Ceramic ink for digital inkjet printing and a method for manufacturing a ceramic product.

Description

Descriptive Report of the Invention Patent for CERAMIC INK FOR DIGITAL INKJET PRINTING AND METHOD FOR MANUFACTURING A CERAMIC PRODUCT.

[001] Divided from BR112021003434-0 filed on 09 / 11 / 2019

[002] The present invention relates to a ceramic ink for digital inkjet printing. More particularly, the invention relates to an ink for the digital decoration of articles made of ceramic material that undergoes heat treatment at high temperatures, for example, such as ceramic building parts, tiles, bathroom and kitchen work surfaces and sanitary ware.

[003] As is known, in the last two decades digital inkjet printing has become established as the reference technology for decorating ceramic articles, especially tiles and ceramic articles for floors and coverings. This technology employs inks comprising a solid part, formed primarily of pigment and ceramic materials, and a liquid part, primarily of an organic nature, capable of carrying the dry part during the printing stage.

[004] US 9,765,228 B2 and CN 103787693 A describe ceramic inks in which the wet phase comprises glycol ether, for example, ethylene glycol or propylene glycol. WO 2016 / 031914 describes inks in which the liquid phase is formed primarily of esterified fatty acids of natural origin. Esters have gradually replaced glycol ethers for ink production because they make it possible to improve printing performance as they are less subject to drying during the actual printing stage. Other substances used for liquid phase formation are naphthalene and isoparaffins as described in WO 2016 / 0319143 A.

[005] However, the use of all the substances mentioned above involves the formation of unpleasant odors in the work environment. Petition 870230077114, dated 08 / 30 / 2023, page 8 / 46 2 / 27 In particular, near the printer, and outside the manufacturing facility. Furthermore, during the firing stage that occurs in all ceramic processes, these substances can decompose, forming harmful substances, for example, such as aldehydes and VOCs (volatile organic compounds). In particular, glycol ethers can easily lead to the formation of VOCs, while fatty acid esters tend to decompose at very low temperatures, between 100 and 200°C, with subsequent formation of aldehydes inside the furnace.

[006] As a solution to this problem, WO 2016042097 A proposes the partial replacement of organic vehicles with water. Although on the one hand this solution makes it possible to dramatically reduce odor and harmful emissions, on the other hand it has a negative impact on printing performance.Water-based inks tend to dry out much more easily compared to inks with an organic vehicle, leading to clogging of the printhead nozzles and consequent deterioration in print quality as well as damage to the printhead itself. To improve the printing performance of water-based inks, conditioners are installed upstream of the printer, which are able to cool the surface of the ceramic material before printing in order to slow down water evaporation.

[007] WO 2016 / 185416 A1 proposes an alternative solution in which ceramic articles are glazed and printed before drying in order to ensure evaporation of the liquid part of the ink at moderate temperatures that do not cause degradation of the molecules into odorous and harmful substances. However, this solution is only effective as long as the amount of ink to be deposited on the ceramic piece is limited, and consequently it is only appropriate for the production of some products, and not for all digital applications currently used. Petition 870230077114, dated 08 / 30 / 2023, page 9 / 46 3 / 27

[008] Therefore, as taught by the previous technique, in order to limit harmful and odorous emissions, while maintaining good printing performance, it becomes necessary to modify the ceramic article manufacturing facility, as well as the associated production process and the range of products marketed.

[009] The present invention aims primarily to provide an alternative ceramic ink for digital inkjet printing which, according to some embodiments thereof, is intended to solve one or more of the problems of the prior art.

[0010] An object of the present invention is to overcome the aforementioned disadvantages of the prior art, in the context of an efficient, simple, and moderately cost-effective solution. These objects are achieved through the features of the invention given in the independent claim. The dependent claims present preferred and / or particularly advantageous aspects of the invention.

[0011] The present invention, according to its first independent aspect, relates to a ceramic ink for digital printing comprising a solid part provided with at least one ceramic component and a liquid part provided with at least one first vehicle, wherein said first vehicle comprises at least one component selected from the group comprising: esterified terephthalates, cyclohexane dicarboxylates, citrates. In fact, the ink thus comprises good rheological characteristics, which makes it suitable for digital printing. Furthermore, these substances are of very low volatility and therefore only evaporate when exposed, within the firing oven, to relatively high temperatures, so that they do not decompose into harmful substances, or at least considerably limit the emission of such substances. In addition, these substances are characterized by a molecular structure that is more complex compared to the linear structure. Petition 870230077114, dated 08 / 30 / 2023, page 10 / 46 4 / 27 of fatty acids and therefore possess greater chemical stability. These substances actually decompose by combustion at higher temperatures and over a wider temperature range compared to traditional vehicles, for example, fatty acid esters, etc. In practice, the combustion reactions of such substances, and the associated products, are more defined for generating a limited amount of harmful and odorous emissions. Another advantage of these inks is that their use does not require the adoption of particular means from a technological point of view and therefore they can be used with standard digital printers.

