RU2788513C2 - Ceramic paint for inkjet digital printing - Google Patents

Abstract

FIELD: digital printing on ceramic products.

SUBSTANCE: present invention relates to ceramic inks for digital printing on ceramic products. The composition includes a solid part - a ceramic component - and an organic carrier, in an amount of more than 10 wt.%, representing esterified terephthalates, cyclohexane dicarboxylates, citrates, trimethylol propane esters, esters of fatty acids or aromatic alcohols.

EFFECT: invention makes it possible to reduce harmful and odorous emissions while maintaining the required characteristics.

9 cl, 7 tbl, 4 ex

Description

The present invention relates to ceramic ink for digital inkjet printing. More specifically, the invention relates to a digital finish paint for products made from ceramic material that are heat treated at high temperatures, such as tiles, panels, bathroom and kitchen countertops, and ceramic sanitary ware.

As is known, over the past two decades digital inkjet printing has established itself as the reference technology for the finishing of ceramic products, especially panels and tiles for floors and claddings. This technology uses inks containing a solid part formed predominantly from a pigment and a ceramic material, and a liquid part, predominantly of organic origin, which is capable of carrying the dry part during the printing stage.

US 9765228 B2 and CN 103787693 A describe ceramic paints in which the wet portion contains a glycol ether such as ethylene glycol or propylene glycol. Document WO 2016/031914 describes paints in which the liquid part is formed predominantly from esterified fatty acids of natural origin. Esters are gradually replacing glycol ethers in ink formulations as they offer the opportunity to improve print performance as they are less prone to drying out during the actual printing stage. Other substances used to prepare the liquid phase are naphthalene and isoparaffins, as described in WO 2016/0319143 A.

However, the use of all the substances mentioned above entails the appearance of unpleasant odors both in the working area, in particular near the printer, and outside the production plant. Moreover, during the firing step, which takes place in all ceramic manufacturing processes, these substances can decompose to form harmful substances such as aldehydes, and VOCs (volatile organic compounds). In particular, glycol ethers can easily give rise to VOCs, while esters tend to decompose at rather low temperatures between 100 and 200° C., followed by the formation of aldehydes inside the kiln.

As a solution to this problem, WO 2016/042097 A proposes a partial replacement of organic carriers with water. Although, on the one hand, this solution makes it possible to drastically reduce odors and harmful emissions, on the other hand, this negatively affects the printing characteristics. Water-based inks actually tend to dry much more easily than organic-based inks, and this leads to clogged print head nozzles, resulting in poor print quality, as well as damage to the print head itself. To improve the printing performance of water-based inks, air conditioners installed in front of the printer are used, which are able to cool the surface of the tiles before printing, in order to slow down the evaporation of water.

WO 2016/185416 A1 proposes another solution in which the tiles are glazed and printed before drying in order to ensure that the liquid part of the paint evaporates at moderate temperatures which do not cause the molecules to decompose into odorous and harmful substances. However, this solution is only effective if the amount of paint that is applied to the tile is limited and therefore only suitable for some products and not all digital applications in use today.

Thus, in accordance with the teachings of the prior art, in order to limit harmful and odorous emissions and at the same time maintain good printing characteristics, it becomes necessary to modify the installation of the production of tiles, as well as the associated production process and the range of products sold.

The present invention is primarily directed to an alternative ceramic inkjet digital ink which, in some embodiments, addresses one or more of the problems of the prior art.

One object of the present invention is to overcome the disadvantages of the prior art mentioned above in a simple and effective solution at a moderate cost. These objectives are achieved by the essential features of the invention set forth in the independent claim. The dependent claims provide preferred and/or particularly advantageous aspects of the invention.

The present invention, according to its first independent aspect, relates to a ceramic digital printing ink comprising a solid portion provided with at least one ceramic component and a liquid portion provided with at least one first carrier, wherein said first carrier contains at least one component selected from the group including esterified terephthalates, cyclohexane dicarboxylates, citrates. Indeed, the resulting ink has good rheological characteristics that make it suitable for digital printing. Moreover, these substances have a very low volatility and therefore only evaporate when exposed to relatively high temperatures inside the kiln, so that they do not break down into harmful substances, or so that they at least significantly limit the emissions of such substances. Moreover, these substances are characterized by a molecular structure that is more complex than the linear structure of fatty acids and therefore have a higher chemical stability. These substances are actually destroyed when burned at higher temperatures and over a wider temperature range than traditional carriers such as fatty acid esters, etc. In practice, the combustion reactions of such substances and by-products are well defined to generate a limited amount of harmful and odorous emissions. Another advantage of such inks is that their use does not require the introduction of specific means from a technological point of view and, therefore, can be used with standard digital printers.

