Non-fluorinated hybrid sol-gel / silicone resin coating

Abstract

The present invention relates to a coated cooking element (1) for a cooking article or electric cooking appliance, comprising a metallic substrate (2) coated on at least one face (2a) by a coating (3) consisting of the following layers and in this order from the metallic substrate (2): (3a) a sol-gel base layer obtained from at least one sol-gel mixture (SG) comprising a metal alkoxide precursor having an aliphatic chain comprising at least one unsaturation and / or substituted by a thiol group, (3b) optionally one or more discontinuous intermediate layer(s) which may be decorations,and (3c) a topcoat at least partially in contact with layer (3a) and comprising a silicone elastomer obtained from at least one organopolysiloxane bearing reactive vinyl (-CH=CH2) functions and at least one other organopolysiloxane bearing reactive silyl hydride (-Si-H) or reactive thiol (-SH) functions, wherein, when the silicone elastomer of layer (3c) is obtained from at least one organopolysiloxane bearing reactive thiol (-SH) functions, the metal alkoxide precursor of layer (3a) has an aliphatic chain comprising at least one unsaturation and which may further be substituted by a thiol (-SH) group. Figure for abbreviation: Figure 1,

Description

Title of the invention: Hybrid sol-gel / silicone non-fluorinated coating

[0001] The field of the invention is that of culinary articles coated on one of their faces by a coating and more specifically, silicone resin-based coatings of these articles.

[0002] In the field of cookware, fluoropolymer-based coatings, and in particular polytetrafluoroethylene (PTFE) coatings, are well known to the general public for their non-stick and temperature-resistant properties. However, these coatings exhibit low mechanical strength.

[0003] Application WO 2020 / 144051 relates to a fluoropolymer-based coating whose mechanical resistance to abrasion is improved by the integration of inorganic (SiC) and mineral (Al2O3) fillers into the primer and topcoat layers of the coating. The performance gain achieved in terms of mechanical resistance is satisfactory but still not optimal.

[0004] Coatings with a hard base layer coated with a sol-gel coating, such as those described in particular in patents EP 2 334 444 and EP 2 334 445, are also known to improve resistance to mechanical impacts. However, such coatings do not allow for sufficiently precise temperature control.

[0005] Fluoropolymer-based coatings are intended primarily for pans and pots, but other applications can be considered in the field of mold making (molds, cake tins, waffle irons, etc.) or small domestic equipment (rice cookers, fryer vats, electric crepe makers) due to their deep-drawing properties.

[0006] An alternative to PTFE coatings is the use of so-called "ceramic" coatings, developed via a sol-gel process and the use of tetraethyl orthosilicate (EP 2 806 776 B1). These coatings are characterized by their hardness and resistance to mechanical wear, but exhibit brittle behavior and lower anti-adhesion properties compared to fluoropolymer-based coatings.

[0007] In addition, these coatings are poorly suited to molding and small domestic equipment due to their lack of embossability.

[0008] In the field of molding (consumer or industrial), fluoropolymer-based coatings are not as widespread because the temperature resistance requirements are lower (max 220°C) and allow the use of other types of coatings, such as silicone coatings.

[0009] Pure silicone resins are described as non-stick and resistant to temperatures above 220-230°C. On the other hand, they are considered to have poor adhesion to the substrate.

[0010] Conversely, silicone-polyester resins are very common in mold making because they are non-stick while still adhering to the substrate and are compatible with stamping processes. However, they degrade at temperatures above 230°C. Indeed, the operating temperature range for cookware is between 50 and 250°C, and it is not surprising to reach temperatures of 300°C or even 350°C in the case of items with induction bases. The use of silicone-polyester resins is therefore not compatible with the operating temperatures in the field of cookware.

[0011] Application WO 2024 / 023472 describes a hybrid sol-gel coating architecture with a sol-gel base coat, one or more intermediate coats comprising one or more colorants, and a top coat comprising a silicone resin. If the coating's performance is satisfactory, its durability could be increased by improving the adhesion of the top coat to the sol-gel base coat.

[0012] Thus, there is a need for cooking articles that guarantee good mechanical resistance, good thermal resistance, simple and flexible implementation - for example in terms of the variety of reagents that can be used - for reasonable industrial costs.

[0013] The present invention also deals with the technical problem of alternative solutions to PTFE-type fluorinated resin-based coatings.

[0014] The present invention proposes an alternative to coatings based on a majority of PTFE in order to obtain good resistance to mechanical wear of the coatings, in particular by kitchen utensils for culinary articles and thus improve the durability of their mechanical resistance, in particular when hot and / or their cleanability, in order to extend the life of the article. Summary of the invention

[0015] A first object of the invention relates to a coated cooking element (1) for a cooking article or electric cooking appliance, comprising a metallic substrate (2) coated on at least one face (2a) by a coating (3) consisting of the following layers and in this order from the metallic substrate (2):

[0016] (3a) a sol-gel base layer obtained from at least one sol-gel mixture (SG) comprising a metal alkoxide precursor having an aliphatic chain comprising at least one unsaturation and / or substituted by a thiol group,

[0017] (3b) optionally one or more discontinuous intermediate layer(s) which can be decorations, and

[0018] (3c) a finishing layer at least partially in contact with layer (3a) and comprising a silicone elastomer obtained from at least one organopolysiloxane bearing vinyl reactive functions (-CH=CH2) and at least one other organopolysiloxane bearing silyl hydride reactive functions (-Si-H) or thiol reactive functions (-SH),

[0019] wherein, when the silicone elastomer of layer (3c) is obtained from at least one organopolysiloxane bearing reactive thiol (-SH) functions, the metal alkoxide-type precursor of layer (3a) has an aliphatic chain comprising at least one unsaturation and which can further be substituted by a thiol (-SH) group.

[0020] A second object of the invention relates to a method for manufacturing a coated cooking element (1) according to the first object of the invention comprising the following successive steps:

[0021] i. supply of a metallic substrate (2) comprising at least one face (2a) intended to be coated,

[0022] ii. possibly, pretreatment of the face (2a),

[0023] iii. application of the sol-gel base layer (3a) on the face (2a),

[0024] iv. optionally, drying and / or baking of the layer (3a),

[0025] v. where applicable, application of layer(s) (3b),

[0026] vi. optionally, drying of layer(s) (3b) and / or baking of layer(s) (3b) and, where applicable, of layer (3a),

[0027] vii. application of the topcoat (3c),

[0028] viii. cooking of the layers and obtaining the element (1).

[0029] Another object of the invention relates to a cooking article (100) or electric cooking appliance (200) comprising a coated cooking element (1) according to the first object of the invention or capable of being obtained according to the process corresponding to the second object of the invention.

[0030] The present invention has at least one of the following advantages:

[0031] - the coating according to the invention exhibits significant thermal stability during the temperature increases, it is stable up to about 400°C;

[0032] - the coating according to the invention exhibits enhanced mechanical resistance due to the presence of a sol-gel base layer as opposed to a coating consisting of silicone layers only;

[0033] - the coating according to the invention exhibits improved durability due to the nature specific to the metal alkoxide-type precursors of the sol-gel composition of layer (3a) and of the composition of layer (3c) compared to coatings comprising a sol-gel base layer and a silicone coating described in the prior art;

[0034] - the manufacturing process for the coating of the invention requires temperatures lower cooking costs than for a coating comprising PTFE-type fluorinated resins, which improves the environmental impact of the coating of the invention and the energy efficiency of its manufacturing process. DEFINITIONS

[0035] For the purposes of this invention, the term "layer" should be understood to mean a continuous or discontinuous layer. A continuous layer (also called a monolithic layer) is a single unit forming a flat surface that completely covers the area on which it is laid. A discontinuous layer (or non-monolithic layer) may comprise several parts and is therefore not a single unit.

[0036] The term "base coat", "primer coat", "bonding coat" or "bonding primer" means all the layers from the first layer applied directly to the substrate (it is preferable that this layer adheres well to the substrate and provides all its mechanical properties to the coating: hardness, scratch resistance) to the last layer before the first intermediate or decorative layer or the finishing layer if the coating does not include an intermediate layer.

[0037] The term "finish coat" or "topcoat" refers to one or more continuous surface layers applied after the intermediate layer(s) if the coating includes them, or after the primer. Typically, the final finish coat, or even all the finish coats, are transparent, allowing perfect visibility of any decorative layer while protecting all underlying layers from mechanical damage and giving the coating its non-stick properties. Preferably, the final finish coat is intended to be in contact with food.

