EP1780297A2

EP1780297A2 - Process for coating and/or decorating ceramic articles and articles thus obtainable

Info

Publication number: EP1780297A2
Application number: EP06021672A
Authority: EP
Inventors: Mario Doda
Original assignee: Twr Sas Di Mario Doda & C
Current assignee: Twr Sas Di Mario Doda & C
Priority date: 2005-10-18
Filing date: 2006-10-16
Publication date: 2007-05-02
Also published as: ITMO20050267A1; EP1780297A3

Abstract

The present invention refers to a process for coating and/or decorating ceramic articles, which comprises supplying a fired ceramic support and projecting particles of at least a metal or a metal compound in melted or semi-melted state onto at least one portion of the surface of the support to constitute a first coating layer.

Description

The present invention refers to a process for coating and/or decorating ceramic articles and articles thus obtainable.
With particular reference to the ceramic industry, various processes have been known for some time for coating or decorating articles such as tiles or the like, able to give them an appearance similar to that of metal.
For example, the decoration is known of ceramic articles used particularly for covering surfaces by means of the application of glazes with metallic effect such as, for example, the so-called "lustres" on the visible surfaces of shaped and raw ceramic supports.
A subsequent stage relating to the firing of the support worked in this way, performed inside kilns conventionally used in the ceramic industry, permits the consolidation of the glazes for making coatings with metal effect or special decorative designs.
The use is also known of metal powders on raw ceramic supports for the definition of isolated ornamental elements of the insert and relief type.
The metallic powders are, for example, applied at cavities suitably obtained on the visible surface of tiles or the like which, following their melting and consolidation after firing, define a decoration that is lowered with respect to the remaining visible surface.
These known coating and/or decorating processes are not without drawbacks, including the fact that the difference between the heat expansion coefficients of the ceramic support and glaze or the applied metal powders respectively can produce flaking or "crack" breakage of the metallic decoration or coating.
What is more, the ceramic articles decorated in this way are subject to the so-called "delayed cracking", meaning, more specifically, that the cracking phenomenon originated by the above difference in heat coefficients can occur even after firing, during the life of the ceramic article, due to the permanent tensions inside the coating structure or the decoration itself.
Another drawback concerns the use of metals that are not in a pure state, in the form of glazes or powders, for the coating/decoration of manufactured products, in relation to their subsequent recovery for disposal or, possibly, for partial reuse of the raw materials. In fact, the use of impure metals negatively affects relevant environmental impact and generally results in the recovered manufactured products being classified as special waste, which makes disposal complicated and costly.
It should also be noted that during the firing cycle of a ceramic support coated or decorated with glazes to which metals have been added, harmful fumes are generated and, in general, emissions that have a negative impact on the environment.
The ceramic articles produced in this way cannot be used for the magnetic shielding of interiors, for which the use is known of metal panels, generally made of copper, fitted on walls or floors inside premises, so as to represent a magnetic shield (Faraday cage).
The shielding effect created by the panels is able to insulate from external magnetic fields, electronic computers, for example, designed to perform functions of considerable importance or, generally, electronic devices the operation of which is strongly affected by the action of magnetic fields.
These known metal panels are not without drawbacks, including the fact that they do not ensure a good visual impact of the interiors thus covered and require the application of further decorative surfaces or their installation inside the walls themselves, with consequently greater complexity of the installation operations and higher costs.
The primary aim of this invention is to eliminate the drawbacks complained of above relating to known processes, and to excogitate a process that makes it possible to coat ceramic articles with a layer of metal, restricting at the same time the possibility of the formation of faults or breakages in the coating/decoration during the process itself or, afterwards, during the life span of the article, following its use.
Another purpose of the invention is to excogitate a process for coating and/or decorating ceramic articles that permits obtaining ceramic articles that can be used for the magnetic shielding of interiors.
A further purpose of the invention is to excogitate a process that permits making coated or decorated ceramic articles made of materials that are easy to dispose of, both during the manufacturing cycle and during internal recycling and, finally, with a softer environmental impact.
As part of such technical aim, another purpose of the present invention is to achieve the preceding aims with a simple structure, of relatively practical implementation, safe use and effective operation, as well as of a relatively low cost.
This aim and these purposes are all achieved by the present process for coating and/or decorating ceramic articles, characterized in that it comprises supplying a fired ceramic support and projecting particles of at least a metal or a metal compound in melted or semi-melted state onto at least one portion of the surface of said support to constitute a first coating layer.
Further characteristics and advantages of the present invention will appear even more evident from the detailed description of a preferred, but not exclusive, form of embodiment of a process for coating and/or decorating ceramic articles, illustrated by way of non limiting example in the accompanying drawings, wherein:

