MXPA98006351A - Method for enamelling glass substrates, enamel composition used and resulting products - Google Patents

Abstract

The invention concerns an enamel composition more easily recycled comprising at least a glass composition and containing, as pigment(s), at least one or several manganese compounds, this composition further having a melting point less than 750°C. The invention also concerns an enamelling method using this composition and the resulting enamelled products.

Description

PROCEDURE FOR ENAMELING GLASS SUBSTRATES, COMPOSITION OF USED ENAMEL AND PRODUCTS OBTAINED DESCRIPTION The present invention relates to the deposit of enamel on a glass substrate, mainly? U over a glazing. It relates in particular to a new enamel composition and to a new process for making an enamel layer on a glass substrate, as well as to the enameled products obtained with that process. Enamels are well known in the state of the art and are used in particular for coating glass substrates, such as glazing, in the automotive industry or in the construction industry. Among other things, they allow to form inscriptions or layers Ü decorative, conductive coatings, protective layers, especially ultraviolet radiation protection layers for the adhesive layers or adhesive cords intended for mounting the glazing in the body, mask, especially masks for hiding collector bands of heating networks or for hiding the adhesive cords mentioned above, etc ... The enamels that are used to coat glass substrates, are generally formed (before application on the substrate and cooking ) by a powder comprising a glass frit (which must form the matrix of the glass) and by pigments (as dyes especially, these pigments can also form part of the frit); the frit and the pigment are 1U based on metallic oxides, and a medium or "vehicle" that allows the application and temporary adhesion of the enamel on a substrate. The medium, which is selected according to the destination of the enamel, must ensure a good suspension of the particles of the frits and pigments that are used and must be consumed at the latest when the enamel is cooked. This medium can include solvents, thinners, oils, resins, etc ... A problem with enamelled glass substrates 2? that exist, is the difficulty of recircular those products, in particular in the manufacture of glass substrates in the form of sheets (encristalados). For encristalados that have to satisfy many requirements in matter of coloration, of luminous tranemieión and / or energetics etc., it is important in fact that the glass waste that was reintroduced under ground form (pulverized glass) in the melting furnaces that are used to manufacture in glazing, do not disturb the compositions already present customarily and do not give products that do not meet the required requirements. If non-enameled powdered glass can be reintroduced in a glass-making oven by flotation, at rates generally of the order of 20% to 30% by weight of the furnace charge, the enameled powdered glass, on the other hand, generally produces the appearance of undesirable residual colorations or non-molten residual islets in the formed glass sheets. Therefore, in the most favorable cases, the rate of pulverized glass that can be reintroduced in these kilns does not exceed 2% to 3% in relation to the load of the kilns (the enamel is generally from 0.1% to 0.5%). % by weight of that pulverized glass). The object of the present invention is that of U providing an improved enamel composition and an enameling process which makes it possible to obtain improved glazed (especially glazed) glass substrates, in particular enameled substrates which can be recirculated more easily (especially in the production process). of encristalados) than the enameled substrates that already exist; the enamelled layers that are obtained, also present, preferably, the characteristics customarily required (in terms of opacity and coloration, above all) for the enamelled layers that the encristalados for automotive vehicles must cover. The object of the invention is achieved by means of the enamel composition, which composition comprises at least one glass frit and which comprises, as a pigment (s), at least one or more manganese compounds; this composition also has a melting temperature lower than 750 ° C. In an advantageous embodiment of the invention, the enamel composition further comprises less than 10% by weight (relative to the composition), and preferably less 5% by weight, of silver particles. Particularly preferably, it comprises less than 10%, advantageously less than 5% by weight of silver particles and of any other silver-based compound and / or comprises less than 10%, advantageously less than 5% by weight of particles. of silver and of any other conductive particle (i.e., in the latter case, it comprises less than 10%, advantageously less than 5% conductive particles). In particular, the compositions according to the invention without silver particles and / or silver-based compounds and / or other conductive particles and / or certain heavy cumbersome metals which are mentioned below (in particular lead or lead oxides) , present