[0038] The term "decoration" or "decoration layer" means one or more continuous or discontinuous layers comprising a pigment composition. The decoration may be in the form of one or more patterns, or one or more colors. A decoration is clearly visible to the user with the naked eye and at a typical viewing distance.

[0039] For the purposes of this invention, "sol-gel composition" or "sol-gel" means a composition synthesized via the sol-gel process from a liquid-phase precursor solution, which is transformed into a solid by a series of chemical reactions (hydrolysis and condensation) at low temperature. The resulting composition may be either organo-mineral or entirely mineral.

[0040] For the purposes of this invention, "organo-mineral composition" means a composition whose network is essentially inorganic, but which includes organic groups, particularly due to the precursors used and the coating curing temperature. Such a composition is generally obtained by a sol-gel process.

[0041] For the purposes of this invention, "all-mineral composition" means a composition consisting of a completely inorganic material, free from any organic group. Such a composition is generally obtained by sol-gel process with a firing temperature of at least 400°C, or from tetraethoxysilane (TEOS) type precursors with a firing temperature that may be lower than 400°C.

[0042] For the purposes of this invention, "thermochromic pigment or pigment composition" means a pigment or pigment composition that changes color with temperature within a given temperature range, this change being reversible. This color change is visible to the user with the naked eye at normal viewing distances.

[0043] The term "thermostat pigment" means a pigment which does not exhibit a change of colour when subjected to a temperature rise within a given temperature range or which exhibits a change of hue when subjected to a temperature rise within a given temperature range so small that it is not visible to the user with the naked eye and at a conventional operating distance.

[0044] By the term “d50”, we mean, in the context of the present invention, the maximum dimension that 50% of the particles have by number.

[0045] The term "coating" means all the layers covering the metallic substrate and adhering to that substrate.

[0046] The term “silicone resin-based coating” means a coating which comprises one or more silicone resin(s) in one or more of its layers.

[0047] The coating obtained according to the invention is advantageously solid. The term "solid" means the characteristic of a cohesive material insoluble in water, in common solvents, or in food components such as aqueous or fatty mixtures, even if the material may exhibit high hardness or high flexibility such as an elastomer.

[0048] For the purposes of this invention, the term "cooking article" should be understood as an object intended for cooking. To this end, it is intended to receive heat treatment. The cooking article thus comprises at least one "inner surface" or "cooking surface," the coating of which is intended to come into contact with food during cooking.

[0049] For the purposes of this invention, the term "object intended to receive heat treatment" means an object that will be heated by an external heating system, such as pans, pots, sauté pans, woks, etc. barbecue grills and which is capable of transmitting the heat energy supplied by this external heating system to a material or food in contact with said object.

[0050] For the purposes of this invention, the term "electric cooking appliance" means a heating object having its own heating system, such as an electric crepe maker, electric raclette grill, electric fondue set, electric grill, electric griddle, electric cooker, bread maker, or electric pressure cooker. The electric cooking appliance thus comprises at least one "cooking surface," the coating of which is intended to come into contact with food during cooking.

[0051] In the present invention, the % by weight are expressed in dry weight, i.e. without solvent. FIGURES

[0052] [Fig. 1]: Diagram of cooking element (1) according to the invention

[0053] [Fig.2]: Diagram of cooking element (1) according to the invention with a layer (3b)

[0054] [Fig.3]: Diagram of a cooking article according to the invention

[0055] [Fig.4]: Diagram of an electric cooking appliance according to the invention DETAILED DESCRIPTION OF THE INVENTION

[0056] The present invention relates to a coated cooking element (1) for a cooking article or electric cooking appliance, comprising a metallic substrate (2) coated on at least one face (2a) by a coating (3) consisting of the following layers and in this order from the metallic substrate (2):

[0057] (3a) a sol-gel base layer obtained from at least one sol-gel mixture (SG) comprising a metal alkoxide precursor having an aliphatic chain comprising at least one unsaturation and / or substituted by a thiol group,

[0058] (3b) optionally one or more discontinuous intermediate layer(s) which can be decorations, and

[0059] (3c) a finishing layer at least partially in contact with layer (3a) and comprising a silicone elastomer obtained from at least one organopolysiloxane bearing vinyl reactive functions (-CH=CH2) and at least one other organopolysiloxane bearing silyl hydride reactive functions (-Si-H) or thiol reactive functions (-SH),

[0060] wherein, when the silicone elastomer of layer (3c) is obtained from at least one organopolysiloxane bearing reactive thiol (-SH) functions, the metal alkoxide-type precursor of layer (3a) has an aliphatic chain comprising at least one unsaturation and which can further be substituted by a thiol (-SH) group.

[0061] Advantageously, the layers (3a), optionally (3b), and (3c) form a coating (3) which coats the metallic substrate (2). This coating (3) has non-stick properties and forms a non-stick coating.

[0062] Advantageously, the layer (3a) is in contact with the metallic substrate (2) by one of its faces by its face (2a).

[0063] At least one coated face (2a) of the metallic substrate is therefore a cooking face. In other words, the coating of the cooking element (1) according to the invention is intended to come into contact with food.

[0064] Advantageously, the finishing layer (3c) is intended to be brought into contact, by one of its faces (5), with food during cooking.

[0065] The coating of the cooking element (1) according to the invention does not comprise a fluorinated polymer, also called a fluoropolymer. In other words, said coating is free of fluorinated polymers.

[0066] Fig. 1 represents a coated cooking element (1) according to the invention.

[0067] METALLIC SUBSTRATE

[0068] Advantageously, said metallic substrate (2) is a substrate of aluminum, stainless steel, cast iron or aluminum, iron, titanium or copper, or a multilayer metallic substrate.

[0069] For the purposes of this invention, aluminium means a metal consisting of 100% aluminium or an aluminium alloy.

[0070] The metallic substrate (2) may be a multilayer substrate, for example, bilayer or trilayer. Such multilayer substrates may be obtained, for example, by co-lamination, by hot diffusion under load (solid state bonding), or by hot or cold impact bonding. Preferably, the metallic substrate (2) comprises alternating layers of metal and / or metal alloy. Preferably, the metallic substrate is a multilayer substrate whose face (2a) is made of aluminum alloy or stainless steel.

[0071] Advantageously, the thickness of the metallic substrate (2) is between 0.5 mm and 10 mm.

[0072] Advantageously, the face (2a) of the metallic substrate (2) has previously undergone a surface treatment to improve the adhesion of the coating to said substrate.

[0073] According to one embodiment, the surface of the face (2a) of the metallic substrate (2) has undergone a surface treatment, said surface treatment being a chemical attack, a brushing, a hydration, a sandblasting, a shot blasting, a physicochemical treatment of the plasma or corona or laser type, a chemical activation or a combination of these different techniques.

[0074] As examples of usable metallic substrates in the present invention, anodized or unanodized aluminum substrates may advantageously be mentioned, if applicable polished, brushed, sandblasted, shot-blasted or micro-blasted, substrates in anodized or non-anodized aluminum alloy, possibly polished, brushed, sandblasted or micro-blasted, substrates in steel possibly polished, brushed, sandblasted, shot-blasted or micro-blasted, substrates in stainless steel possibly polished, brushed, sandblasted or micro-blasted, substrates in cast steel, aluminum or iron, substrates in copper possibly hammered or polished.

[0075] Advantageously, the substrate can be chosen from substrates comprising ferritic stainless steel / aluminum / austenitic stainless steel layers, substrates comprising stainless steel / aluminum / copper / aluminum / austenitic stainless steel layers, cast aluminum caps, aluminum or aluminum alloy caps lined with an outer stainless steel base, metallic co-laminated substrates, for example two-layer co-laminated substrates comprising a stainless steel layer (for example intended to form the inner face of the article) and an aluminum or aluminum alloy layer, anodized or not (for example intended to form the outer face of the article).

[0076] Advantageously, the average arithmetic roughness Ra of the surface of the face (2a) of the metallic substrate (2) is greater than or equal to 1 pm.

[0077] The arithmetic mean roughness Ra is measured using a roughness tester according to ISO 4287. Ra represents the arithmetic mean of the deviations from the mean. Surface topography can be studied, in particular, with a profilometer with a probe equipped with a fine stylus fitted with a diamond tip, or with an optical metrology device such as the Altisurf®, in which a chromatic confocal sensor allows for non-contact measurement. The study of this surface topography makes it possible to define the arithmetic mean roughness Ra.

