WO2018096506A1

WO2018096506A1 - Water-soluble ink

Info

Publication number: WO2018096506A1
Application number: PCT/IB2017/057410
Authority: WO
Inventors: Claudio GALTAROSSA; Giovanni BERRUTO
Original assignee: Bio-River S.R.L.
Priority date: 2016-11-25
Filing date: 2017-11-27
Publication date: 2018-05-31
Also published as: IT201600119673A1

Abstract

A solvent-free, water-soluble ink for calcographic printing comprises from 21 to 31 % of at least one first binding compound that is soluble or dilutable in water, selected from the group of alkyd resins or ketonic resins that are liquid at room temperature; from 2 to 7 % of at least one second binding compound that is solid at room temperature and is chemically compatible with the first binding compound; from 5 to 30 % of a colouring pigment; from 0.2 to 0.8 % of at least one drying compound suitable for promoting drying of the ink; from 6 to 13 % of a first additive for controlling the fluidity of the ink and from 0 to 22 % of a second additive, wherein the above-mentioned percentages are percentages by weight of ink.

Description

Water-soluble ink

DESCRIPTION

The invention relates to a water-soluble ink, in particular an ink for use in intaglio or chalcographic printing.

In particular, the invention relates to a solvent-free ink that is water-soluble. The invention also relates to a method for producing said ink, to the use of said ink in a chalcographic printing process, and to documents and banknotes printed by intaglio or chalcographic printing using said ink.

The printing of important documents, for example official documents or identity documents such as passports or the like, or the printing of banknotes, requires high-quality printing to be carried out with features that will prevent counterfeiting and falsification of the documents printed or the banknotes. Such documents are preferably printed by the calcographic printing process. The term "calcographic printing", as used in the present patent application, applies to printing methods in which the ink is transferred from a matrix engraved with the design to be printed onto a substrate that will carry the final print.

The matrix preferably takes the form of a plate made of steel or copper, or the form of a cylinder.

In calcographic printing, the model or image to be printed is produced on the cylindrical or plate-shaped matrix. Ink is then applied to the matrix and any excess ink is removed. After this, the matrix is pressed at a desired pressure onto the substrate to be printed so as to transfer the ink thereto.

The substrate can be, for example, paper or plastics material in sheet form . The ink for printing official documents or banknotes must comply with specific characteristics. Said ink must have suitable rheological properties to allow the printing to be carried out properly and at the same time must have chromatic stability before, during, and particularly after, printing.

Furthermore, the ink must be sufficiently filmable to generate a layer of a suitable thickness on the banknotes and to generate a print with sharp, well- defined outlines.

Furthermore, the ink must have suitable drying times to avoid excessively slowing down the printing process and to avoid smudging which can reduce the printing quality.

To achieve the aforesaid properties, various ink formulations have been developed for printing banknotes or identity documents by calcographic printing.

Said formulations contain a specific amount of pigments and solvents, usually derived from petroleum, which mechanically disperse the pigments. The solvents used are monomeric or oligomeric and are made to reticulate after printing in a drying phase of the inks.

One defect of known inks is that they are highly polluting because of the solvents used in their formulation.

One example in the prior art is represented by US patent application US 5,569,701.

Furthermore, to remove ink residues from the devices used in the printing process, specific detergents are required, similar to the solvents used in the inks. Sodium sulphoricinate, ammonium sulphoricinate and caustic soda are usually used in the cleaning mixture for this purpose.

Water from cleaning printing devices is therefore highly polluted and polluting, both because of the detergents used and because of the petroleum-derived solvents initially present in the inks.

Furthermore, the presence of petroleum-derived solvents means that, usually, known inks dry very easily and therefore cannot be released into the air.

In fact, these inks dry on the surface, especially when stored inside a tin, forming a surface film that must be removed before use.

This also involves considerable wastage of material .

Another defect of known inks is that they require a drying phase in which the ink is dried and, if necessary, reticulation thereof is promoted.

To this end, specific agents can be used, if appropriate, to promote reticulation, for example heat provided in suitable drying ovens into which hot, dry air is introduced to dry the ink and, if necessary, trigger reticulation reactions.

Alternatively, in some systems, UV radiation can be used in order to cause reticulation of the inks.

The aim of the present invention is to obviate the disadvantages of the prior art.