many advantages, as explained below. By "enamel composition" is meant, according to the invention, the enamel composition considered before it is cooked; the enamel after baking is essentially in the form of a colored glassy matrix. By "melting temperature of the enamel composition" is meant, according to the invention, the melting temperature of the enamel in its form as it is deposited on the substrate to be coated. This "melting temperature" is also commonly referred to as "cooking temperature" or "fusibility temperature". In the field of glazes, corresponds to the minimum temperature at which a "sufficient" fritting of the composition is observed; this "sufficient" frittering is mainly due to a disappearance of the effect of capillarity of the enamel in the course of the fritting. The man of the prior art, knows how to measure this temperature - or melting, for example going through a pen-source of ink (ie more precisely a felt) on the enamel (after it has been brought to a temperature of treatment and then cooled) and noting the lowest treatment temperature for which the trace left through the enamel cooled by the ink solvents are absorbed by the enamel by capillarity, disappears. At the time of making an enameled substrate, the temperature selected to cook the enamel deposited on the substrate, that temperature is then selected, preferably greater than or equal to the melting temperature. As a general rule and preferably, the melting temperature of the enamel composition according to the invention is lower than 700 ° C. According to the invention, the enamel composition comprises at least one or more of the manganese compounds (it is generally a single compound, but it can be a mixture of different manganese compounds) as a pigment (s). Preferably, it comprises that (those) manganese compound (s) as the main pigment (s), that is to say that the enamel composition may optionally comprise one or more other pigments, but that, in this case, the rate of every other eventual pigment remains below the rate of compound (s) of manganese. In a particularly advantageous manner (for reasons linked to recirculation above all), the composition (s) of the manganese represent (s) at least 50% by weight of the pigments present, preferably 75% by weight of the pigments. present and in a particularly preferred manner, is (are) the only pigment (s) that is used in the composition according to the invention. In particular, the enamel composition according to the invention advantageously contains no chromium oxides, no copper oxides, no cobalt oxides, no nickel oxides and in general does not contain other coloring compounds, such as copper chromates, cobalt chromates. , etc ... and / or other coloring oxides such as iron oxides, etc. The manganese compound (s) is (are) U supplied preferably in the form of manganese salt and / or manganese oxide (s) (for example Mn02 and / or Mn203 and / or Mn304 and / or MnO), to the enamel composition according to the invention, particularly preferably in the form of manganese carbonate (s) and / or Mn02. Depending on the mode of preparation of the enamel composition, it can also be provided (s) or presented under one of the other form (e) in the composition (especially in the form of others). manganese derivatives). As a general rule, it gives one or more manganese oxide (s) (preferably Mn O ^, optionally accompanied by Mn203, at the latest at the time of enamel cooking on the coated substrate.) It is generally advantageous, especially in the In case the manganese compound (s) being used is not in crystallized form, treating the manganese compound (s) in order to obtain a re-arrangement structural, for example of the crystallization type, within said compound (s), for example by subjecting the enamel according to the invention, to a thermal treatment (the re-arrangement can sometimes be operated at the time of enamel cooking but being generally caused by an independent heat treatment before cooking); this re-arrangement favors the obtaining of enamel layers that have improved properties, especially in terms of opacity, coloration and / or anti-adhesive properties. The rate of pigment (s) (advantageously of co-product (s) of manganese) in the frit (s) / pigment (s) of the composition according to the invention is generally between 10% and 50% by weight, preferably between 15% and 40% by weight and, particularly preferably, between 20% and 35% by weight (in relation to the fritted set (s) / pigment (s), especially for reasons Opacity and conductivity of the enamel layer The glass frit according to the invention is a vitrifiable mixture comprising oxides selected especially among the oxides commonly used in enamel frits, for example selected from silicon oxides , of zinc, of bismuth, of sodium, of boron, of lithium, of potassium, of calcium, of aluminum, of magnesium, etc., or also between the oxides of barium, of strontium, of antimony, etc ... preference (for reasons linked to recirculation especially), the fritting of glass in a frit comprising less than 1% (advantageously less than 0.1% and, particularly advantageously, less than 0.05%) by weight of