[0078] GEL-SOLD LAYER (3a)

[0079] A sol-gel layer is obtained from one or more sol-gel mixtures. A sol-gel layer is obtained via the sol-gel process from metal polyalkoxylate precursors, preferably with a hybrid network, generally silica with grafted alkyl groups. A sol-gel (SG) layer is generally obtained from at least one sol-gel (SG) mixture comprising at least one metal oxide and at least one metal alkoxide precursor.

[0080] The formation of sol-gel mixtures as described below (layer (3a)) consists of mixing an aqueous composition A comprising at least one metal oxide and a solution B comprising at least one metal alkoxide precursor. The mixing is advantageously carried out in a ratio of 40 to 75% by weight of the aqueous composition A relative to the weight of the sol-gel composition (A + B), so that the amount of metal oxide represents 5 to 50% by weight of the sol-gel composition (A + B) in the dry state.

[0081] The aqueous composition A may further comprise a solvent, in particular a solvent comprising at least one alcohol. Preferably, the alcohol is a C6-I alcohol. A C6-I alcohol is defined as a saturated hydrocarbon chain, linear or branched, comprising 1 to 6 carbon atoms and including a hydroxyl group (-OH) attached to a carbon atom. Examples include ethanol, n-propanol, and isopropanol.

[0082] The aqueous composition A may further comprise at least one silicone resin, in particular as defined below.

[0083] The aqueous composition A may further include a coloring agent, for example a pigment, in particular as defined below.

[0084] The aqueous composition A may further comprise a filler, in particular as defined below.

[0085] The aqueous composition A may also include fumed silica, the function of which is to regulate the viscosity of the sol-gel composition and / or the gloss of the dry coating.

[0086] The aqueous composition A typically comprises:

[0087] i) 5 to 50% by weight relative to the total weight of the aqueous composition A of at least one colloidal metal oxide,

[0088] ii) 0 to 20% by weight relative to the weight of composition A of a solvent comprising at least one alcohol,

[0089] iii) possibly 0.05 to 3% by weight relative to the total weight of said aqueous composition A of at least one silicone resin,

[0090] iv) 5 to 30% pigment, and

[0091] v) 2 to 30% charge.

[0092] Solution B may further comprise a Brønsted or Lewis acid. Advantageously, the metal alkoxide precursor of solution B is mixed with one or more Lewis acids, organic or mineral, representing 0.01 to 10% by weight of the total weight of solution B.

[0093] Specific examples of acids that can be used for mixing with the metal alkoxide precursor are acetic acid, citric acid, hydrochloric acid, formic acid, maleic acid, tartaric acid or oxalic acid.

[0094] Solution B may further comprise a solvent, in particular a solvent comprising at least one alcohol.

[0095] Solution B may further comprise at least one silicone resin, in particular as defined below.

[0096] Solution B may further comprise a colouring agent, such as glitter, preferably metallic, in particular as defined below.

[0097] According to an advantageous embodiment of the process of the invention, solution B may comprise a mixture of one of the alkoxysilanes as defined below and a metal alkoxide (for example, of aluminium, zirconia, titanium...

[0098] According to a preferred embodiment, the sol-gel mixture is synthesized via the sol-gel method from a sol-gel mixture comprising or consisting of a metal alkoxide precursor as described below, and optionally: - a colloidal metal oxide type precursor, - a solvent, preferably alcoholic, - a Brønsted or Lewis acid, preferably an acid selected from acetic acid, citric acid, hydrochloric acid, formic acid, maleic acid, tartaric acid or oxalic acid, - additives selected from at least one silicone resin, at least one pigment, at least one filler, glitter, including metallic glitter, fumed silica, or a mixture thereof, or - a mixture of these.

[0099] Thus, the sol-gel mixture is preferably mineral or organomineral, and may comprise at least one silicone resin, at least one pigment, at least one filler, glitter, particularly metallic glitter, fumed silica, or a mixture thereof. The SG composition may also comprise a solvent, particularly an alcoholic solvent, especially in trace amounts, and / or an acid, preferably an acid selected from acetic acid, citric acid, hydrochloric acid, formic acid, maleic acid, tartaric acid, or oxalic acid.

[0100] The sol-gel layer (3a) is obtained from at least one sol-gel mixture (SG) comprising a metal alkoxide type precursor having an aliphatic chain comprising at least one unsaturation and / or substituted by a thiol group.

[0101] Preferably, a metal alkoxide selected from the group consisting of: is used as a precursor.

[0102] - precursors conforming to the general formula MifORiL, ।,R|,

[0103] - precursors responding to the general formula M2(OR2)(n 2)R2 R2 ,

[0104] - precursors responding to the general formula M3(OR3)(n_3)R3 R3 R3 ,and

[0105] - their mixtures,

[0106] n being an integer corresponding to the maximum valence of the metals Mb M2 or M3j

[0107] Mi, M2 or M3 designating a metal chosen from Si, Zr, Ti, Sn, Al, Ce, V, Nb, Hf, Mg or Ln;

[0108] with:

[0109] - Ri,R2 or R3 designating an alkyl group,

[0110] - R, denoting an aliphatic chain comprising at least one unsaturation and / or replaced by a thiol group,

[0111] - R2 denoting an aliphatic chain comprising at least one unsaturation and / or substituted by a thiol group; and

[0112] R2 designating an alkyl group, or designating an identical or different aliphatic chain comprising at least one unsaturation and / or substituted by a thiol group;

[0113] - R3' denoting an aliphatic chain comprising at least one unsaturation and / or substituted by a thiol group, and R3 and R3 denoting an identical or different alkyl group; or

[0114] R3' denoting an aliphatic chain comprising at least one unsaturation and / or substituted by a thiol group, and, independently, R3 denoting an identical or different aliphatic chain comprising at least one unsaturation and / or substituted by a thiol group, and R3 denoting an alkyl group; or

[0115] R3', R3 and R3 independently designating an aliphatic chain, identical or different, comprising at least one unsaturation and / or substituted by a thiol group.

[0116] According to embodiments,

[0117] - Rj denotes an aliphatic chain comprising at least one unsaturation;

[0118] - R2 denotes an aliphatic chain comprising at least one unsaturation; and

[0119] R2 designates an alkyl group or designates an identical or different aliphatic chain comprising at least one unsaturation;

[0120] - R3' denotes an aliphatic chain comprising at least one unsaturation, and R3 and R3 designates an identical or different alkyl group; or

[0121] R3' denotes an aliphatic chain comprising at least one unsaturation, and, Independently, R3 denotes an identical or different aliphatic chain comprising at least one unsaturation, and R3 denotes an alkyl group; or

[0122] R3', R3 and R3 independently designate an aliphatic chain, identical or different, including at least one unsaturation.

[0123] According to embodiments,

[0124] - Rj designates an aliphatic chain substituted by a thiol group;

[0125] - R2 designates an aliphatic chain substituted by a thiol group; and

[0126] R2 designates an alkyl group or designates an identical or different aliphatic chain substituted by a thiol group;

[0127] - R3' denotes an aliphatic chain substituted by a thiol group, and R3 and R3 designates an identical or different alkyl group; or

[0128] R3' denotes an aliphatic chain substituted by a thiol group, and, Independently, R3 designates an identical or different aliphatic chain substituted with a thiol group, and R3 designates an alkyl group; or

[0129] R3', R3 and R3 independently designate an aliphatic chain, identical or different, substituted by a thiol group.

[0130] Advantageously, the alkyl groups contain from 1 to 12 carbon atoms, preferably from 1 to 8 carbon atoms.

[0131] Advantageously, aliphatic chains comprising at least one unsaturation include from 2 to 14 carbon atoms. Aliphatic chains may include at least one terminal vinyl group or at least one unsaturated -CH=CH- group. Advantageously, aliphatic chains comprising at least one unsaturation are linear chains. Advantageously, aliphatic chains comprising at least one unsaturation are linear, comprise from 2 to 14 carbon atoms, and have a terminal vinyl group. Thus, advantageously, aliphatic chains comprising at least one unsaturation have the formula CH2=CH-(CH2)n-, with n ranging from 0 to 12.

