Non-fluorinated hybrid sol-gel / silicone resin coating

Abstract

The present invention relates to a coated cooking element (1) for a cookware or electric cookware, comprising a metal substrate (2) coated on at least one surface (2a) with at least the following layers, in order: (3a) a base layer comprising one or more sol-gel compositions, (3b) one or more intermediate layer polymers comprising one or more colorants and, optionally, one or more silicone resins and / or one or more thermoplastic resins, and / or one or more fillers and / or one or more additives, and (3c) a finish layer that comes into contact with food during cooking and comprises one or more silicone resins and, optionally, one or more thermoplastic polymers, and / or one or more fillers and / or one or more additives and / or flakes. The present invention also relates to a method for producing the coated cooking element (1) of the present invention, and to a cookware or electric cookware comprising the coated cooking element (1) of the present invention.

Description

[Technical Field]

[0001] The field of the invention is that of cookware coated with a coating on one of their surfaces, more precisely that of cookware coated with a silicone resin-based coating on these items. [Background technology]

[0002] In the field of cookware, coatings based on fluoropolymers, and in particular polytetrafluoroethylene (PTFE), are commonly known for their non-stick and heat-resistant properties.

[0003] However, these coatings have low mechanical strength.

[0004] US Patent No. 5,949,999 relates to fluoropolymer-based coatings in which the mechanical resistance to abrasion is improved by incorporating organic fillers (SiC) and mineral fillers (Al2O3) into the primer and finish layers of the coating.

[0005] The performance improvements achieved in terms of mechanical strength are satisfactory, but still not optimal.

[0006] Coatings with a hard base layer coated with a sol-gel coating, as described in particular in US Pat. No. 5,629,492 and US Pat. No. 5,629,492, are also known to improve resistance to mechanical shocks, but such coatings do not allow for sufficiently accurate temperature control.

[0007] Fluoropolymer-based coatings are primarily intended for frying pans and pots, but other applications can be envisaged due to their stampability in the field of molding (molds, cake plates, waffle makers, etc.) or small household appliances (rice cookers, fryer inserts, electric crepe makers).

[0008] An alternative to PTFE coatings is the use of so-called "ceramic" coatings, which have been developed through the sol-gel process and the use of tetraethyl orthosilicate (Patent Document 4). These coatings have the particular characteristics of being hard and resistant to mechanical wear, but have a brittle behavior and are less non-stick compared to coatings based on fluoropolymers.

[0009] Furthermore, these coatings lack stampability and are therefore not suitable for molding or small domestic devices.

[0010] In the area of molding (consumer or industrial), fluoropolymer-based coatings are less popular because they have lower heat resistance constraints (up to 220°C), allowing the use of other types of coatings, such as silicone.

[0011] Pure silicone resins are described as being non-sticky and resistant to temperatures above 220-230°C. Instead, they are considered to have poor adhesion to substrates.

[0012] Conversely, silicone polyester resins are extremely popular in the molding industry because they adhere to substrates, are compatible with stamping processes, and are non-stick. However, they decompose at temperatures above 230°C. In fact, the operating temperature range for cookware is between 50 and 250°C, and for induction bases, they can reach temperatures of 300 or 350°C. Therefore, their use is incompatible with the operating temperatures in the cookware industry.

[0013] However, control of the cooking temperature is an essential parameter, necessary for successful cooking and to ensure preservation of the physicochemical properties of the anti-stick coating.

[0014] With this in mind, consumer-oriented cooking start temperature indicators have been developed to indicate, via a color change, the temperature at which the consumer can begin cooking, thus avoiding the possibility of overheating the food.

[0015] The technology is generally based on the use of thermochromic pigments, which change color between room temperature and 250°C depending on the properties of the material.

[0016] Examples of sol-gel coatings are given in US Pat. No. 5,629,499. It should be noted that the sol-gel coatings of the present application do not include silicone resins.

[0017] In addition to thermochromic pigments, other visual differentiating agents can be added to the coating (Patent Documents 6 and 7).

[0018] Patent document 8 describes the development of a two-layer coating based on a silicone resin combined with 0.5-20% (base layer) of a high-temperature thermoplastic material, resulting in a coating that is mechanically resistant, adheres to the substrate, and does not stick. The nature of the thermoplastic resin varies between the base layer (PEEK) and the finish layer (PPS), and it is located primarily in the base layer, ensuring adhesion to the substrate. This patent does not describe a temperature indicator.

[0019] US Pat. No. 5,629,499 proposes a two-layer silicone / thermoplastic coating architecture that is much more concentrated in thermoplastic materials and does not even describe the integration of a colored indicator based on thermochromic pigments. [Prior art documents] [Patent documents]

[0020] [Patent Document 1] International Application Publication No. 2020 / 144051 [Patent Document 2] European Patent No. 233444 [Patent Document 3] European Patent No. 233445 [Patent Document 4] European Patent No. 280676 [Patent Document 5] French Patent Application Publication No. 3110590 [Patent Document 6] European Patent Application Publication No. 2675328 [Patent Document 7] European Patent No. 2412846 [Patent Document 8] European Patent No. 2319631 [Patent Document 9] U.S. Patent Application Publication No. 2022 / 0073785 Summary of the Invention [Problem to be solved by the invention]

[0021] Therefore, improved cooking utensils are needed, in particular those that allow better control, especially visual control, of the cooking of food while ensuring good mechanical strength, good heat resistance, simple and flexible implementation (e.g., in terms of the variety of reagents that can be used) at reasonable industrial costs. [Means for solving the problem]

[0022] A first object of the present invention relates to a coated cooking element (1) for a cooking utensil or electric cooking appliance, comprising a metal substrate (2) coated on at least one surface (2a) with at least the following layers in this order from said metal substrate (2): (3a) a base layer comprising one or more sol-gel compositions; (3b) one or more intermediate layers of one or more colorants, optionally one or more silicone resins; and / or one or more thermoplastic polymers; and / or one or more fillers; and / or an intermediate layer comprising one or more additives; (3c) A finish layer intended to come into contact with food during cooking, consisting of one or more silicone resins, one or more thermoplastic polymers; and / or one or more fillers; and / or one or more additives; and / or flakes, including the finishing layer.

[0023] Another object of the present invention relates to a method for producing the coated cooking element (1) according to the invention, comprising the following successive steps: i. providing a metal substrate including at least one surface to be coated; ii. optionally, pretreating the surface of the metal substrate to be coated; iii. applying a sol-gel based layer to the surface to be coated; iv. Optionally, drying and / or curing the base layer; and v. applying at least one intermediate layer (3b); vi. Optionally, drying said intermediate layer(s) (3b); vii. applying at least one finishing layer (3c); viii. Curing all of the base layer (3a), intermediate layer (3b) and finish layer (3c).

[0024] Another object of the present invention relates to a cooking utensil comprising a coated cooking element according to the invention.

[0025] Another object of the invention relates to an electric cooking appliance comprising a coated cooking element and a heat source configured to heat said coated cooking element, characterized in that said coated cooking element is according to the invention.

[0026] The present invention has at least one of the following advantages. The coating according to the present invention has a thermochromic functionality with clear visibility, with a contrasting color change over a targeted core temperature range, for example around food cooking temperatures for cookware. The coating according to the invention is able to provide good temperature control during the cooking of food, which is necessary not only for health and taste reasons but also for safety and to limit overheating to the point of weakening the coating. -The thermochromic properties of thermochromic pigment compositions are reversible, meaning that after a color change under the influence of heat, the compound returns to its initial state and color when the temperature is reduced, and this color change cycle (reversibility) can be repeated indefinitely. The coating according to the invention has a high thermal stability during temperature increase and is stable up to about 450°C. The coating according to the invention has enhanced mechanical strength due to the presence of the sol-gel based layer compared to a coating comprising only a silicone layer.

[0027] The method of making the coating of the present invention requires lower curing temperatures than coatings containing PTFE-type fluorinated resins, which improves the environmental impact of the coating of the present invention and the energy efficiency of its manufacturing method. [Brief explanation of the drawings]

[0028] [Figure 1] FIG. 1 shows a cooking element according to the invention in which layer (3b) is continuous and covers the entire layer (3a). [Figure 2] FIG. 10 is a diagram of a cooking element according to the invention in which layer (3b) does not cover the entire layer (3a) but forms a decoration. [Figure 3] FIG. 1 is a diagram of a cooking element according to the invention, in which layer (3b) consists of two decorations (i) and (j). [Figure 4] 4A is a pattern distribution map showing adjacent non-overlapping patterns, 4B is a partially overlapping pattern, and 4C is a four-overlapping pattern. [Figure 5] 1 is a diagram of a cooking utensil according to the present invention; [Figure 6] 1 is a diagram of an electric cooking appliance according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0029] definition The term "layer" should be understood to mean, for purposes of the present invention, a continuous layer or a discontinuous layer. A continuous layer (also called a monolithic layer) is a single whole that forms an all-solid block that completely covers the surface on which it is placed. A discontinuous layer (or non-monolithic layer) may include multiple parts and is not a single whole.

[0030] The terms "base layer", "primary layer", "adhesion layer" or "adhesion primer" are understood to mean any layer of the first layer that is applied directly to the substrate (this layer preferably adheres well to the substrate and gives the coating all its mechanical properties, i.e. hardness, scratch resistance).

[0031] The term "finishing layer" or "finish" is understood to mean a continuous, transparent surface layer which protects the decorative layer from mechanical damage and confers its anti-adhesive properties to the coating while allowing the decorative layer to be fully visible. Preferably, the final finishing layer is intended to come into contact with food.

[0032] The term "decoration" or "decorative layer" is understood to mean one or more continuous or discontinuous layers containing a pigment composition. The decoration can be in the form of one or more patterns and one or more colors. The decoration is clearly visible to the user with the naked eye and at a conventional distance for use in household appliances.

[0033] The term "overlapping layers" is understood to mean partially or completely superimposed layers. These layers may be in the form of partially overlapping patterns, for example concentric disks.

[0034] The term "adjacent layers" is understood to mean layers that are not superimposed. These layers may be in the form of identical or different non-overlapping patterns, preferably uniformly distributed.

