Tempered glass ceramic articles

Abstract

This invention provides glass-ceramic articles, such as cooking plates, that can be used to obtain greater mechanical strength. [Solution] A glass ceramic article comprising a base material such as at least one glass ceramic plate, wherein the base material is coated in at least one area on its underside with a fibrous structure comprising fibers and a resin matrix, wherein the fibrous structure comprises fibers selected from glass fibers, carbon fibers, aramid fibers, quartz fibers, Kevlar fibers, and mixtures thereof.

Description

[Technical Field]

[0001] This invention relates to the field of glass ceramics. More specifically, this invention relates to articles or products made of glass ceramics, in particular glass ceramic plates intended for use as furniture surfaces and / or cooking surfaces.

[0002] Glass ceramic articles are defined as articles based on a substrate (e.g., a plate) made of a non-porous glass ceramic material, which may have accessories or additional (decorative or functional) elements as required for its ultimate purpose. An article may refer to the substrate only, or it may refer to a substrate with additional fittings (e.g., a cooking plate with a control panel, heating elements, etc.). [Background technology]

[0003] Glass ceramics are originally glass, also known as precursor glass, matrix glass, or green glass, whose specific chemical composition allows for controlled crystallization through appropriate heat treatment, a process called ceramicization. This particular, partially crystallized structure gives glass ceramics their characteristic properties.

[0004] Currently, different types of glass ceramics exist, and each of these variants is the result of extensive research and countless tests. This is because modifying these plates and / or their manufacturing methods without risking adverse effects on the desired properties is extremely difficult.

[0005] Glass ceramic plates also need to possess sufficient mechanical strength required in their field of use. In particular, for use as cooking plates in household appliances or as furniture surfaces, glass ceramic plates need to have good resistance to pressure and impact (support, and dropping of cooking utensils, etc.).

[0006] Typically, glass-ceramic plates are used as cooking plates or can be combined with heating elements in other applications, such as forming fireplace inserts. More recently, their use has expanded to other areas of daily life: glass-ceramic plates can be used as furniture surfaces, particularly to form workbenches, central islands, consoles, and so on. The surface area occupied by these new applications is larger than in the past.

[0007] The French Patent Application Publication No. 2868065, in the name of the applicant, describes a glass-ceramic plate whose mechanical strength is enhanced by the addition of a paint that is applied by screen printing and polymerized in air at 250°C. This layer is deposited over the entire underside. [Overview of the project] [Problems that the invention aims to solve]

[0008] The purpose of this invention is to obtain greater mechanical strength.

[0009] Currently, the following is also possible to increase the impact strength of glass ceramic plates: - Increase the thickness, - Alternatively, implement strict control over the manufacturing process: limit friction / scratching on the underside, or strengthen quality control over defects at the furnace exit. [Means for solving the problem]

[0010] The inventors have demonstrated that the impact strength of a glass-ceramic plate can be improved by applying a resin-containing fiber structure, particularly a structure commonly known as a "prepreg," to the underside of the glass-ceramic plate. [Brief explanation of the drawing]

[0011] [Figure 1]Figure 1 shows the strength results of Examples 1a, 1b, and 1c compared to Reference Example 1. [Figure 2] Figure 2 shows the strength results of Examples 3a, 3b, and 3c compared to Reference Example 3. [Figure 3] Figure 3 shows the results of Comparative Example 4 compared to Reference Example 4. **DETAILED DESCRIPTION OF THE INVENTION**

[0012] The present invention relates to a glass-ceramic article comprising at least one substrate, such as a glass-ceramic plate, said substrate being coated in at least one area of its lower surface with a fibrous structure comprising fibers and a resin matrix, particularly a polymer resin matrix.

[0013] In particular, the article according to the invention is a cooking device further comprising one or more heating elements.