[0132] Advantageously, aliphatic chains substituted with a thiol group comprise from 1 to 14 carbon atoms. These aliphatic chains include at least one terminal -SH group. Advantageously, aliphatic chains substituted with a thiol group are linear chains. Advantageously, aliphatic chains substituted with a thiol group are linear, comprise from 1 to 14 carbon atoms, and have a terminal -SH group. Thus, advantageously, aliphatic chains substituted with a thiol group have the formula -(CH2)nSH, with n ranging from 1 to 14.

[0133] Advantageously, M is the silicon with a valence of 4 (n=4). In this case, the metal alkoxide precursor is an alkoxysilane having an aliphatic chain comprising at least one unsaturation and / or substituted by a thiol group.

[0134] Alkoxysilane may be selected from the group consisting of: - a trialcoxysilane bearing an aliphatic chain comprising at least one unsaturation and / or substituted by a thiol group, - a dialcoxysilane bearing one or two aliphatic chains comprising at least one unsaturation and / or substituted by a thiol group, - a monoalkoxysilane bearing one, two, or three aliphatic chains comprising at least one unsaturation and / or substituted by a thiol group, and - their mixtures.

[0135] Advantageously, alkoxysilane is chosen from the group consisting of:

[0136] - a trialcoxysilane bearing an aliphatic chain comprising at least one unsaturation,

[0137] - a dialcoxysilane bearing one or two aliphatic chains comprising at least an unsaturation,

[0138] - a monoalkoxysilane bearing one, two or three aliphatic chains comprising at least one unsaturation,

[0139] - and their mixtures.

[0140] Advantageously, the precursor is a trialcoxysilane corresponding to the general formula Si(ORi)3Ri, a dialcoxysilane corresponding to the general formula Si(OR2)2R2 R2 or a monoalkoxysilane corresponding to the general formula Si(OR3)R3 R3 R3, or mixtures thereof, the R groups being as described above.

[0141] Advantageously, the alkoxysiloxane precursor is: - a trialcoxysilane corresponding to the general formula Si(ORi)3Ri, Ri being a methyl or ethyl group and R'1 being a linear aliphatic chain comprising 2 to 14 carbon atoms and a terminal vinyl function - a dialcoxysilane corresponding to the general formula Si(OR2)2R2 R2 , R2 being a methyl or an ethyl, R2 being a linear aliphatic chain comprising from 2 to 14 carbon atoms and a terminal vinyl function, and R2 being a methyl, an ethyl or a linear aliphatic chain comprising from 2 to 14 carbon atoms and a terminal vinyl function; - a monoalkoxysilane corresponding to the general formula Si(OR3)R3 R3 R3: • R3 being a methyl or an ethyl, • R3 being a linear aliphatic chain comprising from 2 to 14 carbon atoms and a terminal vinyl function, • R3 and R3 being independently of each other a methyl, an ethyl or a linear aliphatic chain comprising from 2 to 14 carbon atoms and a terminal vinyl function; or - their mixtures.

[0142] Advantageously, in this embodiment, the linear aliphatic chains comprising from 2 to 14 carbon atoms and a terminal vinyl function are identical to each other.

[0143] According to some embodiments, the alkoxysiloxane precursor is: - a trialcoxysilane corresponding to the general formula Si(ORi)3Ri, Ri being a methyl or an ethyl and R' i being a linear aliphatic chain comprising 2 to 4 carbon atoms and a terminal vinyl function; - a dialcoxysilane corresponding to the general formula Si(OR2)2R2 R2 , R2 being a methyl or an ethyl, R2 being a linear aliphatic chain comprising 2 to 4 carbon atoms and a terminal vinyl function, and R2 being a methyl, an ethyl or a linear aliphatic chain comprising 2 to 4 carbon atoms and a terminal vinyl function; - a monoalkoxysilane corresponding to the general formula Si(OR3)R3 R3 R3: • R3 being a methyl or an ethyl, • R3 being a linear aliphatic chain comprising 2 to 4 carbon atoms and a terminal vinyl function, • R3 and R3 being independently of each other a methyl, an ethyl, or a linear aliphatic chain comprising 2 to 4 carbon atoms and a terminal vinyl function; or - their mixtures.

[0144] Alkoxysilane may be vinyltrimethoxysilane (VTMO), vinyltriethoxysilane (VTEO), trivinylmethoxysilane (TVMO), trivinylethoxysilane (TVEO) or mixtures thereof.

[0145] When the alkoxysilane precursor has one or two aliphatic chains comprising at least one unsaturation, it can be the only alkoxysilane in the sol-gel composition.

[0146] This could therefore be: - a trialcoxysilane carrying an aliphatic chain comprising at least one unsaturation, - a dialcoxysilane carrying one or two aliphatic chains comprising at least one unsaturation - a monoalkoxysilane carrying one or two aliphatic chains comprising at least one unsaturation.

[0147] For example, the sol-gel composition may comprise vinyltrimethoxysilane or vinyltriethoxysilane as the sole alkoxysilane.

[0148] Such alkoxysilanes can also be considered in mixtures.

[0149] According to embodiments, an alkoxysilane precursor bearing one or two aliphatic chains comprising at least one unsaturation or a mixture of such precursors can be used in mixture with a trialcoxysilane bearing an aliphatic chain comprising at least one unsaturation.

[0150] For example, vinyltrimethoxysilane can be used in a mixture with trivinylmethoxysilane or vinyltriethoxysilane can be used in a mixture with trivinylethoxysilane

[0151] The at least one sol-gel mixture for layer (3a) may further comprise a metal alkoxide-type precursor not carrying unsaturation.

[0152] The at least one sol-gel mixture for layer (3a) may comprise one or more alkoxysilane precursors bearing at least one aliphatic chain comprising at least one unsaturation in mixture with at least one metal alkoxide precursor not bearing an unsaturation.

[0153] Advantageously, the metal alkoxide-type precursor without unsaturation is chosen from the group consisting of methyltrimethoxysilane (MTMS), tetraethoxysilane (TEOS), methyltriethoxysilane (MTES), dimethyldimethoxysilane, and mixtures thereof.

[0154] Thus advantageously, layer (3c) is obtained from a sol-gel mixture including: - vinyltrimethoxysilane (VTMO) or vinyltriethoxysilane (VTEO), and, - trivinylmethoxysilane (TVMO) or trivinylethoxysilane (TVEO), and - methyltrimethoxysilane (MTMS) or methyltriethoxysilane (MTES).

[0155] Examples of alkoxysilane mixtures for the sol-gel mixture for layer (3c) include the following mixtures: - vinyltrimethoxysilane and methyltrimethoxysilane, - vinyltrimethoxysilane and methyltriethoxysilane - trivinylmethoxysilane and methyltrimethoxysilane - trivinylmethoxysilane and methyltriethoxysilane - vinyltrimethoxysilane, trivinylmethoxysilane and methyltrimethoxysilane - vinyltrimethoxysilane, trivinylmethoxysilane and methyltriethoxysilane - vinyltriethoxysilane and methyltrimethoxysilane, - vinyltriethoxysilane and methyltriethoxysilane - trivinylethoxysilane and methyltrimethoxysilane - trivinylethoxysilane and methyltriethoxysilane - vinyltrimethoxysilane, trivinylethoxysilane and methyltrimethoxysilane - vinyltrimethoxysilane, trivinylethoxysilane and methyltriethoxysilane - vinyltriethoxysilane, trivinylmethoxysilane and methyltrimethoxysilane - vinyltriethoxysilane, trivinylmethoxysilane and methyltriethoxysilane - vinyltriethoxysilane, trivinylethoxysilane and methyltrimethoxysilane - vinyltriethoxysilane, trivinylethoxysilane and methyltriethoxysilane

[0156] The sol-gel layer (3a) can be obtained by successively depositing several identical or different sol-gel mixtures as described above, and then implementing a heat treatment step enabling the obtaining of a single sol-gel layer (3a).

[0157] The heat treatment step can be the cooking step viii. of the process which is the subject of the invention as described below.

[0158] The layer (3a) may comprise at least one metal oxide, preferably a colloidal metal oxide selected from colloidal silica and / or colloidal alumina and / or colloidal zirconia and / or colloidal titanium.

[0159] Advantageously, the thickness of the layer (3a) is between 1 pm and 100 pm, preferably between 30 pm and 60 pm.