According to a preferred embodiment, the first carrier may be of organic origin, non-polar or low polarity. Non-polar substances can actually improve print quality and reduce the need for printer maintenance. Substances that are polar and therefore water soluble tend to mix with the steam released from the tile during printing, forming a solution that settles on the head and is difficult to clean and remove. Moreover, according to a preferred embodiment, said first carrier may have a boiling point above 250°C, preferably above 300°C, even more preferably above 350°C, for example above 450°C. With this solution, the first ink carrier evaporates during the firing step only when it reaches the portion of the kiln characterized by a hot, dry atmosphere. Under such conditions, the first carrier is almost completely oxidized, producing no odorous or harmful substances other than the usual combustion products, carbon dioxide and carbon monoxide. For example, under such conditions, the hydrolysis reaction is hindered, so that alcohols are not formed, which can subsequently be oxidized to aldehydes.

Preferably, the first carrier may have a molecular weight above 190 g/mol, for example above 250 g/mol, preferably above 300 g/mol. More preferably, the molecular weight of the first carrier is less than 700 g/mol, for example less than 600 g/mol, preferably less than 500 g/mol. In fact, although, on the one hand, the molecular weight helps to partially set the boiling point of the first component, that is, a high boiling point corresponds to a high molecular weight, on the other hand, it helps to control the viscosity of said first carrier, and therefore it is necessary to correctly determine the relationship between volatility and rheological paint behavior.

According to a preferred embodiment, the first carrier may have a kinematic viscosity at 40°C in the range between 1 and 40 cSt, for example between 2 and 30 cSt, preferably between 3 and 20 cSt. It should be noted that by setting the correct viscosity of the first carrier, it is possible to maximize its amount in order to minimize the amount of other components of the liquid part that can determine the rheological behavior of the paint, but which can cause the formation of odorous and/or harmful substances.

According to a preferred embodiment, the amount of the first carrier relative to the total weight of the ink may be at least 10% by weight, for example at least 30%, preferably at least 50%.

According to a first preferred embodiment of the invention, the first carrier contains at least one esterified terephthalate or a mixture of esterified terephthalates. Such substances have the general form shown in formula 1:

Formula 1

,

,

where the groups R and R' may be aliphatic and/or branched groups. It should be noted that, in accordance with some embodiments, the groups R and R' may primarily be the same. Examples of possible aliphatic groups are methyl, ethyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, etc. Examples of esterified terephthalates are dimethyl terephthalate (DMT (DMT)), diethyl terephthalate, dipropyl terephthalate, diallyl terephthalate, dibutyl terephthalate, dipentyl terephthalate (DPT (DPT)), diisopentyl terephthalate, dihexyl terephthalate, diheptyl terephthalate, dioctyl terephthalate (DOTP), di-2-DEHT ethylhexyl terephthalate, dinonyl terephthalate, didecyl terephthalate, bis-5-hydroxypentyl terephthalate, 3-hexylpentyl terephthalate, butyl-3-hexylpentyl terephthalate, 4-methylpentyl-2-propyl terephthalate, ethyl 3-hexyl terephthalate, 3-methylbutyl-2-pentyl terephthalate, 4,4- dimethylpentyl-3-pentyl-terephthalate, 2-methylbutylpentylterephthalate, di(2-methylbutyl)-terephthalate. Surprisingly, it has been found that esterified terephthalates have suitable rheological properties for use as paints and at the same time have high volatility, and are also reactive at high temperatures, which allows decomposition by combustion predominantly to carbon dioxide, carbon monoxide or other components that are non-toxic or give little smell. In particular, there is a very low emission of aldehydes and formaldehydes. It should be noted that such substances are known to be plasticizers in the plastic materials industry, but their use as paints is not known.

