Composition of enamel, glass articles comprising it, and their production processes

Abstract

Enamel composition, glass article, and method for obtaining them. The invention relates to an enamel composition comprising a glass frit, an organic medium, and enameled cullet. The invention also relates to a method for obtaining said composition from enameled glass reduced to enameled cullet and mixed with an enamel composition comprising at least a glass frit, an organic medium, and optionally a mineral pigment. Finally, the invention relates to a glass article comprising a glass substrate coated with a layer of enamel formed from the composition according to the invention, as well as to a method for obtaining this glass article comprising a step of printing the composition according to the invention onto a glass substrate.

Description

Title of the invention: Enamel composition, glass article comprising it and their methods of production. Prior art

[0001] The invention relates to the fields of enamel compositions, glass articles coated with such compositions and their methods of obtaining them.

[0002] Enamel compositions are commonly used to improve the aesthetic, mechanical and thermal properties of glass substrates.

[0003] Enamel compositions generally comprise a glass frit, for example, bismuth borosilicate glass, an organic medium, and at least one pigment. A glass frit consists of fine particles of a low-melting-point glass, which, under the effect of a firing heat treatment, softens and adheres to the glass sheet. When this heat treatment is applied to an enamel composition, a mineral layer is formed: the enamel layer. This layer adheres strongly to the glass, for example, to hold pigment particles in place. Enamel layers can have a decorative or aesthetic function, but also a protective one.

[0004] For example, in the field of automotive glazing, layers of enamel, generally black and opaque, are often deposited on a portion of the glazing, usually in the form of a peripheral strip designed to protect against ultraviolet radiation the polymer seals used to fix and position the glazing in the body openings. They also make it possible to conceal said seals as well as other elements located on the glazing such as electrical connections or collector strips, designed to collect electricity.

[0005] In the field of flat glass, enamels are used for example to decorate surfaces such as building facades, shower partitions or mirrors, thus offering a wide variety of designs and finishes.

[0006] Some known glazing systems comprise sheets of glass coated on the same surface with a stack of thin layers followed by a layer of enamel. For example, in the building sector, there are glazing systems called "spanes," used for building facades, in which the glass sheet is entirely covered with a layer of colored and decorative enamel. Solar control layers are sometimes placed beneath the enamel layer to limit the building's heating due to solar radiation.

[0007] In the prior art, various enamel compositions have been developed to meet specific requirements. For example, patent application WO 2022 / 078715 describes an enamel composition comprising at least two glass frits of sizes The composition consists of particles with different glass transition temperatures, as well as a pigment and an organic medium. It aims to improve the mechanical properties of the enamel by utilizing a heterogeneous microstructure. However, this approach does not consider the use of recycled materials to reduce environmental impact.

[0008] It has also been considered to introduce enameled glass into float glass, but this method is limited to enamels containing black (CuCr2O4) or white (TiO2) pigments and is not recommended for soda-lime silico float glass. Difficulties encountered include problems with coloration, compatibility with the glass, regulatory issues, and toxic emissions, due to the pigments used in the enamels. Description of the invention

[0009] According to a first aspect, the invention relates to an enamel composition comprising at least one glass frit, an organic medium and enameled calcine.

[0010] According to another aspect, the invention relates to a glass article comprising a glass substrate coated with a layer of enamel formed from an enamel composition according to the invention.

[0011] According to a third aspect, the invention relates to a method for obtaining an enamel composition according to the invention, comprising: • the supply of enameled glass, • the reduction of said enameled glass into an enameled cullet, and • the mixture of the enameled calcine with an enamel composition comprising at least one glass frit, an organic medium and optionally a mineral pigment.

[0012] According to a fourth and final aspect, the invention relates to a method for obtaining a glass article according to the invention comprising a step of printing a composition according to the invention onto a glass substrate. Brief description of the figures

[0013] [Fig-1] is a graph showing the evolution of the lightness in reflection L* observed in SCE mode, as a function of the sintering or firing temperature for enamel layers corresponding to reference A and the 4 samples of example 1 according to the invention.