[0160] LAYER (3c)

[0161] The top layer (3c) comprises an elastomeric silicone obtained from at least one organopolysiloxane bearing vinyl reactive functions (-CH=CH2) and at least one other organopolysiloxane bearing silyl hydride reactive functions (-Si-H) or thiol reactive functions (-SH).

[0162] When the silicone elastomer of layer (3c) is obtained from at least one organopolysiloxane bearing reactive thiol (-SH) functions, the metal alkoxide-type precursor of layer (3a) has an aliphatic chain comprising at least one unsaturation and which may further be substituted by a thiol (-SH) group.

[0163] Advantageously, the top layer (3c) further comprises:

[0164] - one or more thermoplastic polymers, and / or

[0165] - one or more additive(s), and / or

[0166] - one or more coloring agents.

[0167] At least one organopolysiloxane bearing reactive vinyl functions (-CH=CH2) and at least one other organopolysiloxane bearing reactive silyl hydride functions (-Si-H) or reactive thiol functions (-SH) are precursors which react to obtain an elastomeric silicone.

[0168] The silicone elastomer of layer (3c) forms a network which can be made up of a combination of 4 simple organosiloxane units designated M, D, T and Q depending on the degree of substitution by the oxygen of the silicon atom, as described in the following table, where R is an organic substituent described later.

[0169] [Tables 1] Structure Degree of substitution by oxygen Symbol 1 M ? '"OSrO"" R 2 0 R Ô ï 3 T ô è 4 Q

[0170] The precursors of the elastomer are organopolysiloxanes. These macromolecules are formed of M, D, T, and / or Q units as described in the table, where R is independently an alkyl group, in particular methyl, or aryl group, in particular phenyl, different natures of R being able to be present on the same macromolecule.

[0171] Organopolysiloxanes can be either linear or sparsely branched (majority of D groups). Linear or sparsely branched organopolysiloxanes are generally liquid, more or less viscous at room temperature, and are called silicone oils.

[0172] Organopolysiloxanes bearing reactive (3c) layer functions are precursors that react by crosslinking, which is a polyaddition. This crosslinking occurs through a reaction between the reactive vinyl (-CH=CH2) functions present on one of the organopolysiloxanes and the reactive silyl hydride (-Si-H) or reactive thiol (-SH) functions present on the other organopolysiloxane mixed with the first.

[0173] This crosslinking can be achieved by thermal activation, UV irradiation activation, or chemical activation. Preferably, this crosslinking occurs in the presence of a catalyst or a radical initiator.

[0174] According to an embodiment in which the silicone elastomer of the layer (3c) is obtained from at least one organopolysiloxane bearing reactive vinyl functions (-CH=CH2) and at least one other organopolysiloxane bearing reactive silyl hydride functions (-Si-H), the reaction is preferably carried out in the presence of a metallic catalyst, for example platinum or a suitable platinum-based catalyst such as the Karstedt catalyst or the Ashbys catalyst.

[0175] According to an embodiment in which the silicone elastomer of layer (3c) is obtained from at least one organopolysiloxane bearing reactive vinyl functions (-CH=CH2) and at least one other organopolysiloxane bearing functions In thiol (-SH) reagents, the reaction preferentially occurs in the presence of a radical initiator. In one embodiment, this may be a thermally activated radical initiator such as 2,2'-Azobis(2-methylpropionamidine) dihydrochloride (or V50). In another embodiment, it may be a radical initiator activated by UV irradiation such as Irgacure®651 (2,2-Dimethoxy-2-phenylacetophenone).

[0176] Advantageously, organopolysiloxanes bearing reactive functions of the (3c) layer are silicone oils.

[0177] Reactive functional groups are present on each organopolysiloxane, with at least one such group and two, three, or more, as far as the molecular structure allows. Silicone oils containing at least one reactive functional group are called "reactive oils." The reactive functional groups may be located either at the ends of the macromolecular chain (termination) or distributed along the chain.

[0178] Advantageously, the thickness of the topcoat (3c) is between 0.1 pm and 10 pm, preferably between 0.5 pm and 5 pm, particularly preferably between 1 pm and 2 pm.

[0179] The finishing layer (3c) is at least partially in contact with the layer (3a).

[0180] According to some embodiments, the finishing layer (3c) covers the entire surface of the surface of layer (3a).

[0181] According to other embodiments, one or more discontinuous intermediate layer(s) (3b) are positioned between layer (3a) and the finishing layer (3c). In this case, the finishing layer (3c) is in contact on part of its surface with the discontinuous intermediate layer(s) (3b) and on another part of its surface with layer (3a).

[0182] Fig. 2 illustrates an embodiment in which a discontinuous intermediate layer (3b) is positioned between layer (3a) and the finishing layer (3c).

[0183] The discontinuous intermediate layer(s) (3b) are as described below.

[0184] LAYER(S) (3b)

[0185] According to embodiments, the coated substrate comprises one or more discontinuous intermediate layers (3b) which may be decorations.

[0186] The layer(s) (3b) do not cover the entire layer (3a) and may form at least one decoration.

[0187] Advantageously, the thickness of the layer(s) (3b) is between 1 pm and 100 pm, preferably between 2 pm and 30 pm, particularly preferably between 3 pm and 10 pm.

[0188] COATING

[0189] The different layers of the coating according to the invention may include other components such as thermoplastic polymers, fillers, additives, coloring agents and / or silicone resins.

[0190] THERMOPLASTIC POLYMERS

[0191] Advantageously, the thermoplastic polymer(s) is / are chosen from the group consisting of aromatic thermoplastic polymer(s) such as polyaryletherketone(s) (PAEK), poly(arylethersulfones) (PAES), poly(arylene sulfides) (PAS) or poly(phenylene oxide) (PPO), liquid crystal polymers, heterocyclic thermoplastic polymers and mixtures thereof.

[0192] Advantageously, the layer (3c) comprises one or more thermoplastic polymer(s), preferably in a weight proportion of said layer less than 15%, preferably 10%.

[0193] Heterocyclic thermoplastic polymers

[0194] By way of suitable examples of heterocyclic thermoplastic polymers according to the invention are polyetherimides (PEI), polyimides (PI), polyamideimides (PAI) and polybenzymidazole (PBI), or mixtures thereof.

[0195] PAEK

[0196] Advantageously, the polyaryletherketone(s) (PAEK) is / are chosen from the group consisting of: polyetherketones (PEK), polyetheretherketone (PEEK), polyetherketoneketones (PEKK), polyetheretherketoneketones (PEEKK) and polyetherketoneetherketoneketones (PEKEKK), particularly preferably is / are PEEK.

[0197] CHARGES

[0198] The fillers as defined in the invention provide mechanical reinforcement and can also impart hydrophobic properties, while improving the mechanical strength and thermal conductivity of the coating. The fillers do not solely serve to impart color to the coating, but can contribute to this function.

[0199] Advantageously, the filler(s) is / are chosen from the group consisting of ceramic fillers (SiO2, etc.) and / or mineral and / or metallic fillers (Al2O3, TiO2, etc.) and / or silicas and / or diamond particles.

[0200] Preferably, the filler(s) is / are chosen from the group consisting of metal oxides, metal carbides, metal oxynitrides, metal nitrides, and mixtures thereof. Advantageously, said metal is boron or a transition metal, such as at least one of the elements chosen from Ni, Ti, Zr or Hf.

[0201] Preferably, the charge(s) is / are chosen from the group consisting of:

[0202] - Reinforcement charges: hard organic or inorganic charges; the charges Hard inorganic materials are preferably silicon carbide particles or of alumina or zirconia or graphite, or ceramics, or carbonate, or hydrated alumina, aluminum trihydroxide or one or more metal oxide(s), graphite, graphene;

[0203] - other fillers for reinforcement selected from metallic oxides: silica, micas, lamellar charges, clays such as montmorillonite, sepiolite, gypsite, kaolinite and laponite, zinc dioxide, quartz, and zirconium phosphate, alumina, zirconia, zinc oxide, copper oxide, iron oxide;

[0204] - fillers selected from reinforcing fibers: glass or carbon fiber or aramid;

[0205] - conductive charges comprising a boron carbide and / or a boron nitride and / or a transition metal carbide and / or a transition metal nitride: characterized in that the transition metal is at least one of the elements selected from Ni, Ti, Zr or Hf;

[0206] - lamellar charges that can confer lubricating properties, such as by Examples include clays, graphene, graphite, and tungsten sulfide.