[0012] According to the preferred embodiment, the first vehicle can be of an organic, non-polar or low-polarity nature. Non-polar substances make it possible to improve print quality and limit the need for maintenance work on the printer. Substances that are polar, and therefore water-soluble, tend to mix with the vapor emitted from the ceramic article during printing, forming a solution that is deposited on the print head and proves difficult to clean and remove. Furthermore, according to a preferred embodiment, said first vehicle can have a boiling point above 250°C, preferably above 300°C, even more preferably above 350°C, for example, above 450°C. In this solution, the first ink vehicle evaporates during the firing stage only when it reaches a part of the oven characterized by a dry, hot environment.Under such conditions the first vehicle oxidizes almost completely without producing odorous or harmful substances, apart from the normal combustion products, carbon dioxide and carbon monoxide. For example, under these conditions the hydrolysis reaction is hindered, so there is no formation of alcohols, which can subsequently oxidize to aldehydes.

[0013] Preferably, the first vehicle may comprise a. Petition 870230077114, dated 08 / 30 / 2023, p. 11 / 46 5 / 27 Molecular weight above 190 g / mol, for example, above 250 g / mol, preferably above 300 g / mol. Furthermore, it is preferable for the molecular weight of the first vehicle to be less than 700 g / mol, for example, less than 600 g / mol, preferably less than 500 g / mol. In fact, while molecular weight partly helps determine the boiling point of the first component—that is, a high boiling point corresponds to a high molecular weight—it also helps determine the viscosity of said first vehicle, and is therefore necessary to identify the correct balance between volatility and rheological behavior of the paint.

[0014] According to a preferred embodiment, the first vehicle may have a kinematic viscosity at 40°C between 1 cSt and 40 cSt, for example, between 2 cSt and 30 cSt, preferably between 3 cSt and 20 cSt. It should be noted that identifying the correct viscosity value of the first vehicle makes it possible to maximize its quantity in order to minimize the quantity of other components of the liquid part capable of regulating the rheological behavior of the paint, but which may cause the formation of odorous and / or harmful substances.

[0015] According to the preferred embodiment, the quantity of the first vehicle may represent, in relation to the total weight of the paint, at least 10% by weight, for example, at least 30%, preferably at least 50%.

[0016] According to a preferred first embodiment of the invention, the first vehicle comprises at least one esterified terephthalate, or a mixture of esterified terephthalates. Such substances have a generic form of the type indicated in Formula 1: Petition 870230077114, dated 08 / 30 / 2023, p. 12 / 46 6 / 27 Formula 1 where R and R' may comprise aliphatic and / or branched groups. Note that according to some embodiments, the R and R1 groups may initially be identical. Examples of possible aliphatic groups are methyl, ethyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, etc.Examples of esterified terephthalates can be: dimethyl terephthalate (DMT), diethyl terephthalate, dipropyl terephthalate, diallyl terephthalate, dibutyl terephthalate, dipentyl terephthalate (DPT), diisopentyl terephthalate, dihexyl terephthalate, diheptyl terephthalate, dioctyl terephthalate (DOTP or DEHT), di-2-ethyl hexyl terephthalate, dinonyl terephthalate, didecyl terephthalate, bis-5-hydroxypentyl terephthalate, 3-hexyl pentyl terephthalate, butyl-3-hexyl pentyl terephthalate, 4-methyl pentyl-2-propyl terephthalate, ethyl-3-hexyl terephthalate, 3-methyl butyl-2-pentyl terephthalate, 4,4-dimethyl pentyl-3-pentyl terephthalate, 2-methyl butyl pentyl terephthalate, di-(2-methyl butyl).The inventors surprisingly found that esterified terephthalates have suitable rheological properties for use as paints, while also possessing high volatility and reactivity at high temperatures, allowing degradation by combustion primarily into carbon dioxide, carbon monoxide, or other components that are non-toxic or produce little odor. In particular, there is very limited emission of aldehydes and formaldehydes. Note that such substances are known to be plasticizers in the polymer materials industry, but their use as paints is unknown.

[0017] According to a second preferred embodiment of in Petition 870230077114, dated 08 / 30 / 2023, p. 13 / 46 7 / 27 Convention, the first vehicle comprises at least one cyclohexane carboxylate or a mixture of cyclohexane carboxylates. Such substances have a generic form of the type indicated in Formula 2: Formula 2 where R and R' may comprise aliphatic and / or branched groups. Note that according to some embodiments the R and R' groups may initially be identical. Examples of possible aliphatic groups are methyl, ethyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, etc. Examples of esterified cyclohexane dicarboxylates may be: dimethyl cyclohexane-1,2-dicarboxylate, diethyl cyclohexane-1,2dicarboxylate, dipropyl cyclohexane-1,2-dicarboxylate, diallyl cyclohexane-1,2-dicarboxylate, dibutyl cyclohexane-1,2-dicarboxylate, dipentyl cyclohexane-1,2-dicarboxylate, dihexyla cyclohexane-1,2dicarboxylate, diheptyl cyclohexane-1,2-dicarboxylate, dioctyl cyclohexane-1,2-dicarboxylate, di-2-ethyl hexyl terephthalate, dinonyl cyclohexane-1,2-dicarboxylate, diisononyl cyclohexane-1,2-dicarboxylate, didecyl cyclohexane-1,2-dicarboxylate, diundecyl cyclohexane-1,2dicarboxylate.The inventors surprisingly found that cyclohexane carboxylates have suitable rheological properties for use as paints and at the same time have high volatility as well as reactivity at high temperatures, allowing degradation by combustion primarily into carbon dioxide, carbon monoxide, or other components that are non-toxic or produce little odor. In particular, there is very limited emission of aldehydes and formaldehydes. Note that such substances are known. Petition 870230077114, dated 08 / 30 / 2023, p. 14 / 46 8 / 27 are known to be plasticizers in the polymer materials industry, but their use as paints is unknown.

