WO2014191971A2

WO2014191971A2 - Procedure for the manufacture of inks for the digital printing on ceramic products

Info

Publication number: WO2014191971A2
Application number: PCT/IB2014/061847
Authority: WO
Inventors: Paolo SERPAGLI
Original assignee: Lizel S.R.L.
Priority date: 2013-05-30
Filing date: 2014-05-30
Publication date: 2014-12-04
Also published as: WO2014191971A3

Abstract

The procedure for the manufacture of inks for the digital printing on ceramic products comprises the steps of: - making at least a first wet grinding (I; Ia) of at least a first ceramic pigment (1) in powder form, having a first coloring, and of at least a first vehicle-substance (2) in liquid form, to obtain a first concentrated mixture (3); - providing at least a dilution vehicle-substance (11) in liquid form for the dilution of the first concentrated mixture (3); - making an ultrasound mixing (II) of the first concentrated mixture (3) and of the dilution vehicle- sub stance (11) to obtain an ink (12) for the digital printing on ceramic products.

Description

PROCEDURE FOR THE MANUFACTURE OF INKS

FOR THE DIGITAL PRINTING ON CERAMIC PRODUCTS

Technical Field

The present invention relates to a procedure and a machine for the manufacture of inks for digital printing on ceramic products.

Background Art

In the ceramic industry, it is known to decorate tiles and slabs of ceramic materials using digital printing.

To perform this technique, special inks are used specifically studied to:

- be supplied in a particularly precise way during printing;

resist high temperatures considering that, once decorated, the ceramic tiles undergo a kiln firing treatment.

The inks are made starting with a series of colored metal oxides, which are ground and mixed together with a liquid vehicle in a particularly long working procedure (about 40 hours) and which is highly energy consuming.

It is therefore easy to appreciate how the cost of manufacture of traditional inks is particularly high.

The inks are made by specialized manufacturers, each of which has its own range of inks, with colors and shades different to those of other companies. The inks are therefore used by the ceramic product manufacturers to load specific digital printers fitted along their production line.

The digital printers are usually loaded with a particularly low number of inks of different color (usually four), the remaining colors being obtained by combining these few inks.

During printing, in fact, the digital printer control software controls the supply of inks on the various points of the surface of the tiles to be decorated and, at the points where two or more inks are superimposed, permits obtaining different colors, nuances and shades.

Because the inks provided by one ink manufacturer are different to those provided by another ink manufacturer, for a ceramic product manufacturer changing ink suppliers is never a simple matter.

In these cases, in fact, a difficult and problematic operation has to be performed concerning the reprogramming of the digital printer control software so that, during printing, the inks of the new supplier combine together and reproduce on the tile the same color effect obtained using the previous supplier's inks.

Such reprogramming operation must inconveniently be performed for all the products of the ceramic product manufacturer, and this consequently results in a heavy work load which calls for the stoppage of the digital printers for a long time and with the risk in any case of not managing to perfectly reproduce the previously obtained color effects.

To this must be added that the cost of the reprogramming operation, assessed both in terms of skilled labor used and production line down times, is very high. Nor should the fact be neglected that the ceramic product manufacturer that decides to change ink supplier needs, for a certain amount of time, to terminate warehouse stocks of old inks, and meanwhile start the supply by the new ink manufacturer, with considerable logistic complications.

Description of the Invention

The main aim of the present invention is to provide a procedure for the manufacture of inks for digital printing on ceramic products which allows to manufacture inks in a more practical, easier, functional and economical manner compared to the techniques currently employed.

Within this technical aim, a further object of the present invention is to enable the manufacture of inks with colors and shades also significantly different to one another.

Another object of the present invention is to provide a procedure for the manufacture of inks for digital printing on ceramic products which can overcome the above mentioned drawbacks of the prior art in the ambit of a simple, rational, easy and effective to use as well as low cost solution.

The above mentioned objects are achieved by the present procedure for the manufacture of inks for digital printing on ceramic products according to claim 1.