[0207] Preferably, the filler(s) is / are chosen from the group consisting of alumina, silicon carbide, tungsten carbide, boron nitride, quartz, and mixtures thereof.

[0208] Advantageously, the fillers present in the sol-gel layer (3a) or the optional intermediate layer(s) (3b) are hard inorganic fillers, preferably oxides, carbides, metal nitrides, preferably alumina, silicon carbides or fumed silica.

[0209] Certain hard inorganic fillers, such as silicon carbide, in addition to their mechanical reinforcement properties, also have the advantage of being conductive fillers, thus providing excellent thermal conductivity. Adding this type of filler improves cooking performance by enhancing heat diffusion from the metallic substrate to the food in contact with the coating.

[0210] Advantageously, the average diameter d50 of the charges is between 0.1 and 50 pm, advantageously still between 5 and 15 pm.

[0211] Advantageously, the proportion of fillers in a layer is between 0.5 and 30% by dry weight relative to the total weight of said layer after baking, preferably between 5 and 20%.

[0212] Advantageously, the proportion of charges in layer (3a) is greater than 20% by weight, preferably greater than 30% by weight, relative to the total weight of said layer.

[0213] ADDITIVES

[0214] Advantageously, said additives are chosen from the group consisting of antifoaming agents, dispersing agents, wetting agents, thickeners, pH adjusters, reactive silicone oils.

[0215] Said antifoaming agent(s) (is) preferably chosen from the group consisting of mineral oils, diols, hydrocarbons, glycerides, oxyrane, emulsified fatty acids.

[0216] The surfactant(s) is / are preferably chosen from the group consisting of glycol ether, ethoxylated alcohol excluding alkyl phenol ethoxylates (APEs), gemini surfactants.

[0217] The dispersing agent(s) is / are preferably chosen from the group consisting of anionic dispersants such as fatty acid derivatives.

[0218] Said thickeners are preferably chosen from the group consisting of acrylic-based or polyurethane-based copolymer, cellulose, fumed silica.

[0219] Said pH adjusters are preferably chosen from the group consisting of Brønsted bases: ammonia, amines (triethylamine, triethanolamine...), hydroxides (sodium hydroxide, potassium hydroxide...), carbonates.

[0220] Advantageously, the proportion of additives in layer (3a) is less than 1% by weight relative to the total weight of said layer.

[0221] Advantageously, the proportion of additives in the layer (3c) is less than 20% by weight relative to the total weight of said layer.

[0222] COLOURING AGENTS

[0223] Advantageously, the colouring agent(s) is / are chosen from the group consisting of thermochromic pigments, thermostable pigments, glitter, preferably holographic glitter, and mixtures thereof.

[0224] Advantageously, the proportion of colouring agents in the layers (3a), optional (3b), and (3c) is between 0.5 and 50% by dry weight relative to the total weight of said layer after baking.

[0225] Advantageously, the proportion of coloring agents in the (3a) and optional (3b) layers ranges from 10 to 40% by weight relative to the total weight of said layer.

[0226] Advantageously, the proportion of coloring agents in layer (3c), when present, is less than 10% by weight relative to the total weight of said layer.

[0227] Advantageously, the proportion of coloring agents in layers (3a), optional (3b), and (3c) may be the same or different.

[0228] Advantageously, the nature of the coloring agents in the layers (3a), optional (3b), and (3c) may be identical or different.

[0229] Advantageously, layer (3c) is transparent. In this case, if it includes coloring agents, these coloring agents are glitter.

[0230] Thermochromic pigments

[0231] Preferably, the thermochromic pigment(s) is / are chosen from the group consisting of Bi2O3, Fe2O3, V2O5, WO3, CeO2, In2O3, Yi^CaojeTii^Vo.ieCW Agi, (Bix xAx)(Vi_yMy)O4avec - x is equal to 0 or x is between 0.001 and 0.999, - y is equal to 0 or y is between 0.001 and 0.999, - A and M are chosen from the group consisting of nitrogen, phosphorus, an alkali metal, an alkaline earth metal, a transition metal, a post-oxidation metal, a metalloid, or a lanthanide, - A and M are different from each other.

[0232] Preferably, A and M different from each other are B and / or Mg.

[0233] Preferably, x and y are 0, that is, the pigment (Bii.xAx)(Vi yMy)O4 is Bismuth Vanadate (BiVO4). Advantageously, a BiVO4 with a monoclinic scheelite crystallographic structure at room temperature is used.

[0234] Heat-stable pigments

[0235] Preferably, the thermostable pigment(s) is / are chosen from the group consisting of:

[0236] - Titanium rutile-type yellow pigment,

[0237] - Yellow pigment derived from bismuth, for example selected from the vanadates of stabilized bismuth (Py i84)

[0238] - Red pigment, for example selected from perylene red (for example PR149, PR178 and PR224), iron oxide,

[0239] - Orange pigment of the bismuth oxyhalide type (PO85),

[0240] - Bismuth vanadate orange pigment (PO86)

[0241] - Zinc tin titanium orange pigment (PO82)

[0242] - Orange pigment of cerium sulfide (PO75; PO78)

[0243] - Yellow-orange rutile-type pigment of antimony titanium chromium (PBr24)

[0244] - Yellow-orange pigment of the tin and zinc rutile type (Py2i6)

[0245] - Yellow-orange pigment of niobium oxide tin zinc sulfide (Py227)

[0246] - Orange-yellow pigment of double oxides of tin and niobium

[0247] - Co3(PO4)2

[0248] - LiCoPO4

[0249] - CoA12O4

[0250] - Cr2O3

[0251] - TiO2

[0252] - Black pigment PBk28 (Copper chromite black spinel)

[0253] - and their mixtures.

[0254] Sequins

[0255] The glitter used in the context of the present invention can be independently selected from mica glitter, coated or uncoated, silica glitter, coated or uncoated, aluminum glitter, coated or uncoated, iron oxide glitter, coated or uncoated, or mica or silica glitter coated with titanium dioxide. The glitter used in the context of the present invention can be treated to give a particular color effect.

[0256] Advantageously, the glitter(s) is / are particles selected from the group consisting of mica particles, aluminum particles, mica coated with titanium dioxide, or mixtures thereof.

[0257] Hologram sequins

[0258] Advantageously, the glitter(s) is / are holographic glitter, that is to say a mixture of magnetizable and non-magnetizable particles.

[0259] Magnetizable particles may advantageously be particles comprising at least one ferromagnetic metal. These magnetizable particles may be homogeneous, i.e., made of the same material, or composite, i.e., having a core-shell structure in which the ferromagnetic metal is located in the core and / or the shell of said particles. Examples of composite magnetizable particles include mica flakes coated with iron oxide Fe2O3 or stainless steel fibers coated with a sol-gel material, as corrosion protection during the coating application stages, or plastic material flakes coated with iron oxide Fe2O3, or flakes whose core is made of a ferromagnetic metal and whose shell is made of a plastic material or a sol-gel material.

[0260] According to one embodiment, a portion of said magnetizable particles is oriented so as to form a three-dimensional decoration.

[0261] Advantageously, the magnetizable particles and / or the non-magnetizable particles are colored on the surface.

[0262] Advantageously, the non-magnetizable particles are made of mica, aluminum, or mica coated with titanium dioxide.

[0263] Advantageously, the magnetizable particles consist of iron, iron oxide, aluminum coated with iron, or mica coated with iron, the iron being in ferritic form.

[0264] SILICONE RESINS

[0265] In the description text, the expression "#silicone resin#" is used interchangeably to refer to silicone before or after crosslinking. In the description text, the expression "silicone" refers to an organopolysiloxane material. Crosslinking is the step that transforms the silicone is transformed into an insoluble material, for example by polyaddition, polycondensation, or dehydrogenation. Crosslinking is carried out using precursors, which are generally silicone oils or resins, that crosslink to obtain a three-dimensional network forming a material called silicone resin, as described herein.

[0266] This crosslinking can be achieved by thermal activation, or chemical activation using a catalyst, such as platinum.

[0267] Advantageously, the silicone resin(s), obtained after crosslinking of their precursors, i.e. crosslinked(s), is / are chosen from the group comprising methyl silicones and / or phenyl silicones and / or methyl-phenyl-silicones, methyl silicone-polyester resins (copolymers), phenyl silicone-polyester resins (copolymers), methyl-phenyl silicone-polyester resins (copolymers), silicone-alkyd resins (copolymers), modified silicone resins and their mixtures.