[0018] According to a third embodiment of the invention, the first vehicle comprises at least one citrate or a mixture of citrates. Such substances have a generic form of the type indicated in Formula 3: Formula 3 where R, R', R' and R'' may comprise aliphatic and / or branched groups. Note that according to some embodiments the R, R', R' and R'' groups may initially be identical. Examples of possible aliphatic groups are methyl, ethyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, etc. Examples of citrates may be: acetyl tributyl citrate (ATBC), acetyl trihexyl citrate, tris-(2-ethylhexyl) oacetyl citrate, butyryl trihexyl citrate, triethyl acetyl citrate. The inventors found that citrates have suitable rheological properties for use as paints, and at the same time have high volatility as well as reactivity at high temperatures that allow degradation by combustion primarily into carbon dioxide, carbon monoxide or other components that are not toxic or produce little odor. Note that such substances are known to be plasticizers in the polymer materials industry, but their use as paints is unknown.

[0019] According to a fourth preferred embodiment of the invention, the first vehicle comprises at least one trimethylol propane ester (also indicated as fatty acid esters of polypropylene alcohols) Petition 870230077114, dated 08 / 30 / 2023, p. 15 / 46 9 / 27 dricos), or a mixture of trimethylolpropane esters. Such substances have a generic form of the type shown in Formula 4: Formula 4 R3 R2 0 where R1, R2, and R3 may comprise aliphatic and / or branched groups. Note that according to some embodiments, the R2 and R2, R3 groups may initially be identical. Examples of possible aliphatic groups are methyl, ethyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, etc. Examples of esterified terephthalates include: 1,1,1-tris-(hydroxymethyl)propane triheptanoate, 1,1,1-tris-(hydroxymethyl)propane tricoate, 1,1,1-tris-(hydroxymethyl)propane trioleate, 1,1,1-tris-(hydroxyethyl)propane triheptanoate, 1,1,1-tris-(hydroxypropyl)propane triheptanoate, 1,1,1-trimethylolethane valerate, 1,1,1-trimethylolethane trilaurate, 1,1,1-trimethylolethane tricaprylate, 1,1,1-trimethylolethane tripellargonate.The inventors surprisingly found that trimethylolpropane esters have suitable rheological properties for use as paints, while also possessing high volatility and reactivity at high temperatures, allowing degradation by combustion primarily into carbon dioxide, carbon monoxide, or other components that are non-toxic or produce little odor. In particular, there is little emission of aldehydes and formaldehydes.

[0020] According to a fifth preferred embodiment of the invention, the first vehicle comprises at least one fatty acid ester of aromatic alcohols (also indicated as alcohol esters). Petition 870230077114, dated 08 / 30 / 2023, p. 16 / 46 10 / 27 aromatic alkoxylated polyhydric acids and carboxylic acids), or a mixture of fatty acid esters of aromatic alcohols. Such substances have a generic form of the type indicated in Formula 5: Formula 5 where R1 and R2 may comprise aliphatic and / or branched groups. Note that according to some embodiments, the R1 and R2 groups may initially be identical. Examples of possible aliphatic groups are methyl, ethyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, etc. Examples of esterified terephthalates may be: 2-phenoxyethyl octanoate, 2-phenoxymethyl octanoate; 2-phenoxyethyl heptanoate; 2-phenoxyethyl nonanoate; 2-phenoxyethyl decanoate; 2-phenoxypropyl octanoate; 2-phenoxybutyl octanoate; methyl 4-phenoxybutanoate; isopropyl 4-phenoxybutanoate; 2-phenoxyethyl propionate; 2-phenoxyethyl butyrate; 2-phenoxyethyl valerate; 2-phenoxyethyl 3-methylbutanoate; 2-phenoxyethyl octanoate; 2-phenoxyethyl docosanoate; 2-phenoxyethyl pentadecanoate; 2-phenoxyethyl palmitate.The inventors surprisingly found that trimethylolpropane esters have suitable rheological properties for use as paints and at the same time have high volatility as well as reactivity at high temperatures, allowing degradation by combustion primarily into carbon dioxide, carbon monoxide, or other components that are non-toxic or produce little odor. In particular, there is very limited emission of aldehydes and formaldehydes.

[0021] According to a sixth preferred embodiment, the first vehicle can be formed from any combination or mixture of the substances described with reference to the first, second, third, fourth, or fifth preferred embodiment. Petition 870230077114, dated 08 / 30 / 2023, p. 17 / 46 11 / 27

[0022] According to some embodiments, the liquid portion of the ink may also comprise a second vehicle. For example, the second vehicle may be configured to regulate the rheology of the liquid portion of the ink. Advantageously, the second vehicle may comprise a substance or a mixture of organic substances that are non-polar or have low polarity. The second vehicle may be selected from the group comprising: glycol ethers, alcohols, lactates, glycol ether acetates, aldehydes, ketones, cyclic or linear aliphatic hydrocarbons, aromatic hydrocarbons, oils, alkyl carbonates, fatty acid esters, and polymers such as polyacrylates, polymethacrylates, and block copolymers.