In particular, one aim of the invention is to provide an ink for calcographic printing that has good rheological properties and at the same time has a low environmental impact.

Another aim of the invention is to provide an ink that maintains a practically unchanged thickness during and after the drying phases.

Another aim is to provide an ink for calcographic printing that is water-soluble.

In particular, one aim is to provide an ink that is water-soluble even at room temperature. Another aim is to provide an ink free of problematic toxic solvents or additives. Another aim is to provide an ink that dries well so as to reduce drying times and costs.

Another aim of the invention is to provide an ink that has increased surface hardness and resistance to hydrolysis.

Another aim of the invention is to provide an ink that allows the life of the cleaning roller to be increased.

In particular, one aim of the invention is to provide an ink that requires no specific reagents for drying.

These and other aims are achieved by the invention in accordance with the following claims.

According to the invention, a solvent-free, water-soluble ink for calcographic printing is provided which comprises, relative to the total weight of said ink: from 21 to 31 % by weight of at least one first binding compound that is soluble in water at room temperature and selected from the group of alkyd resins or ketonic resins liquid at room temperature;

from 2 to 7 % by weight of at least one second binding compound that is solid at room temperature and is chemically compatible with the first binding compound;

from 5 to 30 % by weight of at least one colouring pigment;

from 0.2 to 0.8 % by weight of at least one drying compound suitable for promoting drying of the ink;

from 6 to 13 % by weight of at least one first additive for controlling the fluidity of the ink, said at least one first additive comprising petroleum wax and/or carnauba extract. The percentages stated in the present document are percentages by weight relative to the total weight of the ink.

The ink of the invention is advantageously free of petroleum-derived solvents. By virtue of the invention, an ink is obtained that has a limited environmental impact, is water-soluble and can therefore be washed off with water.

No specific detergents are required for removing the ink of the invention from printing devices.

This considerably reduces the environmental impact of a printing process carried out with the ink of the invention.

At the same time, an ink is obtained that has good rheological properties and allows long-lasting, high-quality prints to be produced.

Preferably, the ink of the invention is water-soluble at room temperature.

In this context, the term "solvent-free ink" refers to an ink that does not contain any solvents, in particular those derived from petroleum processing.

The ink of the invention is therefore composed substantially totally of ink that remains deposited on the application surface during and after the drying phase. In particular, this ink does not contain any solvents that evaporate during the drying phase of said ink. The drying phase can be related, for example, to a reticulation and/or solidification phase of the aforesaid ink.

The ink of the invention, in addition to having a limited environmental impact compared with known inks, also differs from inks containing solvents in that it produces a print which has a constant thickness which does not vary over time.

The use of solvent-based inks involves significant and major variations in printing thickness, and in fact the thickness can be reduced by up to 60 % of the initial thickness during and after drying, which occurs at the same time as evaporation of the solvent.

The ink of the invention has a viscosity that allows excellent printing on the desired medium and simultaneously limits the phenomena of dragging and wear on the printing rollers.

The viscosity of the ink of the invention measured at room temperature is > 100,000 cp.

By virtue of the invention, an ink is obtained that can be applied correctly and uniformly to the printing rollers and can then be correctly printed on a desired medium, producing a long-lasting and high-quality print.

Following numerous laboratory tests, the Applicant has discovered that a combination of the first binding compound, which is water-soluble at room temperature, the second binding compound and the first additive according to the present invention allows a solvent-free ink to be produced that is water- soluble at room temperature.

The at least one first binding compound of the printing ink for calcographic printing of the present invention is selected from the group of alkyd resins that are soluble in water, or dilutable in water, and liquid at room temperature. Medium-oil or long-oil resins, having an oil percentage of > 40 % by weight, are particularly preferred.

Alkyd resins, having a high percentage of dry matter, preferably > 80 % by weight, are particularly preferred.

The percentage of oil, according to example international reference standards, is calculated by methods known to a person skilled in the art, for example: weight of oil divided by the weight of all the reagents less the weight of the water produced, the result being multiplied by one hundred to give a percentage.

In one version, several alkyd resins that are liquid at room temperature can be provided.

The at least one second binding compound is different from the first binding compound and is solid at room temperature.

The first and second binding compounds are compatible with one another so as to form an ink that is stable over time.

