactory with relatively low additive percentages, while retaining interesting barrier properties, without unsustainably increasing the cost price of the formulation and with substantial environmental gains such as those mentioned above.

Claims (13)

Use of an epoxy-silicone copolymer, that is to say a polyorganosiloxane provided with branches comprising epoxy functions, for the manufacture of an anti-writing surface coating of a bank note. Use according to claim 1, in which said polyorganosiloxane corresponds to one of the following formulas:

(formula a)

or :(formula b),

formulas in which:

• R represent hydrocarbon groups that are identical or different from each other,
• R ¹ represent hydrogen atoms or hydrocarbon groups identical or different from each other,
• R ² represents a hydrocarbon group with at least one carbon atom, a group which can also contain an oxygen atom,
• n ≥ 1 and m ≥ 1 and n > m, n and m being integers,
• R ³ represents a hydrocarbon group with at least one carbon atom;
• X is a carbon atom and its o index is greater than or equal to 0

Use according to claim 1, in which said polyorganosiloxane corresponds to one of the following formulas:

(formula c)

or :(formula c’),

formulas in which:

• R ⁴ is a methyl substituent or a methylene bridging inside cyclohexyl and chemically stable,

the combination of formula (b) and formula (c’) being excluded. Use according to claim 3, wherein said polyorganosiloxane corresponds to formula (c). Fluid composition crosslinkable under ultraviolet radiation, characterized in that it comprises a matrix with cationic crosslinking, as well as an epoxy-silicone copolymer, that is to say a polyorganosiloxane provided with branches comprising epoxy functions . Composition according to claim 5, characterized in that said polyorganosiloxane corresponds to one of the following formulas:

(formula a)

or :(formula b),

formulas in which:

• R represent hydrocarbon groups that are identical or different from each other,
• R ¹ represent hydrogen atoms or hydrocarbon groups identical or different from each other,
• R ² represents a hydrocarbon group with at least one carbon atom, a group which can also contain an oxygen atom,
• n ≥ 1 and m ≥ 1 and n > m, n and m being integers,
• R ³ represents a hydrocarbon group with at least one carbon atom;
• X is a one-carbon atom and its o index is greater than or equal to 0.

Composition according to claim 6, characterized in that said polyorganosiloxane corresponds to one of the following formulas:

(formula c)

or :(formula c’),

formulas in which:

• R ⁴ is a methyl substituent or a methylene bridging inside cyclohexyl and chemically stable,

the combination of formula (b) and formula (c’) being excluded. Composition according to one of claims 5 or 7, characterized in that the cationically crosslinked matrix comprises a cycloaliphatic di-epoxide, preferably in an amount of at least 50% by weight. Composition according to one of claims 5 to 8, characterized in that said polyorganosiloxane is present in an amount of at least 5% by weight, preferably between 5 and 15% and even more preferably between 8 and 12%. Composition according to one of claims 5 to 9, characterized in that it also comprises a PFPE-tetra urethane acrylate mixed with ethyl acetate and butyl acetate. Composition according to claim 10, characterized in that said PFPE-tetra urethane acrylate is present in an amount of at least 0.5% by weight, preferably between 0.5 and 5%, and even more preferably between 2 and 4%. Bank note, characterized in that at least one of its opposite faces carries an anti-writing surface coating formed of a composition according to one of claims 6 to 11 which has undergone crosslinking under ultra-high radiation. purple. Bank note according to the preceding claim, characterized in that said anti-writing surface coating has an anti-writing rating greater than 8.5 if said at least one side is printed intaglio or calendered, or 4, 5 otherwise,
preferably greater than 10 if said at least one side is printed intaglio or calendered, or 6 otherwise,
and more preferably greater than 13 if said at least one side is printed intaglio or calendered, or 9 otherwise.