[0035] For the purposes of the present invention, the term "sol-gel composition" is understood to mean a composition synthesized by the sol-gel route from a solution based on precursors in the liquid phase that are converted into a solid at low temperature by a series of chemical reactions (hydrolysis and condensation). The composition thus obtained may be organo-mineral or entirely mineral.

[0036] For the purposes of the present invention, the term "organo-mineral composition" is intended to mean a composition whose network is essentially inorganic but which contains organic groups, in particular due to the precursors used and the curing temperature of the coating. Such compositions are generally obtained by a sol-gel process.

[0037] For the purposes of the present invention, the term "fully inorganic composition" is understood to mean a composition composed of fully inorganic materials, without any organic groups. Such compositions are generally obtained by a sol-gel process having a curing temperature of at least 400°C, or from precursors of the tetraethoxysilane (TEOS) type, having a curing temperature that may be below 400°C.

[0038] The term "reference temperature pigment composition" is understood to mean a composition containing a pigment that, at a given temperature, indicates to the user that the optimum use temperature has been reached. This indication is made by comparing the color of the thermochromic pigment composition with the color of the reference temperature pigment composition. The optimum use temperature is reached either when the colors are identical or when the colors are visually very different.

[0039] A "reference temperature pigment composition" may include a pigment having: - at the optimum temperature of use, has the same color as the thermochromic pigment composition, *This pigment has the same color at room temperature as the thermochromic pigment composition at its optimum use temperature and does not change color with temperature. * Or, the pigment has a color different from the color of the thermochromic pigment composition at room temperature, and changes to the same color as the thermochromic pigment composition at the optimum use temperature, -Whether this pigment changes color with temperature changes or not, a color that is very different from the color of the thermochromic pigment composition at the optimum use temperature.

[0040] The optimum use temperature can be achieved when the color of the reference temperature pigment composition corresponds to the color shown in the user guide for the household product containing the coating of the present invention or the color shown on a color scale provided to the user with the item.

[0041] The reference temperature pigment composition can be, for example, a cooking reference temperature pigment composition or an indication of the risk of overheating. The reference temperature pigment composition is thermochromic or heat stable.

[0042] For the purposes of this invention, the term "thermochromic semiconductor" should be understood to mean an inorganic or organic compound that exhibits a reversible color change with increasing temperature. The gradual and reversible thermochromism of these semiconductor compounds is associated with a decrease in the band gap width of the semiconductor due to the expansion of the material. Indeed, the periodicity of the anion-cation network leads to the concentration of energy levels into energy bands. The higher-energy filled energy band is called the valence band, while the lower-energy empty energy band is called the conduction band. Between these two bands is a forbidden band, called the gap. The color of a semiconductor material can result from the presence of a charge transfer corresponding to the passage of an electron from the valence band to the conduction band on the same atom, or, more commonly, from the passage of an electron from an anion orbital to a cation orbital (interatomic photon absorption).

[0043] In the application areas envisaged for the present invention, optimum conditions are reached when the coating reaches temperatures suitable for cooking food, preferably 100-250°C.

[0044] For the purposes of the present invention, "thermochromic pigment or pigment composition" should be understood to mean a pigment or pigment composition that changes color as a function of temperature in a given temperature range, this change being reversible. This color change is visible to the user with the naked eye and can be used at conventional distances.

[0045] The term "thermostable pigment" is understood to mean a pigment that does not exhibit a color change when exposed to an elevated temperature within a given temperature range, or that exhibits a color change when exposed to an elevated temperature within a given temperature range that is so low that it is not visible to the user with the naked eye and at a conventional distance.

[0046] Preferably, the heat stable pigment has a color difference ΔE between 25°C and 200°C * is less than 10 and ΔE * is defined by the CIE 1976 formula in the CIELAB color space.

[0047]

number

[0048] (L1 * , a1 * and b1 * is the L of the compound at room temperature * a * Characterize the b value, L2 * , a2 * and b2 * is the L of the compound at 200 °C * a * Characterize the b value.)

[0049] The expression "identical in color" shall mean indistinguishable by the user with the naked eye and at conventional use distances.

[0050] "Coating" is understood to mean any layer that covers a metal substrate and adheres to this substrate.

[0051] "Silicone resin-based coating" is understood to mean a coating that contains one or more silicone resins in one or more of its layers. The obtained coating according to the present invention is advantageously solid. "Solid" is understood to mean the properties of a sticky material that is insoluble in water, in common solvents, in food ingredients such as aqueous or fat mixtures, and the material can be very hard or very flexible, such as elastomers.

[0052] For the purposes of the present invention, the expression "cookware" should be understood to mean an object intended for cooking. For this purpose, it is intended to be subjected to a heat treatment. Thus, the cookware comprises an "inner surface" or "cooking surface", the coating of which is intended to come into contact with food during cooking.

[0053] The expression "object intended to undergo a heat treatment" should be understood for the purposes of the present invention to mean an object that can be heated by an external heating system, such as a frying pan, a saucepan, a sauté pan, a wok, a barbecue grill, etc., and that is capable of transferring the thermal energy supplied by this external heating system to a material or food that comes into contact with said object.

[0054] The expression "electric cooking appliance" should be understood for the purposes of the present invention to mean a heating object having its own heating system, such as an electric crepe maker, an electric raclette maker, an electric fondue maker, an electric grill, a hot plate, an electric cooker, a bread maker, and an electric pressure cooker.

[0055] In the present invention, the weight percentages are expressed as dry weights, i.e. without solvent.

[0056] The present invention relates to a coated cooking element (1) for a cooking utensil or electric cooking appliance, comprising a metal substrate (2) coated on at least one surface (2a) with at least the following layers in the order listed: (3a) a base layer comprising one or more sol-gel compositions; (3b) one or more intermediate layers of one or more colorants, and optionally - one or more silicone resins; and / or - one or more thermoplastic polymers; and / or - one or more fillers; and / or an intermediate layer comprising one or more additives; (3c) A finish layer intended to come into contact with food during cooking, consisting of one or more silicone resins, - one or more thermoplastic polymers; and / or - one or more fillers; and / or - one or more additives; and / or - Flakes, including the finishing layer.

[0057] Advantageously, layers (3a), (3b) and (3c) form a coating (3) that coats the metal substrate (2), said coating (3) having anti-adhesion properties and forming an anti-adhesion coating.

[0058] Advantageously, the layer (3a) is in contact with the metal substrate (2) through one of its faces, via its face (2a).

[0059] At least one coated surface (2a) of the metal substrate is therefore the cooking surface, in other words the coating of the cooking element (1) according to the invention is intended to come into contact with food.

[0060] Advantageously, the top layer (3c) is in contact with the food product through one of its faces, thus forming the cooking surface (5).

[0061] The coating of the cooking element (1) according to the present invention does not contain a fluoropolymer, in other words, said coating is devoid of a fluoropolymer.

[0062] Advantageously, the thickness of the layer (3a) is comprised between 5 μm and 100 μm, preferably between 8 μm and 70 μm, more preferably between 20 and 70 μm, and particularly preferably between 10 μm and 30 μm.

[0063] Advantageously, the thickness of the layer (3b) is comprised between 1 μm and 100 μm, preferably between 2 μm and 30 μm, particularly preferably between 3 μm and 10 μm.

[0064] Advantageously, the thickness of the layer (3c) is comprised between 0.05 μm and 100 μm, preferably between 0.08 μm and 20 μm, particularly preferably between 0.1 μm and 10 μm.

[0065] According to one embodiment, the thickness of the layer (3c) is comprised between 0.1 μm and 2 μm, preferably between 0.2 μm and 1.5 μm.

[0066] According to another embodiment, the thickness of the layer (3c) is comprised between 10 μm and 100 μm, preferably between 20 μm and 85 μm, particularly preferably between 30 μm and 70 μm.

[0067] According to a particular embodiment, the thickness of the layer (3a) is comprised between 5 μm and 100 μm, typically between 20 μm and 70 μm, the thickness of the layer (3b) is comprised between 1 μm and 100 μm, typically between 2 μm and 30 μm; The thickness of the layer (3c) is comprised between 0.05 μm and 100 μm, preferably between 0.08 μm and 20 μm.

[0068] The coating of the cooking element (1) according to the invention may optionally comprise one or more layers (3a) sandwiched between layer(s) (3a) and layer(s) (3b) or between layer(s) (3a) and layer(s) (3c) of one or more silicone resins, optionally - one or more thermoplastic polymers; and / or - one or more fillers; and / or - one or more additives.

[0069] Advantageously, the thickness of the layer (3ab) is comprised between 0.05 μm and 100 μm, preferably between 0.08 μm and 20 μm, particularly preferably between 0.1 μm and 10 μm.

[0070] Metal substrate Advantageously, said metal substrate (2) is a substrate made of aluminium, stainless steel, cast iron or cast aluminium, iron, titanium or copper.

[0071] For the purposes of the present invention, aluminium is understood to mean a metal consisting of 100% aluminium or an aluminium alloy.

[0072] Advantageously, the metal substrate (2) is an aluminum substrate, a stainless steel substrate, or a multilayer metal substrate. The metal substrate (2) may also be a two-layer or three-layer substrate, the multilayer(s) being obtained, for example, by co-lamination, by solid-state bonding, or by hot or cold impact bonding.

[0073] Preferably, the metal substrate (2) comprises alternating layers of metals and / or metal alloys.

[0074] According to one embodiment, the metal substrate (2) is an aluminum alloy substrate, a stainless steel substrate, or a multilayer metal substrate having an aluminum alloy or stainless steel surface (2a).

[0075] Preferably, the metal substrate (2) is an aluminum substrate.

[0076] Advantageously, the thickness of the metal substrate (2) is comprised between 0.5 mm and 10 mm.

[0077] Advantageously, the face (2a) of the metal substrate (2) has previously undergone a surface treatment making it possible to improve the adhesion of the coating to said substrate.

[0078] According to one embodiment, the surface of face (2a) of the metal substrate (2) has undergone a surface treatment, said surface treatment being chemical etching, brushing, hydration, sandblasting, shot blasting, physicochemical treatment of plasma or corona or laser type, chemical activation, or a combination of these different techniques.