lead oxides and, particularly preferably, is a sintering without lead oxides. Also, it is preferably devoid of other clogging elements such as cadmium oxides, fluorine oxides, etc. Particularly advantageously, it is a frit comprising Si02 as a forming oxide. Also preferably, it comprises Bi203 and / or ZnO as intermediate oxide (s) [particularly preferably as the main intermediate oxide (s)]. The terms "forming oxide", "oxide modifier" and "intermediate oxide" are terms well known to the man skilled in the art in the glass industry. The forming oxides are oxides such as Si02, B203, etc., which form the essential constituents of the glassy networks; the modifying oxides are oxides such as CaO, K20, Na20, BaO, etc., which can modify the glassy network and influence properties such as viscosity or melting point; The intermediate oxides are oxides such as Al203, PbO, ZnO, Bi203, etc., which act on their surrounding environment and the proportion with which they are present, the role of the forming oxide and / or the role of the modifying oxide. The enamel composition according to the invention can comprise several mixed glass frits and having different characteristics (especially melting temperatures). According to a preferred embodiment, the enamel composition according to the invention, comprises as frit (s) (the pigments are not taken into consideration) the mixture of the following components in the proportions expressed in percentages by weight (in relation to that mixture). ): Bi203 50 - 70% 5 SiD2 15 - 30% B203 1 - 13% Na02 0.5 - 7% Al203 0.5 - 7% with preference, B203, Na02, Al203 7.5 - 18% U This composition makes it possible to obtain a particularly interesting enamel and that presents, above all, a very good aptitude for recirculation. The enamel composition according to the invention can also comprise a means which allows the desired pouring to the application on the substrate and which allows bonding with the substrate. This medium can be any medium which is customarily used in traditional enamel compositions and can comprise, above all, solvents, thinners, oils, such as pine oils and other vegetable oils, resins such as acrylic resins, petroleum fractions, materials Fumonogenic substances such as cellulose materials, etc. The proportion of the medium in the composition ready to be deposited is preferably between 15% and 40% by weight of that composition. The glaze that is obtained after cooking, has a good opacity that allows above all its use as concealment (for example to protect glue strings of motor vehicles). It is considered that the enamel has a good opacity, if it has an optical density when less than 2.8, preferably at least equal to 3. The optical density (DO) is measured with densitometer, for example the device GRETAG ^ D200 (in which a 550 nm filter is used) U and is linked to the light transmission factor TL by the relation: DO = log 1 / TL On the other hand, whatever the initial color (before cooking) of the enamel composition according to the invention, generally after cooking (at temperatures generally between 550 ° C and 750 ° C), a colored glaze suitable for applications to motor vehicles. Preferably, the enamel composition according to the invention is selected so as to give, after baking, a black enamel (this is the case of the compositions according to the invention comprising manganese salt (s), in particular manganese carbonate). and / or manganese oxide (s) such as Mn? 2, Mn202 and / or Mn 04, and / or U compositions according to the invention devoid of the clogging compounds mentioned above or comprising the frit mentioned above. which precedes in the weight percentages indicated, etc. ..) particularly sought in such applications. By "black enamel", 5 is understood below, an enamel that presents a black color after cooking. In a particularly preferred manner, the enamel composition according to the invention is selected so as to obtain a black enamel having the following colorimetric U-data, in absolute values: L * equal to or less than 5; I a * | equal or less than 2; and | b * | equal or less than 2; and preferably | a * | equal or less than 1; and | b * | equal or less than 1. 5 The colorimetric data L *, a *, and b *, were defined and proposed in 1931 by the International Commission on Lighting (CIÉ) and were the subject of an official CIÉ recommendation in 1976 (International Commission of the Lighting, Official Colorimetry Recommendations, CIÉ Publication No. 15-2, Vienna 1986). The colorimetric data indicated above, are measured in bending, on spectrum-colorimeter Minol ta CH 2002, under illuminant D 65, for the enamel that is on l? a non-colored substrate having a light transmission factor of the order of 90% and a thickness of 4 mm. The substrates coated with the enamel according to the invention also have, due to the fact of the The use of manganese compounds as a whole or part of the pigments, a better ability to be recycled. In this way, when the substrates coated with the enamel presenting the composition according to the invention are reintroduced, in the form of Ü pulverized glass, in a melting furnace of raw materials to produce