Ceramic coatings with apatite carbonate that allow a tactile thermal sensation similar to wood and good resistance against wear, chemical attack and staining

Abstract

In one aspect, the present invention comprises providing an additive or aggregate to be applied directly to one or more of the components of a ceramic coating and which is constituted by carbonate apatites particles which are maintained as aggregates within a matrix of silicoaluminates at firing temperatures of the ceramic coatings, where the main function of these aggregates is to provide the ceramic coating properties selected from the group comprising: low effusivity, wear resistance, resistance to chemical attack and resistance to staining. In other aspects, the present invention comprises providing a ceramic coating incorporating said additive and a method for providing a ceramic coating with properties selected from the group comprising: low effusivity, wear resistance, resistance to chemical attack and resistance to staining.

Claims

1. A ceramic coating comprising a ceramic support body and the following layers: a layer called enamel comprising a glass layer; and a layer called engobe which allows union between the enamel and the ceramic support body, wherein the ceramic coating is characterized by at least one of its layers containing from 0.50% to 30% by weight of an additive comprising carbonate apatites which have in its structure carbonates (CO.sub.3) that partially replace groups PO.sub.4.sup.3- in a 0.1% to 8.0% by weight; wherein carbonate apatites are selected from one or more materials of the group consisting of: natural carbonate apatites, synthetic carbonate apatites, or mixtures thereof and wherein the carbonate apatites are in the form of particles comprising diameters between 100 nanometers and 50 microns.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) In a first aspect, the present invention relates to an additive or aggregate to be applied directly to one or more of the components of a ceramic coating during its production process, wherein said additive comprises: a material selected from the group comprising natural carbonate apatites, synthetic carbonate apatites, or mixtures thereof; wherein the carbonate apatites are in the form of particles of sizes between 100 nanometers and 50 microns.

(2) The additive of the present invention allows the ceramic coatings to maintain their aesthetic and functional properties according to the standards used in the industry. In this way it is possible to improve the thermal comfort to the touch of the ceramic coatings and keep their technical specifications

(3) In a second aspect, the present invention relates to a ceramic coating or coating having a thermal sensation pleasant to the touch similar to that of wood and good resistance to wear.

(4) The ceramic coating of the present invention comprises: a ceramic support body a layer called enamel that consists of a vitreous layer that defines the functional and decorative properties of the ceramic coating; a layer called engobe which allows a good union between the enamel and the ceramic body. wherein the ceramic coating is characterized in that: the enamel layer contains from 0.50% to 30% by weight of the additive of the present invention described above; and/or the engobe layer contains from 0.50% to 30% by weight of the additive of the present invention described above. where according to the ISO 13006 standard used in the industry, in the case of dry pressed products, the ceramic coating is classified into the following groups: Group BI.sub.a having a water absorption capacity between 0% and 0.5%; Group BI.sub.b having a water absorption capacity between 0.5% and 3.0%; Group BII.sub.a having a water absorption capacity between 3.0% and 6.0%; Group BII.sub.b having a water absorption capacity between 6.0% and 10.0%; Group BIII having a water absorption capacity greater than 10.0%; wherein the water absorption is measured in % by weight, according to ISO 10454-3. and wherein the ceramic coating of the present invention has the following specific properties: a wear resistance equal to or greater than PEI 2 according to ISO 13006 standard, essay 10545-7; a resistance to chemical attack equal or superior to GA, GLA and GHA standards according to ISO 13006 standard, essay 10545-13; a stain resistance equal to or greater than Class 3 according to ISO 13006 standard, essay 10545-14; and an effusivity of between 700 Ws.sup.1/2/m.sup.2K y 1,000 Ws.sup.1/2/m.sup.2K.

(5) The ceramic coating of the present invention has a thermal sensation to the touch similar to that of wood thanks to its low effusivity and also have good resistance to wear, resistance to chemical attack and resistance to staining.