Preferably, the first additive of the ink of the invention comprises from 6 to 13 % of at least one additive suitable for controlling the fluidity of the ink of the invention to reduce the friction of the ink. The fluidity-modifying additive is selected from a group comprising petroleum wax and carnauba extract.

The ink of the invention is stable for a period of at least 5 years, i.e. it can be stored for five years without deteriorating.

The ink of the invention is in fact not subject to phenomena of separation of the various components and/or stratification.

The ink produced according to the teaching of the present invention is water- soluble at a range of temperatures between 0 and 100 °C.

Furthermore, the ink of the invention is not subject to surface hardening, especially when contained in tins.

During storage, even for short periods, known varnishes or inks tend to form a harder surface film, the thickness of which depends on the storage time.

At the time of use this film must be removed from the varnish or ink and discarded, which is wasteful of material .

In contrast, after preparation, the ink of the invention can be stored and used when needed without being subject to hardening phenomena and without the need for remixing.

A high-quality print is therefore achieved even when the printing is done a long time after the ink is produced.

In a preferred version, the at least one second binding compound is advantageously of plant origin and is selected from a group comprising rosin, wood oil and tung oil.

In another version, penta rosin ester can be used as a second binding compound.

In a preferred version, the at least one second binding compound is rosin, neutralised rosin being particularly preferred.

In another preferred version, the second binding compound is a phenolic resin of plant or synthetic origin.

The second binding compound can be a maleic or phenolic resin, or a urethane resin.

In one version, several second binding compounds which are solid at room temperature can be provided.

Advantageously, the ink comprises at least one drying compound suitable for promoting surface drying of said ink. To this end, one or more cobalt salts, for example cobalt octoate or cobalt naphthenate, can be used.

Advantageously, the ink comprises at least one drying compound suitable for promoting deep drying of said ink. To this end, one or more zirconium salts and/or calcium salts, for example zirconium octoate or calcium octoate, can be used.

The presence of at least two different drying compounds suitable for promoting surface drying and deep drying of the ink, respectively, makes it possible to considerably reduce the drying operations, to produce homogeneous drying and to increase the final quality of the print obtained. Advantageously, the ink comprises from 0 to 22 % by weight at least of a second additive.

Preferably, the second additive of the ink of the invention comprises at least one dispersing agent in a percentage between 8 and 12 % of the ink so as to promote the dispersion of the at least one colouring pigment.

The dispersing agent is selected on the basis of the pigment present in the ink. Advantageously, this dispersing agent promotes the dispersion in the ink of all the colouring pigments.

A dispersing agent that is liquid at room temperature is advantageously used. Advantageously, the ink comprises from 2 to 6 % of at least one agent, advantageously but not restricted to a plasticising agent for controlling the viscosity of said ink, which plasticising agent is selected from a group comprising methoxy propanol, methoxy ethanol, butyl cellosolve and isopropyl alcohol .

The final quantity of the plasticising agent in the ink is selected on the basis of the viscosity of the ink.

In one version, the second additive comprises from 2 to 6 % of at least one agent, advantageously but not restricted to a plasticising agent for controlling the viscosity of said ink, which plasticising agent is selected from a group comprising methoxy propanol, methoxy ethanol, butyl cellosolve and isopropyl alcohol .

Advantageously, the ink comprises from 10 to 30 % mineral fillers, which can be selected from a group comprising calcium carbonate, baryte and kaolin. In another version, the second additive comprises from 10 to 30 % mineral fillers, which can be selected from a group comprising calcium carbonate, baryte and kaolin.

The calcium carbonate can be natural or prepared artificially, preferably of natural origin.

Advantageously, the ink comprises from 0.1 to 2 % of at least one solubilising agent to improve solubility.

In another version, the second additive comprises from 0.1 to 2 % of at least one solubilising agent to improve solubility.

The at least one solubilising agent is advantageously a compound derived from ammonia, preferably having a boiling point of > 100 °C, preferably > 150 °C. In a preferred version, the solubiliser is selected from a group comprising monoethanolamine and triethanolamine.

According to one embodiment, the ink comprises from 2 to 4 % by weight of maleic anhydride.

This results in an ink which has increased resistance to hydrolysis and improved scratch-resistant properties.