[0023] For example, the second vehicle may comprise dipropylene glycol n-butyl ether, tripropylene glycol n-butyl ether, dipropylene glycol methyl ether, 2-ethyl hexyl palmitate, isopropyl laurate, ethyl hexyl laurate, polyethylene glycol, di-2-ethyl hexyl adipate. Furthermore, according to a preferred embodiment of said second vehicle, it may have a boiling point above 200°C, preferably above 230°C, for example, above 250°C. For example, the second vehicle may comprise a molecular weight above 50 g / mol, for example, above 100 g / mol, preferably above 180 g / mol. Furthermore, it is preferable for the molecular weight of the first vehicle to be less than 700 g / mol, for example, less than 450 g / mol, preferably less than 250 g / mol. The second vehicle may have a viscosity at 40°C between 1 cSt and 30 cSt, for example, between 2 cSt and 20 cSt, preferably between 3 cSt and 10 cSt.

[0024] According to a preferred aspect of the invention, the second vehicle may represent a maximum of 40% by weight, for example, less than 30%, preferably less than 20%, in relation to the total weight of the paint. In this way it is indeed possible to keep the possible volatile emissions of odorous or harmful substances within Petition 870230077114, dated 08 / 30 / 2023, page 18 / 46 12 / 27 acceptable limits that pose no risks while ensuring high print performance.

[0025] In addition, the ink may comprise one or more additives for regulating the physical and rheological properties of the ink. For example, the additives may be dispersants suitable for promoting dispersion of the solid part in the liquid part, surfactants for modifying surface tension, viscosity modifiers, suspending agents, wetting agents, antifoaming agents, dampening agents, biocides, adhesion promoters, glue and / or organic dyes. For example, the additive may comprise glycol ethers, alcohols, lactates, aldehydes, ketones, oils, alkyl carbonates, esters, and polymers such as polyacrylates, polymethacrylates, polyamides and block copolymers.

[0026] According to a preferred aspect of the invention, the additive may represent a maximum of 20% by weight, for example, less than 10%, preferably less than 5%, in relation to the total weight of the ink. In this way it is indeed possible to keep the possible volatile emissions of odorous or harmful substances within acceptable limits that do not pose any risks, while at the same time guaranteeing high printing performance.

[0027] The solid part of the ink comprises at least one ceramic component. Ceramic component means substantially a non-metallic, inorganic component that can be consolidated at high temperatures. Preferably, the ceramic component may comprise one or more inorganic pigments capable of coloring the ink itself. For example, the inorganic pigments may provide a cyan, yellow, magenta, black, white, beige, or brown color to the ink. For example, said pigments may comprise oxides, silicates, and / or zirconates or other compounds of Fe, Co, Sn, Zn, Pr, Ni, Cr, and other metals. The solid part of the ink further Petition 870230077114, dated 08 / 30 / 2023, page 19 / 46 13 / 27 may comprise a frit or a vitreous material capable of promoting the fusing capacity of the ink during firing and its consolidation on the surface of the ceramic product to be printed. Furthermore, the solid part of the ink may comprise raw ceramic materials, for example, but not limited to, clays, kaolins, feldspars, silica, for example, colloidal silica, zirconates, aluminates, silicate oxides, pyroxenes and other minerals in general. It is emphasized that the ink according to the invention can be used with any type of ceramic component, while remaining within the scope of the present invention.

[0028] According to a preferred embodiment, the solid part may represent at least 10% by weight, for example, at least 20%, preferably at least 40%, in relation to the total weight of the ink. The solid part may represent at most 70%, for example, less than 60%, preferably less than 50%, in relation to the total weight of the ink. It should be noted, furthermore, that the solid part may comprise particles having a maximum dimension of 10 µm, for example, 3 micrometers, preferably 1 micrometer. Furthermore, the particles of the solid part may have a particle size distribution with a Dv (10) value below 0.40 pm, a Dv (50) value below 0.70 pm, a Dv (90) value below 0.94 pm, a Dv (97) value below 1.2 pm, where it should be noted that Dv (X) below Y pm means that a fraction of particles equal to X5 has a size below Y pm.

[0029] Note that the fact that the paint comprises a first vehicle having one or more of the characteristics described in relation to the first independent aspect constitutes an inventive concept independently of other characteristics of the paint, in particular, independently of the fact that the paint comprises a solid part and the fact that the solid part is a ceramic component. Therefore, by Petition 870230077114, dated 08 / 30 / 2023, page 20 / 46 14 / 27 For example, another independent aspect of the invention provides an ink comprising at least one component selected from the group comprising: esterified terephthalates, cyclohexane dicarboxylates, citrates. According to this further independent aspect, the ink may comprise an organic pigment or a resin, for example, curable with UV radiation or electrons, or any other substance, and may be used in sectors other than the ceramic sector for the purpose of limiting volatile, odorous emissions. Note that the fact that the ink may comprise a low-volatility vehicle, i.e., a boiling point above 250°C, preferably above 300°C, for example, above 350°C, constitutes an inventive concept independent of the chemical nature of the vehicle.Therefore, a second independent aspect of the invention of ceramic ink for digital printing comprises a solid part provided with at least one ceramic component and a liquid part provided with at least one first vehicle, wherein said first vehicle has a boiling point above 250°C. The ink further comprises one or more of the characteristics described in relation to the first independent aspect. It is further noted that the fact that the ink may comprise a vehicle having a molecular weight above 190 g / mol, for example, above 250 g / mol, preferably above 300 g / mol, constitutes an inventive concept independent of the chemical nature of the vehicle. Therefore, a third independent aspect of the invention of ceramic ink for digital printing comprises a solid part provided with at least one ceramic component and a liquid part provided with at least one first vehicle, wherein said first vehicle has a molecular weight above 190 g / mol.The ink still comprises one or more of the characteristics described in relation to the first independent aspect.

