PREPARATION METHOD OF NANOMETRIC SIZE METAL OXIDE ADDITIVES THAT REDUCE THE TEMPERATURE OF SINTERIZED AND/OR INCREASE PRODUCTIVITY IN THE MANUFACTURE OF CERAMIC PARTS, IMPROVING MECHANICAL PROPERTIES WITHOUT AFFECTING THE GRESIFICATION PROPERTIES OF CERAMIC BODIES, TILES OR COATINGS

Abstract

The object of this invention is a process for manufacturing, conditioning and stabilization of a family of base additives sodium, potassium, boron, silicon, zinc, calcium oxides, among others, prepared by physicochemical and chemical synthesis methods that form nanometric structures, reformulated with deflocculant, sequestrants and dispersants additives that allow to obtain a dispersion or powder capable to decrease the sintering temperature of a ceramic body due to the high fluxing power, which is maximized by the use of nanotechnology in the structures obtained. The process consists in the preparation of nucleation seeds of metal, silicates and carbonates oxides by means of a physicochemical process, and which allow nanometric structures to grow by means of a chemical process in a chemical synthesis process wet basis of sodium, boron, silicon, zinc, potassium and calcium oxides. The combination of these oxides allows structuring elements of high fluxing power due to their high surface area and physicochemical composition. The additives prepared in this invention are chemically stabilized with deflocculating agents, which allow the additives to be incorporated into the aqueous medium grinding process of the ceramic body. Applications made with the additives of this invention allow the sintering temperature of a red body to be reduced from 1150 C. to 1000 C. and in porcelain bodies from 1180 C. to 1050 C., with the use of 0.2 to 5% of the additive, or increasing the speed of the heat treatment by up to 20%, and it can be used in the manufacture of bathroom fittings, molding parts, components for tooling, coatings, valances, enamels, vitrified pastes and other ceramic components. The present invention proposes several nanostructured additive formulations with high performance fluxing properties, which allow to optimize and standardize the sintering process and to improve the mechanical properties of the ceramic body. It also proposes different methods of application of the additive in ceramic formulations.

Claims

1. Process of preparation of nanostructured additives of low melting point consisting of a mixture of metal oxides of Si, Ca, K, Na, B, Zn, P and Al which, when added in ceramic formulations of red and porcelain body, ceramic molding bodies, body for coatings and valances, ceramic materials for tooling, allows to reduce the sintering temperature to values close to 1000 C., maintaining the properties of water absorption, contraction and apparent density.

2. Nanostructured additives of low melting point according to claim 1 acting on ceramic enamel formulations added with metallic silver and/or metallic copper nanoparticles, allowing to reduce the vitrification temperature attributing the microbicidal, antibacterial and antifungal properties.

3. Nanostructured additives manufactured by a milling process consisting of attrition mill in wet basis which is fed from an aqueous dispersion of the compound to be ground in concentrations between 5% and 50%, preferably between 10 and 30%, the particle size of the precursors is 1 to 50 micrometers.

4. Nanostructured additives that in a second stage of product structuring is carried out by chemical synthesis process to achieve the composition of low-melting point metal oxides with a nanometric size containing Si, Ca, Mg, Na, K, B, Zn, Al and P, which are integrated with particles obtained according to claim 4.

5. Nanostructured additives of low melting point according to claim 1 characterized by sintering temperature of red-body and porcelain ceramic matrices from 1130 C. to 1180 C. at values between 980 C. and 1050 C., when using a concentration between 0.2% and 10%, preferably less than 5%.

6. Nanostructured additives of low melting point according to claims 1 and 2, containing nanoparticles of silver and/or copper with sizes smaller than 20 nm that are added to ceramic enamels in concentrations between 0.01% and 5% with respect to the ceramic matrix and that allow reducing the temperature of vitrification, attributing the microbicidal, antibacterial and antifungal properties.

7. Nanostructured additives of low melting point according to claim 1, characterized by allowing the reduction of the thermal cycle time in the sintering process up to 30%, and maintaining the properties of water absorption, contraction and apparent density, and improving mechanical properties up to 25%.

8. Nanostructured additives of low melting point according to claims 1 and 2, which can be added in the milling process of the raw materials of ceramic bodies and enamels, characterized by allowing the integration of the additives of claims 1 and 2 to improve the rheological properties of those in the ceramic formulations, promoting the deflocculation of the species in the milling processes.