[0014] In particular, said fibrous structure comprises fibers selected from glass fibers, carbon fibers, aramid fibers, quartz fibers, Kevlar fibers (Kevlar is a registered trademark), and mixtures thereof. Preferably, the fibers are glass fibers or carbon fibers, and even more preferably glass fibers.

[0015] Advantageously, said fibrous structure has a fiber density of 50 to 1000 g / m , ,

[0017] ,

[0018] , , preferably 100 to 800 g / m 2 , more preferably 150 to 600 g / m 2 .

[0016] In particular, said resin is selected from thermosetting resins, preferably epoxy resins, phenolic resins or polyimide resins.

[0017] The fibrous structure may comprise one or more layers of a woven unidirectional or multiaxial structure, preferably a woven structure.

[0018] In particular, the above structure is deposited over at least 40%, preferably at least 50%, and more preferably at least 60% of the surface of the substrate. Gaps are provided within the fibrous structure at the location of the heating region, optionally at the location of the control strip, and at the edges of the substrate.

[0019] In particular, the fiber structure has a coefficient of thermal expansion that is greater than that of the glass ceramic plate.

[0020] According to certain embodiments, the substrate also includes an enamel coating which is advantageously deposited on the upper surface of the substrate, on a specific portion of its surface.

[0021] Another object of the present invention is a method for manufacturing a glass ceramic article comprising at least one substrate, such as a plate, made of a glass ceramic material, wherein a fibrous structure comprising fibers and a resin matrix is ​​applied to the substrate, and the thus coated substrate is subjected to heat treatment under pressure or vacuum (in an autoclave).

[0022] The heat treatment is generally carried out at a temperature of 100 to 200°C, preferably 120 to 150°C, at a pressure of 100 to 400 millibars, preferably 150 to 350 millibars, for a period of 30 minutes to 3 hours, preferably 40 minutes to 2 hours, and more preferably 50 minutes to 1 hour 30 minutes.

[0023] The glass-ceramic articles according to the present invention are, in particular, plates, devices, or appliances for cooking or any furniture, which integrate (or include, or are formed from) at least one substrate made of glass-ceramic material. (The substrate is most commonly in the form of a plate, which is integrated or mounted in a unit and / or combined with other elements to form a unit). The substrate may, if necessary, have an area with display characters or a decorative area (for example, in combination with a light source), or may be combined with a heating element. In its most common application, the articles according to the present invention are intended to function as cooking plates, which are generally intended to be integrated in a cooktop or cooking appliance that also has a heating element, such as a radiant or halogen heater, or an induction heating element.

[0024] When the article according to this invention is a cooking hob including a heating region and a control strip, before applying the fibrous structure, the latter is pre-cut to the size of the base material, and gaps are cut into the structure in the heating region and optionally in the control panel.

[0025] The thickness of the glass-ceramic substrate is generally at least 2 mm, and especially at least 2.5 mm. It is in mm, and advantageously less than 15 mm, especially about 3 mm to 15 mm, especially The thickness is approximately 3mm to 8mm, or approximately 3mm to 6mm. The base material is preferably flat or semi-flat. A plate (in particular, with a deflection of less than 0.1% in the diagonal direction of the plate, preferably about 0) It is a plate that possesses it.

[0026] The substrate may be based on any glass-ceramic, which is advantageous in that it has a coefficient of thermal expansion (CTE) of zero or nearly zero, particularly 30 × 10⁻¹⁰ (in absolute value) at 20–700°C. -7 K -1 Below 15 × 10°C, especially between 20 and 700°C. -7 K -1less than, or even 5×10 -7 K -1 and has a CTE of less than

[0027] The present invention is particularly advantageous for substrates with a dark appearance, which have low permeability and low diffusivity and, in particular, for glass-ceramics up to 6 mm thick, inherently have a light transmittance T of less than 40%, particularly less than 5%, particularly 0.2 to 2% L , and an optical transmittance of 0.5 to 3% (determined in a known manner by taking the ratio between the transmitted intensity and the incident intensity at a given wavelength) with respect to a wavelength of 625 nm included in the visible range, based on any glass-ceramic