[0030] A fourth independent aspect of the invention provides for the use, Petition 870230077114, dated 08 / 30 / 2023, p. 21 / 46 15 / 27 as a vehicle in ceramic inks, of at least one component selected from the group comprising: esterified terephthalates, cyclohexane dicarboxylates, citrates. It is obvious that each of these substances may comprise one or more of the characteristics described in relation to the first independent aspect. A fifth independent aspect of the invention provides a method for producing a manufactured ceramic product comprising the steps of: providing a semi-finished ceramic product, printing at least one ceramic ink onto a surface of said semi-finished ceramic product; heat treatment of said semi-finished product at a temperature above 400°C to obtain the manufactured ceramic product, wherein the ink may comprise one or more of the characteristics described with reference to the first, second and / or third independent aspects.According to the preferred embodiment, the printing step involves a digital inkjet printing step using at least one ink according to a predetermined design or field – filled onto the entire surface to be decorated. The printing step may involve printing one or more inks, for example, of different colors, or printing inks of different colors and inks capable of creating visual effects, such as gloss or engravings. According to a preferred aspect of the invention, at least 0.1 g / m² of ink, for example, at least 1 g / m², preferably 10 g / m² of ink, are printed during the printing step.

[0031] According to the preferred embodiment, the manufactured product is a ceramic product, for flooring or roofing, or a manufactured plate of ceramic material. However, it should be noted that the manufactured product can be any object made of ceramic material, for example, such as a laboratory, kitchen or bathroom work surface, or sanitary ware, tableware, a roof tile, or a building material. Petition 870230077114, dated 08 / 30 / 2023, page 22 / 46 16 / 27

[0032] Ceramic material means any material obtained through high-temperature sintering of pulverized minerals, for example, such as clays, feldspars, kaolin, quartz, carbonates, silicates, zirconium and / or aluminum oxide. Some examples of ceramic material may be porcelain utensils, single-fired ceramic bodies, white or red, majolica, terracotta. However, for the purposes of the present invention, ceramic material also means glass and glass-ceramic materials.

[0033] The stage of providing raw semi-finished ceramic product may comprise a stage of molding a mixture comprising pulverized raw ceramic materials and a binder such as water, for example. The mixture may be molded by static or continuous pressing, extrusion, molding or other molding techniques. Said semi-finished product is usually described as green insofar as it has not yet been fired at high temperatures and has not been dried, but still comprises a liquid binder.

[0034] In addition, the method may include a drying step of the semi-finished product to remove some of the water from the mixture, so as to provide the mixture with good mechanical strength during the successive stages of the production process. Drying may occur by subjecting the semi-finished product to a temperature above 100°C. Drying may occur before or after the ink printing step, preferably before.

[0035] The method may also include a step of applying one or more coating layers to the surface of the semi-finished product.

[0036] For example, the coating layers may comprise a primer coating configured to cover at least partially, preferably completely, the surface of the Petition 870230077114, dated 08 / 30 / 2023, page 23 / 46 17 / 27 semi-finished product to be decorated, for example, the top surface of a tile. In this way, the primer coating can cover the color of the semi-finished product as well as make said semi-finished product waterproof; furthermore, it can be suitable to receive the decoration on itself, or it can define the base for the decoration. The primer coating can be white, beige, brown, gray, or any other color. The primer coating preferably comprises an enamel and / or semi-liquid enamel or a smaltobbio (enamel slip). The primer coating can be applied dry or wet, through any coating technique, for example, such as cascade coating, bell coating, airless brushing, flexography, or screen printing.According to a preferred embodiment, the primer coating can be applied by inkjet printing of a ceramic ink as described with reference to the first independent aspect, where the coating material represents, at least partially, the solid portion of the ink.

[0037] The coating layers may further comprise a protective coating that covers at least partially, preferably completely, the surface to be decorated and that is suitable for being positioned above the decoration so as to cover and protect it. Advantageously, the protective coating may be transparent or translucent so as to allow the underlying decoration to be seen. The protective coating may further comprise filler materials or additives suitable for providing new functionalities and / or for improving the surface properties of the decorative layer, for example, anti-wear, anti-slip, antibacterial or anti-stain properties. In addition, the protective coating may be used in combination with the Petition 870230077114, dated 08 / 30 / 2023, page 24 / 46 18 / 27 Primer coating, or the protective coating may be applied over the top of the primer coating. Preferably, the protective coating may comprise a glaze (transparent enamel) or a coarse sand. The protective coating may be applied dry or wet, by any coating technique, for example, such as cascade coating, bell coating, airless brushing, flexography or screen printing. According to a preferred embodiment, the protective coating may be applied by inkjet printing of a ceramic ink as described with reference to the first independent aspect, wherein the coating material represents, at least partially, the solid portion of the ink.