9. Nanostructured additives of low melting point according to claim 1 that can be added to the mixing and grinding process of raw materials commonly used in the manufacture of tiles and ceramic and sanitary coatings, in concentrations according to claim 3, which allow to carry out the processes of drying, pressing, enamelling and decorating without modifications, and allowing to improve the sintering processes in furnaces for producing red or gray porcelain ceramic.

10. Nanostructured additives of low melting point according to claim 2 that can be added to the mixing and grinding process of raw materials commonly used in the manufacture of ceramic paste, in concentrations according to claim 4, which allow to carry out the application and decorating processes without modifications, and allowing to improve the sintering processes in furnaces for producing ceramic tiles or pastes.

11. Nanostructured additives of low melting point according to claims 1 and 2 characterized by being a high density aqueous dispersion that can be added as an additive in the mixing and grinding processes used in the manufacture of ceramic materials.

12. Nanostructured additives of low melting point according to claims 1 and 2, characterized by being a micronized powder that can be added as an additive in the mixing and grinding processes used in the manufacture of ceramic materials.

13. Nanostructured additives of low melting point according to claims 1 and 2 with a high energy grinding process using a planetary mill or high kinetic energy ball mill to obtain the product of claim 12.

14. Nanostructured additives of low melting point according to claims 1 and 2 in which the nanometric compounds obtained in claim 13 are added to the product of claim 3 after drying and pulverizing particles.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 Schematization of the process of preparation of nanostructures of oxides, carbonates and silicates of the precursor metals by means of a physicochemical sequence of particle size reduction, consisting of a wet basis high-energy mill, a slurry preparation tank and its addition elements, and finally a dispersion tank assembled to the mill by a recirculation system for particle size control.

[0021] FIG. 2 Scheme depicting the process of preparing nanostructures by chemical route, using as primary elements or nucleation seeds, nanostructures obtained by physicochemical process and consisting of the wet basis addition of up to 5 reagents and a dosage system of antibacterial additives and control of stability, dispersion and deflocculation according to the type of application in the ceramic body.

[0022] FIG. 3 Schematic representation of the process of drying the dispersion of nanoparticles in wet basis and consisting of a filtration process by press or centrifuge and its subsequent drying in tray furnaces, rotary furnace or flash oven, except for the latter, the dry product passes to a grinder. As an alternative to the filtration system, a spray dryer is schematized which allows obtaining product in a single process.

[0023] FIG. 4 Schematic representation of the product preparation process using a high-kinetic ball rotor mill, which is fed with nanostructures obtained from the previously dried physicochemical process and powdered and integrated precursor reagents, which are conditioned according to two procedures, the first consists of an individual pulverization of the reagents in a hammer mill or a disk mill and their subsequent addition to the high energy mill, while the second allows the integration of the reagents in a high speed mixing system and then add them to the high energy mill.

[0024] FIG. 5 Gresification diagram of a ceramic body added with the nanofunction product compared to a standard ceramic body.

[0025] FIG. 6 Microstructures obtained by scanning electron microscopy of a ceramic body with 5% nano fluxing additive treated at 1050 C. compared to a standard ceramic body without additive, where the drawing on the left represents the material without additive and non-sintered particles are seen, while on the right the drawing shows the microscopy of the sintered body due to the presence of the nano additive.

DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention describes a family of fluxing nanostructured additives and their production process, which can be presented in aqueous dispersion-dissolution or powder, are applied to ceramic bodies in the process of grinding or integration of body components and prior to formation via by pressing, molding or emptying of the ceramic component. Which allow to achieve an equalized sintering at lower temperatures and/or at lower thermal cycle times.

[0027] The process of integrating the components into the formula plays a preponderant role in the result of the fluxing capacity of the additive, since it allows structures to be formed with a high surface area and a low melting chemical composition. The formulations that can be developed with the process object of the present invention allow to be incorporated into different processes of integration in the wet basis without making changes to the process and with minor modifications in the formulation.