[0028] "Inherently" is understood to mean that the substrate has such transmission characteristics by itself, without the presence of any coating. Optical measurements are carried out in accordance with the EN410 standard. In particular, the visual transmittance T L is measured in accordance with the EN410 standard, using illuminant D65, and is the total transmittance (in particular integrated over the visible range and weighted by the spectral sensitivity curve of the human eye), taking into account both direct transmission and possible diffuse transmittance. The measurements are carried out, for example, using a spectrophotometer equipped with an integrating sphere (in particular by the spectrophotometer marketed by Perkin Elmer under the product name Lambda950)

[0029] According to one embodiment, the substrate has a black or brown appearance and, in combination with a light source arranged below, makes it possible to display an illumination area or a decoration while hiding any element below. This may be based on a black glass-ceramic having crystals of the β-cristobalite structure in the residual glass phase, the absolute value of its expansion coefficient being advantageously 15×10 -7 K -1 or less, or even 5×10 -7 K -1The following may be the glass ceramic plates, for example, those marketed by Eurokera under the name Kerablack+. In particular, glass ceramics having the composition described in European Patent Application Publication No. 0437228, U.S. Patent No. 5070045, or French Patent Application No. 2657079, or glass ceramics refined with tin, preferably containing less than 0.1% arsenic oxide, as described in International Publication No. 2012 / 156444, or glass ceramics refined with one or more sulfides, as described in International Publication No. 2008053110.

[0030] According to one embodiment, the substrate may have an upper surface that has been matted with acid.

[0031] According to another embodiment, the substrate is opaque and / or low-transparency, while being diffusive and sufficiently transparent (transparency is lightness L). * (provided by) and the glass material is, in its bulk, specially colored or tinted as specified below (this coloring includes white and lightness L * (This includes all colors with more than 10 shades, but excludes dark colors such as black or dark brown.)

[0032] The glass ceramics used may have compositions such as those described in the patent applications published under the following numbers: European Patent Application Publication No. 1300372, U.S. Patent No. 6706653, International Publication No. 9906334, International Publication No. 2007113242, European Patent Application Publication No. 1840093, U.S. Patent No. 2007213192, U.S. Patent No. 7476633, Patent No. 2009531261, International Publication No. 2012156444, International Publication No. 2012001300, and German Patent Application Publication No. 202012011811. These glass ceramics are particularly lithium aluminosilicate glass ceramics and advantageously include colorants.

[0033] Advantageously, for example, a glass ceramic is used, which is obtained by ceramicization starting from glass containing the following components and / or having the following composition: Expressed as mass percentages within the following ranges: SiO2: 52-75%; Al2O3: 18-27%; Li2O: 2.5-5.5%; K2O: 0-3%; Na2O: 0-3%; ZnO: 0-4%; MgO: 0-5%; CaO: 0-2.5%; BaO: 0-3.5%; SrO: 0-2%. TiO2: 0-5.5%; ZrO2: 0-3%; P2O5: 0-8%; B2O3: 0-5%, preferably within the following ranges, expressed as mass percentages: SiO2: 55-70%; Al2O3: 18-24%; Li2O: 2.5-4.5%; K2O: 0-2.0%; Na2O: 0-2.0%; ZnO: 1.5-4%; MgO: 0.20-5%; CaO: 0-1%; BaO: 0-3%; SrO: 0-1.4%; TiO2: 1.8-5%; ZrO2: 0-2.5%; P2O5: 0-8%; B2O3: 0-5%. This composition may also include additional colorants as needed.

[0034] The substrate according to the present invention may, if necessary, be coated with other coatings or layers having a functional effect (such as an overflow prevention layer or an opacity layer), and / or decorative, particularly localized, such as a normal pattern based on enamel (for example, on the top surface to form a simple pattern or logo), or a layer of opaque paint on the underside of the substrate. In particular, the substrate may be coated with at least one layer of enamel and / or paint, particularly a glossy type layer, locally or not locally.