(6) In a third aspect, the present invention relates to a method for providing to a ceramic coating, properties selected from the group comprising: low effusivity, wear resistance, resistance to chemical attack and resistance to staining, wherein the ceramic coating comprises a ceramic body support; a layer called enamel that consists of a vitreous layer that defines the functional and decorative properties of the ceramic coating; a layer called engobe which allows a good union between the enamel and the ceramic body, wherein said method comprises adding to the layer called enamel from 0.50% to 30% by weight of the additive or aggregate during the elaboration of said components in the steps where ingredients are incorporated within any known production process of ceramic coatings.

(7) In a fourth aspect, the present invention relates to a method for providing to a ceramic coating properties selected from the group comprising: low effusivity, wear resistance, resistance to chemical attack and resistance to staining, wherein the ceramic coating comprises a body ceramic support; a layer called enamel that consists of a vitreous layer that defines the functional and decorative properties of the ceramic coating; a layer called engobe which allows a good union between the enamel and the ceramic body, where said method comprises adding to the layer called engobe from 0.50% to 30% by weight of the additive or aggregate during the elaboration of said components in the steps where ingredients are incorporated within any known production process of ceramic coatings.

(8) In a fifth aspect, the present invention relates to a method for providing to a ceramic coating properties selected from the group comprising: low effusivity, wear resistance, resistance to chemical attack and resistance to staining, wherein the ceramic coating comprises a body ceramic support; a layer called enamel that consists of a vitreous layer that defines the functional and decorative properties of the ceramic coating; a layer called engobe which allows a good union between the enamel and the ceramic body, wherein said method comprises adding to the layer called enamel from 0.50% to 30% by weight of the additive or aggregate; and adding to the so-called engobe layer from 0.50% to 30% by weight of the additive or aggregate during the preparation of said components in the steps of incorporating ingredients within any known production process of ceramic coatings.

(9) The additive or aggregate object of this invention has in its structure carbonates (CO.sub.3) that partially replace PO.sub.4.sup.3-groups in 0.1% to 8.0% by weight. This additive, when subjected to the typical firing cycle of the ceramic coatings, it thermally reacts, releasing CO.sub.2 and O.sub.2, which generates a closed microporosity as a consequence of the partial decomposition of the remaining carbonate groups found in the structure of the carbonate apatites. This closed microporosity generated during the firing process is what imparts to the ceramic coatings its low thermal effusivity.

EXPERIMENTS

(10) During the process of development of the additive and the ceramic coating of the present invention that has a low thermal effusivity, the determination of the thermal properties of the coatings that are currently marketed, was carried out using equipment acquired expressly for the measurements (C-Therm TCi Thermal Conductivity Analyzer). The equipment performs the measurement based on the principle of the “Transient Plane Source Method”) which consists of analyzing the transfer of energy between a controlled heat source in a flat way and the material under study and in measuring the temperature change of the latter as a function of time.

(11) The heat source, which in turn serves as a resistive temperature detector, is a highly sensitive thermoelectric sensor that is placed on the surface of the material whose thermal properties are to be evaluated. By applying a known and constant electrical current to the sensor, a small amount of heat is produced which will result in an increase in temperature at the interface between the sensor and the material to be measured.

(12) The speed with which the temperature increases at the interface will depend on how quickly the heat propagates in the material being measured. Once the applied current is known and constant, the increase in temperature will in turn be reflected in a variation of the sensor potential recorded as a function of time; by means of suitable mathematical models, these data, together with the variation of temperature with time and heat flow, make it possible to calculate the thermophysical properties of the material without the need for further experimentation.

(13) The equipment allows to determine quickly and simultaneously the thermal conductivity and thermal effusivity of materials in different state of aggregation; effusivity is precisely the property that is used to evaluate the thermal sensation to the touch of materials.

(14) To carry out the measurement, the face of the sample whose thermal properties were to be analyzed, is placed on the sensor which is in turn mounted on a base that holds it fixed in a vertical position. A weight is placed on the sample to ensure good contact with the sensor, and between them, a small amount of a contact agent having a good thermal conductivity is added to avoid heat leaks that may alter the measurement. The conductivity and effusivity measurements were made in triplicate; the value taken in each test was also the average of 5 repetitions.