[0028] The reagent preparation process consists of two stages described as A and B, stage B is divided into two types of processing according to the type of material to be obtained, liquid (B1) or powder (B2); in stage A (FIG. 1) a physicochemical process is involved in which the silicates, oxides and carbonates of precursor metals can be miniaturized at nanometric particle size levels. This physicochemical process consists of an aqueous attrition mill which is fed from an aqueous dispersion of the compound to be ground in concentrations ranging from 5% to 50%, preferably from 10 to 30%, the particle size of the precursors is 1 micrometer to 50 micrometers, the milling is stabilized and dispersed using rheological modifiers, controlling the pH of the dispersion, among which are polyacrylates, amines, silicates, citrates, lignins, lignosulfonates, hydroxylated stearates, hydroxides and weak organic acids, anionic polymers, cationic polymers, among others. During the grinding process the particle size can be controlled by the process time allowing a stable dispersion with high solids content, with particle size ranging from 1 micrometer to 50 nanometers, preferably from 50 nm to 500 nanometers. The particle size polydispersity can be controlled depending on the type of dispersant and the control of the potential Z of the dispersed particles, the by-product obtained is a stable dispersion of particles with a composition with fluxing capacity that must be complemented with a low melting point composition chemically structured to achieve melting points below 600 C. In step B1 of product manufacturing a chemical synthesis process is carried out to achieve the composition of metal oxides of low melting point, the morphology and size of the structures is essential in the sintering process in the application, since with smaller size of the structures is possible to obtain a larger surface area, which allows the structures to melt with less energy due to the high surface energy it contains. The production process in stage B consists in obtaining structured composite products of metal oxides of nanometric size of Si, Ca, Na, K, B, Zn, Al and P, such compounds are formed on the surface of the physicochemically obtained particles (stage A), previously dispersed in the aqueous dispersion (FIG. 2), adding in a controlled manner five precursors and an additive to a reactor where the stirring speed between 400 and 1000 RPM is controlled with a marine type propeller, in a process in batch. During the process of adding the reagents in sequence, the agitation speed is progressively increased as the volume and viscosity of the dispersion-dissolution increases, the reagents in this process can be added in liquid and/or powder according to the desired solids composition according to the following ratio: reagent 1: 65-75%, reagent 2: 15-20%, reagent 3: 5-10%, reagent 4: 5-10%, reagent 5: 1-2%, where reagents 1, 2, 3 and 5 can be liquid, while reagent 4 is a powder. To improve the process of integration of the latter, it is possible to perform a prior aqueous dispersion.

[0029] The process sequence for step B1 described (FIG. 2) consists in first feeding to the reactor the dispersion of particles obtained from the by-product derived from the process of step A, followed by reagent 1, once the desired quantity of reagent 1 has been fed, the reactor agitation system is started at 550-650 rpm, reagent 1 is kept under agitation for a time ranging from 5 to 15 minutes, then reagent 2 is fed followed by reagent 3 to the reactor by using the dosing system in a total time ranging from 2 to 10 minutes, after 2 to 5 minutes after the end of the previous addition, reagent 4 is incorporated and the stirring speed is increased from 700 to 1000 rpm, keeping these conditions of agitation for a time ranging from 10 to 20 minutes. In the case of reagent 4 it is possible to make a previous dispersion in water by using a mechanical stirring system at a stirring speed of between 500-600 rpm, to finish the reagent 5 is added to the reactor and the speed of stirring is adjusted at 500 rpm holding it for 10 minutes. For the conditioning of the product depending on the application, the additive is added in the formulation in proportions ranging from 5 to 15% by weight of the final formulation. The additive consists of rheological modifying elements, deflocculants that allow the incorporation of the product in different stages of the production process of industrialized ceramic pieces.

[0030] The reagents and additives consist of a mixture of the precursor agents that can be dissolved according to the described sequence of the stage process, which in turn recrystallize using as forming core particles previously obtained by physicochemical process, within the precursors are acids and strong bases, acids and weak bases, carbonates, silicates, borates, nitrates, phosphates, aluminates, chlorides, bromides, fluorides and oxides, of silicon, calcium, potassium, boron, zinc, sodium, magnesium and aluminum, whereby products are obtained that, depending on their application, contain compositions ranging from 30 to 50% sodium oxide, 30 to 50% silicon oxide, 0 to 30% boron oxide, 0 to 10% potassium oxide, 1 to 5% calcium oxide, 0 to 1% aluminum oxide.