According to a second preferred embodiment of the invention, the first carrier contains at least one cyclohexanecarboxylate or a mixture of cyclohexane-carboxylates. Such substances have the general form shown in Formula 2:

Formula 2

,

,

where the groups R and R' may be aliphatic and/or branched groups. It should be noted that in accordance with some embodiments, the groups R and R' in the first place may be the same. Examples of possible aliphatic groups are methyl, ethyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, etc. Examples of esterified cyclohexanedicarboxylates are dimethylcyclohexane-1,2-dicarboxylate, diethylcyclohexane-1,2-dicarboxylate, dipropylcyclohexane-1,2-dicarboxylate, diallylcyclohexane-1,2-dicarboxylate, dibutylcyclohexane-1,2-dicarboxylate, diphenylcyclohexane-1 ,2-dicarboxylate, dihexylcyclohexane-1,2-dicarboxylate, diheptyl-cyclohexane-1,2-dicarboxylate, dioctylcyclohexane-1,2-dicarboxylate, di-2-ethylhexylterephthalate, dinonylcyclohexane-1,2-dicarboxylate, diisononylcyclohexane-1,2 -dicarboxylate, didecylcyclohexane-1,2-dicarboxylate, diundecylcyclohexane-1,2-dicarboxylate. Surprisingly, it has been found that cyclohexane carboxylates have suitable rheological properties for use as paints and at the same time have high volatility, and are also reactive at high temperatures, which allows decomposition by combustion predominantly to carbon dioxide, carbon monoxide or other components that are non-toxic or give slight smell. In particular, there is a very limited emission of aldehydes and formaldehydes. It should be noted that such substances are known to be plasticizers in the plastic materials industry, but their use as paints is not known.

According to a third preferred embodiment, the first carrier contains at least one citrate or a mixture of citrates. Such substances have the general form shown in formula 3:

Formula 3

,

,

where the groups R, R', R" and R"' may be aliphatic and/or branched groups. It should be noted that in accordance with some embodiments, the groups R, R', R" and R"' in the first place may be the same. Examples of possible aliphatic groups are methyl, ethyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, etc. Examples of citrates are: acetyltributyl citrate (ATBC (ATBC)), acetyl trihexyl citrate, O-acetyl tris(2-ethylhexyl) citrate, butyryl trihexyl citrate, triethyl acetyl citrate. It has been found that citrates have suitable rheological properties for use as paints and at the same time have high volatility and are also reactive at high temperatures, which allows decomposition by combustion predominantly to carbon dioxide, carbon monoxide or other components that are non-toxic or give little odor. It should be noted that such substances are known to be plasticizers in the plastic materials industry, but their use as paints is not known.

According to a fourth preferred embodiment of the invention, the first carrier comprises at least one trimethylol propane ester (also referred to as polyol fatty acid ester) or a mixture of trimethylol propane esters. Such substances have the general form shown in formula 4:

Formula 4

,

,

where the groups R1, R2 and R3 may be aliphatic and/or branched groups. It should be noted that in accordance with some variants of the implementation of the groups R2 and R2, R3 in the first place may be the same. Examples of possible aliphatic groups are methyl, ethyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, etc. Examples of esterified terephthalates are 1,1,1-tris(hydroxymethyl)propane triheptanoate, 1,1,1-tris(hydroxymethyl)propane tricocoat, 1,1,1-tris(hydroxymethyl)propane trioleate, 1,1,1 triheptanoate -tris(hydroxyethyl)propane, 1,1,1-tris(hydroxypropyl)propane triheptanoate, 1,1,1-trimethylolethane valerate, 1,1,1-trimethylolethane trilaurate, 1,1,1-trimethylolethane tricaprylate, tripelargonate 1,1,1-trimethylolethane. Surprisingly, it has been found that trimethylol propane esters have suitable rheological properties for use as paints and at the same time have high volatility and are also reactive at high temperatures, which allows decomposition by combustion predominantly to carbon dioxide, carbon monoxide or other components that are non-toxic or give slight smell. In particular, there is a very limited emission of aldehydes and formaldehydes.

According to a fifth preferred embodiment of the invention, the first carrier comprises at least one fatty acid aromatic alcohol ester (also referred to as aromatic alkoxylated polyhydric alcohol carboxylic acid ester) or a mixture of fatty acid aromatic alcohol esters. Such substances have the general form shown in formula 5:

Formula 5

,

,

where groups R1 and R2 may be aliphatic and/or branched groups. It should be noted that in accordance with some variants of the implementation of the groups R1 and R2 in the first place may be the same. Examples of possible aliphatic groups are methyl, ethyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, etc. Examples of esterified terephthalates are: 2-phenoxyethyloctanoate, 2-phenoxymethyloctanoate, 2-phenoxyethylheptanoate, 2-phenoxyethylnonanoate, 2-phenoxyethyldecanoate, 2-phenoxypropyloctanoate, 2-phenoxybutyloctanoate, 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. Surprisingly, it has been found that trimethylol propane esters have suitable rheological properties for use as paints and at the same time have high volatility and are also reactive at high temperatures, which allows decomposition by combustion predominantly to carbon dioxide, carbon monoxide or other components that are non-toxic or give slight smell. In particular, there is a very limited emission of aldehydes and formaldehydes.