The above mentioned objects are also achieved by the present machine for the manufacture of inks for digital printing on ceramic products according to claim 17. Brief Description of the Drawings

Other characteristics and advantages of the present invention will become evident from the description of some preferred, but not exclusive, embodiments of a procedure for the manufacture of inks for digital printing on ceramic products, illustrated by way of an indicative, but not limitative example in the accompanying drawings in which:

Figures 1 and 2 are schematic views showing a first embodiment of the procedure according to the invention;

Figures 3 to 5 are schematic views showing a second embodiment of the procedure according to the invention;

Figure 6 is a schematic view showing the machine according to the invention. Embodiments of the Invention

With particular reference to the embodiment shown in the figures 1 and 2, the steps of the procedure according to the invention have been indicated by I and II.

Step I of the procedure consists in making at least a first wet grinding of at least a first ceramic pigment 1 in powder form, having a first coloring, and at least a first vehicle- sub stance 2 in liquid form, to obtain a first concentrated mixture 3. The first ceramic pigment 1 is a colored inorganic substance which can be used to decorate ceramic products and, e.g., consists of a colored metal oxide.

The first ceramic pigment 1 has a coloring chosen from the list of colors comprising: black, white, cyan, pink, yellow and brown.

The first vehicle- sub stance 2, instead, consists e.g. of a solvent or a mixture of glycol ether-based solvents, containing groups of alkyl-ether groups of the ethylene glycol, 2-methoxyethanol, 2-etoxyethanol, 2-butoxyethanol type.

During the first wet grinding I at least a first dispersing substance 4 can also be present.

The first dispersing substance 4, e.g., consists of DISPERBYK®.

The first ceramic pigment 1, the first vehicle-substance 2 and the first dispersing substance 4 are dosed during the first wet grinding I so as to obtain a first concentrated mixture 3 having the following weight concentrations evaluated with respect to the total weight of the first concentrated mixture 3: first ceramic pigment 60 - 70 %

first vehicle- sub stance 20 - 35 % first dispersing substance 5 - 10 %

Before the first wet grinding I, the first ceramic pigment 1 has a grain size bigger than 12 μπι while, after the first wet grinding I, the first ceramic pigment 1 has a grain size smaller than 1,5 μιη.

The reduction in the grain size of the first ceramic pigment 1 occurs in the presence of the first vehicle- sub stance 2 which is in liquid form and, therefore, we can correctly speak of a wet grinding.

The first wet grinding I usefully occurs inside a mill with loose grinding bodies

5.

The procedure according to the invention thus envisages a step not illustrated in detail in the illustrations which consists in providing at least a dilution vehicle- substance 11 in liquid form for the dilution of the first concentrated mixture 3. The dilution vehicle- substance 11 consists e.g. of a solvent or a mixture of glycol ether-based solvents, containing groups of alkyl-ether groups of the ethylene glycol, 2-methoxyethanol, 2-etoxyethanol, 2-butoxyethanol type; the dilution vehicle- sub stance 11 can coincide with the first vehicle-substance 2 or it can be different.

The step II of the procedure consists in making an ultrasound mixing of the first concentrated mixture 3 and of the dilution vehicle- sub stance 11 to obtain an ink 12 for the digital printing on ceramic products; the use of ultrasounds permits intimately joining the components to be mixed quickly and very efficiently obtaining an ink with high rheological capacities and coloring properties.

During the ultrasound mixing II at least a dilution dispersing substance 13 is also present.

Similarly to the first dispersing substance 4, the dilution dispersing substance 13 also consists for example of DISPERBYK®; alternative embodiments cannot however be ruled out wherein the dilution dispersing substance 13 is different to the first dispersing substance 4.