[0031] As a variant of the production process for stage B, a high energy mill is used to achieve the integration and reaction of the components of the formula by means of the mechanosynthesis of reagents preferably incorporated in solid (step B2), keeping the proportions of oxides sought for the product, the precursors are integrated by a pulverization and mixing process, this process is integrated but not limited to the following processes and equipment (FIG. 4), a) pulverization of reagents 1, 2, 3, 4 and 5 (solids) using a hammer mill, a disk mill or similar equipment to obtain a powder with a particle size of less than 500 micrometers for each of the reagents. Integration of the components in a high energy grinding process using a planetary mill or high kinetic energy ball mill as a reactive grinding element, performing a reagent mechanosynthesis, the product is added in the last stage of the integration process using low speeds, other additives can be added in the process of integrating the flux into the ceramic material. b) Integration of 2 to 3 reagents maintaining the proportion of final oxides in a high-speed mixing process (1500 to 3000 RPM) and the subsequent reaction in high energy mills. In both processes corresponding to stage B2, the nanometric compounds obtained from stage A are added by physicochemical process after drying and pulverizing the by-product particles (FIG. 3) of the first stage according to the scheme described in FIG. 3. The nanostructures obtained from the stage A production process are incorporated in this stage B2 as powder, the production process of these particles as described in FIG. 3 can be taken to a filter press, or a centrifuge to obtain a cake that is then taken to a drying process in a tray furnace or a rotary furnace and as a last option to flash furnace to obtain the final product, in the case of trays or rotary furnace, it is necessary to pass the material through a grinder to achieve granulometry suitable for the next stage of the process. As an alternative to this drying process, a spray dryer is outlined, which allows to obtain the necessary product in a single step.

[0032] This invention allows to obtain a liquid or powder compound product that is added to the industrialized production process in the grinding stage of the clays and components of the ceramic body, the inclusion of the fluxing additive can also be carried out for dry grinding and during subsequent stages to the milling process and prior to drying by trays, spray drying and any other similar process, among the applications described in the present invention are: body for red ceramic floor, ceramic porcelain floor tile, ceramic body for bathroom and pieces of molding, tooling ceramics that contain high zirconium content, ceramic body for wall and facade coating, valances and decoration material, enamel application, engobes and gloss with the addition of silver, copper or zinc oxide nanoparticles that allow preparation of antibacterial surfaces using concentrations ranging from 100 parts per million at 5% maximum of antibacterial nanoparticles in the last ceramic layer of the product.

[0033] The family of additives obtained from the described processes subject to this invention, which contain nanostructures as primary elements, are presented in aqueous dispersion with a density ranging from 1.1 to 1.7 g/mL, preferably from 1.3 to 1.6 g/mL, while the solids content ranges from 35 to 60% preferably from 40 to 50% with a pH of 10 to 14.

[0034] The powdered additives are presented with a granulometry of less than 500 microns, preferably between 1 and 75 microns, the free moisture content is less than 10%, preferably less than 5%.

[0035] Additives used in concentrations ranging from 0.25 to 3% in the ceramic body formulation allow to improve the sintering process, reducing the heat treatment time by 1 to 15% according to the application and/or lower the temperature of heat treatment at a rate of 0 to 50 degrees Celsius, while using these in concentrations of 3 to 10%, it allows decreasing sintering temperature at a rate of 50 to 150 degrees Celsius at the same smelting time and/or decrease the heat treatment time at a rate of 5 to 25%, according to the application ceramic material and process conditions.

[0036] For the incorporation of additives in the ceramic materials, these can be added to the process water prior to the milling process, in the mill as an additive, in a process of incorporation after the formation of the slip after the milling process, in a powder mixer prior to the pressing or molding process, among other methods, as long as the process properties are met according to each stage. The formulation of the additive is defined by the type of ceramic body, the incorporation methodology and the process properties, maintaining the operating conditions with minimal changes.

[0037] The properties of the modified ceramic body with the fluxing nanoadditives object of this invention were evaluated to determine the gresification curves, the mechanical properties, appearance, X-ray diffraction analysis, thermogravimetric analysis, scanning electron micrographs, which determines that the additives improve the sintering process at a low concentration, representing a low cost possibility to reduce production costs and minimize the carbon footprint.