figure 1 is a schematic axonometric view of the projection phase of a first coating layer and of a ceramic support relating to the process according to the invention;
figure 2 is a schematic axonometric view of the ceramic article complete with a first coating layer and relating to the process according to the invention;
figure 3 is a schematic axonometric view of soaking in an electrolytic bath and of a ceramic article relating to the process according to the invention;
figure 4 is a schematic axonometric view of the finished ceramic article relating to the process according to the invention.

With special reference to the above figures, a ceramic article, particularly of the tile type or the like, coated and/or decorated following the process according to the invention has been generally designated by reference number 1.
The finished ceramic article 1 comprises a fired ceramic support 2 featuring a visible surface 2a at least partially covered by a first, continuous, layer 3, made of a metal material or a metal compound.
In particular, as shown in figure 4, the visible surface 2a of the ceramic support 2 is completely covered by the first layer 3, which has a substantially flat and uniform conformation, and which is preferably made of a metal or a metal compound chosen, for example, from among copper (Cu), nickel (Ni), titanium (Ti) and steel. The use of other types of metals cannot however be ruled out.
A second layer 4, preferably made of material of the chrome (Cr), nickel (Ni), copper (Cu), titanium (Ti) or steel type, is distributed on at least one portion of the first layer 3 for protective and/or decorative purposes.
For example, as shown in the specific form of embodiment in figure 4, the second layer 4 is distributed on the first layer 3 to form a decoration composed of a first portion shaped like a frame, with rectangular outlines, which is defined near the outer edge of the article 1 and which encloses a second rectangular portion.
The ceramic support 2 is made using conventional pressing, injection moulding, extrusion or drawing methods and the subsequent firing of a mix of substantially frost-proof material and preferably made of porcelain stoneware.
The process according to the invention, implemented to make the article 1 described above, comprises a first cleaning phase of at least one portion of the visible surface of the ceramic support 2 by means of surface abrasion of the mechanical type, for example by sand-blasting, able to obtain a surface with controlled roughness.
Subsequently, a thermal spray operation of the plasma spray, HVOF (High Velocity Oxygen Fuel) or flame spray type, permits the melting of metal powders, preferably copper, and their projection towards the visible portion of surface 2a thus polished, where these solidify quickly and create a superimposed layer structure, forming the first layer 3.
In the particular embodiment of the invention illustrated in the above figures, the visible surface 2a of the ceramic support 2 completely undergoes the cleaning operation and is subsequently covered with the first layer 3.
Following the thermal spray operation, a surface finish phase of the mechanical type can be envisaged for the first layer 3 by polishing, satin-finishing or lapping able to achieve the required thickness and roughness values.
The ceramic article 1 thus obtained can be used for the magnetic insulation of interiors such as, for instance, electromechanical workshops, electronic printout processing departments, taping and/or recording rooms or, in general, to insulate electronic devices that are particularly sensitive to the action of outside magnetic fields.
In particular, the ceramic articles 1 featuring the first layer 3 of the above-described metal material are arranged side by side for covering the walls of such interiors to form a magnetic shield for insulating against any external magnetic fields.
A further decoration phase can be performed on the ceramic article 1 thus obtained, by means of the application of a second layer 4 of coating and/or decoration on at least one portion of surface of the first layer 3.
In particular, a template 5, suitably shaped to reproduce the appearance of the required decoration, is temporarily applied to the article 1 on at least one predetermined portion of the first layer 3.
As shown in figure 3, the template 5, generally made of material of the non-metal type, can for example be shaped like a substantially rectangular frame.
Afterwards, the ceramic support 2 with the template 5 thus applied is soaked in an electrolytic bath 6 inside a tank 7, and the second layer 4 is composed, by electrolytic deposition, for example, of nickel (Ni) or chrome (Cr), on the remaining portion of surface of the first layer 3 not insulated by the template 5.
Alternatively, the second layer 4 can be applied to the first layer 3 by thermal spraying and can involve the application of materials such as, for example, copper (Cu), titanium (Ti) or steel.
In the particular form of embodiment of the invention shown in the figures, the multi-layer coating of the article 1 is only composed of the first and the second layer 3 and 4; one or more auxiliary layers cannot however be ruled out made of different materials which, by means of methods equivalent to those previously described, can be applied above the second layer 4 or placed between the latter and the first layer 3.
It has in actual fact been found how the described invention achieves the set purposes and, in particular, the fact is underlined that the application of the first layer of metal material following the firing of the ceramic support permits avoiding the formation of faults or breakages in the coating which are typical of conventional processes, and also restricts the possibility of breakage during the life span of the article, as a result of its use.
In particular, it permits avoiding breakages such as cracking or delayed cracking, typical of the application of a coating or decoration in a pre-fired metal material of the ceramic support.
Moreover, the application of the first layer on the entire visible surface of the ceramic support, and the use of a plurality of such articles arranged side by side for the covering of walls, permits the magnetic shielding of interiors as an alternative to currently known metal panels.
The use of metal materials, such as copper, to make the first layer, instead of the impure metal powders or metal-effect glazes conventionally used, ensures that the ceramic articles thus obtained are easy to dispose of and, if so required, that the metal materials can be recovered for subsequent use, with consequent softening of the relevant environmental impact.
The invention thus conceived is susceptible of numerous modifications and variations, all of which falling within the scope of the inventive concept.
Furthermore all the details can be replaced with others that are technically equivalent.
In practice, the materials used, as well as the shapes and dimensions, may be any according to requirements without because of this moving outside the protection scope of the following claims.