The first concentrated mixture 3, the dilution vehicle- sub stance 11 and the dilution dispersing substance 13 are dosed during ultrasound mixing II so as to obtain an ink 12 with the following weight concentrations evaluated with respect to the total weight of the ink 12:

first concentrated mixture 45 - 57 % dilution vehicle- sub stance 38 - 50 % dilution dispersing substance 0 - 5 %

Usefully, during the ultrasound mixing II, one or more additive substances can be added with anti-foam, anti-agglomeration function or the like; if present, these additive substances are added in the following weight concentration evaluated with respect to the total weight of the ink 12:

additive substances 0 - 2 %

The step of ultrasound mixing II comprises the selection of the quantities of first concentrated mixture 3 and of dilution vehicle-substance 11 (and, if present, also of dilution dispersing substance 13 and of additive substances) depending on the type of ink to obtain.

In other words, the first concentrated mixture 3 and the dilution vehicle- substance 11 are dosed so as to obtain an ink 12 with the desired characteristics in terms of rheological capacities and coloring properties.

The ultrasound mixing II occurs inside an automatic and programmable machine 14 able to select the quantity of first concentrated mixture 3 and the quantity of dilution vehicle- sub stance 11 (and, if present, also of dilution dispersing substance 13 and of the additive substances).

More in detail, the machine 14 is an ultrasound mixer which mixes the first concentrated mixture 3 and the dilution vehicle- sub stance 11 under the effect of ultrasounds which permit obtaining the intimate union and homogenization of the mixed components.

Usefully, the machine 14 can be connected to a tank containing the dilution vehicle- sub stance 11 and to a container containing the first concentrated mixture 3, from which are taken the quantities required to obtain the desired ink.

With particular reference to the embodiment shown in the figures from 3 to 5, by la, lb and II are indicated the steps of the procedure according to the invention. The step la consists in a first wet grinding completely the same as the first wet grinding I which permits obtaining the first concentrated mixture 3 shown in the figure 1, to the detailed description of which full reference is made.

The step lb of the procedure consists on the other hand in making at least a second wet grinding of at least a second ceramic pigment 6 in powder form, having a second coloring different to the first coloring, and of at least a second vehicle- sub stance 7 in liquid form, to obtain a second concentrated mixture 8. Similarly to the first ceramic pigment 1 , the second ceramic pigment 6 is also a colored inorganic substance usable to decorate ceramic products and, for example, consists of a colored metal oxide, having a different color to that of the first ceramic pigment 1.

Like the first ceramic pigment 1, the second ceramic pigment 6 also has a coloring chosen from the list of colors comprising: black, white, cyan, pink, yellow and brown.

In other words, the first ceramic pigment 1 and the second ceramic pigment 6 have two different colors chosen among black, white, cyan, pink, yellow and brown.

Similarly to the first vehicle- sub stance 2, the second vehicle- sub stance 7 also consists for example of a solvent or a mixture of glycol ether-based solvents, containing groups of alkyl-ether groups of the ethylene glycol, 2- methoxyethanol, 2-etoxyethanol, 2-butoxyethanol type; the first vehicle- substance 2 and the second vehicle- sub stance 7 can coincide.

During the second wet grinding lb, at least a second dispersing substance 9 can also be present.

Similarly to the first dispersing substance 4, the second dispersing substance also consists e.g. of DISPERBYK®.

The second ceramic pigment 6, the second vehicle- sub stance 7 and the second dispersing substance 9 are dosed during the second wet grinding lb so as to obtain a second concentrated mixture 8 in the following weight concentrations evaluated with respect to the total weight of the second concentrated mixture 8:

second ceramic pigment 60 - 70 % second vehicle- sub stance 20 - 35 % second dispersing substance 5 - 10 %

Before the second wet grinding lb, the second ceramic pigment 6 has a grain size bigger than 12 μπι while, after the second wet grinding lb, the second ceramic pigment 6 has a grain size smaller than 1,5 μπι.

The reduction in grain size of the second ceramic pigment 6 occurs in the presence of the second vehicle- sub stance 7 which is in liquid form and, therefore, in this case too we can correctly speak of a wet grinding.

The first concentrated mixture 3 and the second concentrated mixture 8 have a coloring deriving from that of the first ceramic pigment 1 and of the second ceramic pigment 6 respectively, and therefore different the one to the other.