[0038] In order to better understand the properties of the additives object of this invention, some examples of the formulations and application methods, manufacturing methods and evaluations of the characteristics of the materials are shown below.

EXAMPLE 1

[0039] In the premixed tank for slurry preparation (FIG. 1), 100 to 250 kg of water are added, followed by stabilizing and moisturizing additives, then 100 to 200 kg of the material to be ground are added to the tank maintaining intense agitation for correct incorporation, using a notched disk disperser and a speed from 500 to 1500 RPM, the particles to be ground with sizes just below 45 microns are integrated in the dispersion until reaching the desired solids concentration, which ranges from 10 to 50% by adjusting the pH with an acid or base to reach a Z potential above 50 at absolute value.

[0040] Once the dispersion has been carried out, it passes through a high energy attrition mill at 800 to 1200 RPM in the milling chamber agitator, the material recirculates between the dispersion tank and the mill, controlling the particle size with laser light scattering equipment until reaching a nanometric scattering, the pH is controlled at all times and upon reaching the target size between 50 and 500 nm depending on the material, it is taken to the storage tank.

[0041] The nanostructures obtained from this process and which are the primary element of the subsequent reaction are subject to a drying process through a press filter until a solids content range between 40 and 60% is reached achieving a consistent paste that is subsequently dried in a tray furnace at 140 C. until a humidity of less than 5%, preferably less than 1%, is reached, the slabs obtained are passed through a hammer sprayer to obtain a fine powder.

[0042] The nanostructured powder is taken to a dry high energy ball mill, where the previously sprayed reactive components are added by adjusting the proportions to 30 to 50% of sodium oxide, 30 to 50% of silicon oxide, 0 to 30% of boron oxide, 0 to 10% of potassium oxide, 1 to 5% of calcium oxide, 0 to 1% of aluminum oxide. In the formulation, 2 to 10% of nanoparticles prepared by physicochemical process are included in the formulation, the mechanosynthesis achieved in the dry high energy milling process is achieved at speeds above 400 RPM and up to 900 RPM, in an air environment.

[0043] The product is added with antimicrobial agents only in the case of coatings, in the final part of the process and it is integrated at speeds ranging from 200 to 400 RPM. To finally obtain the final powder product.

EXAMPLE 2

[0044] In a process similar to example 1, the dispersion of dispersion nanostructures obtained from the physicochemical process of aqueous milling is taken and it is transferred to a reactor in a wet basis where the reagents are added to achieve a proportion ranging from 30 to 50% of sodium oxide, 30 to 50% of silicon oxide, 0 to 30% of boron oxide, 0 to 10% of potassium oxide, 1 to 5% of calcium oxide, 0 to 1% of aluminum oxide. Once the integration of the reagents is achieved, an additive that provides antibacterial and antifungal properties is added in a low proportion, to finally be added with rheological modifiers in the case of the integration of the additive in mills. in a wet basis.

[0045] The product is obtained in liquid in a dispersion-solution of stable nanostructures that can be added to a ceramic body to confer fluxing properties, and only in the case of formulations with antimicrobials to form low melting point antimicrobial surfaces.

EXAMPLE 3

[0046] In a 1 L ball mill dedicated for milling ceramic materials with a 1:1 ball load with the ceramic body, the ceramic body was incorporated and a deflocculant additive was added at a concentration of 0.1 to 0.5% base solids, with a proportion of solids in water ranging from 50 to 70%, preferably from 60 to 68%, and a total milling time of 8 to 15 minutes for 300 to 600 g of solids, a slip of standard material is obtained which is compared under the same conditions by adding nanoflux additive in a proportion of 0.25 to 3 wt % base solids of the additive against the ceramic body. A slip is obtained which is subsequently dried and processed to a particle size of less than 500 microns, with this powder specimens are prepared in cylindrical and rectangular prism pieces for the evaluation of the curves of gresification, in the pressing process humidity is maintained between 3 to 8%, after the pressing process the pieces are dried and transferred to the heat treatment process.