glass sheet (at temperatures generally of the order of 1350 ° C to 1500 ° C), the coloring of the enamel usually disappears and does not interfere with the coloring of the glass that 25 results from the raw materials that are used. The ability to recirculate the composition according to the invention, as well as its opacity and color characteristics, are particularly improved when the enamel composition comprises less than 10% silver particles, or less than 10% silver particles and of any other silver based compound, or less than 10% conductive particles, as indicated above, in particular when the composition is devoid of those silver particles and / or those conductive particles and / or of those silver-based compounds (silver can especially pose problems in the course of recirculation and can give an undesirable brown coloration to the enamel). In the same way, the recirculated suitability and / or the opacity and color characteristics of the ink and / or optionally the mechanical properties of the enameled glasses are still improved when the composition comprises less than 1% and is devoid of one or more of the other cumbersome components mentioned above (such as lead, chromium, copper, cobalt, nickel, iron, cadmium or compounds, for example) metal oxides, which comprise at least one of those metals). In addition to the advantages associated with the recirculation and the satisfactory properties obtained in terms of opacity and coloration, it is noted that the enamel composition according to the invention is also for laying $ easy and is more economical due to the use of the manganese compound (s); these compounds are less expensive than the compounds customarily used as pigments in enamel compositions. The pigments represent 10% to 50% by weight of the fritted set (s) / pigment (s); the cost gain can be particularly important. The enamel composition according to the invention can be obtained by adjusting the manganese compound (s) (and optionally the other pigment (s)) in the form of powder (s) to a glass frit powder, these (ies) frit (s) are already in suspension in a medium or not. In this case, the granulometry of the fritted unit (s) / pigment (s) in powder form is preferably selected so that at least 90% by weight of the particles forming the powder have a smaller diameter at 40 μm and, particularly preferably, less than 20 μm; the selection of a granulometry of this type allows the opaqueness of the enamel obtained after cooking to be further improved. The fritted set (s) / pigment (s) of the composition according to the invention can also be obtained according to the following procedure (hereinafter referred to as "direct process"): the fusion of a mixture of appropriate raw materials is carried out to obtain the whole frit (s) / pigment (s) desired (for example a mixture of bismuth oxide, silicon oxide, boric acid U and / or borax, sodium carbonate and / or sodium nitrate, alumina and carbonate) of manganese and / or Mn 2, when it is sought to obtain a fritted set (s) / pigment (s) comprising the frit of composition expressed in the foregoing, in weight percentages and 5 comprising Mn 2 in pigment quality) at temperatures of the order of 1000 ° C to 1300 ° C; this melting is preferably followed by a treatment such as an annealing, at temperatures below approximately 480 ° C / 500 ° C, to obtain a structural rearrangement within the mixture (in particular within the the) pigment (s)] and, eventually, germs of crystallization develop. Then, the mixture is milled to give a fused set (s) / pigment (s) which is presented in the form of powder. Preferably, the grinding that is carried out is a fine grind so that at least 90% by weight of the particles forming the resulting powder have a diameter of less than 40 μm, preferably less than 20 μm, and , particularly preferably, less than 10 μm (this fine grinding allows to obtain better results in terms of enamel opacity) Then, optionally, the powder is heat treated, generally between 400 ° C and 600 ° C, in order to stabilize the mixture and reinforce the coloring of the enamel from this powder (for example, give it a "more black" coloration.) The direct procedure is particularly interesting, above all it is simpler, faster and more economical than the traditional methods of making compositions It is generally possible to obtain 15 glazes that have a darker color than those obtained by mixing a powder of glass frit (s) and a powder of the compound (s) of the Anganeso, in particular, generally allows to obtain enamels having colorimetric coordinates indicated in which 2U precedes (ie: L * equal to or less than 5; | * | equal or less than 2; and | b * [equal or less than 2). The fritted set (s) / pigment (e) of the composition is generally suspended in a medium in order to obtain a composition that can be deposited on a substrate. According to the enameling process of the invention, at least a part of the glass substrate with an enamel composition according to the invention is coated, and then the enamelled substrate is subjected to a heat treatment in order to bake the enamel and, if it is the case, in order to develop