[0079] Advantageously, the surface (2a) of the substrate to which the coating (3) according to the invention is applied can be treated to increase its specific surface; in the case of aluminum substrates, this treatment can be carried out by anodizing (creating tubular alumina structures), by chemical etching, by sandblasting, by brushing, by shot blasting, or by adding material by techniques such as thermal spraying (flame, plasma or arc spraying). Other metal substrates can also be polished, sandblasted, brushed, microbead blasted, or can receive additional material by techniques such as thermal spraying (flame, plasma or arc spraying).

[0080] Metal substrates that can be used in the present invention advantageously include optionally polished, brushed, sandblasted, shot blasted or microbead blasted, anodized or non-anodized aluminum substrates, optionally polished, brushed, sandblasted or microbead blasted, anodized or non-anodized aluminum alloy substrates, optionally polished, brushed, sandblasted or microbead blasted, steel substrates, optionally polished, brushed, sandblasted or microbead blasted, stainless steel substrates, cast steel, aluminum or iron substrates, optionally hammered or polished copper substrates.

[0081] Advantageously, the substrate may be chosen from substrates comprising ferritic stainless steel / aluminium / austenitic stainless steel layers, substrates comprising stainless steel / aluminium / copper / aluminium / austenitic stainless steel layers, cast aluminium lined with an outer stainless steel bottom, a shell made of aluminium or an aluminium alloy, metal co-laminate substrates, for example two-layer co-laminate substrates comprising a stainless steel layer (for example intended to constitute the inner surface of the item) and an anodised or non-anodised layer of aluminium or an aluminium alloy intended to constitute the outer surface of the item.

[0082] Advantageously, the arithmetic mean roughness Ra of the surface of the face (2a) of the metal substrate (2) is 1 μm or more.

[0083] The arithmetic mean roughness Ra is measured using a profilometer according to ISO 4287. Ra represents the arithmetic mean of deviations from the mean. Surface topography can be studied using optical metrology devices, such as profilometers equipped with probes equipped with fine diamond-tipped styluses, or Altisurf®, whose confocal chromaticity sensors allow for non-contact measurements. Studying this surface topography makes it possible to define the mean arithmetic roughness Ra.

[0084] Sol-gel compositions Sol-gel compositions, also called SG compositions, are organo-mineral or completely mineral sol-gel compositions. These compositions, synthesized by the sol-gel route from metal polyalkoxylate-type precursors, preferably generally have a hybrid silica network with grafted alkyl groups. Sol-gel (SG) compositions are generally obtained from sol-gel (SG) mixtures containing at least one colloidal metal oxide and at least one metal alkoxide-type precursor.

[0085] The metal oxide is preferably a colloidal metal oxide selected from colloidal silica and / or colloidal alumina.

[0086] Preferably, a metal alkoxide is used selected from the group consisting of: -General formula M1 (OR1) n the corresponding precursor; -General formula M2 (OR2) (n-1) a precursor corresponding to R2'; and -General formula M3 (OR3) (n-2) a precursor corresponding to R3'2, R1, R2, R3 or R3′ represents an alkyl group; R2' represents an alkyl or phenyl group; n is an integer corresponding to the maximum valence of metal M1, M2, or M3; M1, M2 or M3 represents a metal selected from Si, Zr, Ti, Sn, Al, Ce, V, Nb, Hf, Mg or Ln.

[0087] Advantageously, the metal alkoxide of the SG mixture is an alkoxysilane.

[0088] Alkoxysilanes that can be used in the SG mixture of the method of the present invention include, among others, methyltrimethoxysilane (MTMS), tetraethoxysilane (TEOS), methyltriethoxysilane (MTES), dimethyldimethoxysilane, and mixtures thereof.

[0089] Preferably, the alkoxysilanes MTES and TEOS are used, as they have the advantage of not containing methoxy groups. In fact, methoxy hydrolysis leads to the formation of methanol in sol-gel formulations, which, given its toxicological classification, requires additional precautions during application. Conversely, hydrolysis of ethoxy groups produces only ethanol, which has a more favorable classification and therefore creates less restrictive application requirements for sol-gel coatings.

[0090] The formation of this SG composition consists in mixing an aqueous composition A containing a colloidal metal oxide with a solution B containing a metal alkoxide, advantageously in a ratio of 40 to 75% by weight of the aqueous composition relative to the weight of the sol-gel composition (A+B), so that the amount of colloidal metal oxide corresponds to 5 to 50% by weight of the sol-gel composition (A+B) in the dry state.

[0091] The aqueous composition A may also comprise a solvent, in particular a solvent comprising at least one alcohol, which solvent will hereinafter be referred to as "alcoholic solvent".

[0092] The alcohol is preferably a C1-C6 alcohol. A C1-C6 alcohol refers to a saturated, linear or branched hydrocarbon chain having 1 to 6 carbon atoms and containing a hydroxyl group (-OH) attached to a carbon atom. Examples include ethanol, n-propanol, and isopropanol.

[0093] Aqueous composition A may also comprise at least one silicone resin, in particular as defined below.

[0094] The aqueous composition A may also contain pigments, especially as defined below.

[0095] Aqueous composition A may also contain mineral fillers, especially as defined below.

[0096] Aqueous composition A may also contain pyrogenic silica, the function of which is to adjust the viscosity of the sol-gel composition and / or the gloss of the dried coating.

[0097] Aqueous composition A typically comprises: i) 5 to 50 wt. % of at least one colloidal metal oxide, based on the total weight of aqueous composition A; ii) 0 to 20% by weight, relative to the weight of composition A, of a solvent comprising at least one alcohol; iii) optionally 0.05 to 3 wt. % of at least one silicone oil, relative to the total weight of the aqueous composition A; iv) 5-30% pigment; v) 2-30% mineral fillers.

[0098] Solution B may further comprise a Bronsted or Lewis acid. Advantageously, the precursors of solution B of the metal alkoxide type are mixed with an organomineral Lewis acid representing between 0.01 and 10% by weight of the total weight of solution B.

[0099] Specific examples of acids that can be used for mixing with the metal alkoxide precursor are acetic acid, citric acid, ethyl acetoacetate, hydrochloric acid, or formic acid.

[0100] Solution B may also contain a solvent, in particular a solvent containing at least one alcohol.

[0101] Solution B may also comprise at least one silicone resin, in particular as defined below.

[0102] Solution B may also contain flakes, preferably metal flakes, in particular as defined below.

[0103] According to an advantageous embodiment of the method of the invention, solution B may comprise a mixture of one of the alkoxysilanes defined above and an aluminium alcoholate.

[0104] According to a preferred embodiment, the sol-gel composition is synthesized by a sol-gel method from a sol-gel mixture comprising or consisting of a precursor of the metal alkoxide type, optionally a colloidal metal oxide precursor; - a solvent, preferably alcoholic; - a Brønsted or Lewis acid, preferably chosen from acetic acid, citric acid, ethyl acetoacetate, hydrochloric acid or formic acid, and - additives selected from at least one silicone resin, at least one pigment, at least one advantageous mineral filler, flakes, in particular metal flakes, pyrogenic silica, or mixtures thereof; - or a mixture thereof.

[0105] Thus, the SG composition is preferably mineral or organomineral and may comprise at least one silicone resin, at least one pigment, at least one advantageous mineral filler, flakes, in particular metal flakes, pyrogenic silica, or mixtures thereof. The SG composition may also comprise a solvent, in particular a trace amount of an alcohol solvent, and / or an acid, preferably an acid selected from acetic acid, citric acid, ethyl acetoacetate, hydrochloric acid, or formic acid.

[0106] Silicone resin In the present text, the term "silicone resin" is used interchangeably to refer to silicone before or after crosslinking. In the present text, the term "silicone" refers to an organopolysiloxane material. Crosslinking is a process that converts silicone into an insoluble material, for example, by polyaddition, polycondensation, or dehydrogenation. Crosslinking is carried out using precursors, typically silicone oils or resins, that crosslink to obtain a three-dimensional network that forms the material referred to in the description as silicone resin.

[0107] This crosslinking can be achieved by thermal activation or chemical activation using a catalyst such as platinum.

[0108] The silicone resin may be obtained from a precursor, such as a crosslinkable oil or resin, soluble in a solvent or in an emulsion in water, preferably selected from silicon hydrides, silicone oil resins containing at least one vinyl group (-CH=CH2), silicone resins or silicone polyester resins (copolymers) containing at least one alkoxy group, such as methoxy or ethoxy, and / or silicone or silicone-polyester resins (copolymers) containing at least one alkoxy group, in particular ethoxy or hydroxy groups, and mixtures thereof. These precursors have the ability to crosslink to obtain silicone resins characterized by their insolubility and substantially solid form.

[0109] Advantageously, these precursors are polymers or oligomers in the form of silicone oils with different branching degrees, or silicone resins with different crosslinking degrees, such as silicone-polyester, silicone-alkyd, silicone-polyurethane or silicone-epoxy resins, or copolymers of silicone resins, or mixtures of silicone oils, silicone resins and copolymers of silicone resins. The silicon atoms can be substituted with alkyl (especially methyl) or aryl (especially phenyl) groups or mixtures thereof. The oils or resins preferably contain one or more (two, three or more) hydroxy or alkoxy functional groups (especially methoxy, ethoxy, butoxy) as substituents of the silicon atoms.

[0110] Advantageously, the silicone resins obtained after crosslinking, i.e. after crosslinking, of their precursors are selected from the group consisting of methylsilicone resins and / or phenylsilicone resins and / or methylphenylsilicone resins, methylsilicone polyester resins (copolymers), phenylsilicone polyester resins (copolymers), methylphenylsilicone polyester resins (copolymers), silicone alkyd resins (copolymers), modified silicone resins and mixtures thereof.

[0111] Advantageously, the silicone resin is selected from the group consisting of methylsilicone resins and / or phenylsilicone resins and / or methylphenylsilicone resins, methylsilicone polyester resins (copolymers), phenylsilicone polyester resins (copolymers), methylphenylsilicone polyester resins (copolymers), silicone alkyd resins (copolymers), modified silicone resins and mixtures thereof.