[0047] The absorption properties of water in the non-additive material correspond to the heat treatment temperature at 12 to 20% for 1000 C., 8 to 18% for 1050 C., 8 to 15% for 1100 C., and 3 to 8% for 1150 C., while for the body with the nanoflux additive it corresponds to 8 to 18% for 1000 C., 5 to 12% for 1050 C., 3 to 8% for 1050 C. and 0.5 to 3% for 1150 C. In the case of contraction for the standard ceramic body, contractions were found from 0 to 2% for 1000 C., 0 to '3% for 1050 C., 0 to 3% for 1100 C. and 4 to 6% for 1150 C., while for the body with nanoadditives between 1 to 2% for 1000 C., 2 to 5% for 1050 C., 1 to 7% for 1100 C. and 1 to 7% for 1150 C., in the last two cases in concentrations greater than 1% of the additive in the ceramic body it was found that the ceramic body exceeded the ideal sintering temperature reaching the expansion zone, therefore the optimum sintering temperature decreased with the use of nanoadditives in proportions less than 3% at 50 to 100 degrees Celsius.

EXAMPLE 4

[0048] In a 1 L ball mill dedicated for milling ceramic materials with a 1:1 ball load with the ceramic body, the ceramic body was incorporated and a deflocculant additive was added at a concentration of 0.1 to 0.5% base solids, with a proportion of solids in water ranging from 50 to 70%, preferably from 60 to 68%, and a total milling time of 8 to 15 minutes for 300 to 600 g of solids, a slip of standard material is obtained which is compared under the same conditions by adding nanoflux additive in a proportion of 3 to 7 wt % solid base of the additive against the ceramic body. A slip is obtained which is subsequently dried and processed to a particle size of less than 500 microns, with this powder specimens are prepared in cylindrical and rectangular prism pieces for the evaluation of the curves of gresification, in the pressing process humidity is maintained between 3 to 8%, after the pressing process the pieces are dried and transferred to the heat treatment process.

[0049] The absorption properties of water in the non-additive material correspond to the heat treatment temperature at 12 to 20% for 1000 C., 8 to 18% for 1050 C., 8 to 15% for 1100 C., and 3 to 8% for 1150 C., while for the body with the nanoflux additive it corresponds to 4 to 10% for 1000 C., 3 to 8% for 1050 C., 1 to 8% for 1050 C. and 0.5 to 2% for 1150 C. In the case of the contraction for the standard ceramic body, contractions were found from 0 to 2% for 1000 C., 0 to 3% for 1050 C., 0 to 3% for 1100 C. and 4 to 6% for 1150 C., while for the body with nanoadditives between 1 to 6% for 1000 C., 1 to 8% for 1050 C., 1 to 3% for 1100 C. and finally 3 to 7% for 1150 C., in the bodies treated with nanoadditive, it was found that the ideal sintering temperature was exceeded reaching the expansion zone, therefore the optimum sintering temperature decreased with the use of nanoadditives at 50 to 150 degrees Celsius.

EXAMPLE 5

[0050] According to methodology of examples 3 and 4, heat treatments are carried out in a flask taking the material to 1050 C. for 30 min and 120 min using nanoflux additive concentrations between 3 to 10%, preferably from 5 to 7%, while the standard material does not contain nanoflux. For the treatment performed at 30 minutes, contractions between 2 to 4% for the standard material were obtained while for the nanoadditive material the contraction reaches 3 to 8%, on the other hand the percentage of absorption for the standard ranges from 14 to 16% while for the nanoadditive material it reaches 1.5 to 4.5%, which represents a better sintering of the ceramic body, promoted by the presence of the melting materials in the formulation.

[0051] In the case of heat treatment at 120 C., a percentage of water absorption for the standard of 10 to 12% was obtained while the nanoflux material reached a water absorption of 0.03 to 1.48%, in the case of contraction in standard, values between 4 to 6% were obtained, while for the nanoadditive material values of 0.3 to 5.4% were found, in most cases the ceramic body was over sintered which means that it was found in expansion.

EXAMPLE 6

[0052] Based on the procedure set forth in Example 5, a heat treatment was performed at 1140 C. for 30 minutes using nanoflux in a proportion between 1 and 3% with respect to the ceramic body, the percentage of absorption shown for the standard material is between 2 and 5%, while the additive material reached a water absorption of 0.2 to 0.5%.

[0053] It is noted that in connection to this date, the best method known by the applicant to implement said invention is the one clearly resulting from the description of this invention.