The applicant analysed this produced effect by means of a crockmeter produced by Atlas Electric Devices.

According to the investigation procedure, a white cloth soaked in water or other contrast liquids is rubbed over the ink to check the indelibility thereof at a preset pressure.

In particular, tests were carried out on banknotes printed with inks produced according to teaching known in the prior art and with inks produced according to the teaching of the present invention.

All the banknotes were rubbed with a cloth soaked in water and caustic soda at 1 % by weight.

The Applicant noted that banknotes printed with inks produced according to teaching known in the prior art lose about 20 % of their colour after 10 passes.

On the other hand, banknotes printed with inks produced according to the teaching of the present invention lose about 20 % of their colour after 17 passes. This indicates that the inks of the invention have a markedly higher resistance.

Preferably, the ink comprises from 1 to 2 % by weight of chloroparaffin . This technical feature makes it possible to obtain an ink which has reduced friction on the cleaning rollers of the machines, which increases the average life of the roller.

This allows the life of the rollers to be increased by up to 70 %.

A further subject-matter of the invention is a method for producing a solvent- free, water-soluble ink for calcographic printing.

According to the method of the invention, from 21 to 31 % by weight of a first binding compound that is soluble or dilutable in water, selected from a group comprising alkyd resins or ketonic resins liquid at room temperature, and from 2 to 7 % by weight of a second solid binding compound are mixed in a planetary mixer, wherein the second binding compound that is solid at room temperature is introduced into the mixer before the first binding compound and heated to a temperature between 70 and 90 °C to fluidify it.

Subsequently, when the second binding compound has reached the desired fluidity, the first binding compound is added and the first and the second binding compounds are mixed together.

When the first and the second binding compounds are mixed together the heating of the mixer is stopped and the mixture obtained is gradually cooled. According to the method of the invention, of from 5 to 30 % by weight of at least one colouring pigment, from 0.2 to 0.8 % by weight of at least one drying compound suitable for promoting the drying of the ink, and from 6 to 13 % by weight of at least one first additive are added to the mixture of the first and second binding compounds to control the fluidity of the ink.

In a preferred version, the first additive comprises petroleum wax and/or carnauba extract.

Advantageously, according to the method, 0 to 22 % by weight at least of a second additive is added in order to optimise or add specific properties of the ink.

These components of the ink are mixed in the mixer preferably without stopping the operation of said mixer.

In addition to adding additives to the mixture, according to the method, the various compounds are mixed in so as to produce a printing ink.

The additives are added starting from the most viscous additives and ending with the most fluid additives.

Advantageously, the additives are mixed in the mixer without stopping the operation of said mixer.

The at least one first binding compound is advantageously selected from the group of alkyd resins that are soluble or dilutable in water and liquid at room temperature. Medium-oil or long-oil resins, having an oil percentage of > 40 %, are particularly preferred.

The percentage of oil is calculated by methods known to a person skilled in the art, in line with specific international reference standards, for example: weight of oil divided by the weight of all the reagents less the weight of the water produced, the result being multiplied by one hundred to give the percentage value.

Alkyd resins which have a high percentage of dry matter, preferably > 80 %, are particularly preferred.

The at least one first and at least one second binding compound are compatible with one another so as to form an ink that is stable over time.

The ink of the invention is stable for a period of at least 5 years.

Penta rosin ester, or a phenolic resin of plant or synthetic origin, a maleic or phenolic resin, or a urethane resin can be used as a second binding compound.

The at least one drying compound suitable for promoting surface drying of said ink can be one or more cobalt salts, for example cobalt octoate or cobalt naphthenate.

The at least one drying compound suitable for promoting deep drying of said ink can be one or more zirconium salts and/or calcium salts, for example zirconium octoate or calcium octoate.

The presence of at least two different drying compounds suitable for promoting surface and deep drying of the ink respectively makes it possible to considerably reduce the drying operations, to obtain homogeneous drying and to increase the final quality of the print obtained.

Advantageously, according to the method of the invention, a second additive comprising at least one dispersing agent in a percentage between 8 and 12 % of the ink is added to promote the dispersion of the at least one colouring pigment. The at least one dispersing agent is selected on the basis of the pigment present in the ink.

A dispersing agent that is liquid at room temperature is advantageously used. Preferably, this dispersing agent promotes the dispersion of all the colouring pigments.