According to a sixth preferred embodiment, the first carrier may be formed from any combination or mixture of the substances described with reference to the first, second, third, fourth or fifth preferred embodiments.

In accordance with some embodiments, the liquid ink portion may also contain a second carrier. For example, the second carrier may be selected to control the rheology of the liquid ink portion. Advantageously, the second carrier may contain a substance or mixture of substances that are non-polar or have low polarity. The second carrier may be selected from the group consisting of glycol ethers, alcohols, lactates, glycol ether acetates, aldehydes, ketones, linear or cyclic aliphatic hydrocarbons, aromatic hydrocarbons, oils, alkyl carbonates, fatty acid esters, and polymers such as polyacrylates, polymethacrylates and block copolymers.

For example, the second carrier may contain dipropylene glycol n-butyl ether, trippropylene glycol n-butyl ether, dipropylene glycol methyl ether, 2-ethylhexyl palmitate, isopropyl laurate, ethylhexyl laurate, polyethylene glycol, di-2-ethyl-hexyl adipate.

Furthermore, according to a preferred embodiment of said second carrier, it may have a boiling point above 200°C, preferably above 230°C, for example above 250°C. For example, the second carrier may have a molecular weight greater than 50 g/mol, such as greater than 100 g/mol, preferably greater than 180 g/mol. More preferably, the molecular weight of the first carrier is less than 700 g/mol, for example less than 450 g/mol, preferably less than 250 g/mol. The second carrier may have a viscosity at 40°C in the range between 1 and 30 cSt, for example between 2 and 20 cSt, preferably between 3 and 10 cSt.

According to a preferred aspect of the invention, the second carrier may be present in an amount of at most 40% by weight, for example less than 30%, preferably less than 20%, relative to the total weight of the ink. Therefore, it is actually possible to keep the fugitive emissions of odorous or harmful substances within acceptable levels that do not pose any risk, while at the same time guaranteeing high print performance.

In addition, the paint may contain one or more additives to control the physical and rheological properties of the paint. For example, the additives may be dispersants suitable for aiding the dispersion of a solid portion in a liquid portion, surface tension modifying surfactants, viscosity modifiers, suspending agents, wetting agents, defoamers, wetting agents, biocides, adhesion promoters, adhesive, and /or organic colorants. For example, the additive may contain glycol ethers, alcohols, lactates, aldehydes, ketones, oils, alkyl carbonates, esters, and polymers such as polyacrylates, polymethacrylates, polyamides, and block copolymers.

According to a preferred aspect of the invention, the additive may be present in an amount of at most 20% by weight, for example less than 10%, preferably less than 5%, relative to the total weight of the paint. Therefore, it is actually possible to keep the fugitive emissions of odorous or harmful substances within acceptable levels that do not pose any risk, while at the same time guaranteeing high print performance.

The solid part of the paint contains at least one ceramic component. "Ceramic component" means a substantially inorganic non-metallic component that can be consolidated at high temperatures. Preferably, the ceramic component may contain one or more inorganic pigments capable of coloring the paint itself. For example, inorganic pigments can impart a blue-green, yellow, magenta, black, white, beige, or brown color to a paint. For example, these pigments may contain oxides, silicates and/or zirconates or other compounds of Fe, Co, Sn, Zn, Pr, Ni, Cr and other metals. The solid portion of the ink may further comprise a frit or otherwise vitreous material capable of promoting the fusibility of the ink during firing and bonding to the surface of the ceramic article to be printed. Moreover, the solid part of the paint may contain ceramic raw materials, for example, but not limited to, clays, kaolins, feldspars, silica, for example, colloidal silicon dioxide, zirconates, aluminates, oxide silicates, pyroxenes, and other minerals in general. It can be emphasized that the paint according to the invention can be used with any type of ceramic component while remaining within the scope of the present invention.

According to a preferred embodiment, the solids may be present in an amount of at least 10% by weight, for example at least 20%, preferably at least 40%, relative to the total weight of the paint. The solids may be present in an amount of at most 70%, for example less than 60%, preferably less than 50%, relative to the total weight of the paint. It should also be noted that the solid part may contain particles having a size of 10 µm, for example 3 µm, preferably 1 µm. Moreover, the solids particles may have a particle size distribution with a Dv(10) value below 0.40 µm, a Dv(50) value below 0.70 µm, a Dv(90) value below 0.94 µm, a Dv(97) value below 1.2 µm, and it should be noted that Dv(X) below Y µm means that the proportion of particles equal to X% has a particle size below Y µm.