Claims

Process for coating and/or decorating ceramic articles, characterized in that it comprises supplying a fired ceramic support and projecting particles of at least a metal or a metal compound in melted or semi-melted state onto at least one portion of the surface of said support to constitute a first coating layer.
Process according to claim 1, characterized in that said surface is the visible surface of said article.
Process according to one or more of the preceding claims, characterized in that said projecting comprises thermal spraying said particles onto at least one portion of said surface.
Process according to one or more of the preceding claims, characterized in that said thermal spraying is of the plasma spray and/or HVOF and/or flame spray type.
Process according to one or more of the preceding claims, characterized in that it comprises a preliminary cleaning phase of at least one portion of said surface.
Process according to one or more of the preceding claims, characterized in that said cleaning phase of said surface is made by surface abrasion of the mechanical type.
Process according to one or more of the preceding claims, characterized in that it comprises making a finish operation of the mechanical type of said at least first layer.
Process according to one or more of the preceding claims, characterized in that said making a finish operation comprises grinding and/or polishing and/or satin-finishing and/or lapping said at least first layer.
Process according to one or more of the preceding claims, characterized in that it comprises forming at least one second layer made of at least a metal or a metal compound onto at least one portion of said first layer.
Process according to one or more of the preceding claims, characterized in that said forming comprises the electrolytic deposition of said second layer by soaking said first layer in an electrolytic bath.
Process according to one or more of the preceding claims, characterized in that said forming comprises applying a template substantially made of a non-metal material onto at least one portion of said first layer and the subsequent electrolytic deposition of said second layer by soaking said first layer in an electrolytic bath.
Process according to one or more of the preceding claims, characterized in that said forming comprises applying said second layer by thermal spray.
Ceramic article obtainable with the process according to claims from 1 to 12, characterized in that it comprises a fired ceramic support, and at least a first covering layer of at least one portion of the surface of said ceramic support which is made of at least a metal or metal compound.
Ceramic article, according to claim 13, characterized in that said surface is the visible surface of said ceramic support.
Ceramic article according to claims from 13 to 14, characterized in that it comprises at least a second coating layer of at least one portion of said at least one first layer which is made of at least a metal or metal compound.
Ceramic article according to claims from 13 to 15, characterized in that said ceramic support is in a substantially frost-proof material.
Ceramic article according to claims from 13 to 16, characterized in that said ceramic support is made of porcelain stoneware.
Use of ceramic article according to claims from 13 to 17 for covering surfaces, characterized in that a plurality of said ceramic articles are arranged side by side to form a magnetic shielding.