The second wet grinding lb usefully occurs inside a mill with loose grinding bodies 10.

The mill with loose grinding bodies 10 used for the second wet grinding lb can be different to the mill with loose grinding bodies 5 used in the first wet grinding I; in this case we avoid any chance of the different coloring of the first concentrated mixture 3 staining the second concentrated mixture 8, thus compromising the coloring.

It cannot however be ruled out that the mill with loose grinding bodies 10 used for the second wet grinding lb be the same used in the first wet grinding I, after washing aimed at removing the residues of first concentrated mixture 3.

Similarly to the embodiment shown in the figures 1 and 2, the solution shown in the figures from 3 to 5 also provides for a step not shown in the illustrations which consists in providing at least a dilution vehicle- sub stance 11 in liquid form; in this case, the dilution vehicle- sub stance 11 is able to dilute both the first concentrated mixture 3 and the second concentrated mixture 8.

The dilution vehicle- substance 11 consists e.g. of a solvent or a mixture of glycol ether-based solvents, containing groups of alkyl-ether groups of the ethylene glycol, 2-methoxyethanol, 2-etoxyethanol, 2-butoxyethanol type; the dilution vehicle- sub stance 11 can coincide with the first vehicle- sub stance 2 and/or with the second vehicle- sub stance 7, or can be different.

Step II of the procedure again consists in a step of ultrasound mixing which, in this case, involves the first concentrated mixture 3, the second concentrated mixture 8 and the dilution vehicle- sub stance 11 to obtain an ink 12 for the digital printing on ceramic products, having a third coloring different to the first coloring of the first ceramic pigment 1 and to the second coloring of the second ceramic pigment 6.

During the ultrasound mixing II the previously-mentioned dilution dispersing substance 13 is also present, full reference to the detailed description of which is made.

Similarly to the first dispersing substance 4 and to the second dispersing substance 9, the dilution dispersing substance 13 also consists e.g. of DISPERBYK®; alternative embodiments cannot however be ruled out wherein the dilution dispersing substance 13 is different to the first dispersing substance 4 and/or to the second dispersing substance 9.

The first concentrated mixture 3, the second concentrated mixture 8, the dilution vehicle- sub stance 11 and the dilution dispersing substance 13 are dosed during the ultrasound mixing II so as to obtain an ink 12 with the following weight concentrations evaluated with respect to the total weight of the ink 12:

first concentrated mixture 40 - 57 % second concentrated mixture 0 - 10 % dilution vehicle- sub stance 38 - 50 % dilution dispersing substance 0 - 5 %

As will be seen, the concentration of second concentrated mixture 8 can also be equal to 0 %, in which case the ink 12 is only obtained as combination of first concentrated mixture 3, dilution vehicle- sub stance 11 and dilution dispersing substance 13 as in the embodiment in the figures 1 and 2.

As in the solution shown in the figures 1 and 2, furthermore, during the ultrasound mixing II one or more additive substances can be added with anti- foam, anti-agglomerating function or the like; if present, these additive substances are added in the following weight concentration evaluated with respect to the total weight of the ink 12:

additive substances 0 - 2 %

The step of ultrasound mixing II comprises the selection of the quantities of the first concentrated mixture 3, of the second concentrated mixture 8 and of the dilution vehicle-substance 11 (and, if present, also of the dilution dispersing substance 13 and of the additive substances) depending not only on the required rheological capacity and coloring property characteristics, but also on the third coloring to obtain.

In other words, the first concentrated mixture 3, the second concentrated mixture 8 and the dilution vehicle-substance 11 are dosed so as to obtain an ink 12 with a third pre- determined coloring.

The ultrasound mixing II occurs inside a programmable machine 14 able to make the selection of the quantity of first concentrated mixture 3, of the quantity of second concentrated mixture 8 and of the quantity of dilution vehicle- sub stance 11 (and, if present, also of dilution dispersing substance 13 and of the additive substances).