It should be noted that the fact that the ink contains a first carrier having one or two of the features described in connection with the first independent aspect constitutes the concept of the invention regardless of other features of the ink, in particular regardless of the fact that the ink contains a solid part, and from the fact that the hard part is a ceramic component. Thus, for example, a further independent aspect of the invention provides a paint containing at least one component selected from the group consisting of esterified terephthalates, cyclohexanedicarboxylates, citrates. In accordance with this additional independent aspect, the paint may contain an organic pigment or resin, e.g. UV or electron curable, or any other substance, and may be used in applications other than ceramics to limit odorous, fugitive emissions.

It should be noted that the fact that the paint may contain a carrier with low volatility, i.e. with a boiling point above 250°C, preferably above 300°C, for example above 350°C, constitutes the concept of the invention, regardless of the chemical nature of the carrier . Therefore, the second independent aspect of the invention of ceramic digital printing ink includes a solid part provided with at least one ceramic component and a liquid part provided with at least one first carrier, in which said first carrier has a boiling point above 250°C. . The paint will further include one or more of the features described in connection with the first independent aspect.

In addition, it should be noted that the fact that the paint may contain a carrier having a molecular weight above 190 g/mol, for example, above 250 g/mol, preferably above 300 g/mol, constitutes the concept of the invention, regardless of the chemical nature of the carrier. Therefore, a third independent aspect of the invention of a ceramic digital ink includes a solid portion provided with at least one ceramic component and a liquid portion provided with at least one first carrier, wherein said first carrier has a molecular weight greater than 190 g/mol. The paint further includes one or more of the features described in connection with the first independent aspect.

The fourth independent aspect of the invention provides for the use as a carrier in ceramic paints of at least one component selected from the group including esterified terephthalates, cyclohexane dicarboxylates, citrates. Obviously, each of these substances may include one or more of the features described in connection with the first independent aspect.

The fifth independent aspect of the invention provides a method for producing a finished ceramic product, which involves the steps: obtaining a semi-finished ceramic product, printing at least one ceramic paint on the surface of the specified semi-finished ceramic product; heat treatment of the specified semi-finished product at a temperature above 400°C to obtain a finished ceramic product; in which the paint may include one or more of the features described in relation to the first, second and/or third independent aspect.

According to a preferred embodiment, the printing step comprises a digital inkjet printing step with at least one ink in a given pattern or over the entire field over the entire surface to be finished. The printing step may involve printing with one or more inks, such as different colors, or printing with different colors of inks and inks capable of producing visual effects such as gloss or embossing. According to a preferred aspect of the invention, during the printing step, the ink is printed at least 0.1 g/m ^{2 of} ink, eg at least 1 g/m ² , preferably 10 g/m ^{2 of} ink.

According to a preferred embodiment, the finished product is a floor or cladding tile or panel of ceramic material. However, it should be noted that the finished product may be any object made of ceramic material, such as a laboratory, kitchen or bathroom worktop, or ceramic sanitary ware, tableware, roof tiles or building material.

"Ceramic material" means any material obtained by high temperature sintering of mineral powders such as, for example, clays, feldspars, kaolin, quartz, carbonates, silicates, zirconium and/or alumina. Some examples of ceramic materials can be stoneware, monoporous white or red cabinet ceramics, majolica, terracotta. However, in relation to the present invention, the ceramic material also means glass and glass-ceramic materials.

The step of obtaining a raw semi-finished ceramic product may include the step of forming a mixture containing powders of ceramic raw materials and a binder such as water, for example. The mixture may be molded by static or continuous compression, extrusion, casting, or other molding methods. Said semi-finished product is usually described as "raw", since it has not been annealed at high temperatures and has not been dried, but still contains a liquid binder.

In addition, the method may include the step of drying the semi-finished product to remove some of the water from the mixture in order to give the mixture good mechanical strength during subsequent stages of the production process. Drying can take place when the semi-finished product is exposed to temperatures above 100°C. Drying can be carried out before or after the ink printing step, preferably before this step.

The method may further include the step of applying one or more layers of coating to the surface of the semi-finished product.