[0035] The articles according to the present invention may further have one or more light sources and / or one or more heating elements (e.g., one or more radiant or halogen elements and / or one or more ambient atmosphere gas burners and / or one or more induction heating elements) arranged in relation to or in combination with a base material, generally on the underside of the base material. In particular, the articles according to the present invention have good heat resistance, making them suitable for use with various types of heaters. In particular, the products according to the present invention do not undergo thermal degradation at temperatures above 400°C. Temperatures above 400°C are achievable, especially in applications such as use as a cooking plate.

[0036] If necessary, this method may include cutting operations (generally prior to ceramicization), such as cutting by water jet or mechanical scoring using a scoring wheel, and may also include subsequent shaping operations (such as polishing and chamfering). [Examples]

[0037] Ball drop test: A test has been developed to confirm the impact strength of glass-ceramic plates. In this experiment, a sample of the glass-ceramic substrate is placed on a wooden frame, and a 500g steel ball bearing is dropped from a height of 5 to 195cm (increasing by 5cm increments until the sample breaks).

[0038] The results table includes the following: - The height of the sample that was damaged at the lowest ball drop height; - The height of the sample that was damaged at the highest drop height; and - The average height of all samples.

[0039] A sample that withstood an impact of 195 cm is considered to have broken at 195 cm. This slightly underestimates the average drop height.

[0040] <Example 1> Figure 1: Reference Example 1: 300 x 300 mm 2 Furthermore, a ball drop test was conducted on 10 white glass ceramic plates of the Kerawhite® type, each 6 mm thick.

[0041] Example 1a: 300 x 300 mm 2 Five samples of Kerawhite® type white glass ceramic, each 6 mm thick, were covered on their undersides with three layers of TenCat Laminate 7781-impregnated fabric. Each layer was impregnated with epoxy resin at a density of 300 g / m². 2 It contains glass fibers.

[0042] Next, the samples were subjected to autoclaving.

[0043] Example 1b: 300 x 300 mm 2 The underside of eight samples of Kerawhite® type white glass ceramic, each 6 mm thick, was covered with a single layer of Sicomin CBX401-impregnated fabric. The fabric was impregnated with epoxy resin (IMP503Z) and had a density of 400 g / m². 2 It contains glass fibers.

[0044] Next, the samples were heat-treated at atmospheric pressure and 130°C for 1 hour and 30 minutes.

[0045] Example 1C (comparison): 300×300mm 2 Five samples of Kerawhite® type white glass ceramic, each 6 mm thick, were coated on their undersides with a non-fiber-reinforced Loctite EA9497 type epoxy resin. The resin was polymerized in air without heat treatment.

[0046] <Example 2> Reference Example 2: Similar to Example 1, 300 x 300 mm 2Furthermore, the same white glass ceramic plates of the Kerawhite® type, each with a thickness of 6 mm, are used. In this example, they are deposited on a flat laminated wooden support with a thickness of 28 mm.

[0047] Example 2: The underside of the sample was covered with three layers of TenCat Laminate 7781 type impregnated fabric. Each layer contained glass fibers with a density of 300 g / m2, impregnated with epoxy resin.

[0048] Next, the sample was heat-treated under vacuum at 120°C for 1 hour. During the test, the sample was placed on a 28 mm thick laminated wood support.

[0049] <Example 3> Figure 2: Reference Example 3: A 6mm thick black glass ceramic plate, Kerablack+ (registered trademark) type, is used. In this example, the dimensions are 900 x 600 mm. 2 That is the case.

[0050] Example 3a: The underside of the sample was covered with two layers of GG204T Serge type impregnated fabric. Each layer was impregnated with epoxy resin and had a density of 220 g / m². 2 Contains carbon fiber.