[0112] The silicone resin may be obtained from a precursor chosen in particular from silicon hydrides, silicone resins containing at least one vinyl group (-CH=CH), silicone-polyester resins (copolymers) containing at least one methoxy group, and / or silicone-polyester resins (copolymers) containing at least one ethoxy group, and mixtures thereof.

[0113] The silicone resin of the single layer (3) forms a network that can be composed of a combination of four simple organosiloxane units, designated M, D, T and Q, depending on the degree of substitution of silicon atoms with oxygen, as described in the table below, where R is an organic substituent as described below.

[0114] [Table 1]

[0115] Organopolysiloxane materials or polymers are obtained by crosslinking precursors, which can be monomers or polymers, or by crosslinking intermediates, which can be oligomers. Organopolysiloxane polymers can also be obtained from mixtures of these different types of precursors. The crosslink density is higher when the network contains more T and Q units than D units. The distribution of M, D, T, and Q units depends on the chemical structure of the precursor, particularly the distribution of M, D, T, and Q within the precursor.

[0116] The polymeric precursors are organopolysiloxanes. These macromolecules are formed from M, D, T, and / or Q units as listed in the Tables, where R is independently an alkyl group, particularly methyl, or an aryl group, particularly phenyl, and different types of R can be present on the same macromolecule.

[0117] Organopolysiloxanes can be either linear or slightly branched (mostly D groups), or branched or highly branched (mostly T and Q groups). Linear or slightly branched organopolysiloxanes are generally liquid, more or less viscous at room temperature, and are called silicone oils. Branched or highly branched (pre-crosslinked) organopolysiloxanes form networks on the scale of individual macromolecules and are called silicone resins. At room temperature, the resins are in substantially solid form or, provided they have a fairly low molecular weight, in liquid form, particularly in the form of a solution in a solvent or in the form of an aqueous emulsion. They can be copolymerized with non-silicon-containing organic polymers or oligomers, especially those selected from polyester, acrylic, alkyd, polyurethane, and epoxy resins.

[0118] When crosslinking is by hydrolysis-polycondensation, it is carried out by means of reactive hydroxy or alkoxy functional groups, especially methoxy, ethoxy or butoxy, present on the organopolysiloxane.

[0119] When the crosslinking is an addition polymerization (or hydrosilylation), it is carried out by reaction between vinyl reactive functional groups (-CH=CH2) present on one of the organopolysiloxanes and silicon hydride (Si-H) reactive functional groups present on the other organopolysiloxane mixed with the first one.

[0120] All of these reactive functional groups are present in a quantity of at least one on each organopolysiloxane, and can be present in quantities of two, three, or more, as long as the molecular structure allows. Silicone oils containing at least one reactive function are called "reactive oils." The reactive functional groups can be at the end of the macromolecular chain or distributed along the chain.

[0121] The silicone polyester resins in particular have a silicone / polyester weight ratio, for example 90 / 10, 80 / 20, 70 / 30, 60 / 40, 50 / 50, 40 / 50, 30 / 70, 20 / 80, 10 / 90, advantageously between 80 / 20 and 50 / 50.

[0122] Linear PDMS silicone oils, either pure or pre-emulsified in water, are characterized by their molecular weight, which is a direct function of the viscosity of the pure oil. They are then characterized by the presence or absence of reactive functional groups, such as hydroxyl functional groups (silanols) on silicon atoms, their number, and their position on the molecular chain. For example, reactive oils with viscosities between 50 and 20,000 MPa·s, especially between 300 and 5,000 MPa·s, may be used, and they have at least one reactive functional group, preferably at least two, which may be located at the ends of the chain.

[0123] Polymer precursors that react by addition polymerization can include, for example, polymethylhydrosiloxanes, vinylmethylsiloxanes, (especially linear) vinyl-terminated polydimethylsiloxanes (PDMS), vinyl-terminated diphenylsiloxane-dimethylsiloxane copolymers, hydride-terminated polydimethylsiloxanes, hydride-terminated polyphenylmethylsiloxanes, cyclic vinylmethylsiloxanes, vinyl-MQ resins, trimethylsilyl-terminated polymethylhydrosiloxanes, methylhydrosiloxane and trimethylsiloxane-terminated dimethylsiloxane copolymers, hydrogenated MQ resins, and the like, as well as combinations thereof.

[0124] The polymeric precursors reacted by hydrolysis-polycondensation, whether silicone resins or silicone oils, can include, for example, poly(methylsilsesquioxane), poly(propylsilsesquioxane), poly(phenylsilsesquioxane), polydimethylsiloxane (PDMS), trimethylsilyl-terminated polydimethylsiloxane (PDMS), hydroxyl-terminated polydimethylsiloxane (PDMS), silanol-terminated polydimethylsiloxane (PDMS), silanol-terminated polyphenylsiloxane (PDMS), silanol-terminated diphenylsiloxane-dimethylsiloxane copolymer, poly(2-acetoxyethylsilsesquioxane), organically modified alkoxysilanes and their oligomers, and all similar macromolecules thereof, and mixtures thereof.

[0125] Organopolysiloxane materials or polymers can also be obtained by crosslinking a mixture of one or more monomer precursors and one or more polymer precursors, as described above, and one or more oligomer precursors, which may be linear, branched, or cyclic. These oligomer precursors have a lower molecular weight than the polymer precursors. To promote a high crosslink density in the final organopolysiloxane polymer, polymers and / or oligomer precursors containing more than two, preferably many more than two, reactive functional groups can be added to the mixture as a co-binder.

[0126] The monomers, oligomers and / or polymer precursors, especially silicone resins, whether copolymerized with the organic polymer, act as polymeric binders to obtain a solid organopolysiloxane polymer in combination with the thermoplastic resin of each layer.

[0127] Silicone oil-type organopolysiloxane precursors can be considered additives when added in small amounts (typically 0.1-5% dry) to the overall formulation of a layer independently of other ingredients for the formation of a solid organopolysiloxane polymer.

[0128] Crosslinking may require a catalyst: In the case of crosslinking of organopolysiloxanes by hydrolysis-polycondensation, the formulation may contain metal catalysts such as platinum, tin, zinc, zirconium and cerium-based metal complexes, in particular platinum-cyclovinylmethyl-siloxane complexes, tin ethylhexanoate, zinc ethylhexanoate, zirconium ethylhexanoate, cerium ethylhexanoate and tin dibutyl laurate.

[0129] When crosslinking organopolysiloxanes by hydrosilylation, the addition of a catalyst may be necessary: this may be, for example, a platinum or suitable platinum-based catalyst such as Karstedt's catalyst or Ashby's catalyst.

[0130] A crosslinker may be present, for example a crosslinker having a Si-H bond.

[0131] According to one embodiment, the proportion of silicone resin in layer (3b) is greater than or equal to 20% by weight, respectively, relative to the total weight of layer (3b).

[0132] According to another embodiment, the proportion of silicone resin in layer (3b) is greater than or equal to 40% by weight, respectively, relative to the total weight of layer (3b).

[0133] According to yet another embodiment, the proportion of silicone resin in layer (3b) is greater than or equal to 50% by weight, respectively, relative to the total weight of layer (3b).

[0134] According to one embodiment, the proportion of silicone resin in layer (3c) is greater than or equal to 20% by weight, respectively, relative to the total weight of layer (3c).

[0135] According to another embodiment, the proportion of silicone resin in layer (3c) is greater than or equal to 40% by weight, respectively, relative to the total weight of layer (3c).

[0136] According to yet another embodiment, the proportion of silicone resin in layer (3c) is greater than or equal to 50% by weight, respectively, relative to the total weight of layer (3c).

[0137] According to one embodiment, the proportion of silicone resin in each layer (3ab) is greater than or equal to 20% by weight relative to the total weight of layer (3c).

[0138] According to another embodiment, the proportion of silicone resin in layer (3ab) is greater than or equal to 40% by weight, respectively, relative to the total weight of layer (3ab).

[0139] According to yet another embodiment, the proportion of silicone resin in layer (3ab) is equal to or greater than 50% by weight, respectively, relative to the total weight of layer (3ab).

[0140] thermoplastic polymer Advantageously, the thermoplastic polymer is selected from the group consisting of aromatic thermoplastic polymers such as polyaryletherketones (PAEKs), poly(arylethersulfones) (PAESs), poly(arylene sulfides) (PASs) or poly(phenylene oxides) (PPOs), liquid crystal polymers, heterocyclic thermoplastic polymers, and mixtures thereof.

[0141] PAEK Advantageously, the polyaryletherketone (PAEK) is selected from the group consisting of polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetheretherketoneketone (PEEKK) and polyetherketoneetherketoneketone (PEKEKK), and in a particularly preferred manner is PEEK.

[0142] Other aromatic thermoplastic polymers Suitable examples of the aromatic thermoplastic polymer(s) according to the present invention include poly(phenylene oxide) (PPO), poly(aryl ether sulfone) (PAES) polymers, in particular polyether sulfone (PES), polyphenylene ether sulfone (PPSU), poly(arylene sulfide) (PAS), and in particular polyphenylene sulfide (PPPS), liquid crystal polymers, and mixtures thereof.

[0143] Heterocyclic Thermoplastic Polymers Suitable examples of heterocyclic thermoplastic polymers according to the present invention include polyetherimide (PEI), polyimide (PI), polyamideimide (PAI) and polybenzimidazole (PBI), or mixtures thereof.

[0144] Advantageously, the thermoplastic polymer is selected from the group consisting of polyethersulfone (PES), polyphenylene ether sulfone (PPSU), polyamideimide (PAI), polyimide (PI), poly(phenylene oxide) (PPO), poly(arylene sulfide) (PAS), polyetherimide (PEI), polybenzimidazole (PBI), liquid crystal polymer (LCP), polyphenylene sulfide (PPS), polyaryletherketone (PAEK) including polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetheretherketoneketone (PEEKK), polyetherketoneetherketoneketone (PEKEKK), and mixtures thereof.

[0145] According to one variant, the PAEK is used in the form of a suspension, the PAEK particles in the PAEK suspension having a particle size with a dD50 of approximately 10 μm to 15 μm.