For example, the coating layers may include a primer coating, configured to cover at least partially, preferably completely, the surface of the semi-finished product to be finished, for example, the top surface of the tile. Therefore, the base coat may cover the color of the semi-finished product, as well as make the semi-finished product impervious, moreover, it may be acceptable for applying a finish to it or may determine the basis for the finish. The primer can be white, beige, brown, gray or any other color. The primer preferably contains enamel and/or engobe or smaltobbio (smaltobbio, "enamel slip"). The primer coat can be applied dry or wet using any coating method such as cascade coating, funnel coating, airless airbrushing, flexography or screen printing, for example. According to a preferred embodiment, the primer coating may be inkjet printed with the ceramic paint described in connection with the first independent aspect, wherein the coating material is at least in part a solid paint charge.

The cover layers may further include a protective coating which covers at least partially, preferably completely, the surface of the finish and which is suitable for placement over the finish to cover and protect it. Advantageously, the protective coating may be transparent or translucent so that the underlying finish is visible. The protective coating may further comprise fillers or additives suitable for imparting new functional qualities and/or for imparting surface properties to the finish layer, such as anti-wear, anti-slip, anti-bacterial or anti-contamination properties. In addition, a protective coating may be used in combination with a primer coating, or a protective coating may be applied over the primer coating. Preferably, the protective coating may comprise a glaze (clear enamel) or an abrasive. The protective coating may be applied dry or wet using any coating method such as cascade coating, funnel coating, airless airbrushing, flexography or screen printing. According to a preferred embodiment, the protective coating may be inkjet printed with the ceramic paint described in connection with the first independent aspect, wherein the coating material is at least in part a solid ink charge.

In accordance with an embodiment of the invention, the heat treatment, also known as "calcination", 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 porcelain stoneware tiles, the heat treatment takes place at a temperature of approximately 1200° C. or higher. The finished product is subjected to the specified processing for a time that is a function of the geometry and dimensions of the resulting product. For example, in the case of ceramic tiles or panels, the finished product is thermally treated for less than 5 hours, such as less than 3 hours, preferably less than 1 hour.

In accordance with a preferred embodiment, the method may include printing and thermal processing for the raw semi-finished product or semi-finished product formed from compressed unconsolidated powders. According to another embodiment, the method may include printing and heat treating a semi-finished product that has been fired or has already been heat treated at high temperature in advance to consolidate the powders.

Other features and advantages of the invention will become apparent upon reading the following detailed description, which is provided by way of illustration and without limitation of the invention.

Details of two exemplary embodiments in accordance with the preferred embodiments of the invention are given below. In both examples, the paint is applied by printing on 500 m ^{2 of} untreated porcelain stoneware tiles measuring 90×90 cm. The raw tiles are then dried in a tunnel dryer to reduce the residual water content of the mixture. In other examples, the raw tiles are dried after glazing and finishing.

The dried raw tiles are then decorated with inkjet printing. In a preferred example, the tiles are inkjet glazed. In practice, in all the examples below, the hard part is formed from ceramic enamel. The ink is printed over the entire field so as to maximize the amount applied to the tiles, and in particular, the ink is applied at a rate of 25 g/m ² .

The tiles are then thermally treated in a roller kiln at temperatures up to 1205°C for a cycle of 44 minutes.

Prior to each sampling for emission analysis, clean tile pieces (unprinted) are placed in the kiln for a total of 1 hour to zero out emissions from pieces printed with an ink other than the ink being tested.

Emissions of VOCs (volatile organic compounds), non-methane VOCs, formaldehyde, all aldehydes, hydrofluoric acid and odorants are measured for each example. Emissions are measured by sampling in the chimney of the kiln, i.e. where the concentration of such substances is highest.

The concentration of VOCs and non-methane VOCs in flue gases inside the chimney is measured directly in the chimney using a FID (Flame Ionization Detector).

Samples of formaldehyde, aldehydes and hydrofluoric acid are taken using suitable spargers so that their concentration can be measured by special analytical methods in the laboratory, for example, using ion exchange chromatography, gas chromatography and high performance liquid chromatography (HPLC).

Odorants are selected for laboratory analysis using olfactometry in accordance with EN 13725:2004. Some examples of odorants are nitrogen-containing compounds, sulfides, unsaturated compounds, oxygen-containing compounds, halogenated compounds, aldehydes, ketones, carboxylic acids, amines, alcohols, and groups containing sulfur. However, it should be emphasized that olfactometry does not determine the concentration of such substances, but only the olfactory susceptibility of such substances, even when they are mixed with each other.

The results of the two examples are then compared with the results of tests on a zero (0) sample, carried out under the same conditions, that is, with the same amount of printed ink and the same heat treatment conditions, but with a conventional ink having the formulation shown in Table 1.