[0014] [Fig.2] is also a graph showing the evolution of the lightness in reflection L* observed in SCE mode, depending on the sintering or baking temperature but for enamel layers corresponding to reference B and the 4 samples of example 2 according to the invention.

[0015] [Fig.3] presents scanning electron microscope views in backscatter mode of enamel layers corresponding to reference B on the left and ) a sample of example 2 on the right. Detailed description

[0016] The present invention therefore proposes to introduce enameled calcine into an enamel composition.

[0017] For the purposes of the invention, "enameled cullet" means a recycled material from used enameled glass, for example from waste, in particular from industrial production, or from a dismantling site.

[0018] The present invention proposes a new method of valorization for enameled glass. Thus, it makes it possible to increase the quantity of "wasterial" (or material derived from waste) in enamel compositions and enameled glass articles.

[0019] To this end, and according to a first aspect, the invention relates to an enamel composition comprising at least a glass frit, an organic medium and enameled calcine.

[0020] In a preferred embodiment, the composition according to the invention comprises from 1% to 30%, in particular from 2% to 20% and preferably from 5% to 15% by weight of glazed calcine relative to the total weight of the composition.

[0021] The use of enameled cullet as a filler in the enamel compositions according to the invention makes it possible to achieve thermo-mechanical properties closer to those of glass, thus reducing the risks of embrittlement of glass articles enameled using these compositions, said risks being due to differences in coefficient of thermal expansion between glass and enamel.

[0022] Moreover, compared with other mineral fillers such as ceramics, enameled calcine exhibits good compatibility and good adhesion with glass frit, the main constituent of known enamel compositions.

[0023] Said calcin has a D90 less than or equal to 50 pm, in particular less than or equal to 30 pm and preferably less than or equal to 20 pm.

[0024] The term "enamel composition" refers to a pre-firing composition comprising an organic medium. This composition is liquid, particularly so that it can be deposited onto a substrate, for example a sheet of glass, in the form of a wet enamel layer. The generic term "enamel" refers to both the composition and the dry or wet layer.

[0025] Firing results in the elimination of the organic medium and the formation of an enamel layer, a term used to describe the enamel coating. After firing, the enamel coating therefore comprises a vitreous matrix obtained from the glass frit. This firing is typically carried out at temperatures of at least 500 °C, in particular of at least 600 °C, preferably of at least 650 °C, and generally of no more than 700 °C.

[0026] The organic medium is intended to facilitate the application of the composition to a substrate and its adhesion to the substrate before sintering. This organic medium typically comprises solvents, diluents, oils, and / or resins.

[0027] The glass frit and / or the glass matrix is ​​preferably made of zinc and / or bismuth borosilicate glass. Preferably, the glass frit and / or the glass matrix is ​​bismuth silicate.

[0028] When the enamel includes pigments, these may be pigments comprising at least one oxide selected from the oxides or sulfides of chromium, copper, iron, manganese, cobalt and nickel.

[0029] In a particular embodiment of the invention, the enamel (therefore also the composition according to the invention) comprises black pigments, preferably copper and / or iron chromates.

[0030] A black enamel is particularly advantageous when deposited on the periphery of a sheet of glass intended for the automotive industry in order to conceal and protect against ultraviolet radiation seals, connector elements, or sensors.

[0031] Thus, in a preferred embodiment, an enamel composition according to the invention comprises a mineral pigment, preferably a black pigment.

[0032] According to another aspect, the invention relates to a method for obtaining an enamel composition according to the invention comprising • the supply of enameled glass, • the reduction of said enameled glass into an enameled cullet, and • the mixture of the enameled calcine with an enamel composition comprising at least one glass frit, an organic medium and optionally a mineral pigment.

[0033] The reduction of enameled cullet glass into cullet advantageously includes a grinding step, in particular using a planetary mill, optionally followed by a sorting step, in order to obtain a particle size of enameled cullet such that it has a D90 less than or equal to 50 µm, in particular less than or equal to 30 µm, and preferably less than or equal to 20 µm.