[0146] Advantageously, the nature of the thermoplastic polymer(s) in layers (3b) and (3c) may be the same or different.

[0147] Advantageously, layer (3b) comprises one or more thermoplastic polymers, preferably in an amount less than 30% by weight of said layer, preferably less than 20%.

[0148] Advantageously, layer (3c) comprises one or more thermoplastic polymers, preferably representing less than 50% by weight of said layer, preferably less than 40%.

[0149] Advantageously, layer (3ab) comprises one or more thermoplastic polymers, preferably less than 50% by weight of said layer, preferably less than 40%.

[0150] According to one embodiment, layers (3b) and (3c) comprise one or more thermoplastic polymers, the proportion of thermoplastic polymer in layer (3c) being preferentially greater than the proportion of thermoplastic polymer in layer (3b).

[0151] According to another embodiment, layers (3b) and (3c) comprise one or more thermoplastic polymers, the proportion of thermoplastic polymer in layer (3b) being greater than the proportion of thermoplastic polymer in layer (3c).

[0152] Filler Fillers for the purposes of the present invention make it possible to provide mechanical reinforcement and also to provide hydrophobic properties while improving the mechanical strength and thermal conductivity of the coating.

[0153] Fillers do not have the sole function of providing color to a coating, but can contribute to it.

[0154] The presence of a filler with good thermal conductivity makes it possible to compensate for the low thermal conductivity of the PAEK polymer.

[0155] Advantageously, the fillers are selected from the group consisting of ceramic fillers (such as SiO2) and / or mineral and / or metallic fillers (Al2O3, TiO2, etc.) and / or silica and / or diamond particles.

[0156] Preferably, the filler is selected from the group consisting of metal oxides, metal carbides, metal oxynitrides, metal nitrides, and mixtures thereof.

[0157] Advantageously, said metal is a transition metal, such as at least one of the elements chosen from B, Ni, Ti, Zr or Hf.

[0158] More preferably, the filler is selected from the group consisting of: Reinforcing fillers: organic or inorganic hard fillers. The inorganic hard fillers are preferably particles of silicon carbide or alumina or zirconia or graphite or ceramics or carbonates or alumina hydrate, aluminium hydroxide or one or more metal oxides, graphite, graphene.

[0159] other reinforcing fillers selected from metal oxides: silica, mica, lamellar fillers, clays such as montmorillonite, sepiolite, gypsum, kaolinite and laponite, zinc dioxide, quartz, and zirconium phosphate, alumina, zirconia, zinc oxide, copper oxide, iron oxide; - a filler chosen from reinforcing fibers: glass or carbon or aramid fibers.

[0160] Conductive fillers containing transition metal carbides and / or transition metal nitrides, characterized in that the transition metal is at least one element selected from B, Ni, Ti, Zr or Hf; For example, tertiary boron nitride, diamond particles, metal particles, - Lamellar fillers that can impart lubricating properties such as clay, graphene or graphite.

[0161] Preferred fillers in combination with the organopolysiloxane are: - reinforcing fillers: silica or carbonates, with a filler content of minimum 10-15% by weight and maximum 60% by weight; Alumina, alumina hydrate, aluminum hydroxide, -d50<0.1μm and BET specific surface area>30m 2 / g, preferably 30 to 500m 2 / g of silica (precipitated or pyrogenic), -or mixtures of quartz and silica, diatomaceous earth or crushed quartz, titanium, mica, talc, kaolin, barium sulfate, hydrated lime, zinc oxide, expanded vermiculite, unexpanded vermiculite, calcium carbonate, etc.

[0162] More preferably, the filler is selected from the group consisting of alumina, silicon carbide, tungsten carbide, boron nitride, quartz, and mixtures thereof.

[0163] Advantageously, the average diameter d50 of the fillers is comprised between 0.1 and 50 μm, more advantageously between 5 and 15 μm.

[0164] Advantageously, the proportion of filler in the layer is comprised between 0.5 and 30% by dry weight, preferably between 5 and 20%, relative to the total weight of said layer after hardening.

[0165] Advantageously, the proportion of filler in layer (3b) is less than 10% by weight relative to the total weight of said layer.

[0166] Advantageously, the proportion of filler in the layer(s) (3ab) is less than 10% by weight relative to the total weight of said layer.

[0167] Advantageously, the proportion of filler in layer (3c) is less than 10% by weight relative to the total weight of said layer.

[0168] Advantageously, the proportion of filler in layers (3b) and (3c) is less than 10% by weight, relative to the total weight of layer (3b) / relative to the total weight of layer (3c), respectively.

[0169] additives Advantageously, said additives are selected from the group consisting of antifoaming agents, dispersants, wetting agents, thickeners, pH adjusters, and reactive silicone oils.

[0170] The antifoaming agent is preferentially selected from the group consisting of mineral oils, diols, hydrocarbons, glycerides, oxiranes and emulsifying fatty acids.

[0171] The surfactants are preferentially selected from the group consisting of glycol ethers, ethoxylated alcohols excluding alkylphenol ethoxylates (APE), and gemini surfactants.

[0172] The dispersant is preferentially selected from the group consisting of anionic dispersants such as fatty acid derivatives.

[0173] Said thickener is preferentially selected from the group consisting of acrylic or polyurethane copolymers, cellulose and pyrogenic silica.

[0174] The pH adjuster is preferably selected from the group consisting of ammonia, amines (such as triethylamine and triethanolamine), hydroxides (such as sodium hydroxide and potassium hydroxide), and carbonates.

[0175] Advantageously, the proportion of additives in layer (3a) is less than 20% by weight relative to the total weight of said layer.

[0176] Advantageously, the proportion of additives in layer (3b) is less than 20% by weight relative to the total weight of said layer.

[0177] Advantageously, the proportion of additives in layer (3c) is less than 20% by weight relative to the total weight of said layer.

[0178] Advantageously, the proportion of additives in layers (3a), (3b) and (3c) is less than 20% by weight relative to the total weight of layers (3a) / (3b) / (3c).

[0179] Advantageously, the proportion of additives in layer (3ab) is less than 20% by weight relative to the total weight of said layer.

[0180] coloring agent Advantageously, the colorant is selected from the group consisting of thermochromic pigments, heat stable pigments, flakes, preferably holographic flakes, and mixtures thereof.

[0181] Advantageously, the proportion of colorant in layers (3b) and (3c) is between 0.5 and 50% by dry weight relative to the total weight of said layers after hardening.

[0182] Advantageously, the proportion of colorant in layer (3b) ranges from 10% to 40% by weight relative to the total weight of said layer.

[0183] Advantageously, the proportion of colorants in layer (3c), if they are present, is less than 10% by weight relative to the total weight of said layer.

[0184] Advantageously, the proportions of colorants in layers (3b) and (3c) may be the same or different.

[0185] Advantageously, the nature of the colorants in layers (3b) and (3c) may be the same or different.

[0186] thermochromic pigments Preferably, the thermochromic pigment(s) is / are Bi2O3, Fe2O3, V2O5, WO3, CeO2, In2O3, Y 1.84 Ca 0.16 Ti 1.84 V 0.16 O 1.84 , AgI, (Bi 1-x A x )(V 1-y M y )O4, -x is equal to 0 or x is between 0.001 and 0.999; - y is equal to 0 or is comprised between 0.001 and 0.999; A and M are selected from the group consisting of nitrogen, phosphorus, alkali metals, alkaline earth metals, transition metals, poor metals, metalloids, or lanthanides; A and M are different from each other.

[0187] If you know that A and M are different from each other: A is an alkali metal and can be selected from Li, Na, K, Rb and Cs; M is an alkali metal and can be selected from Li, Na, K, Rb and Cs; A is an alkaline earth metal and can be selected from Be, Mg, Ca, Sr and Ba; M is an alkaline earth metal and can be selected from Be, Mg, Ca, Sr and Ba; A is a transition metal and may be selected from Sc, TiCr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Ta, W, and Ir; M is a transition metal and may be selected from Sc, TiCr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Ta, W, and Ir; A is a poor metal and can be selected from Al, An, Ga, In, Sn, M is a poor metal and can be selected from Al, Zn, Ga, In and Sn; A is a metalloid and can be selected from B, Si, Ge, and Sb; M is a metalloid and may be selected from B, Si, Ge, and Sb; A is a lanthanide and may be selected from La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; -M is a lanthanide and can be selected from La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

[0188] Preferably, A and M, which are different from each other, are B and / or Mg.

[0189] Preferably, the pigment (Bi 1-x A x )(V 1-y M y )O4 has a monoclinic schellite crystallographic form at room temperature.

[0190] Preferably, x and y are equal to 0, i.e., the pigment (Bi 1-x Ax )(V 1-y M y )O4 is bismuth vanadate (BiVO4). Advantageously, BiVO4 with the monoclinic schellite crystal structure is used at room temperature.

[0191] Bismuth vanadate is a yellow inorganic compound of formula BiVO4 that is widely used due to its coloring properties and its lack of toxicity. It is recorded in the Color Index International Database as QI Pigment Yellow 184 and is sold, among others, by Heubach (Vanadur®), BASF (Sicopal®), FERRO (Lysopac) or Bruchsaler Farbenfabrik (Brufasol®).

[0192] Heat Stable Pigments Preferably, the heat stable pigment is -Titanium rutile type yellow pigment, Yellow pigments derived from bismuth, such as stabilized bismuth vanadate (Py 184 ) a yellow pigment selected from red pigments, such as perylene red (e.g., PR 149 , PR 178 and PR 224 ), iron oxide; -Orange pigment of bismuth oxyhalide type (PO 85 ) -Orange pigment of bismuth vanadate (PO 86 ); -Zinc tin titanium dioxide orange pigment (PO 82 ); -Cerium sulfide orange pigment (PO 75 ; PO78); - Rutile type antimony titanium chromium orange yellow pigment (PBr 24 ), -Rutile type tin and zinc orange yellow pigment (Py 216 ); -Niobium oxide, tin zinc sulfide, orange yellow pigment (Py227 ) ; -Orange-yellow pigment made from a composite oxide of tin and niobium.

[0193] -Co3(PO4)2, -LiCoPO4; -CoAl2O4; -Cr2O3; -TiO2; -Black pigment PBk28 (copper chromite black spinel); - and mixtures thereof.