Advantageously, provision is made to mix from 6 to 13 % of at least one first additive for controlling the fluidity of the ink of the invention, to reduce the friction of the ink.

This first, fluidity-modifying additive is selected from a group comprising petroleum wax and carnauba extract.

Advantageously, according to the method of the invention, from 10 to 30 % of mineral fillers, which can be selected from a group comprising calcium carbonate, baryte and kaolin, is mixed in.

Advantageously, according to the method of the invention, from 0.1 to 2 % of at least one solubilising agent derived from ammonia, preferably having a boiling point of > 100 °C, preferably > 150 °C, is mixed in to improve the solubility of the ink in water. In a preferred version, the solubiliser is selected from a group comprising monoethanolamine and triethanolamine.

Finally, according to the method of the invention, advantageously from 2 to 6 % of at least one plasticising agent is mixed in to control the viscosity of said ink, said plasticising agent being selected from a group comprising methoxy propanol, methoxy ethanol, butyl cellosolve and isopropyl alcohol .

The final quantity of the plasticising agent in the ink is selected on the basis of the viscosity desired for the ink of the invention.

The plasticising agent is preferably introduced at the end of mixing if the viscosity of the ink needs to be reduced.

A few preferred examples of formulations of printing ink according to the invention are now provided.

Example 1

Liquid waterborne alkyd resin 25 %, rosin 5 %, wetting agent 10 %, petroleum wax 10 %, pigment from 7 to 30 %, fillers (calcium carbonate or baryte) from 10 to 30 %, methoxy propanol from 2 to 6 %, cobalt octoate 0.15 % and zirconium octoate 0.15 %.

Other formulations were prepared in which the rosin was substituted with maleic resin or phenolic resin .

The actual percentages of pigment were selected on the basis of the type of colour to be produced and the colour intensity required.

Example 2

Liquid waterborne alkyd resin 25 %, rosin 5 %, wetting agent 10 %, petroleum wax 10 %, pigment from 7 to 30 %, fillers (calcium carbonate or baryte) from 10 to 30 %, methoxy propanol from 2 to 6 %, cobalt octoate 0.15 %, zirconium octoate 0.15 % and mono octanol amine from 0.1 to 2 %. Other formulations were prepared in which the rosin was substituted with maleic resin or phenolic resin .

Example 3

Liquid waterborne alkyd resin from 21 to 28 %, rosin from 3 to 7 %, wetting agent from 8 to 12 %, petroleum wax from 7 to 13 %, pigment from 7% to 30 %, fillers (calcium carbonate or baryte) from 10 to 30 %, methoxy propanol from 2 to 6 %, cobalt octoate from 0.15 to 0.35 % and zirconium octoate from 0.15 to 0.35 %.

The actual percentages of pigment were selected on the basis of the type of colour to be produced and the colour intensity required, and the percentages of the remaining components were calibrated so as produce an ink which has the desired rheological characteristics and is suitable for producing good quality printing.

Formulations corresponding to those shown above were also prepared by adding mono octanol amine from 0.1 to 2 % to the formulations to further improve the water solubility of the inks produced and, therefore, the ability to wash off encrusted ink from the printing devices.

Example 4

Water-soluble ketonic resin that is solid at room temperature from 24 to 31 %, wood oil from 2 to 4 %, thickener from 1 to 3 %, wetting agent from 8 to 12 %, carnauba extract from 6 to 12 %, pigment from 5 to 25 %, kaolin from 8 to 28 %, methoxy propanol from 2 to 6 %, cobalt naphthenate from 0.15 to 0.25 %, calcium octoate from 0.15 to 0.40 % and triethanolamine from 2 to 3 % to improve water solubility.

The inks produced in the invention underwent various printing tests, which demonstrated that said inks are effective in producing long-lasting prints and suitable for printing identity documents such as passports, identity papers etc., and for printing banknotes.

The inks of the invention have proved suitable for carrying out calcographic printing on a substrate producing a thickness of from 10 to 70 microns, preferably from 20 to 60 microns, and for being deposited on paper substrates or polymer substrates.

The printing tests demonstrate a high degree of indelibility, good relief, high definition of fine lines and good drying of the ink.