(15) Before analyzing the samples, the proper functioning of the sensor was calibrated and checked using a standard reference material supplied by the manufacturer, with a certified value of thermal conductivity. In this case, the standard material used was Pyroceram 9606™ which is a ceramic glass developed in the 50s by the company Corning Glass Works (now Corning Inc) for NASA, and which is used thanks to its thermal properties that are reliable and extraordinarily stable.

(16) To analyze the contribution of each component (ceramic body, engobe and enamel) to the thermal properties of the coating, the conductivity and effusivity in calcined ceramic bodies without engobe and enamel was determined, as well as in other ceramic bodies that only had the engobe, or with both engobe and enamel (finished product).

(17) Table 1 shows the results obtained from some ceramic tiles of natural products and commercial ceramic coatings without the incorporation of carbonate apatites which were used as reference.

(18) Table 2 shows the measurements of thermal effusivity and conductivity made to tile coatings without aggregates and with carbonate apatites aggregates according to the present invention. As shown in Table 2, in all cases it was found that the ceramic coatings with carbonate apatites aggregates showed lower values of thermal effusivity.

(19) TABLE-US-00001 TABLE 1 effusivity values and thermal conductivity of some commercial ceramic coatings, natural products and synthetic products. EFFUSIVITY CONDUCTIVITY KIND OF MATERIAL (Ws  /m.sup.2K) k (W/mK) CERAMIC COATINGS CLASSIFIED ACCORDING TO ISO 13006 STANDARD Group BIa 1698 1.467 Group BIIa 1599 1.289 Group BIII 1218 0.916 NATURAL PRODUCTS Granite 2479 2.960 Marble 2055 2.140 Wood 684 0.310 SYNTHETIC PRODUCTS Cellulosic thermoplastic floors 948 0.573 Vinyl floor 622 0.251

(20) TABLE-US-00002 TABLE 2 Effusivity values and thermal conductivity of some prototypes of ceramic coatings without carbonate apatites aggregates and with carbonate apatites aggregates according to the present invention. TYPE OF MATERIAL EFFUSIVITY CONDUCTIVITY THAT IS ADDED (Ws  /m.sup.2K) k (W/mK) MODIFIED ENGOBE AND STANDARD ENAMEL Nanometric silica 1528 1.177 Nanometric alumina 1567 1.238 Refractory fiber 1573 1.247 of Al—Si—Zr Refractory fiber of Al—Si 1572 1.245 With addition of 1044 0.674 carbonate apatites STANDAR ENGOBE AND MODIFIED ENAMEL Nanometric silica 1559 1.223 Nanometric alumina 1564 1.218 Refractory fiber 1548 1.204 of Al—Si—Zr Refractory fiber of Al—Si 1563 1.230 With addition of 1122 0.758 carbonate apatites MODIFIED ENGOBE AND ENAMEL Refractory fiber 1560 1.225 of Al—Si—Zr Refractory fiber of Al—Si 1548 1.207 With addition of 941 0.565 carbonate apatites

(21) As can be seen in table 2, the presence of carbonate apatites aggregates in the different types of ceramic coatings, significantly reduces the thermal conductivity and the effusivity of the ceramic coatings.

(22) Table 3 shows effusivity and thermal conductivity values for ceramic coatings classified within Group BIa (water absorption capacity between 0% and 0.5%); which were processed at maximum firing temperatures of between 1170° C. and 1210° C. Also in Table 3 are shown values of effusiveness and thermal conductivity for ceramic coatings classified within Group BIIa (water absorption capacity between 3.0% and 6.0%), which were processed at maximum firing temperatures of between 1125 and 1170° C. In both types of coatings, carbonate apatites aggregates were added according to the present invention.

(23) TABLE-US-00003 TABLE 3 Ceramic coatings classified as Group BIa that have a water absorption capacity between 0% and 0.5% and of Group BIIa, which have a water absorption capacity between 3.0% and 6.0% with aggregates of carbonate apatites according to the present invention. PART OF THE CONDUC- COATING EFFUSIVITY TIVITY WHERE IT SAMPLE (Ws½/m.sup.2K) k (W/mK) WAS ADDED CERAMIC COATINGS OF GROUP BIa (water absorption capacity between 0% and 0.5%) Standard 1698 1.467 N/A Prototype 160226-3 with 1098 0.732 ENGOBE carbonato apatitas Prototype 160226-4 with  934 0.558 ENGOBE + carbonate apatites BASE CERAMIC COATINGS OF GROUP BIIa (water absorption capacity between 3.0% and 6.0%). Standard 1496 1.110 NA Prototype 150521-6 with 1141 0.779 ENGOBE carbonate apatites Prototype 151104-2 with  901 0.520 ENGOBE + carbonate apatites BASE Prototype 151104-3 with  852 0.470 ENGOBE + carbonate apatites BASE