[0034] According to another aspect, the invention relates to a glass article comprising a glass substrate coated with a layer of enamel formed from an enamel composition according to the invention.

[0035] Such a glass article may be glazing for buildings or glazing for transport vehicles, whether land, rail, sea, or air. When the glass article is glazing for a motor vehicle, it may be a roof or canopy, of a rear window or windshield. By "building glazing" we mean glazing intended for windows as well as for outdoor and / or urban furniture, furnishings and / or domestic or professional refrigerated equipment.

[0036] The glass substrate suitable for a glass article according to the invention can be a sheet of mineral glass, optionally thermally tempered or chemically strengthened and / or laminated with at least one other sheet of glass by means of a lamination interlayer.

[0037] The lamination interlayer is for example a sheet of polyvinyl butyral (PVB).

[0038] Automotive glazing, particularly roofs and windshields, is usually laminated; this can also be the case for building glazing, for safety reasons. In this case, the face of the glass sheet coated with the enamel layer is preferably an inner face of the glazing.

[0039] The term "inner face" refers to any face of a glass pane in the glazing, positioned opposite the passenger compartment of a vehicle. For example, for tempered glass, this could be the face in contact with the interior of the vehicle's passenger compartment, or, in the case of laminated glass, the inner face of the outer pane, that is to say, the one located on the side of the lamination interlayer.

[0040] In a particular embodiment of the invention, the glass substrate is a sheet of glass selected from float glass, soda-lime silicon, aluminosilicate, and borosilicate sheets. Preferably, the glass substrate in a glass article according to the invention is a sheet of soda-lime silicon float glass.

[0041] Thus, in a preferred embodiment, the substrate of a glass article according to the invention is a mineral glass sheet, optionally thermally tempered or chemically strengthened and / or laminated with at least one other glass sheet by means of a lamination interlayer, in particular chosen from float, soda-lime, aluminosilicate and borosilicate glass sheets, preferably a soda-lime silico glass sheet.

[0042] Float glass is obtained by a process consisting of pouring molten glass onto a bath of molten tin.

[0043] The glass sheet can be flat, particularly when the glass article is building glazing, or curved, especially when the glass article is vehicle glazing. The glass sheet is generally flat at the time the enamel composition is deposited and can subsequently be curved.

[0044] When the glass sheet is mechanically strengthened, that is to say, in particular, hardened or thermally tempered, it is heated to a temperature of approximately 600 °C or more, this treatment potentially causing the glass to warp, and then rapidly cooled to create counter-pressure stresses on its surface. The enamel firing preferably takes place during this heat treatment.

[0045] The glass sheet can be clear or tinted, for example in green, blue, grey or bronze.

[0046] Preferably, the glass sheet has a thickness of 0.7 to 19 mm, in particular 1 to 10 mm, in particular 2 to 6 mm, and preferably 2 to 4 mm.

[0047] In a glass article according to the invention, the thickness of the enamel layer can be from 1 pm to 100 pm, in particular from 5 pm to 50 pm and preferably from 10 pm to 40 pm.

[0048] According to another aspect of it, the present invention relates to a method of obtaining a glass article according to the invention, comprising a step of printing a composition according to the invention onto a glass substrate.

[0049] In one embodiment of the invention, the printing step is carried out by screen printing and / or by digital printing.

[0050] A screen printing process comprises the deposition, notably using a squeegee, of a paste-like liquid, in the context of the invention the enamel composition according to the invention, onto a substrate through the mesh of a screen printing screen. The mesh of the screen is blocked in the portion corresponding to the areas of the substrate that must remain uncovered, so that the paste-like liquid can only pass through the screen in the areas to be printed, according to a predefined pattern. The selective blocking of the mesh is therefore performed according to the negative of the pattern to be printed.

[0051] This selective sealing is generally achieved by applying a photocurable resin to the screen and then by exposing the parts of the screen to be sealed to ultraviolet radiation.