Furthermore, these inks allow an improved printing process to be achieved. Furthermore, the inks of the invention all proved washable with water. The printing rollers were cleaned effectively using water, if necessary with extremely small amounts of conventional detergents, for example sodium hydroxide and potassium hydroxide.

The environmental impact of the inks of the invention and, therefore, the related printing processes is extremely low, especially when compared with the environmental impact of known printing processes.

With the ink of the invention it is not necessary to use sodium sulforicinate and ammonium sulforicinate in the cleaning mixture.

It should be noted that a fully operational calcographic machine requires about 400 litres of water per hour, which is then disposed of using a suitable purifier. Therefore, since water that is less polluting is produced using the inks of the invention, there is a notable reduction in the environmental impact when using the inks of the invention, compared with known printing processes.

During the printing phase, 70 % of the product is not used and is therefore disposed of; it is therefore obvious that in using the waterborne solvent, the savings in unused product are substantial .

A printing process is therefore obtained that has a total environmental impact that is notably smaller than known methods.

Furthermore, since no hazardous solvents are present the risks for operators are extremely low.

The inks of the invention are free of aromatic solvents such as toluol, xylol and benzol, which are usually used and which evaporate during the printing phase, emitting highly toxic vapours.

With the formulations of the inks of the invention it is possible to clean the printing devices with pure water at the end of work, or when changing colour, because the ink is water-soluble.

The ink of the invention dries well : sheets coming out of the printing unit have no ink drag marks even if the sheets are taken out before they reach the ventilation system .

This involves a simplified drying phase and a reduction of up to 80 % in the heat of the drying oven.

Furthermore, compositions of the inks of the invention are characterised by low volatility and can be left in the open air because they do not form hard crusts of unusable product.

Claims

1. Solvent-free, water-soluble ink for calcographic printing which comprises, relative to the total weight of said ink:

from 21 to 31 % by weight of at least one first binding compound that is water-soluble at room temperature, selected from the group of alkyd resins or ketonic resins that are liquid at room temperature;

from 5 to 30 % by weight of a colouring pigment;

from 6 to 13 % by weight of at least one first additive for controlling the fluidity of the ink, said first additive comprising petroleum wax and/or carnauba extract.

2. Ink according to the preceding claim, wherein said at least one first binding compound comprises a medium-oil or long-oil resin, having an oil percentage of > 40 % by weight, or a mixture of medium-oil or long-oil resins.

3. Ink according to either claim 1 or claim 2, wherein said at least one second binding compound is of plant origin and is selected from a group comprising rosin, wood oil, tung oil, penta rosin ester or phenolic resins or mixtures thereof, and/or is a resin of synthetic origin, preferably maleic or phenolic resin, or urethane resin.

4. Ink according to any one of the preceding claims, wherein said at least one drying compound comprises a drying compound suitable for promoting surface drying of said ink, selected from a group comprising one or more cobalt salts such as cobalt octoate or cobalt naphthenate.

5. Ink according to any one of the preceding claims, wherein said at least one drying compound comprises a drying compound suitable for promoting deep drying of said ink, selected from a group comprising one or more zirconium salts and/or calcium salts, for example zirconium octoate or calcium octoate.

6. Ink according to any one of the preceding claims, wherein said first additive comprises from 6 to 13 % of at least one additive suitable for controlling the fluidity of said ink, preferably selected from a group comprising petroleum wax and carnauba extract.

7. Ink according to any one of the preceding claims, comprising from 0 to 22 % by weight at least of a second additive and wherein said second additive comprises from 8 to 12 % by weight of at least one dispersing agent to promote the dispersion of the at least one colouring pigment.

8. Ink according to claim 6, wherein said second additive comprises from 2 to 6 % by weight of at least one plasticising agent for controlling the viscosity of said ink, selected from a group comprising methoxy propanol, methoxy ethanol, butyl cellosolve, isopropyl alcohol and/or from 0.1 to 2 % of at least one solubiliser for improving the solubility of said ink in water, said at least one solubiliser advantageously being a compound that is derived from ammonia and has a boiling temperature of > 100 °C, preferably > 150 °C, said compound most preferably being monoethanolamine or triethanolamine.

9. Ink according to either claim 7 or claim 8, wherein said second additive comprises from 0.1 to 2 % of at least one solubilising agent to improve the solubility of said ink.