[0038] According to the embodiment of the invention, the heat treatment, also known as firing, is carried out at a maximum temperature above 450°C, for example, above 700°C, preferably above 1000°C. For example, in the case of producing tiles from ceramic material obtained by firing in the temperature range of 1200 to 1300°C of certain clays originating from sedimentary deposits with low iron content of porcelain, the heat treatment occurs at a temperature of about 1200°C or higher. The manufactured product is subjected to said treatment for a time that is a function of the geometry and dimensions of the product to be obtained. For example, in the case of ceramic tiles or plates, the manufactured product is heat treated for a time of less than 5 hours, for example, less than 3 hours, preferably less than 1 hour.

[0039] According to the preferred embodiment, the method may provide for printing and heat treatment of a raw semi-finished product, or one formed from a compact of unconsolidated sprays. According to other embodiments, the method may provide for printing and heat treatment of a semi-finished product that Petition 870230077114, dated 08 / 30 / 2023, page 25 / 46 19 / 27 was burned or had already been subjected to high-temperature heat treatment to consolidate the spray.

[0040] Further features and advantages of the invention will become clear from reading the following detailed description, given for illustrative purposes only, and not limitingly.

[0041] Details of two examples of embodiments according to preferred embodiments of the invention are given below. In both examples, the ink was printed onto 500 m2 raw porcelain tiles measuring 90x90 cm. The ceramic mixture, in atomized form, was formed by stationary pressing. The raw tiles were then dried in a tunnel dryer to reduce the residual water content in the mixture. According to other examples, the raw tiles can be dried after being glazed and decorated.

[0042] The dried raw tiles were then decorated by inkjet printing. In practice, in all examples given below, the solid part is formed from a ceramic glaze. The ink was printed over the entire field in order to maximize the amount applied to the tiles and, in particular, 25 g / m2 of ink was applied.

[0043] The tiles were then thermally treated in a roller furnace to a temperature of 1205oC for a cycle of 44 minutes.

[0044] Before each sampling for emissions analysis, unprinted tile pieces were placed in the oven for a total of one hour to zero out emissions derived from pieces printed with an ink different from that under examination.

[0045] Emissions of VOCs (volatile organic compounds), Non-methane VOCs, formaldehyde, total aldehydes, hydrofluoric acid, and odorous substances were measured for each sample. Emissions were measured by sampling at the furnace chimney, i.e., where the concentration of such substances is highest. Petition 870230077114, dated 08 / 30 / 2023, page 26 / 46 20 / 27

[0046] The concentration of VOCs and non-methane VOCs in the flues inside the chimney was measured directly in the chimney by FID (flame ionization detector).

[0047] Formaldehydes, aldehydes and hydrofluoric acid were sampled using appropriate bubblers in order to be able to measure their concentration through specific analytical techniques in the laboratory, for example, ion exchange chromatography, gas chromatography, and high-performance liquid chromatography (HPLC).

[0048] Odoriferous substances were sampled for laboratory analysis by olfactometry according to standard EN 13725:2004. Some examples of odoriferous substances are nitrogen-containing compounds, sulfides, unsaturated compounds, oxygen-containing compounds, halogenated compounds, aldehydes, ketones, carboxylic acids, amines, alcohols, and sulfur-containing groups. However, it should be emphasized that olfactometry does not determine the concentration of such substances, but only the olfactory perception capacity of such substances even when they are mixed.

[0049] The results of the two examples were then compared with those of a test performed on a sample 0, conducted under the same conditions, i.e., same amount of ink printed and same heat treatment conditions, but with a conventional ink comprising the formulation given in Table 1. Table 1 Component Percentage by weight (%) Solid part 41 First vehicle 37 Second vehicle 16 Additive 6 where the first vehicle is 2-ethylhexyl palmitate. This vehicle comprises Petition 870230077114, dated 08 / 30 / 2023, page 27 / 46 The first vehicle is 21 / 27, which has a boiling point of 414°C, a molecular weight of 369 g / mol, and a viscosity at 40°C of 7.6 cSt. The second vehicle is dipropylene glycol n-butyl ether (DOW Dowanol DPnB). This vehicle has a boiling point of 230°C, a molecular weight of 190 g / mol, and a viscosity at 40°C of 3.4 cSt.