[0051] Next, the samples were treated under vacuum at 120°C for 1 hour.

[0052] Example 3b (comparison): The underside of the sample was covered with two layers of GG204T Serge type impregnated fabric. Each layer was impregnated with epoxy resin, with a density of 220 g / m². 2 Contains carbon fiber.

[0053] Next, the samples were treated at 120°C for 1 hour.

[0054] Example 3c: The underside of another sample is a glass fiber fabric (300g / m²) impregnated with epoxy resin. 2The sample was then covered with a layer of ). The sample was then heat-treated at 130°C and 250 mbar for 1 hour.

[0055] <Example 4> Figure 3: Reference Example 4: A 6mm thick black glass ceramic plate of the same Kerablack+(registered trademark) type as in Example 3 is used. In this example, the dimensions are 300 x 300 mm. 2 That is the case.

[0056] Example 4 (Comparison): The underside of five samples was covered with epoxy adhesive, and then covered with EV200 type glass fiber fabric (not pre-impregnated).

[0057] The fabrics are bonded by hand without heat treatment. The resin is polymerized in the atmosphere.

[0058] result: Figure 1 shows the fracture height (average, minimum, and maximum) for Example 1.

[0059] Figure 2 shows the fracture height (average, minimum, and maximum) for Example 3.

[0060] Figure 3 shows the fracture height (average, minimum, and maximum) for Example 4.

[0061] The following table shows the break height values ​​for each exemplary embodiment obtained during the ball drop test. * This indicates that the plate withstood the ball's impact from this height without sustaining any damage.

[0062] [Table 1]

[0063] Holding the fragments: Examples 1a, 1b, 2, 3a, 3c and Example 4 made it possible to demonstrate that glass-ceramic fragments are retained during fracture. In the reference example, it was never possible to retain fragments when the substrate fractured. In Example 1c (using a non-fiber resin), fragment retention was not possible.

[0064] Damage height: Examples 1a, 1b, 2, and 3a and 3c demonstrate significantly improved resistance to the impact of a dropped 500g ball compared to their respective reference examples. Example 4 (unimpregnated fabric, bonded without heat treatment) does not show a significant improvement in impact strength.

[0065] Articles according to this invention can be advantageously used, in particular, to create novel cooking plates for ranges or hobs, or novel workbenches, consoles, sideboards, central islands, and the like. This disclosure includes the following aspects: <Aspect 1> A glass-ceramic article comprising at least one substrate, for example, a glass-ceramic plate, The substrate is coated in at least one region on its lower surface with a fibrous structure including fibers and a resin matrix. Glass ceramic articles. <Aspect 2> The glass ceramic article according to embodiment 1, characterized in that the structure includes fibers selected from glass fibers, carbon fibers, aramid fibers, quartz fibers, Kevlar fibers, and mixtures thereof. <Aspect 3> The aforementioned structure is 50-1000 g / m² 2 Preferably 100-800 g / m² 2 Comfortable 150-600g / m 2 A glass ceramic article according to embodiment 1 or 2, characterized by having a fiber density. <Aspect 4> The glass ceramic article according to any one of embodiments 1 to 3, characterized in that the resin is selected from thermosetting resins. <Aspect 5> The glass ceramic article according to any one of embodiments 1 to 4, characterized in that the resin is selected from epoxy resin, phenolic resin, or polyimide resin. <Aspect 6> The glass ceramic article according to any one of embodiments 1 to 5, characterized in that the fiber structure comprises one or more layers of a woven, unidirectional or multiaxial structure. <Aspect 7> A glass ceramic article according to any one of embodiments 1 to 6, characterized in that the structure is deposited over at least 40%, preferably at least 50%, and more preferably at least 60% of the surface of the substrate. <Aspect 8> The glass ceramic article according to any one of embodiments 1 to 7, characterized in that the fiber structure has a coefficient of thermal expansion greater than the coefficient of thermal expansion of the glass ceramic plate. <Pattern 9> A glass ceramic article according to any one of embodiments 1 to 8, characterized in that the substrate also includes an enamel coating on a specific portion of its surface. <Aspect 10> The glass ceramic article according to claim 9, characterized in that the enamel coating is disposed on the upper surface of the substrate. <Aspect 11> A method for manufacturing a glass ceramic article, comprising at least one substrate, for example, a plate, made of a glass ceramic material, A fibrous structure containing fibers and a resin matrix is ​​applied onto this substrate. Next, the substrate coated in this manner is subjected to heat treatment under pressure or vacuum (in an autoclave). method. <Aspect 12> The method according to embodiment 11, characterized in that the heat treatment is performed at a temperature of 100 to 200°C, preferably 120 to 150°C. <Aspect 13> The method according to embodiment 11 or 12, characterized in that the heat treatment is performed at a pressure of 100 to 400 millibars, preferably 150 to 350 millibars. <Aspect 14> The method according to any one of embodiments 11 to 13, characterized in that the heat treatment is carried out for 30 minutes to 3 hours, preferably 40 minutes to 2 hours, and more preferably 50 minutes to 1 hour 30 minutes. <Aspect 15> The method according to any one of claims 11 to 14, wherein the article is a cooking plate having a heating region and a control panel, and before applying the fiber structure, the fiber structure is pre-cut to the size of the base material, and gaps are cut into the structure at the heating region and optionally at the control panel.