Similarly to what is shown in figure 2, the machine 14 consists e.g. of an ultrasound mixer which mixes the first concentrated mixture 3, the second concentrated mixture 8 and the dilution vehicle- sub stance 11 under the effect of ultrasounds which permit obtaining the intimate union and homogenization of the mixed components.

Usefully, the machine 14 can be connected to a tank containing the dilution vehicle- sub stance 11 and to two containers containing the first concentrated mixture 3 and the second concentrated mixture 8, from which are taken the quantities required to obtain the required ink.

Even more usefully, the machine 14 is connected to a number of containers greater than two, which contain a corresponding number of concentrated mixtures 3, 8 of different coloring obtained by means of the procedures described in the steps la and lb.

In other words, the steps la and lb can be repeated to obtain concentrated mixtures in all the listed colors: black, white, cyan, pink, yellow and brown. The machine 14, therefore, has at disposal all the concentrated mixtures 3, 8 and manages their ultrasound mixing to obtain a very high number of inks 12 of different colorings.

This way, it is possible to reproduce any coloring, in a practical, easy and functional way, including those of already existing inks made by the different ink manufacturers operating on the market.

A possible detailed representation of the machine 14 is shown in figure 6, wherein the machine 14 comprises at least a base frame 15 for resting on the ground onto which is mounted at least a mixing receptacle 16 for mixing at least a concentrated mixture 3, 8 and the dilution vehicle- sub stance 11, to obtain the ink 12.

The mixing receptacle 16 is mounted on the base frame 15 for the interposition of at least a weighing device 17, which allows weighing the mixing receptacle 16 and its contents.

With the mixing receptacle 16, furthermore, are associated at least a viscosity sensor 18, able to measure the viscosity of the ink 12, and a temperature sensor 19, able to measure the temperature of the ink 12.

The machine 14, in practice, is able to recognize and monitor, during mixing, the rheological properties of the ink 12 such as viscosity, temperature (thanks to the sensors 18, 19) and density (thanks to the weighing device 17).

In the mixing receptacle 16 is arranged at least partially a stirrer device 20, of the type of a mechanical blade stirrer, which stirs the ink 12 and keeps it moving inside the mixing receptacle 16.

With the mixing receptacle 16 is associated at least a forced circulation circuit 21 for the forced circulation of the ink 12.

In other words, the forced circulation circuit 21 defines a recirculation current which takes the ink 12 from the mixing receptacle 16, moving it away from this, before reintroducing it.

The forced circulation circuit 21 comprises:

- at least a pipe 22, 23, 24 having a first extremity 25 associated in correspondence to the bottom of the mixing receptacle 16 and a second extremity 26 ending up in correspondence to the top of the mixing receptacle 16; and

at least a pumping device 27 associated with the pipe 22, 23, 24 for pumping the ink from the first extremity 25 to the second extremity 26. The pipe 22, 23, 24, in particular, is split into:

a first section 22 extending from the first extremity 25 to the pumping device 27;

a second section 23 extending from the pumping device 27 to an articulated joint 29;

a third section 24 extending from the articulated joint 29 to the second extremity 26.

The articulated joint 29 has a valve element 30 for diverting the flow inside the forced circulation circuit 21 towards an unloading section 28 through which the ink 12, once mixed, is unloaded into a bin 31 or the like.

With the forced circulation circuit 21 is associated at least an ultrasound generating device 32 able to charge the ink 12 with ultrasounds for the ultrasound mixing of the concentrated mixture 3, 8 and of the dilution vehicle- substance 11.

In the embodiment shown in the figure 6, there are two ultrasound generating devices 32, arranged in series.

The ultrasound generating devices 32 are arranged along the second section 23 of the pipe 22, 23, 24.

With the forced circulation circuit 21 is also associated a cooling device 33 able to cool the ink 12.

Treatment with ultrasounds does in fact tend to heat the ink 12 and the presence of the cooling device 33 permits controlling its temperature.

The cooling device 33 is arranged downstream of the ultrasound generating devices 32 and, e.g., it is arranged along the third section 24 of the pipe 22, 23, 24.