[0194] flake The flakes that can be used in the context of the present invention can be independently selected from coated or uncoated mica flakes, coated or uncoated silica flakes, coated or uncoated aluminum flakes, and coated or uncoated iron oxide flakes. Titanium dioxide-coated mica or silica flakes. The flakes that can be used in the context of the present invention can be treated to impart specific color effects.

[0195] Advantageously, the flakes are particles selected from the group consisting of mica, aluminium, titanium dioxide coated mica particles or mixtures thereof.

[0196] Holographic Flakes Advantageously, the flakes are holographic flakes, in other words a mixture of magnetizable and non-magnetizable particles.

[0197] The magnetizable particles may advantageously be particles containing at least one ferromagnetic metal. These magnetizable particles may be of homogeneous nature, i.e., composed of the same material, or of composite nature, meaning that they have a core-shell structure in which the ferromagnetic metal is located in the core and / or shell of the particle. Examples of composite magnetizable particles include mica flakes coated with iron oxide Fe2O3 or stainless steel fibers coated with sol-gel materials as protection against corrosion during the coating process, or flakes made of plastic materials coated with iron oxide Fe2O3, or flakes in which the core is a ferromagnetic metal and the shell is formed of plastic materials or sol-gel materials.

[0198] According to one embodiment, some of the magnetizable particles are oriented to form a three-dimensional decoration.

[0199] Advantageously, the mixture of magnetizable and non-magnetizable particles is present in an amount between 1% and 5% by weight, preferably between 2% and 3% by weight of the layer.

[0200] Advantageously, the proportion of non-magnetizable particles in the mixture of magnetizable and non-magnetizable particles is comprised between 15% and 40% by weight relative to the total weight of the mixture of magnetizable and non-magnetizable particles.

[0201] Advantageously, the magnetizable particles have a dimension D50 of less than or equal to 23 μm.

[0202] The term "D50" is understood for the purposes of the present invention to mean the largest dimension exhibited by 50% of the particles by number.

[0203] Advantageously, the non-magnetizable particles have a dimension D90 comprised between 20% and 250% of the dimension D90 of the magnetizable particles.

[0204] The term "D90" is understood for the purposes of the present invention to mean the largest dimension exhibited by 90% of the particles by number.

[0205] Advantageously, the magnetizable particles and / or the non-magnetizable particles are colored on the surface.

[0206] Advantageously, the non-magnetizable particles consist of mica, aluminium or mica coated with titanium dioxide.

[0207] Typically, the magnetizable particles are composed of iron, iron oxide, iron-coated aluminum, or iron-coated mica, the iron being in ferrite form.

[0208] decoration According to one embodiment, the layer(s) (3b) are continuous and cover the entire layer (3a) (see Figure 1).

[0209] According to another embodiment, the layer(s) (3b) do not cover the entire layer (3a) but form (form) at least one decoration (see Figure 2).

[0210] Advantageously, the layer(s) (3b) comprise (comprise) several decorations, one (i) comprising one or more thermochromic pigments and the other (j) comprising at least one reference temperature pigment composition (see Figure 3).

[0211] According to one embodiment, each of the two decorations (i) and (j) is in the form of adjacent, non-overlapping patterns, for example, each decoration is represented by a different geometric pattern that is uniformly distributed over the entire surface and alternates with respect to each other (see FIG. 4A).

[0212] According to another embodiment, the two decorations (i) and (j) are partially overlapping, for example each decoration is represented by a different, partially overlapping geometric pattern evenly distributed over the surface (see FIG. 4B).

[0213] Preferably, the two decorations (i) and (j) overlap either because one of the two decorations is a continuous layer and the other decoration covers it in the form of a pattern, or because the two decorations (i) and (j) are in the form of overlapping patterns (see Figure 4C).

[0214] method The present invention also relates to a method for producing a coated cooking element (1) according to the invention, comprising the following successive steps:

[0215] i. Providing a metal substrate (2) comprising at least one surface (2a) to be coated; ii. optionally pretreating the surface (2a) of the metal substrate (2) intended to be coated; iii. applying a sol-gel based layer (3a) to said surface (2a) to be coated; iv. Optionally drying and / or curing said base layer (3a); v. applying at least one intermediate layer (3b), typically by pad printing, screen printing, inkjet printing, or flexographic printing; and vi. Optionally, drying said intermediate layer(s) (3b); vii. applying at least one finishing layer (3c); viii. Curing all base layers (3a), intermediate layers (3b) and finish layers (3c).

[0216] Step (iii) is particularly carried out in connection with the sol-gel compositions described above.

[0217] According to one embodiment, at least one intermediate layer (3b) is applied to the at least one base layer (3a) and / or at least one finishing layer (3c) is applied to the at least one intermediate layer (3b).

[0218] Advantageously, the steps of the method according to the invention make it possible to coat a metal substrate (2) with a coating (3) formed by three layers (3a), (3b) and (3c). Generally, these three layers are wet during their application. "Wet layer" is understood for the purposes of the present invention to mean that the layer contains all or part of its solvent.

[0219] Preferably, all or part of the solvent in the wet layer is removed naturally or by physical treatment, such as heat drying, air drying, or vacuum treatment.

[0220] Advantageously, the coating composition according to the invention may also comprise at least one solvent. Advantageously, the solvent may be protic. Advantageously, the solvent may be non-toxic.

[0221] The solvent that can be used in the coating composition according to the invention may advantageously comprise at least one alcohol, preferably chosen from isopropanol, methanol, ethanol, and mixtures thereof.

[0222] The coating is applied in several layers. In this case, the deposition of at least one layer of the coating (3) according to the invention onto at least one of the two opposite faces of the substrate is repeated several times. Preferably, a drying step is carried out between the application of each layer, and after the application of the last layer, the coated substrate is hardened. The application of the coating (3) to the substrate (2) by the method according to the invention makes it possible to obtain a heat-stable coating layer.

[0223] The coating formulation applied is generally in aqueous form, with the polymer of the polymeric phase being in the form of a suspension. Other non-aqueous solvents may also be suitable.

[0224] Advantageously, the method for producing the coated cooking element (1) according to the invention comprises, after the application of each layer, one or more drying steps between 80 and 150° C. Drying can be carried out by convection or infrared.

[0225] The coating according to the invention can be applied to a shaped substrate or to locally flat areas of a shaped substrate by the method according to the invention. A thermally stable coating layer is obtained. This coating layer is generally wet.

[0226] Advantageously, the method for producing a coated cooking element (1) according to the invention comprises a step of shaping said substrate (2) before step iii. Shaping is also called stamping.

[0227] The coating is preferentially carried out by spraying.

[0228] The process according to the invention advantageously comprises a step viii of curing the elements obtained in step vii of the process. For the purposes of the present invention, curing of the coated substrate is understood to mean a heat treatment which makes it possible not only to densify the coating layer applied to the substrate, but also to crosslink the organopolysiloxane precursor (silicone resin).

[0229] Curing is carried out in step viii. Generally, the curing temperature in step viii is comprised between 230°C and 420°C.

[0230] Advantageously, the method for producing a coated cooking element (1) according to the invention comprises a single final curing step viii of all applied layers, which single curing step is carried out simultaneously for all applied layers.

[0231] The application steps (iii) and (vii) can be carried out by electrostatic powder coating, by spraying in a solvent or aqueous phase, by screen printing, by roller printing, or by digital printing.

[0232] Preferably, step (vii) is carried out in particular by electrostatic powder coating or by spraying in a solvated or aqueous phase.

[0233] For the purposes of the present invention, curing of a coated substrate is understood to mean a heat treatment that makes it possible not only to densify the coating layer applied to the substrate, but also to crosslink the organopolysiloxane precursor (silicone resin).

[0234] Curing step iv, if performed, is typically carried out at a temperature between 200°C and 350°C for a period of 5 to 30 minutes.

[0235] Typically, the substrate has the final shape of the cooking utensil, with a concave inner surface 2a intended to be placed on the side of the food that is likely to be introduced into the food, and a convex outer surface intended to be placed on the side of the heat source.

[0236] Preferred Configuration According to one embodiment, the present invention relates to a coated cooking element (1) for a cooking utensil or an electric cooking appliance, comprising a metal substrate (2) coated, on at least one face (2a), or exclusively coated, with the following three layers superimposed in this order from the metal substrate (2): (3a) a base layer comprising one or more sol-gel compositions; (3b) one or more intermediate layers of one or more colorants, and optionally - one or more silicone resins; and / or - one or more thermoplastic polymers; and / or - one or more fillers; and / or - one or more additives, (3c) A finish layer intended to come into contact with food during cooking, consisting of one or more silicone resins, optionally (3c) one or more thermoplastic polymers; and / or - one or more fillers; and / or - one or more additives; and / or - Flakes.

[0237] According to one embodiment, the base layer (3a) is made of an SG composition synthesized by a sol-gel method from an SG mixture consisting of precursors of the metal alkoxide type, such as TEOS or MTES, a colloidal metal oxide precursor; - a solvent, preferably alcoholic; an acid selected from acetic acid, citric acid, ethyl acetoacetate, hydrochloric acid or formic acid; and optionally - at least one pigment, at least one advantageous mineral filler, an additive chosen from flakes, in particular metal flakes, pyrogenic silica, or mixtures thereof, preferably additives chosen from pigments and / or fillers.

[0238] Typically, the thickness of the layer (3a) is comprised between 5 μm and 30 μm.

[0239] Preferably, the colorant of the intermediate layer(s) (3b) comprises pigments and / or flakes, advantageously holographic flakes.