(24) As can be seen in table 3, the presence of carbonate apatites aggregates significantly reduces the thermal conductivity and effusivity of the coatings classified according to ISO 13006 as Group BIa, which have a water absorption capacity between 0% and 0.5% and of Group BIIa, which have a water absorption capacity between 3.0% and 6.0%.

(25) In the case of ceramic coatings classified as Group BIII having a water absorption capacity greater than 10.0%, aggregates of carbonate apatites were also added according to the present invention and were treated at maximum firing temperatures of between 1100° C. and 1140° C., obtaining values of effusivity and thermal conductivity similar to those of ceramic coatings classified Group BIIa, which have a water absorption capacity between 3.0% and 6.0% within the same ISO 13006 standard.

(26) One of the most used international standards is ISO 13006; specifically, to evaluate the wear of ceramic coatings the most used method is the PEI (Porcelain Enamel Institute); by which and according to ISO 10545-7 the abrasion resistance of the enameled surface is determined.

(27) The resistance to stains is determined according to the standard ISO 10545-14 and the chemical resistance is determined according to the standard ISO 10545-13. Table 4 shows the results of these two tests performed on ceramic coatings prepared with carbonate apatites aggregates according to the present invention.

(28) TABLE-US-00004 TABLE 4 Test results according to ISO-10545 (resistance to abrasion, resistance to stains and resistance to chemicals) practiced to commercial coatings (standard) and to coatings with carbonate apatites aggregates according to the present invention. Prototype 151104-3 with Standard carbonate apatites RESISTANCE TO ABRASION OF THE SURFACE (ESSAY ISO 10545-7) Resistance PEI IV IV RESISTANCE TO STAINS (ESSAY ISO 10545-14) Iodine in alcohol Class 5 Class 5 GreenishAgent Class 5 Class 5 (Cr2O3) Aceite de oliva Class 5 Class 5 Azul de metileno 1% Class 5 Class 5 RESISTANCE TO CHEMICAL PRODUCTS (ESSAY ISO 10545-13) Sodium hypochlorite GA GA Ammonium Chloride GA GA 100 g/l Citric acid100 g/l GLA GLA  HCl 3% GLA GLA HCl 18% GHA GHA  KOH 30 g/l GLA GLA KOH 100 g/l GHA GHA Lactic Acid5 % GHA GHA
Classification for Spotting Agents Class 1=The stain is not removed by any means Class 2=The stain is removed with appropriate solvent of strong activity during 24 h. Class 3=The stain is removed by mechanical means (rotating brush) and strong cleaning agent. Class 4=The stain is removed with a weak activity cleaning agent (common soap) Class 5=The stain is removed with running water.
Classification for Salt Solutions for Pool GA=No visible effect GB=Clear appearance modification. GC=Visible effect on cut sides, uncut sides and on the surface.
Classification for Weak Solutions of Acids and Bases GLA=No visible effect GLB=Clear appearance modification. GLC=Visible effect on cut sides, uncut sides and on the surface.
Classification for Strong Solutions of Acids and Bases GHA=No visible effect GHB=Clear aspect modification. GHC=Visible effect on cut sides, uncut sides and on the surface.
PEI Classification for Enameled Ceramic Tiles

(29) TABLE-US-00005 Visible effect at # of revolutions Class 100 0 150 I 600 II 750, 1500 III 2100, 6000, 12000 IV GREATER THAN V 12001

(30) Finally it must be understood, that the additive and the ceramic coating of the present invention is not limited to the described and illustrated practices, and that persons having ordinary skill in the art can, with the teachings provided by the invention, suggest modifications to the ceramic coating and method of the present invention.