Preferably, the cooling device 33 consists of a refrigeration unit or the like, e.g., of the adjustable type, i.e., which is able to vary the refrigerating power.

The machine 14 also has a plurality of containers 34 for the containment of a plurality of concentrated mixtures 3, 8 having different coloring the one to the other.

The containers 34 are associated with the base frame 15 and are arranged in fluidic connection with the mixing receptacle 16 along a plurality of connection lines 35 having respective valve means 36 for the loading of the mixing receptacle 16 with the concentrated mixtures 3, 8. With the base frame 15 is also associated a tank 37 for the containment of the dilution vehicle- sub stance 11; the tank 37 is arranged in fluidic connection with the mixing receptacle 16 by means of a corresponding connection line 35 interlocked to respective valve means 36 for the loading of the mixing receptacle 16 with the dilution vehicle- sub stance 11.

In the same way, auxiliary containers 38 can also be provided for containing the dilution dispersing substance 13 and for the additive substances 39, wherein the auxiliary containers 38 are arranged in fluidic connection with the mixing receptacle 16 along corresponding connection lines 35 having respective valve means 36 for loading the mixing receptacle 16.

The machine 14 is controlled by means of at least a processing and control unit 40 associable with a storage unit 41 containing predefined data for obtaining a plurality of inks 12.

The processing and control unit 40 is able to select the quantities of concentrated mixtures 3, 8, of dilution vehicle- sub stance 11 and, if present, of dilution dispersing substance 13 and of additive substances 39, to take from the containers 34, from the tank 37 and from the auxiliary containers 38 depending on the pre-established data loaded in the storage unit 41.

The predefined data, for example, concern:

- the formulations of the inks 12 to obtain, i.e., the specific concentrations of the various ingredients to be mixed to obtain an ink 12 with a particular coloring and/or with determinate physical characteristics;

the rheological properties which the ink 12 must have at the end of mixing, such as, e.g., the density and viscosity values at a certain temperature.

The processing and control unit 40 is operatively connected to valve means 36 to command its opening and closing and to load the mixing receptacle 16 with the quantities required to obtain the ink 12.

Furthermore, the processing and control unit 40 is operatively connected to the weighing device 17, to the viscosity sensor 18 and to the temperature sensor 19 to monitor the mixing procedure of the ink 12 and, if necessary, to operate in a retroactive manner adding one or more of the concentrated mixtures 3, 8, of the dilution vehicle-substance 11, of the dilution dispersing substance 13 and of the additive substances 39 until the required ink 12 is obtained.

The processing and control unit 40, furthermore, is also operatively connected to the pumping device 27, to the ultrasound generating devices 32, to the cooling device 33 and to the valve element 30 to control the operation of the forced circulation circuit 21.

Preferably, the storage unit 41 is of the portable type and associable with the processing and control unit 40 by means of the USB port; this way the storage unit 41 can be removed from the machine 14 and also acts as a system security and start/stop key.

Once the storage unit 41 has been removed in fact, the processing and control unit 40 loses access to the predefined data and the machine 14 is unable to operate.

The procedure and the machine 14 forming the subject of the present invention are very conveniently suited to be used by an ink manufacturing company, which implements all the procedure steps I, la, lb and II starting with the raw materials, right up to the required ink 12, which is sold to the end user, i.e., a manufacturer of ceramic products that uses the ink 12 for the digital printing of its products.

Furthermore, the present procedure is very conveniently suited to be put into practice in part by the ink manufacturer and in part by the ceramic product manufacturer.

In other words, the ink manufacturer limits itself to putting into practice the steps I, la and lb and to supplying the end user with the concentrated mixtures 3, 8.

The ceramic product manufacturer, on the other hand, equips itself with the machine 14 which, once supplied with the concentrated mixtures 3, 8 made by the ink manufacturer, is able to manufacture all the inks in the required colorings.