[0240] According to a variant, the intermediate layer(s) (3b) are: one or more colorants, in particular pigments and / or flakes, advantageously holographic flakes; one or more thermoplastic polymers advantageously chosen from polyamideimides (PAI), polyimides (PI), polyetherimides (PEI), polybenzimidazoles (PBI), polyethersulfones (PES), polyphenylene ether sulfones (PPSU), polyaryletherketones (PAEK), and mixtures thereof; · 0-10% fillers; · 0-20% additives; optionally one or more silicone resins, It consists of:

[0241] According to another variant, the intermediate layer(s) (3b) are: one or more colorants, in particular pigments and / or flakes, advantageously holographic flakes; · 0-10% fillers; · 0-20% additives; one or more silicone resins; and optionally one or more thermoplastic polymers advantageously chosen from polyamideimides (PAI), polyimides (PI), polyetherimides (PEI), polybenzimidazoles (PBI), polyethersulfones (PES), polyphenylene ether sulfones (PPSU), polyaryletherketones (PAEK), and mixtures thereof, It consists of:

[0242] According to a particular variant, the intermediate layer(s) (3b) do not comprise a silicone resin.

[0243] According to another particular variant, the intermediate layer(s) (3b) are: one or more colorants, in particular pigments and / or flakes, advantageously holographic flakes; one or more thermoplastic polymers advantageously chosen from polyamideimides (PAI), polyimides (PI), polyetherimides (PEI), polybenzimidazoles (PBI), polyethersulfones (PES), polyphenylene ether sulfones (PPSU), polyaryletherketones (PAEK), and mixtures thereof; · 0-10% fillers; · 0-20% additives; one or more silicone resins, It consists of:

[0244] According to a particular embodiment, the coating comprises two intermediate layers (3b), at least one of which is decorative. Advantageously, the layer(s) (3b) consist of several decorations, one (i) comprising one or more thermochromic pigments and the other (j) comprising at least one reference temperature pigment composition.

[0245] Typically, the thickness of the intermediate layer(s) (3b) is comprised between 3 μm and 10 μm.

[0246] Preferably, the intermediate layer(s) (3b) only partially cover the base layer (3a).

[0247] According to one embodiment, the finishing layer (3c) is composed of one or more silicone resins and optionally one or more thermoplastic polymers.

[0248] According to another embodiment, the finishing layer (3c) is composed of one or more silicone resins and one or more thermoplastic polymers.

[0249] Typically, the thickness of the layer (3c) is comprised between 0.1 μm and 10 μm.

[0250] In a particular embodiment, the thickness of sub-layer (3a) is comprised between 5 and 30 μm, the thickness of layer (3b) is comprised between 3 μm and 10 μm, and the thickness of layer (3c) is comprised between 0.1 μm and 10 μm.

[0251] Goods The present invention also relates to a cooking utensil (100) that includes the coated cooking element (1).

[0252] According to one embodiment, the cooking utensil (100) has a heating surface (6) intended to be in contact with an external heat source, opposite a cooking surface (5) intended to be in contact with food during cooking. The cooking surface (5) is typically the surface (2a) intended to be coated with the coating of the present invention.

[0253] Advantageously, the cookware (100) according to the invention is selected from the group consisting of a saucepan, a frying pan, a skillet, a fondue pot, a raclette pot, a Dutch oven, a wok, a sauté pan, a crepe maker, a grill, a griddle, a marmitte, a cocotte, an insert for an electric cooker or a bread maker, or a food mould.

[0254] The present invention also relates to an electric cooking appliance (200) comprising a coated cooking element (1) according to the present invention and a heat source (210) configured to heat the coated cooking element (1).

[0255] Advantageously, the electric cooking appliance (200) is selected from the group consisting of an electric crepe maker, an electric raclette maker, an electric fondue maker, an electric grill, a hot plate, an electric cooker, a bread maker, an electric pressure cooker, a waffle maker, a rice cooker, and a jam maker.

[0256] The cooking utensil according to the invention may in particular be a cooking utensil in which one of the two opposite faces of the substrate is an optionally concave inner face and is intended to be placed on the face on which food is introduced into or onto said commodity, and the other face of the substrate is optionally a convex outer face and is intended to be placed towards a heat source.

[0257] Non-limiting examples of cookware according to the present invention include cookware such as saucepans and frying pans, woks and sauté pans, Dutch ovens and marmites, crepe makers, baking pans and sheets, barbecue griddles and grills, food preparation bowls, among others.

[0258] (Example) The objects, aspects and advantages of the present invention will be better understood from the following description of particular embodiments thereof, given by way of non-limiting examples, with reference to the accompanying drawings, in which:

[0259] Of course, the invention is in no way limited to the described and illustrated embodiments, which are given solely by way of example: modifications remain possible, particularly in terms of the configuration of the various elements or by substitution of technical equivalents, without thereby going beyond the scope of protection of the invention.

[0260] Example of embodiment: Metal substrate: This is an aluminum substrate that has been sandblasted or shot blasted, and then undergoes an appropriate surface treatment to remove organic contaminants.

[0261] The raw materials of layer (3a) are detailed below.

[0262] Raw materials for the intermediate layer (3b), (3b') and the finishing layer (3c): -Silicone resin · RS1: ethoxy-functionalized polyester silicone resin in solvent phase (80% silicone / 20% polyester), viscosity approx. 2000 mPas at 25 °C, solids content = 75%; · RS2: ethoxy-functionalized polyester silicone resin in solvent phase (50% silicone / 50% polyester), viscosity approx. 2000 mPas at 25 °C, solids content = 75%; · RS3: ethoxy-functionalized polyester silicone resin in solvent phase (30% silicone / 70% polyester), viscosity approx. 2000 mPas at 25 °C, solids content = 75%; · RS4: methylphenyl-functionalized polyester silicone resin in solvent phase, viscosity about 2000 mPas at 25 ° C, solids content = 75%; · RS5: methoxy-functionalized polyester silicone resin in solvent phase (50% silicone / 50% polyester), viscosity approx. 2000 mPas at 25 °C, solids content = 75%; · RS6: ethoxy-functionalized methylorganopolysiloxane resin in aqueous emulsion, viscosity at 25 °C about 1500 mPas, solids content = 52%; -alcohol solvents; · Dipropylene glycol n -butyl ether (DPNB); ·2-Methoxy-1-methylethyl acetate (MPA); ·Butyl glycol acetate (BGA); Butyl acetate - surfactants and antifoaming agents; Mineral oil: Tego formex K7 from Evonik, Fatty alcohol polyglycol ethers: Gnapol X080 from Clariant or Tefgitole TMN-100X, -reinforcing fillers, Pyrolytic silica: Levasil CC301, Post-treated dimethyldichlorosilane fumed silica: AEROSIL R972, -Pigments Mica: Iriodin 100 or Iriodin 300 and / or Magnapearl 5000, Cr / Fe oxide: Shikopal Black K0098FK, Carbon black: Derussol F25 or Cabot Monarch 4750, Perylene Red: Parylene Red (PR178) Iron trioxide: brick H856, -Acrylic resin: Rohagit SD 15: 30% acrylic polymer solution in water phase -Silicone oil Polyether-modified polysiloxane: TEGO GLIDE 100, Polydimethylsiloxane oil: CT601M. -Other additives AMP90: Solution of 2-amino-2-methyl-1-propanol: 90% polymer, buffer in aqueous phase Metolat 368: fatty acid ester, Dolfynox 1030: Propoxylated polyglycol ether, wetting agent, Edaplan LA451: anionic ester in ethanol / water, wetting agent, Tego Glide 407: Methylphenyl polysiloxane, flow agent.

[0263] Operating principle of jar mill (mechanical grinding) Ball milling consists of placing the sample to be ground and so-called mill balls in a jar and rotating the jar around its axis at a constant speed. The jar is usually rotated using a roller machine. The sample can be ground dry or dispersed in a suitable solvent (e.g., water or alcohol). The dispersion can also contain specific adjuvants (such as dispersants or antifoaming agents).

[0264] The average diameter of the milling balls must be adapted to the size of the particles to be ground. The finer the particles, the smaller the diameter of the balls used. The total volume of the balls, including the voids between them, is approximately 50-60% of the internal volume of the jar. The balls of different sizes are advantageously distributed according to the following weight ratio in relation to the total weight of the balls: 25% small balls, 50% medium balls, and 25% large balls. The smallest ball size is 2-10 mm. Alumina and stabilized zirconia are commonly used ball materials.

[0265] Examples according to the present invention Preparation of a coating with a black sol-gel primer (layer 3a), two intermediate layers (3b) and (3b') and a finishing layer (3c): The formulation of the base layer 3a (black primer) is prepared from a three-component system (Part A, Part B, and Part C). Part A is colloidal silica with a particle size of less than 200 nm, which can optionally be impregnated with a hydrophobic compound such as PDMS oil. Part B incorporates the reactive silane MTMS and an acid catalyst. Part C incorporates pigments, fillers, solvents, wetting agents, and PDMS oil. PDMS oil can also be introduced into Part B.

[0266] [Table 2]

[0267] The method is as follows.

[0268] Part A is stirred with a shear blade at a speed of 1000 rpm, sufficient to obtain a clear vortex.

[0269] Part B is prepared separately by mixing the silane with the acid, which is then introduced into Part A with stirring: the hydrolysis reaction of MTMS is initiated and must continue for at least 2 hours.

[0270] Part C is then introduced into this mixture by adding the ingredients one by one while stirring. It should be noted that all ingredients of Part C can be premixed separately before introducing this paste into the A+B mixture after the 2 hour reaction.

[0271] Once all ingredients are mixed, stirring is continued for 30 minutes, after which the formulation is stored in a closed glass vial.

[0272] Also, regarding the mixing method, it should be noted that the ingredients of Part C can be first introduced into Part A and stirred for 30 minutes, and then Part B can be introduced alone and mixed for 2 hours to allow the sol-gel reaction to occur.

[0273] The mixture is then left at room temperature for 24 hours before application. The shelf life of this formulation is at least 48 hours.

[0274] The mixture can also be stored in a refrigerator at 5°C: in this case, its shelf life is extended to at least 72 hours.

[0275] The resulting mixture is then filtered through a 50 micron filter before being sprayed onto a sandblasted and degreased aluminum substrate, preheated to 55°C to avoid dripping during coating.

[0276] A step of drying the base layer (3a) at a temperature of less than 100°C is carried out.

[0277] Layer (3a) is cured at 300° C. The temperature is gradually increased and allowed to stabilize at this temperature of 300° C. for 10 minutes.

[0278] The base layer (3a) has a dry thickness of 30 to 40 microns.