Table 1

Component Mass percent (%) hard part 41 First carrier 37 Second carrier sixteen Additive 6

In Table 1, the first carrier is 2-ethyl-hexyl palmitate. This carrier 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 carrier is dipropylene glycol n-butyl ether (DOW Dowanol DPnB). This carrier has a boiling point of 230°C, a molecular weight of 190 g/mol and a viscosity at 40°C of 3.4 cSt.

The hard part contains particles having a maximum size of 1.2 µm with the following particle size distribution: Dv(10) value 0.30 µm, Dv(50) value 0.34 µm, Dv(90) value 0.55 µm, Dv value (97) 0.63 µm. Particle size distribution is measured using a laser diffraction granulometer (Mastersizer 3000, Malvern Panalytical).

In addition, the additive used in sample 0 is a polyamide dispersant manufactured by LUBRIZOL LTD. and known by the trade name SOLSPERSE J980.

Example 1

In the first exemplary embodiment, the paint contains the formulation shown in Table 2.

table 2

Component Mass percent (%) hard part 42 First carrier 32.1 Second carrier 22.5 Additive 3.4

The hard part includes particles having a maximum size of 1.2 µm with the following particle size distribution: Dv(10) value 0.24 µm, Dv(50) value 0.36 µm, Dv(90) value 0.53 µm, Dv value (97) 0.60 µm. Particle size distribution is measured using a laser diffraction granulometer (Mastersizer 3000, Malvern Panalytical).

The first carrier contains acetyltributyl citrate (ATBC (ATBC)) having the following formula:

.

.

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

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

The additive used in the first example is a polyamide dispersant manufactured by LUBRIZOL LTD and known under the trade name SOLSPERSE J980.

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

Table 3 shows the emission concentration measurements for example 0 and example 1, as well as the percentage change between the measured data.

Table 3

Parameter sample 0 Example 1 Change from sample 0 (%) VOC [mg/Nm ³ ] 22.5 18.2 -19.1 Non-methane VOCs [mg/Nm ³ ] 20.7 16.2 -21.7 Formaldehyde [mg/n.m ³ ] 1.6 1.2 -25 All aldehydes [mg/n.m ³ ] 4.4 3.2 -27.3 Hydrofluoric acid [mg/N.m ³ ] 0.6 0.6 0 Odorous substances [ouE/m ³ ] 1165 598 -48.7

ouE=European odor units.

Example 2

In the second exemplary embodiment, the paint contains the formulation shown in Table 4.

Table 4

Component Mass percent (%) hard part 42 First carrier 40 Second carrier 15 Additive 3

The hard part contains particles having a maximum size of 1.2 µm with the following particle size distribution: Dv(10) value 0.24 µm, Dv(50) value 0.37 µm, Dv(90) value 0.54 µm, Dv value (97) 0.62 µm. Particle size distribution is measured using a laser diffraction granulometer (Mastersizer 3000, Malvern Panalytical).

The first carrier selected in the second example contains dipentyl terephthalate (DPT (DPT)) having the following formula:

.

.

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

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

The additive used in the second example is a polyamide dispersant manufactured by LUBRIZOL LTD and known under the trade name SOLSPERSE J980.

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

Table 5 shows the emission concentration measurements for example 0 and example 2, as well as the percentage change between the measured data.

Table 5

Parameter Sample 0 Sample 2 Measurement relative to sample 0 (%) VOC [mg/Nm ³ ] 22.5 19.3 -14.2 Non-methane VOCs [mg/Nm ³ ] 20.7 17.6 -15.0 Formaldehyde [mg/n.m ³ ] 1.6 0.9 -43.8 All aldehydes [mg/n.m ³ ] 4.4 2.9 -34.1 Hydrofluoric acid [mg/N.m ³ ] 0.6 0.5 -16.7 Odorous substances [ouE/m ³ ] 1165 408 -65.0

As can be seen from the results in Table 3 and Table 5, the use of paints according to the preferred paint embodiments makes it possible to reduce odor emissions by more than 40% relative to conventional paints. In addition, the paints according to the invention make it possible to reduce VOC emissions by at least 15% relative to conventional paints, while reducing aldehyde and formaldehyde emissions by more than 25%.

Numerous modifications and variations of the invention are possible, conceived in this way, all within the scope of the concept of the invention.

Example 3

In the third example, the paint contains the formulation shown in Table 6.