[0050] The solid part comprises particles having a maximum dimension of 1.2 µm with the following particle size distribution: Dv (10) of 0.30 µm, Dv (50) of 0.34 µm, Dv (90) of 0.55 µm, Dv (97) of 0.63 µm. The particle size distribution was measured using a laser diffraction particle size analyzer (Mastersizer 3000, Malvern Pananalytical). Furthermore, the additive used in sample 0 is a polyamide dispersant produced by LUBRIZOL LTD. and known under the registered trademark SOLSPERSE J980. Example 1

[0051] In the first embodiment, the ink comprises the formulation given in Table 2. Table 2 Component Percentage by weight (%) Solid part 42 First vehicle 32.1 Second vehicle 22.5 Additive 3.4

[0052] The solid part comprises particles having a maximum dimension equal to 1.2 pm with the following particle size distribution: Dv (10) of 0.24 pm, a value of Dv (50) of 0.36 pm, a value of Dv (90) of 0.53 pm, a value of Dv (97) of 0.60 pm. The particle size distribution was measured with a laser diffraction particle size analyzer (Mastersizer 3000, Malvern Panalytical). The first vehicle comprises acetyl tributyl citrate (ATBC) having the following formula: Petition 870230077114, dated 08 / 30 / 2023, page 28 / 46 22 / 27

[0053] The first vehicle selected in the first example has a boiling point of 331 °C. In addition, the first vehicle selected in the first example has a molecular weight of 402.48 g / mol and a viscosity of 15.9 cSt at 40°C.

[0054] The second vehicle selected in the first example is dipropylene glycol n-butyl ether (DOW Dowanol DPnB). This vehicle has a boiling point of 230°C, a molecular weight of 190, and a viscosity at 40°C of 3.4 cSt.

[0055] The additive used in the first example is a polyamide dispersant produced by LUBRIZOL LTD and known by the trademark SOLSPERSE J980.

[0056] The ink thus obtained has a viscosity of 13.9 cSt at 40°C (measured with a Malvern Panalytical Kinexus type rheometer), a surface tension of 27.5 mN / m (measured using a capillary tensiometer) and a density of 1359 g / L.

[0057] Table 3 shows the results of emission concentration measurements for example 0 and example 1, as well as the percentage change between the measured results. Table 3 Parameter Sample 0 Example 1 Relative change for Sample 0 (%) VOCs [mg / Nm3] 22.5 18.2 -19.1 Non-methane VOCs [mg / Nm3] 20.7 16.2 -21.7 Formaldehyde [mg / Nm3] 1.6 1.2 -25 Total aldehydes [mg / Nm3] 4.4 3.2 -27.3 Hydrofluoric acid [mg / Nm3] 0.6 0.6 0 Odoriferous substances [ouE / m3] 1165 598 -48.7 Petition 870230077114, dated 08 / 30 / 2023, page 29 / 46 23 / 27 Example 2

[0063] In the second embodiment, the ink comprises the formulation given in Table 4. Table 4 Component Percentage by weight (%) Solid part 42 First vehicle 40 Second vehicle 15 Additive 3

[0058] The solid part comprises particles having a maximum dimension equal to 1.2 micrometers with the following particle size distribution: Dv (10) of 0.24 micrometers, a value of Dv (50) of 0.37 micrometers, a value of Dv (90) of 0.54 micrometers, a value of Dv (97) of 0.62 micrometers. The particle size distribution was measured with a laser diffraction particle size analyzer (Mastersizer 3000, Malvern Panalytical). The first vehicle selected in the second example comprises dipenyl terephthalate (DPT) having the following formula:

[0059] The first vehicle selected in the second example has a boiling point of 353°C. In addition, the first vehicle selected in the second example has a molecular weight of 306.4 g / mol and a viscosity of 13.1 cSt at 40°C.

[0060] The second vehicle selected in the second example is dipropylene glycol n-butyl ether (DOW Dowanol DPnB). This vehicle has a boiling point of 230°C, a molecular weight of 190°C, and a viscosity at 40°C of 3.4 cSt.

[0061] The additive used in the second example is a dispersant po Petition 870230077114, dated 08 / 30 / 2023, page 30 / 46 24 / 27 liamide produced by LUBRIZOL LTD and known by the registered trademark SOLSPERSE J980.

[0062] The ink thus obtained has a viscosity of 16.4 cSt at 40°C (measured with a Malvern Panalytical Kinexus type rheometer), a surface tension of 29.2 mN / m (measured by a capillary tensiometer) and a density of 1367 g / L.

[0063] Table 5 shows the results of emission concentration measurements for example 0 and example 2, as well as the percentage change between the measured results. Table 5 Parameter Sample 0 Sample 2 Relative change for sample 0 (%) VOCs [mg / Nm3] 22.5 19.3 -14.2 Non-methane VOCs [mg / Nm3] 20.7 17.6 -15.0 Formaldehyde [mg / Nm3] 1.6 0.9 -43.8 Total aldehydes [mg / Nm3] 4.4 2.9 -34.1 Hydrofluoric acid [mg / Nm3] 0.6 0.5 -16.7 Odoriferous substances [ouE / m3] 1165 408 -65.0

[0064] As can be seen from the results given in Table 3 and Table 5, the use of paints according to the preferred embodiments of the paint makes it possible to reduce emissions of odorous substances by more than 40% compared to conventional paints. In addition, the paints according to the invention make it possible to reduce VOC emissions by at least 15% compared to conventional paints, while the reduction in aldehyde and formaldehyde emissions is greater than 25%.