[0268] PROCEDURE

[0269] The invention also relates to a method for manufacturing a coated cooking element (1) according to the invention comprising the following successive steps:

[0270] i. supply of a metallic substrate (2) comprising at least one face (2a) intended to be coated,

[0271] ii. possibly, pretreatment of the face (2a),

[0272] iii. application of the sol-gel base layer (3a) on the face (2a),

[0273] iv. optionally, drying and / or baking of the layer (3a),

[0274] v. where applicable, application of layer(s) (3b),

[0275] vi. optionally, drying of layer(s) (3b) and / or baking of layer(s) (3b) and, where applicable, of layer (3a),

[0276] vii. application of the topcoat (3c),

[0277] viii. cooking of the layers and obtaining the element (1).

[0278] Step (iii) is implemented in particular as described above in connection with the sol-gel composition.

[0279] Where appropriate, at least one discontinuous intermediate layer (3b) is applied over the base layer (3a).

[0280] Generally, the coating layers are wet during their application. By wet layer, it is understood in the context of the present invention that the layer comprises all or part of its solvents.

[0281] Advantageously, the manufacturing process for a coated cooking element (1) according to the invention comprises one or more drying steps between 80 and 150°C after the application of each of the layers in order to remove all or part of the solvents from the wet layer. The drying can be carried out either naturally or by a physical treatment (for example, by thermal drying (convection or infrared), by airflow drying, or by vacuum treatment).

[0282] The application of the coating according to the invention by the process according to the invention can be carried out on the shaped substrate or on a locally flat area of ​​the shaped substrate. Advantageously, the process for manufacturing a coated cooking element (1) according to the invention includes a shaping step of said substrate (2) before step iii. The shaping is also called stamping.

[0283] The process according to the invention comprises a step viii. of baking the element obtained at the end of step vii. of the process. By baking the coated substrate, we mean, for the purposes of the present invention, a heat treatment which makes it possible to densify the coating layer(s) applied to the substrate and advantageously to crosslink the organopolysiloxane precursors of the layer (3c).

[0284] Without wishing to be bound by any theory, the cooking step viii. would also allow reactive functions of layer (3a) and reactive functions of layer (3c) to react at the points where layer (3a) and layer (3c) are in contact. For example, the following may react: - part of the silyl hydride functions provided by the at least one organopolysiloxane used for layer (3c) and the unsaturations introduced by the metal alkoxide-type precursor having an aliphatic chain comprising at least one unsaturation of the sol-gel layer (3a), or - part of the thiol functions provided by the at least one organopolysiloxane used for layer (3c) and the unsaturations introduced by the metal alkoxide-type precursor having an aliphatic chain comprising at least one unsaturation of the sol-gel layer (3a), or - part of the vinyl functions provided by the at least one organopolysiloxane used for layer (3c) and the thiol functions introduced by the metal alkoxide type precursor having an aliphatic chain substituted by a thiol group of the sol-gel layer (3a).

[0285] The baking step thus makes it possible to obtain a robust anchoring of the finishing layer (3c) on the sol-gel layer (3a), thus leading to a more durable non-stick coating.

[0286] According to some embodiments, step vi. includes a firing step following, where appropriate, a drying step as described above. The firing step may also be carried out without a prior drying step.

[0287] According to some embodiments, the process comprises a single final co-baking step of the layers during step viii. This single baking step is carried out simultaneously for all the applied layers.

[0288] In this case, the cooking during step viii. is carried out at a temperature ranging from 150°C to 350°C, for a duration of 1 min to 45 min.

[0289] When a layer baking step (3a), and where applicable (3b), is carried out during step vi., the baking step x. is carried out at a temperature ranging from 150°C to 300°C for a duration of 1 min to 45 min. This process is advantageous compared to that comprising only a final baking step because it allows the temperature of the baking step viii to be lowered.

[0290] According to an advantageous arrangement of the invention, the topcoat (3c) is applied to the coated substrate at a deposition rate of less than or equal to 5 g / m2, preferably between 0.1 and 2.5 g / m2, even more preferably between 0.2 and 2 g / m2.

[0291] Advantageously, the process according to the invention further comprises a crosslinking step vii' of the topcoat (3c) subsequent to or simultaneous with step vii and preceding the baking step viii.

[0292] According to one variant, the crosslinking vii'. of the composition of the layer (3c), can be activated for example by heat treatment, at a temperature between 50 and 400°C, preferably between 50 and 300°C, taking into account of course the maximum resistance of the support to heat.

[0293] Advantageously, the crosslinking of the layer composition (3c) is carried out at a temperature of 300°C for a period of 10 min.

[0294] Advantageously, the higher the crosslinking temperature, the shorter the crosslinking time.

[0295] According to one embodiment, the crosslinking step vii' does not require heat treatment, in particular because the support is hot at the time of step vii.

[0296] Steps iii. and vii. of application can be carried out by electrostatic powder coating, by solvent-based or aqueous spray spraying, by screen printing, by roller or by digital printing.

[0297] Preferably, in particular step vii. is carried out by electrostatic powder coating, by spraying in solvent or aqueous phase.

[0298] Typically, the substrate has the final shape of the cooking article with a concave inner face 2a intended to be positioned on the side of the food that may be introduced into said article, and a convex outer face intended to be positioned on the side of a heat source.

[0299] PREFERRED ARCHITECTURES

[0300] According to one embodiment, the invention relates to a coated cooking element (1) for a cooking article or electric cooking appliance, comprising a metallic substrate (2) coated on at least one face (2a) by a coating (3) consisting of the following two layers and in this order from the metallic substrate (2):

[0301] (3a) a sol-gel layer obtained from a sol-gel (SG) mixture comprising a metal alkoxide precursor having an aliphatic chain comprising at least one unsaturation, and

[0302] (3c) a topcoat comprising an elastomeric silicone obtained from less one organopolysiloxane bearing vinyl reactive functions (-CH=CH2) and at least one other organopolysiloxane bearing silyl hydride reactive functions (-Si-H).

[0303] According to another embodiment, the invention relates to a coated cooking element (1) for a cooking article or electric cooking appliance, comprising a metallic substrate (2) coated on at least one face (2a) by a coating (3) consisting of the following two layers and in this order from the metallic substrate (2):

[0304] (3a) a sol-gel layer obtained from a sol-gel (SG) mixture comprising a metal alkoxide precursor having an aliphatic chain comprising at least one unsaturation,

[0305] (3c) a topcoat comprising an elastomeric silicone obtained from less one organopolysiloxane bearing vinyl reactive functions (-CH=CH2) and at least one other organopolysiloxane bearing thiol reactive functions (-SH).

[0306] According to another embodiment, the invention relates to a coated cooking element (1) for a cooking article or electric cooking appliance, comprising a metallic substrate (2) coated on at least one face (2a) by a coating (3) consisting of the following two layers and in this order from the metallic substrate (2):

[0307] (3a) a sol-gel layer obtained from a sol-gel (SG) mixture comprising a metal alkoxide type precursor having an aliphatic chain substituted by a thiol group (-SH),

[0308] (3c) a topcoat comprising an elastomeric silicone obtained from less one organopolysiloxane bearing vinyl reactive functions (-CH=CH2) and at least one other organopolysiloxane bearing silyl hydride reactive functions (-Si-H).

[0309] According to another embodiment, the invention relates to a coated cooking element (1) for a cooking article or electric cooking appliance, comprising a metallic substrate (2) coated on at least one face (2a) by a coating (3) consisting of the following two layers and in this order from the metallic substrate (2):

[0310] (3a) a sol-gel layer obtained from a sol-gel (SG) mixture comprising a metal alkoxide type precursor having an aliphatic chain comprising at least one unsaturation and substituted by a thiol group (-SH),

[0311] (3c) a topcoat comprising an elastomeric silicone obtained from less one organopolysiloxane bearing vinyl reactive functions (-CH=CH2) and at least one other organopolysiloxane bearing silyl hydride reactive functions (-Si-H).

[0312] According to another embodiment, the invention relates to a coated cooking element (1) for a cooking article or electric cooking appliance, comprising a metallic substrate (2) coated on at least one face (2a) by a coating (3) consisting of the following two layers and in this order from the metallic substrate (2):

[0313] (3a) a sol-gel layer obtained from a sol-gel (SG) mixture comprising a metal alkoxide type precursor having an aliphatic chain comprising at least one unsaturation and substituted by a thiol group (-SH),

[0314] (3c) a topcoat comprising an elastomeric silicone obtained from less one organopolysiloxane bearing vinyl reactive functions (-CH=CH2) and at least one other organopolysiloxane bearing thiol reactive functions (-SH).