Claims

1. A method for manufacturing a glass ceramic article, comprising at least one substrate, for example, a plate, made of a glass ceramic material, A fibrous structure containing fibers and a resin matrix is ​​applied onto this substrate. Next, the substrate coated in this manner is subjected to heat treatment under pressure or vacuum (in an autoclave). Here, the fiber structure includes one or more layers of woven, unidirectional, or multiaxial structures. method.

2. The method according to claim 1, characterized in that the heat treatment is performed at a temperature of 100 to 200°C, preferably 120 to 150°C.

3. The method according to claim 1 or 2, characterized in that the heat treatment is performed at a pressure of 100 to 400 millibars, preferably 150 to 350 millibars.

4. The method according to any one of claims 1 to 3, characterized in that the heat treatment is carried out for 30 minutes to 3 hours, preferably 40 minutes to 2 hours, and more preferably 50 minutes to 1 hour 30 minutes.

5. The method according to any one of claims 1 to 4, wherein the article is a cooking plate having a heating region and a control panel, and before applying the fiber structure, the fiber structure is pre-cut to the size of the base material, and gaps are cut into the structure at the heating region and optionally at the control panel.

6. The method according to any one of claims 1 to 5, characterized in that the structure comprises fibers selected from glass fibers, carbon fibers, aramid fibers, quartz fibers, Kevlar fibers, and mixtures thereof.

7. The aforementioned structure has a density of 50 to 1000 g / m². ２ Preferably 100 to 800 g / m ２ More preferably 150 to 600 g / m² ２ The method according to any one of claims 1 to 6, characterized by having the fiber density.

8. The method according to any one of claims 1 to 7, characterized in that the resin is selected from thermosetting resins.

9. The method according to any one of claims 1 to 8, characterized in that the resin is selected from epoxy resin, phenolic resin, or polyimide resin.

10. The method according to any one of claims 1 to 9, characterized in that the structure is deposited over at least 40%, preferably at least 50%, and more preferably at least 60% of the surface of the substrate.

11. The method according to any one of claims 1 to 10, characterized in that the fiber structure has a coefficient of thermal expansion greater than the coefficient of thermal expansion of the glass ceramic plate.

12. The method according to any one of claims 1 to 11, characterized in that the substrate also includes an enamel coating on a specific portion of its surface.

13. The method according to claim 12, characterized in that the enamel coating is disposed on the upper surface of the substrate.

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