[0279] Middle layer (3b) Successive layers (3b) are then deposited by spraying onto layer (3a) selected from the layer compositions described below: layer 3b1, layer 3b2 and layer 3b3.

[0280] [Table 3]

[0281] [Table 4]

[0282] [Table 5]

[0283] The aqueous composition of layer 3b is prepared by ball milling. Ball milling is carried out in a bottle as described above. The sample may be ground dry or dispersed in a suitable solvent (e.g., water, alcohol, or solvent). The dispersion may also contain specific adjuvants (such as dispersants or antifoaming agents).

[0284] The thickness of this layer 3b is comprised between 10 μm and 20 μm, preferably between 12 μm and 15 μm.

[0285] Intermediate layer (3b') and finishing layer (3c) The substrate to which the base layer (3a) and the successive layer (3b) have been applied as described above is then coated with a multi-layer non-stick coating consisting of an intermediate layer 3b' (6-8 μm) and a finishing layer 3c (14-18 μm), which are dried at 100 ° C for 4 minutes. The whole is finally cured at 250 ° C for 1 hour.

[0286] The composition of the intermediate layer (3b') is deposited by spraying: layer 3b'1, layer 3b'2 and layer 3b'3:

[0287] [Table 6]

[0288] [Table 7]

[0289] [Table 8]

[0290] The composition of the finishing layer (3c) is deposited by spraying and is described below: Layers 3c1 to 3c10:

[0291] [Table 9]

[0292] [Table 10]

[0293] [Table 11]

[0294] [Table 12]

[0295] [Table 13]

[0296] [Table 14]

[0297] [Table 15]

[0298] [Table 16]

[0299] [Table 17]

[0300] [Table 18]

[0301] Method for characterizing non-stick coatings: Egg performance test The method for evaluating the properties of anti-adhesive coatings is carried out using the egg test in accordance with AFNOR NF D21-511 paragraph 3.3.2 and is implemented as follows:

[0302] The sample is washed and any remaining water is wiped off the surface.

[0303] The inner surface of the container body is dried in advance.

[0304] The cooking vessel is heated on a gas stove to a temperature of 140-170°C.

[0305] Crack a 60 / 65 caliber egg and pour it into the center of the hot cooking vessel and allow the egg to coagulate (6-9 minutes). Remove the egg from the cooking vessel with a spatula and clean the coating with a damp plant-based sponge. Evaluate the anti-stick properties of the cooking vessel with this action and record the following: Grade 100: The egg can be completely removed with a plastic spatula. Grade 75: Egg not completely removed, but coating can be easily cleaned with a damp sponge. Grade 50: Egg not completely removed, but coating can be cleaned with a damp sponge. Grade 25: Egg not completely removed and coating cannot be cleaned with a damp sponge. Grade 0: The eggs are not removed and the coating cannot be cleaned with a damp sponge.

[0306] [Table 19]

[0307] All coatings according to the invention based on silicone polyester resins have good non-stick properties while adhering to metal.

Claims

1. A coated cooking element (1) for a cooking utensil or electric cooking appliance, comprising a metal substrate (2) coated on at least one surface (2a) with at least the following layers in the order listed from the metal substrate (2): (3a) a base layer comprising one or more sol-gel compositions; (3b) one or more intermediate layers containing one or more colorants, optionally one or more silicone resins; and / or one or more thermoplastic polymers; and / or one or more fillers; and / or an intermediate layer comprising one or more additives; (3c) a finish intended to come into contact with food during cooking, comprising one or more silicone resins, one or more thermoplastic polymers; and / or one or more fillers; and / or one or more additives; and / or flakes, including the finishing layer, A coated cooking element (1).

2. 2. The coated cooking element (1) of claim 1, wherein the silicone resin is selected from the group consisting of methylsilicone resins and / or phenylsilicone resins and / or methylphenylsilicone resins, methylsilicone polyester resins (copolymers), phenylsilicone polyester resins (copolymers), methylphenylsilicone polyester resins, silicone alkyd resins (copolymers), modified silicone resins, and mixtures thereof.

3. 3. The coated cooking element (1) according to claim 1 or 2, wherein the fillers are selected from the group consisting of ceramic fillers and / or mineral and / or metal fillers and / or silica and / or diamond particles.

4. 4. The coated cooking element (1) of any one of claims 1 to 3, wherein the thermoplastic polymer, when present, is selected from the group consisting of polyethersulfone (PES), polyphenylene sulfide (PPS), polyphenylene ether sulfone (PPSU), polyamideimide (PAI), polyimide (PI), poly(phenylene oxide) (PPO), poly(arylene sulfide) (PAS), polyetherimide (PEI), polybenzimidazole (PBI), liquid crystal polymer (LCP), polyaryletherketone (PAEK) including polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetheretherketoneketone (PEEKK), polyetherketoneetherketoneketone (PEKEKK), and mixtures thereof.

5. The coated cooking element (1) according to any one of claims 1 to 4, wherein the colorant, when present, is selected from the group consisting of thermochromic pigments, heat stable pigments, flakes, and mixtures thereof.

6. The thermochromic pigment is Bi ２ O ３ , Fe ２ O ３ , V ２ O ５ , W.O. ３ , CeO ２ , In ２ O ３ , Y １．８４ Ca ０．１６ Ti １．８４ V ０．１６ O １．８４ , AgI, (Bi １－ｘ A ｘ ) (V １－ｙ M ｙ ) O ４ is selected from the group consisting of - x is equal to 0 or x is comprised between 0.001 and 0.999; -y is equal to 0 or is comprised between 0.001 and 0.999; A and M are selected from the group consisting of nitrogen, phosphorus, alkali metals, alkaline earth metals, transition metals, poor metals, metalloids, or lanthanides; The coated cooking element (1) according to claim 5, wherein A and M are different from each other.

7. The heat stable pigment is -Titanium rutile type yellow pigment, yellow pigments derived from bismuth, such as stabilized bismuth vanadate (Py １８４ ) a yellow pigment selected from red pigments, such as perylene red (e.g., PR １４９ , P.R. １７８ and PR ２２４ ), iron oxide; -Orange pigment of bismuth oxyhalide type (PO ８５ ) - Bismuth vanadate orange pigment (PO ８６ ); -Zinc tin titanium dioxide orange pigment (PO ８２ ); -Orange pigment of cerium sulfide (PO ７５ ; PO78); - Rutile type antimony titanium chromium orange yellow pigment (PBr ２４ ), - Rutile type tin and zinc orange yellow pigment (Py ２１６ ) ; -Orange yellow pigment of niobium oxide, tin zinc sulfide (Py ２２７ ) ; -Orange-yellow pigment made from a composite oxide of tin and niobium. -Co ３ (PO ４ ) ２ 、 -LiCoPO ４ ; -CoAl ２ O ４ ; -Cr ２ O ３ ; -Truth ２ ; -Black pigment PBk28 (copper chromite black spinel); - and mixtures thereof.

8. Coated cooking element (1) according to any one of claims 5 to 7, wherein the flakes are holographic flakes which are a mixture of magnetizable and non-magnetizable particles.

9. The coated cooking element (1) according to any one of claims 1 to 8, wherein the metal substrate (2) is a substrate made of aluminium, stainless steel, cast or cast aluminium, iron, titanium or copper.

10. the thickness of the layer (3a) is comprised between 5 μm and 100 μm, typically between 20 μm and 70 μm; the thickness of the layer (3b) is comprised between 1 μm and 100 μm, typically between 2 μm and 30 μm; Coated cooking element (1) according to any one of claims 1 to 9, wherein the thickness of the layer (3c) is comprised between 0.05 μm and 100 μm, preferably between 0.08 μm and 20 μm.

11. 11. The coated cooking element (1) according to any one of claims 1 to 10, wherein the layer (3a) is at least one metal oxide, preferably a colloidal metal oxide selected from colloidal silica and / or colloidal alumina, and preferably an alkoxysilane selected from the group consisting of methyltrimethoxysilane (MTMS), tetraethoxysilane (TEOS), methyltriethoxysilane (MTES), dimethyldimethoxysilane, and mixtures thereof.

12. 12. The coated cooking element (1) according to any one of claims 1 to 11, wherein the proportion of filler in the layers (3b) and (3c), when present, is less than 10% by weight, based on the total weight of the layers (3b) and (3c), respectively.

13. 13. The coated cooking element (1) according to any one of claims 1 to 12, wherein the proportion of additives in the layers (3b) and (3c), when present, is less than 20% by weight, respectively, based on the total weight of the layer (3b) and the total weight of the layer (3c).

14. A method for producing the coated cooking element (1) according to any one of claims 1 to 13, comprising the following successive steps: i. Providing a metal substrate (2) comprising at least one surface (2a) to be coated; ii. Optionally, pretreating the surface (2a) of the metal substrate (2) to be coated; iii. applying a sol-gel based layer to the surface to be coated; iv. Optionally, drying and / or curing the base layer; and v. applying at least one intermediate layer (3b); vi. Optionally, drying said intermediate layer (3b); vii. applying at least one finishing layer (3c); viii. Curing all of the base layer (3a), intermediate layer (3b) and finish layer (3c).

15. A cooking utensil (100) comprising a coated cooking element (1) according to any one of claims 1 to 13.

16. 16. The cooking appliance (100) of claim 15, having a heating surface (6) intended to be in contact with an external heat source, said heating surface (6) being opposite a cooking surface (5) intended to be in contact with food during cooking.

17. 17. The cookware (100) of claim 15 or 16, selected from the group consisting of a saucepan, frying pan, skillet, fondue or raclette pot, Dutch oven, wok, sauté pan, crepe maker, grill, griddle, marmitte, cocotte, insert for an electric cooker or bread maker, or food mold.

18. An electric cooking appliance (200) comprising a coated cooking element (1) according to any one of claims 1 to 13 and a heating source (210) configured to heat the coated cooking element (1).

19. 20. The electric cooking appliance (200) of claim 18, selected from the group consisting of an electric crepe maker, an electric raclette maker, an electric fondue maker, an electric grill, a hot plate, an electric cooker, a bread maker, an electric pressure cooker, a waffle maker, a rice cooker, and a jam maker.

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