[0052] Selective exposure is for example achieved using a slide comprising a transparent support, typically made of polyester, coated with an opaque ultraviolet ink deposited according to the pattern to be printed.

[0053] The mesh of the screen is chosen according to the viscosity and surface tension of the paste as well as according to the desired thickness for the resulting layer of the screen printing deposition.

[0054] The screens used for screen printing enamel compositions according to the invention can comprise from 30 to 100 threads per centimeter, for a thread diameter of 30 to 60 pm.

[0055] According to yet another of its aspects, the present invention relates to an automotive glazing comprising a glass article according to the invention.

[0056] In a glazing according to the invention, the surface on which the enamel layer is spread is called the "enameled area".

[0057] The enameled area is in particular in the form of a peripheral band. That is to say, a band enclosed upon itself which, from each point of the glass article according to the invention, extends towards the interior of the glass article over a certain width, typically from 1 to 20 cm.

[0058] The glazing according to the invention may include an enamelled area comprising 2 to 25%, in particular 3 to 20% and preferably 5 to 15% of the surface of its face coated by the first and second layers.

[0059] The remaining part of the automotive glazing according to the invention, called the "non-enameled area", is generally uncoated.

[0060] Alternatively, it can be coated with a stack of thin films, for example including a low emissivity layer, in particular based on silver or on a transparent electro-conductive oxide such as indium tin oxide or doped tin or zinc oxides. Examples

[0061] A clear and neutral 4 mm thick soda-lime silico float glass marketed by the company Saint-Gobain Glass under the brand name Planiclear (hereinafter "PLC") and covered by screen printing with a black enamel 22 µm thick marketed by the company Vibrantz under the reference 14 40 11, is cut into a plate of 30 mm on each side.

[0062] The plate is then fragmented into pieces with a maximum length of 5 cm, which are crushed to obtain pieces whose largest dimension is at most 3 mm. These pieces are then ground in a planetary mill to obtain an enameled glass powder with a particle size such that it has a D90 of 15 µm (hereinafter "enameled cullet").

[0063] This calcine is then added in a content of 10% by weight relative to the total weight of the enamel, to enamel compositions marketed under references 14 303 and 14 40 11 by the company Vibrantz, corresponding respectively to a bismuth-based enamel used in the automotive industry and to a zinc-based enamel used in glass coating for buildings.

[0064] These mixtures are then each deposited on PLC substrates of 4 mm thickness, 60 mm width and 150 mm length by screen printing using a screen comprising 90 centimeter wires and whose wire diameter is 48 pm, then dried at 160 °C in an infrared dryer.

[0065] Reference samples A and B are thus obtained, each comprising only a commercial enamel (respectively 14 40 11 and 14 303) as well as 2 times 4 samples: a first series (example 1 according to the invention) comprising, in addition to commercial enamel 14 40 11, 10% by weight relative to the total weight of the enameled calcin enamel as previously obtained and a second series (example 2 according to the invention) comprising, in addition to commercial enamel 14 303, 10% by weight relative to the total weight of the enameled calcin enamel as previously obtained.

[0066] Next, the samples are subjected to heat treatment in a gradient furnace comprising 3 zones of different resistances. The settings for the 3 zones are adjusted for 180 seconds at 620 °C, 680 °C and 760 °C, then for 400 seconds at 530 °C, 610 °C and 690 °C respectively. The temperature gradient of the fired enamel is measured as the samples exit the furnace using a pyrometer that records 11 measurement points on the enamel.

[0067] After cooling, it is verified that none of the samples exhibits any optical defects such as microcracks or pineholes. The enamel surface on all three samples thus appears regular, homogeneous, and free of defects. The resulting enamel coatings are approximately 11 µm thick.

[0068] Figure 3 shows scanning electron microscopy (FEG Zeiss microscope) views in backscattering mode of representative samples of reference B on the left and a sample of Example 2 on the right. The observed sections of the enamels were both sintered at 630 °C. Electron backscattering produces a view in which the brightest elements (those scattering the most) are the elements with the highest atomic weight Z. It can then be seen that in the view of Example 2, particles of glazed calcine are easily identifiable, encapsulated within the glassy matrix of the enamel.