Such solution appears particularly convenient in the light of the fact that each manufacturer of ceramic products more often than not already has in production its own catalog of decorated products with pre-established colorings and shades. After a simple preliminary programming and setting operation of the machine 14, the step II of the procedure can be implemented by the end user directly in his/her own production facility starting with the concentrated mixtures 3, 8 supplied by the ink manufacturer.

All this greatly simplifies all the logistic aspects tied to the supply of inks by the ink manufacturer and to the management of the warehouse by the ceramic product manufacturer.

Claims

1) Procedure for the manufacture of inks for the digital printing on ceramic products, characterized by the fact that it comprises the steps of:

making at least a first wet grinding (I; la) of at least a first ceramic pigment (1) in powder form, having a first coloring, and of at least a first vehicle- substance (2) in liquid form, to obtain a first concentrated mixture (3);

providing at least a dilution vehicle-substance (11) in liquid form for the dilution of said first concentrated mixture (3);

making an ultrasound mixing (II) of said first concentrated mixture (3) and of said dilution vehicle- sub stance (11) to obtain an ink (12) for the digital printing on ceramic products.

2) Procedure according to claim 1, characterized by the fact that said ultrasound mixing (II) comprises the selection of the quantities of said first concentrated mixture (3) and of said dilution vehicle- sub stance (11).

3) Procedure according to one or more of the preceding claims, characterized by the fact that it comprises the step of making at least a second wet grinding (lb) of at least a second ceramic pigment (6) in powder form, having a second coloring different to said first coloring, and of at least a second vehicle- substance (7) in liquid form, to obtain a second concentrated mixture (8).

4) Procedure according to claim 3, characterized by the fact that said dilution vehicle- sub stance (11) is able to dilute both said first concentrated mixture (3) and said second concentrated mixture (8).

5) Procedure according to claim 4, characterized by the fact that said ultrasound mixing (II) comprises making an ultrasound mixing (II) of said first concentrated mixture (3), of said second concentrated mixture (8) and of said dilution vehicle- sub stance (11) to obtain said ink (12) for the digital printing on ceramic products, having a third coloring different to said first coloring and said second coloring.

6) Procedure according to claim 5, characterized by the fact that said ultrasound mixing (II) comprises the selection of the quantities of said first concentrated mixture (3), of said second concentrated mixture (8) and of said dilution vehicle- sub stance (11) depending on said third coloring to obtain. 7) Procedure according to one or more of the preceding claims, characterized by the fact that said ultrasound mixing (II) occurs inside a programmable machine (14) able to perform said selection of said quantities.

8) Procedure according to one or more of the preceding claims, characterized by the fact that, during said first wet grinding (I; la), at least a first dispersing substance (4) is also present.

9) Procedure according to claim 8, characterized by the fact that said first concentrated mixture (3) comprises said first ceramic pigment (1), said first vehicle- sub stance (2) and said first dispersing substance (4) in the following weight concentrations evaluated with respect to the total weight of said first concentrated mixture (3):

first ceramic pigment (1) 60 - 70 % first vehicle- sub stance (2) 20 - 35 % first dispersing substance (4) 5 - 10 % 10) Procedure according to one or more of the preceding claims, characterized by the fact that, during said second wet grinding (lb), at least a second dispersing substance (9) is also present.

11) Procedure according to claim 10, characterized by the fact that said second concentrated mixture (8) comprises said second ceramic pigment (6), said second vehicle- sub stance (7) and said second dispersing substance (9) in the following weight concentrations evaluated with respect to the total weight of said second concentrated mixture (8):

second ceramic pigment (6) 60 - 70 % second vehicle- sub stance (7) 20 - 35 % second dispersing substance (9) 5 - 10 %

12) Procedure according to one or more of the preceding claims, characterized by the fact that, during said ultrasound mixing (II), at least a dilution dispersing substance (13) is also present.