10. Ink according to any one of claims 7 to 9, wherein said second additive comprises from 10 to 30 % of mineral fillers, which can be selected from a group comprising calcium carbonate, baryte and kaolin.

11. Ink according to any one of claims 7 to 10, wherein said second additive comprises from 6 to 13 % of at least one additive suitable for controlling the fluidity of said ink, preferably selected from a group comprising petroleum wax or carnauba extract.

12. Ink according to any one of the preceding claims, comprising 25 % by weight of liquid waterborne alkyd resin, 5 % by weight of rosin, 10 % by weight of dispersing agent, 10 % by weight of petroleum wax, from 7 to 30 % by weight of pigment, from 10 to 30 % by weight of fillers (calcium carbonate or baryte), from 2 to 6 % by weight of methoxy propanol, 0.15 % by weight of cobalt octoate and 0.15 % by weight of zirconium octoate.

13. Ink according to any one of claims 1 to 11, comprising 25 % by weight of liquid waterborne alkyd resin, 5 % by weight of rosin, 10 % by weight of dispersing agent, 10 % by weight of petroleum wax, from 7 to 30 % by weight of pigment, from 10 to 30 % by weight of fillers, preferably calcium carbonate or baryte, from 2 to 6 % by weight of methoxy propanol, 0.15 % by weight of cobalt octoate, 0.15 % by weight of zirconium octoate and from 0.1 to 2 % by weight of mono octanol amine.

14. Ink according to any one of claims 1 to 11, comprising from 21 to 28 % by weight of liquid waterborne alkyd resin, from 3 to 7 % by weight of rosin, from 8 to 12 % by weight of dispersing agent, from 7 to 13 % by weight of petroleum wax, from 7 to 30 % by weight of pigment, from 10 to 30 % by weight of fillers, preferably calcium carbonate or baryte, from 2 to 6 % by weight of methoxy propanoi, from 0.15 to 0.35 % by weight of cobalt octoate and from 0.15 to 0.35 % by weight of zirconium octoate.

15. Ink according to any one of claims 1 to 11, comprising from 24 to 31 % by weight of water-soluble ketonic resin, from 2 to 4 % by weight of wood oil, from 1 to 3 % by weight of thickening agent, from 8 to 12 % by weight of dispersing agent, from 6 to 12 % by weight of carnauba extract, from 5 to 25 % by weight of pigment, from 8 to 28 % by weight of kaolin, from 2 to 6 % by weight of methoxy propanoi, from 0.15 to 0.25 % by weight of cobalt naphthenate, from 0.15 to 0.40 % by weight of calcium octoate and from 2 to

3 % by weight of triethanolamine.

16. Ink according to any one of the preceding claims, comprising from 2 to

4 % by weight of maleic anhydride.

17. Ink according to any one of the preceding claims, comprising from 1 to 2 % by weight of chloroparaffin.

18. Ink according to any one of the preceding claims, comprising from 6 to 13 % of at least one further additive suitable for controlling the fluidity of said ink in order to reduce its friction, said further additive being selected from a group comprising petroleum wax and carnauba extract.

19. Ink according to any one of the preceding claims wherein said at least one second binding compound is rosin, neutralised rosin being particularly preferred.

20. Method for preparing a solvent-free, water-soluble ink for calcographic printing, comprising the following phases:

pouring from 2 to 7 % by weight of a second binding compound that is solid at room temperature into a planetary mixer, and heating said compound to a temperature of between 70 °C and 90°C,

pouring from 21 to 31 % by weight of a first binding compound that is soluble or dilutable in water, into said mixer, which compound is selected from the group of alkyd resins or ketonic resins liquid at room temperature, and mixing said first and said second compound,

adding from 5 to 30 % by weight of a colouring pigment,

adding from 0.2 to 0.8 % by weight of at least one drying compound suitable for promoting drying of the ink,

adding from 6 to 13 % by weight of at least one first additive for controlling the fluidity of the ink comprising petroleum wax and/or carnauba extract,

adding from 0 to 22 % by weight at least of a second additive, wherein said addition phases are carried out during mixing without impeding the function of said mixer.

21. Method according to the preceding claim and further comprising adding from 15 to 35 % of further additives for controlling the fluidity of the ink.