[0069] The measurement of the L* reflectance parameter of each sample is also carried out, through the glass on the uncoated side (i.e., the glass side). The measurement is performed under the conditions of the CIE recommendation (1931) using a commercial Minolta CM-600d spectrocolorimeter with a D65 illuminant, an observer at 10° in SCE mode (specular component excluded), and a scatter angle of 8°. These measurements are shown in Figures 1 and 2, where the enamel temperature at the measurement point is plotted on the x-axis and the L* measurement on the y-axis.

[0070] Figure 1 shows the curves corresponding to reference A and the 4 samples of example 1, while Figure 2 shows the curves corresponding to reference B and the 4 samples of example 1.

[0071] From observing the aforementioned Figures, it can be concluded that the addition of enameled calcin to various commercial enamel compositions does not significantly alter their color. Indeed, AE in the Lab* color space as defined in the CIE Recommendation (1931) is representative of the perceived color difference. In the field of enamels, an AE of less than 1.5 is considered characteristic of an imperceptible change in color or brightness.

[0072] The enamels of references A and B are marketed with sintering temperature range indications of 590 °C to 640 °C and 630 °C to 680 °C, respectively. The measurements shown in Figures 1 and 2 demonstrate that, within these ranges, for all samples produced, the colorimetry of examples 1 and 2 according to the invention is not not significantly modified (AE < 1.5) compared respectively to references A and B. It should be noted that the comparison of reference A with the samples of example 1 gives even an AE of less than 0.8 at 640 °C and that of reference B with the samples of example 2 gives an AE of less than 0.4 at 600 °C.

[0073] The results are summarized in the table below: [Tables 2] T * . ' min Sintering range (°C) Reference A 4.38 630-680 Example 1 4.40 630-680 Reference B 3.17 590-640 Example 2 3.28 590-640

[0074] Consequently, an enamel composition according to the invention has its properties of interest (colorimetry, sintering temperature) unchanged compared to an equivalent commercial composition, i.e. devoid of enameled calcine.

Claims

Demands

1. Enamel composition comprising at least one glass frit, an organic medium and enameled calcine.

2. Composition according to the preceding claim, comprising from 1% to 30%, in particular from 2% to 20% and preferably from 5% to 15% by weight of glazed calcine relative to the total weight of the composition.

3. Composition according to any one of the preceding claims, wherein the glazed calcine has a D90 less than or equal to 50 pm, in particular less than or equal to 30 pm and preferably less than or equal to 20 pm.

4. Composition according to any one of the preceding claims, further comprising a mineral pigment, preferably a black pigment.

5. Glass article characterized in that it comprises a glass substrate coated with an enamel layer formed from an enamel composition according to any one of the preceding claims.

6. Glass article according to the preceding claim, wherein the glass substrate is a mineral glass sheet, optionally thermally tempered or chemically strengthened and / or laminated with at least one other glass sheet by means of a lamination interlayer, in particular selected from float, soda-lime, aluminosilicate and borosilicate glass sheets, preferably is a soda-lime silico glass sheet.

7. Glass article according to any one of claims 5 or 6, wherein the thickness of the enamel layer is from 1 pm to 100 pm, in particular from 5 pm to 50 pm and preferably from 10 pm to 40 pm.

8. A method for obtaining an enamel composition according to any one of claims 1 to 4, comprising: • supplying enameled glass, • reducing said enameled glass into an enameled cullet, and • mixing the enameled cullet with an enamel composition comprising at least a glass frit, an organic medium and optionally a mineral pigment.

9. A method for obtaining a glass article according to any one of claims 5 to 7, characterized in that it comprises a 11 step of printing a composition according to any one of claims 1 to 4, on a glass substrate.

10. A method according to the preceding claim, characterized in that the printing step is carried out by screen printing and / or by digital printing.

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