13) Procedure according to one or more of the preceding claims, characterized by the fact that said ink (12) comprises said first concentrated mixture (3), said second concentrated mixture (8), said dilution vehicle-substance (11) and said dilution dispersing substance (13) in the following weight concentrations evaluated with respect to the total weight of said ink (12):

first concentrated mixture (3) 40 - 57 % second concentrated mixture (8) 0 - 10 % dilution vehicle- sub stance (11) 38 - 50 % dilution dispersing substance (13) 0 - 5 %

14) Procedure according to one or more of the preceding claims, characterized by the fact that, before said first wet grinding (I; la), said first ceramic pigment (1) has a grain size bigger than 12 μπι and, after said first wet grinding (I; la), said first ceramic pigment (1) has a grain size smaller than 1,5 μιη.

15) Procedure according to one or more of the preceding claims, characterized by the fact that, before said second wet grinding (lb), said second ceramic pigment (6) has a grain size bigger than 12 μπι and, after said second wet grinding (lb), said second ceramic pigment (6) has a grain size smaller than 1,5 μιτι.

16) Procedure according to one or more of the preceding claims, characterized by the fact that said first vehicle- sub stance (2) and said second vehicle- substance (7) coincide.

17) Machine for the manufacture of inks for the digital printing on ceramic products, characterized by the fact that it comprises:

at least a base frame (15);

at least a mixing receptacle (16) associated with said base frame (15) for the mixing of at least a concentrated mixture (3, 8) and of at least a dilution vehicle- sub stance (11) to obtain an ink (12) for the digital printing on ceramic products;

at least a forced circulation circuit (21) associated with said mixing receptacle (16) for the forced circulation of said ink (12);

at least an ultrasound generating device (32) associated with said forced circulation circuit (21) and able to charge said ink (12) with ultrasounds for the ultrasound mixing of said concentrated mixture (3, 8) and of said dilution vehicle- sub stance (11).

18) Machine according to claim 17, characterized by the fact that it comprises at least a stirrer device (20) arranged at least partially in said mixing receptacle (16) to stir said ink (12).

19) Machine according to claim 17 or 18, characterized by the fact that it comprises at least a weighing device (17) of said mixing receptacle (16).

20) Machine according to one or more of the claims from 17 to 19, characterized by the fact that it comprises at least a viscosity sensor (18) associated with said mixing receptacle (16) and able to measure the viscosity of said ink (12).

21) Machine according to one or more of the claims from 17 to 20, characterized by the fact that it comprises at least a temperature sensor (19) associated with said mixing receptacle (16) and able to measure the temperature of said ink (12).

22) Machine according to one or more of the claims from 17 to 21, characterized by the fact that it comprises at least a cooling device (33) associated with said forced circulation circuit (21) and able to cool said ink (12). 23) Machine according to one or more of the claims from 17 to 22, characterized by the fact that said forced circulation circuit (21) comprises:

at least a pipe (22, 23, 24) having a first extremity (25) associated in correspondence to the bottom of said mixing receptacle (16) and a second extremity (26) ending up in correspondence to the top of said mixing receptacle (16);

at least a pumping device (27) associated with said pipe (22, 23, 24) for pumping said ink (12) from said first extremity (25) to said second extremity (26).

24) Machine according to one or more of the claims from 17 to 23, characterized by the fact that it comprises:

a plurality of containers (34) for the containment of a plurality of said concentrated mixtures (3, 8) having different colorings the one to the other, said containers (34) being associated with said base frame (15) and arranged in fluidic connection with said mixing receptacle (16) for the loading of said mixing receptacle (16) with said concentrated mixtures (3, 8);

at least a tank (37) for the containment of said dilution vehicle- sub stance (11) associated with said base frame (15) and arranged in fluidic connection with said mixing receptacle (16) for the loading of said mixing receptacle

(16) with said dilution vehicle- sub stance (11).

25) Machine according to claim 24, characterized by the fact that it comprises at least a processing and control unit (40) associable with a storage unit (41) containing predefined data for obtaining a plurality of said inks (12), said processing and control unit (40) being able to select the quantities of said concentrated mixtures (3, 8) and of said dilution vehicle- sub stance (11) to take from said containers (34) and from said tank (37) depending on said pre- established data.