crystallization germs or obtain a structural re-arrangement at the level of the pigments. The substrate on which the enamel composition is depositedIt can be a bare glass substrate or a glass substrate already coated with one or more layers of enamel, preferably one or more layers of enamel according to the invention. This sub-layer can consist of one or more glass sheets and can be tempered in order to exhibit improved mechanical and thermal resistance properties. The enamel coated substrate according to the invention comprises at least one glass sheet coated on at least a part of one of its faces with at least one layer of a composition of an enamel having a composition U according to the invention. The enamel according to the invention can also be used to coat other types of substrates. In the enameling procedure of. Glass substrates, especially encristalados according to the invention, the enamel composition is preferably deposited by screen printing on the substrate, and then baked; the cooking is operated, if necessary, during the heat treatment joined to the bending and / or to the tempering of the substrates; the cooking temperatures are generally of the order of 550 ° C to 750 ° C / 800 ° C. Incidentally, it is observed that the enamel according to the invention can advantageously be put into operation with the aid of devices and under the conditions of temperature and pressure customarily used for the putting on the job of the traditional enamels in automotive applications. all. The deposit of the enamel composition can also be made by spraying, by curtain or roll coating, etc .; he The deposit is generally followed by drying, for example by means of infrared rays, to temporarily fix the enamel, for example by removing the diluents from the medium which serve to apply the enamel on the substrate. In the case where it? depositing several layers on the substrate, each layer preferably being dried before depositing the next layer; the cooking is operated on the set of layers. The optional bending and tempering of the 5 glass substrates are operated according to known methods.

Above all, the bending can be carried out by gravity (doming, in particular, of glass pavers in pairs to make panes of glass) or with the help of r matricee and, when the substrates are bulged and tempered, the tempering can be operated after bulging of enamelled substrates, possibly within the same device. In the case where the glass substrates must be bent simultaneously to realize glazing of l? leaves, the enamel is deposited on at least one of the substrates and the substrates are assembled and then bulked; the glass substrates are then separated to insert when an interlayer film of different material is removed, and then the glazing of sheets is obtained by hot assembly and under pressure. It is noted that certain enamel compositions according to the invention have anti-stick (anti-stick) properties; those compositions do not adhere to the other glass sheets or to the matrices that come to be put in 2U contact with them, during the bending operations. Glass substrates, especially encristalados, coated with enamel according to the invention, have an improved ability to recirculation; generally '"^ These substrates are recirculated, especially in the form of pulverized glass in the glass sheet manufacturing furnaces, in particular in ovens, which are used more frequently, to manufacture glass sheets by means of flotation, or "floats" , at rates that can go 5v to at least 1%, even though at least 50% by weight of the furnace charge (the enamel generally constitutes 0.1% to 0.5% by weight of the powdered glass). The enamel-coated substrates according to the invention also have mechanical properties 1U sufficient for use in automotive applications. Other advantages and characteristics of the invention will be apparent in the following examples that illustrate the present invention without limiting it, without however.

EXAMPLE 1: The enamel composition according to this example is made as follows: 100 parts by weight of a fritted 0 (in the form of a powder) comprising 11% by weight of B203, 65% by weight of Bi03, 17.4 are mixed. % by weight of Si02, 2.6% of Na20 and 4% of Al203, to 43 parts by weight of manganese carbonate (in the form of powder), and then put that I mix in suspension in 27 parts by weight of a medium to 25 base of pine oil comprising 3% by weight of acrylic resin, in order to obtain an enamel composition ready to be deposited on a substrate. The composition is deposited on a glass sheet 4 mm thick and then baked between 620 ° C and 750 ° C W approximately. A substrate coated with a black enamel layer having an optical density of 3 is obtained; that substrate can also be tempered. Then, the substrate is milled and introduced into a melting furnace of raw materials to make glass sheets by means of flotation; the substrate represents 50% by weight of the furnace charge (and the enamel represents 0.5% by weight of that substrate). The temperature of the oven is between 1250 ° C and 1500 ° C. There is a discoloration of the enamel and the absence of 5 unmelted parts when leaving the oven.