Table 6

Component Mass percent (%) hard part 45 First carrier 51.4 Additive 3.6

The hard part contains particles having a maximum size of 1.2 µm with the following particle size distribution: Dv(10) value 0.24 µm, Dv(50) value 0.36 µm, Dv(90) value 0.53 µm, Dv value (97) 0.60 µm. Particle size distribution is measured using a laser diffraction granulometer (Mastersizer 3000, Malvern Panalytical).

In this third example, according to the sixth embodiment of the invention, the first carrier is a mixture containing esterified terephthalates and trimethylol propane esters. In particular, the esterified terephthalate is dipentyl terephthalate (DPT) and the trimethylol propane ester is 1,1,1-tris(hydroxymethyl)propane triheptanoate.

Triheptanoate 1,1,1-tris(hydroxymethyl)propane 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:

.

.

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.

The additive used in the third example is a polyamide dispersant manufactured by LUBRIZOL LTD and known under the trade name SOLSPERSE J980.

The ink thus obtained has a surface tension of 28.1 mN/m (measured with a capillary tensiometer) and a density of 145 g/l.

Example 4

In the fourth example, the paint contains the formulation shown in Table 7.

Table 7

Component Mass percent (%) hard part 40 First carrier 31.7 Second carrier 24.6 Additive 3.7

The hard part contains particles having a maximum size of 1.2 µm with the following particle size distribution: Dv(10) value 0.24 µm, Dv(50) value 0.36 µm, Dv(90) value 0.53 µm, Dv value (97) 0.60 µm. Particle size distribution is measured using a laser diffraction granulometer (Mastersizer 3000, Malvern Panalytical).

This fourth example has the feature that the solid part contains calcium silicate (wollastonite) as the main component, for example, essentially consists of it, as the flux component. In this case, the paint is used as an adhesive to apply abrasive to the surface of ceramic tiles. In practice, the abrasive is applied in solid form to the surface of the tile after being printed with ink, such that the abrasive adheres to the ink on the surface of the tile. The flux can help melt the abrasive. This type of paint is also known as digital ceramic adhesives.

The first carrier selected in the fourth example contains dipentyl terephthalate (DPT) having the following formula:

.

.

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

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

The additive used in the fourth example is a polyamide dispersant manufactured by LUBRIZOL LTD and known under the trade name SOLSPERSE J980. In this case, the additive also contains an organic pigment, for example constituting 0.5% by weight of the paint. The organic pigment acts as a marker to show where the adhesive has been printed.

The paint thus obtained has a surface tension of 31 mN/m (measured with a capillary tensiometer) and a density of 1300 g/l.

Claims (23)

1. Ceramic ink for digital printing, containing a solid part provided with at least one ceramic component, and a liquid part free from water and provided with at least one first carrier, where the first carrier is selected from the group including esterified terephthalates , cyclohexane dicarboxylates, citrates, trimethylol propane esters, fatty acid esters of aromatic alcohols, where the first media is at least 10 wt.% relative to the total mass of the paint. 2. Paint according to claim 1, wherein the esterified terephthalates have the general formula

, in which cyclohexanedicarboxylates have the general formula

, in which citrates have the general formula

, in which trimethylolpropane esters have the general formula

, in which the esters of fatty acids and aromatic alcohols have the general formula:

, and in which the groups R, R', R", R", R1 and R2 represent a linear or branched aliphatic group. 3. Paint according to claim 1 or 2, wherein the first carrier has a boiling point above 250°C. 4. Paint according to any one of the preceding claims, containing a second carrier selected from the group consisting of glycol ethers, alcohols, lactates, glycol ether acetates, aldehydes, ketones, linear and/or cyclic aliphatic hydrocarbons, aromatic hydrocarbons, oils, alkyl carbonates, complex fatty acid esters, polyacrylates, polymethacrylates and/or block copolymers. 5. Paint according to claim. 4, in which the content of the second carrier is less than 30 wt.% relative to the total weight of the paint. 6. Paint according to any one of the preceding claims, containing at least one additive, the additive being selected from at least the group consisting of dispersants, surfactants, viscosity modifiers, suspending agents, wetting agents, defoamers, wetting agents. agents, biocides, adhesion promoters, adhesives and colorants. 7. Paint according to claim. 6, in which the content of the additive is less than 5 wt.% relative to the total weight of the paint. 8. The use of esterified terephthalates as a carrier in ceramic paints. 9. A method for obtaining a finished ceramic product, including the steps: obtaining a semi-finished product of a ceramic product; printing paint according to any one of paragraphs. 1-7 on the surface of the semi-finished ceramic product; heat treatment of a semi-finished ceramic product at a temperature above 500°C to obtain a finished ceramic product.