[0065] Numerous modifications and variants of the invention thus conceived are possible, all within the scope of the inventive concept. Petition 870230077114, dated 08 / 30 / 2023, page 31 / 46 25 / 27 Example 3

[0066] In the third example, the ink comprises the formulation given in Table 6. Table 6 Component Percentage by weight (%) Solid part 45 First vehicle 51.4 Additive 3.6

[0067] The solid part comprises particles having a maximum dimension equal to 1.2 pm with the following particle size distribution: Dv (10) of 0.24 pm, a Dv (50) value of 0.36 pm, a Dv (90) value of 0.53 pm, a Dv (97) value of 0.60 pm. The particle size distribution was measured with a laser diffraction particle size analyzer (Mastersizer 3000, Malvern Panalytical). In this third example, according to the sixth embodiment of the invention, the first vehicle comprises a mixture comprising esterified terephthalates and trimethylolpropane esters. In particular, the esterified terephthalates are dipenyl terephthalate (DPT) and the trimethylolpropane esters comprise 1,1,1-tris-(hydroxymethyl)propane triheptanoate. 1,1,1-Tris-(hydroxymethyl)propane triheptanoate has a boiling point of 530°C, a molecular weight of 470.682 g / mol, and a viscosity of 14 cSt at 40°C. 1,1,1-Tris-(hydroxymethyl)propane triheptanoate has the formula: Petition 870230077114, dated 08 / 30 / 2023, pages 32 / 46 26 / 27

[0068] DPT has a boiling point of 353°C, a molecular weight of 306.4 g / mol, and a viscosity of 13.1 cSt at 40°C.

[0069] The additive used in the first example is a polyamide dispersant produced by LUBRIZOL LTD and known by the registered trademark SOLSPERSE J980.

[0070] The ink thus obtained has a surface tension of 28.1 mN / m (measured by capillary tensiometer) and a density of 145 g / L. Example 4

[0071] In the fourth example, the ink comprises the formulation given in Table 7. Table 7 Component Percentage by weight (%) Solid part 40 First vehicle 31.7 Second vehicle 24.6 Additive 3.7

[0072] The solid part comprises particles having a maximum dimension equal to 1.2 pm with the following particle size distribution: Dv (10) of 0.24 pm, a value of Dv (50) of 0.36 pm, a value of Dv (90) of 0.53 pm, a value of Dv (97) of 0.60 pm. The particle size distribution was measured with a laser diffraction particle size analyzer (Mastersizer 3000, Malvern Panalytical). This fourth example has the peculiarity that the solid part comprises, as its main component, for example, calcium silicate (Wollastonite) as a fluxing component. In this case, the ink is used as an adhesive for applying coarse sand to the surface of ceramic articles. In practice, the coarse sand is provided in solid form on the surface of the ceramic article after the ink is printed so that the coarse sand adheres to the ink on the surface of the ceramic article. The Petition 870230077114, dated 08 / 30 / 2023, pages 33 / 46 27 / 27 flux can help reduce coarse sand. This type of ink is also known as digital ceramic adhesives.

[0073] The first vehicle selected in the fourth example comprises dipenyl terephthalate (DPT) having the following formula: THE

[0074] The first vehicle selected in the second example has a boiling point of 353°C. In addition, the first vehicle selected in the second example has a molecular weight of 306.4 g / mol and a viscosity of 13.1 cSt at 40°C.

[0075] The second vehicle selected in the second example is dipropylene glycol n-butyl ether (DOW Dowanol DPnB). This vehicle has a boiling point of 230°C, a molecular weight of 190, and a viscosity at 40°C of 3.4 cSt.

[0076] The additive used in the second example is a polyamide dispersant produced by LUBRIZOL LTD and known by the registered trademark SOLSPERSE J980. In this case, the additive also comprises an organic pigment, for example, 0.5% by weight of the ink. The organic pigment acts as a marker to see where the glue has been printed.

[0077] The ink thus obtained has a surface tension of 31 mN / m (measured by capillary tensiometer) and a density of 1300 g / L.

Claims

1. Ceramic ink for digital inkjet printing comprising a solid portion provided with at least one ceramic component and a liquid portion provided with at least one first vehicle, characterized in that said first vehicle has a boiling point above 250°C, wherein the first vehicle represents at least 30% by weight relative to the total weight of the ink, wherein said first vehicle is esterified terephthalates, wherein said liquid portion comprises a second vehicle selected from the group comprising: glycol ethers, alcohols, lactates, glycol ether acetates, aldehydes, ketones, linear and / or cyclic aliphatic hydrocarbons, aromatic hydrocarbons, oils, alkyl carbonates, fatty acid esters, polyacrylates, polymethacrylates and / or block copolymers, and wherein the content of the second vehicle is less than 30% by weight relative to the total weight of the ink, and wherein the solid portion makes up at least 40% by weight of the ink.

2. Ink according to claim 1, characterized in that the first vehicle has a molecular weight above 190 g / mol, for example, above 250 g / mol, preferably above 300 g / mol.

3. Paint according to claim 1 or 2, characterized in that it comprises at least one additive, wherein said additive may be selected from the group comprising: dispersants, surfactants, viscosity modifiers, suspending agents, wetting agents, antifoaming agents, dampening agents, biocides, adhesion promoters, glue and colorants.

4. Paint according to claim 3, characterized in that the additive content is less than 5% by weight relative to the total weight of the paint.

5. Method for manufacturing a manufactured ceramic product, characterized in that it provides the steps of: - providing a semi-finished ceramic product; - inkjet printing with ink, as defined in any of claims 1 to 4, onto a surface of the semi-finished ceramic product; - heat-treating said semi-finished product at a temperature above 500°C to obtain the manufactured ceramic product.