EXAMPLE 2: An enamel composition is made using 143 parts by weight of an assembly which is obtained by melting at approximately 1200 ° C sodium carbonate, alumina, boric acid, silicon, bismuth oxide and Mn. 2 (or manganese carbonate) followed by an annealing at about 450 ° C (that mixture is then subjected as it is, to a structural rearrangement) and a 5 milled. The obtained set presents the following composition in weight: 7.7% of B203, 45% of Bi203, 12.2% of Si02, 1.8% of Na20, 4.8% of Al203 and 30% of Mn03; this set is added to 27 parts of medium that is used in example 1, and then the composition of enamel that is obtained in that way, is deposited on a glass sheet and treated as in example 1. A substrate coated with a layer of black enamel (this layer is blacker than that obtained in example 1) that has an optical density? of 3, 9 and the following colorimetric coordinates: L * = 2.7; a * = -0.9 and b * = 0.3. Then, the substrate is milled and introduced into a melting furnace as in example 1. The same results are observed as in example 1 (i.e. a decolorization of the enamel and the absence of unmelted parts, when leaving the oven).

COMPARATIVE EXAMPLE: Proceed as in example 1, replacing the manganese carbonate with a traditional pigment, the 2U copper chromate. The glaze that is obtained after cooking is black. However, after the treatment between 1250 ° C and 1500 ° C of the pulverized glass coated with that enamel, in a melting furnace of raw materials to make glass sheets by means of float, it is observed mainly a reeidual green coloration on the leaves of glass that leave the furnace. Likewise, a contamination of the furnace linked to the presence of copper due to the reduction of the oxides is observed. The enamel according to the present example is also more expensive (in the order of 30% more expensive) than the enamel according to example 1 and that of the enamel according to example 2. The enamels according to the invention can be used above all to enrogate encristalados for the automotive and construction industry. í? fifteen or

Claims (14)

1. R E I V I N D I C A I N N E 1.- Enamel composition for glass substrate, whose composition includes when a frit * "glass and comprising, as pigment (s), at least one or more of the manganese compounds, this composition further has a melting temperature lower than 750 ° C.
2. 2.- Composition according to claim 1, characterized in that comprises one or more manganese compound (s) as the main pigment (s)
3. 3. Composition according to any of claims 1 or 2, characterized in that it comprises less than 10% by weight of silver particles.
4. 4.- Composition according to any of the 15 claims 1 to 3, characterized in that the compound (e) of the manganese is (are) supplied in the form of manganese salt and / or manganese oxide (s).
5. 5. Composition according to any of the claims 1 to 4, characterized in that the pigment rate (s) is comprised between 10% and 50% by weight of the frit (s) / pigment (s).
6. 6. Composition according to any of claims 1 to 5, characterized in that it comprises less than 0.1% lead oxides.
7. 7. - Composition according to any of claims 1 to 6, characterized in that the glass frit comprises Si02 as a forming oxide. 5 ^
8. 8.- Composition according to any one of claims I. to 7, characterized in that the glass frit comprises Bi203 and / or ZnO as intermediate oxide (s).
9. 9. Composition according to any one of claims 1 to 8, characterized in that it comprises as frit (s), the mixture of the following components in the proportions expressed in weight percentages: Bi2Os 50-70% Si02 15-30% B203 1 - 13% Na02 0.5 - 7% Al203 0.5 - 7%
10. 10. - Composition according to any of claims 1 to 9, characterized in that 2u also comprises a medium.
11. 11. Process for enameling a glass substrate, in which at least a part of the glass substrate is coated with an enamel composition comprising at least one glass frit and which L understands, as a pigment (s), at least one and several manganese compounds; this composition also has a melting temperature lower than 750 ° C, and then the enameled substrate is subjected to a heat treatment in order to cook the enamel. *
12. 12. Process for manufacturing an enamel composition according to any of claims 1 to 10, in which a fusion of raw materials is carried out at temperatures of the order of 1000 ° C to 1300 ° C, followed possibly by a treatment of annealing; The mixture obtained is then milled to give the fritted set (s) / pigment (s) of the enamel composition.
13. 13. Glazing comprising at least one sheet of glass coated on at least a part of? 5 at least one of its faces, at least a layer of an enamel having a composition according to any of claims 1 to 10.
14. 14 .- Glazing according to claim 13, characterized in that it is coated with a black enamel Aü having the following colorimetric coordinates, in absolute values: L * equal to or less than 5; | a * | equal or less than 2; and | b * | equal or less than 2; these coordinates ee measure for the enamel that is found on a glass euberato having a light transmission factor of the order of 90% and a thickness of 4 mm.