[0315] According to a particular embodiment, the coating further comprises a discontinuous intermediate layer (3b) forming a decoration.

[0316] Advantageously: • the thickness of layer (3a) is between 1 pm and 100 pm, preferably between 30 pm and 60 pm, and • the thickness of the layer(s) (3b), when present, is between 1 pm and 100 pm, preferably between 3 pm and 10 pm, and • The thickness of the topcoat (3c) is between 0.1 pm and 10 pm, preferably between 1 pm and 2 pm.

[0317] ARTICLE

[0318] The invention also relates to a cooking article (100) comprising a coated cooking element (1).

[0319] According to an embodiment illustrated in [Fig. 3], the cooking article (100) comprises a heating surface (6) intended to be in contact with an external heat source, the heating surface (6) being opposite the cooking surface (2a) intended to be coated with the coating of the invention. The cooking surface (5) is typically the face of the coating according to the invention intended to be in contact with the food during cooking.

[0320] Advantageously, the culinary article (100) according to the invention is chosen from the group consisting of saucepan, frying pan, fondue or raclette pan, stockpot, wok, sauté pan, crepe pan, grill, plancha, pot, casserole dish, cooker or bread machine bowl, culinary mold.

[0321] The invention also relates to an electric cooking appliance (200) as illustrated in [Fig.4] comprising a coated cooking element (1) according to the invention and a heating source (210) configured to heat said coated cooking element (1).

[0322] Advantageously, the electric cooking appliance (200) is chosen from the group consisting of electric crepe maker, electric raclette appliance, electric fondue appliance, electric grill, electric plancha, electric cooker, bread machine, electric pressure cooker, waffle makers, rice cookers and jam makers.

[0323] The culinary article according to the present invention may in particular be a culinary article in which one of the two opposite faces of the substrate is an interior face, possibly concave, intended to be disposed on the side of food that may be introduced into or onto said article, and in which the other face of the substrate is an exterior face, possibly convex, intended to be disposed towards a heat source.

[0324] By way of non-limiting examples of cookware conforming to the present invention, mention shall be made in particular of cookware such as saucepans and frying pans, woks and sauté pans, stockpots and casseroles, crepe makers, baking molds and trays, barbecue plates and grills, and preparation bowls. EXAMPLES

[0325] The goals, aspects and advantages of the present invention will be better understood from the following description of a particular embodiment of the invention presented by way of non-limiting example.

[0326] Of course, the invention is in no way limited to the embodiment described and illustrated, which has been given only by way of example. Modifications remain possible, particularly with regard to the composition of the various elements or by substitution of technical equivalents, without departing from the scope of protection of the invention. Examples and counter-examples of implementation:

[0327] Metallic substrate: This is an aluminum support that has been sandblasted or shot-blasted and then subjected to a suitable surface treatment to eliminate organic contaminants.

[0328] The raw materials for the different layers are detailed below.

[0329] Example 1: Preparation of a coating according to the invention

[0330] The coating of Example 1 comprises: - a sol-gel base layer (3a) obtained with a metal alkoxide-type precursor having an aliphatic chain comprising at least one unsaturation, and - a finishing layer (3c 1) comprising an elastomeric silicone obtained in particular from an organopolysiloxane carrying reactive silyl hydride (-Si-H) functions. Base layer (3a)

[0331] The base layer formulation (3a) 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. Part B incorporates the reactive organopolysiloxane VTMO and the acid catalyst. Part C incorporates the pigments, fillers, solvents, wetting agent, and PDMS oil.

[0332] [Tables2] Layer Components (3a) Part % Wet % Baked Colloidal Silica (30%) A 41.2 23.5 VTMO B 29.1 29.5 Acetic Acid B 0.9 0.0 Isopropanol C 3.3 0.0 Butyl Glycol C 0.9 0.0 Hydroxylated PDMS Oil C 1.2 2.3 Black Pigment C 15.5 29.6 Micro Alumina C 7.8 14.9 Wetting Agent C 0.1 0.2 TOTAL 100 100

[0333] The process is as follows:

[0334] Part A is agitated with a shearing blade and a speed of 1000 rpm, sufficient to obtain a net vortex.

[0335] Part B is prepared separately by mixing the silane with the acid, then introduced under stirring into part A: the hydrolysis reaction of VTMO then begins, and must continue for a minimum of 2 hours.

[0336] Next, part C is introduced into this mixture by incorporating the components one by one, always under stirring. It should be noted that we can also pre-mix all the components of part C separately, before introducing this paste into the A+B mixture after the 2 hours of reaction.

[0337] Once all the components have been mixed, stirring continues for 30 minutes, then the formulation is stored in a closed glass bottle.

[0338] It should also be noted, in terms of the mixing process, that we can also first introduce the components of part C into part A, and leave for 30 minutes agitate, then introduce part B alone and mix for 2 hours for the sol-gel reaction.

[0339] The mixture is then left at room temperature for 24 hours before application. The shelf life of this formulation is at least 48 hours.

[0340] The mixture can also be kept in a refrigerator at 5°C: in this case, its shelf life is extended to at least 72 hours.

[0341] The resulting mixture is then filtered with a 50 micron filter before being sprayed onto a sandblasted and degreased aluminium support, preheated to 55°C to prevent any dripping during coating.

[0342] A drying step is carried out at a temperature below 100°C for layer (3a). Layer (3a) has a dry thickness of 40 to 50 microns. Top coat (3cl)

[0343] The (3c 1) layer is obtained after crosslinking the following composition expressed as a relative proportion by dry mass:

[0344] - an organopolysiloxane bearing reactive vinyl functions (-CH=CH2): 100 parts,

[0345] - another organopolysiloxane bearing reactive silyl hydride functions (Si-H): 8 parts, and

[0346] - a metallic catalyst: 6 parts.

[0347] This above dry composition is mixed with a solvent to obtain a dry extract of the order of 50% to 60% by mass.

[0348] The layer (3c 1) is applied and then the assembly is baked at 300°C for 45 minutes. The thickness of the layer (3c 1) thus obtained is 4 µm.

[0349] Example 2: Preparation of a coating according to the invention

[0350] The coating of Example 2 comprises: - a base layer (3a) identical to that of example 1, and - a topcoat (3c2) comprising a silicone elastomer obtained at starting in particular from an organopolysiloxane carrying reactive thiol (-SH) functions. Topcoat (3c2)

[0351] The (3c2) layer is obtained after crosslinking the following composition expressed as a relative proportion by dry mass:

[0352] - an organopolysiloxane bearing reactive vinyl functions (-CH=CH2): 100 parts,

[0353] - another organopolysiloxane bearing reactive thiol functions (-SH): 8 parts, and

[0354] - a radical initiator: 15 shares.

[0355] This above dry composition is mixed with a solvent to obtain a dry extract of the order of 50% to 60% by mass.

[0356] The (3c2) layer is applied and then the assembly is baked at 300°C for 45 minutes. The thickness of the (3c2) layer thus obtained is 4 µm.

[0357] Counterexample 1: Preparation of a coating different from the present invention

[0358] The coating of counterexample 1 comprises: - a base layer (3a') different from that of the invention, and - a finishing layer (3cl) identical to that of example 1. Base layer (3a')

[0359] The wet compositions are obtained from 3 parts (A, B and C) as described for example 1.

[0360] [Tables3] Layer Components (3a') Part % Wet % Baked Colloidal Silica (30%) A 41.2 23.5 MTMS B 29.1 29.5 Acetic Acid B 0.9 0.0 Isopropanol C 3.3 0.0 Butyl Glycol C 0.9 0.0 Hydroxylated PDMS Oil C 1.2 2.3 Black Pigment C 15.5 29.6 Micro Alumina C 7.8 14.9 Wetting Agent C 0.1 0.2 TOTAL 100 100

[0361] The resulting mixture is filtered with a 50 micron filter before being sprayed onto the substrate.

[0362] A drying step is carried out at a temperature below 100°C for the base layer (3a'). The base layer (3a') will have a dry thickness of 40 to 50 microns.

[0363] Once the (3cl) layer has been applied, the assembly is baked at 300°C for 45 minutes. The thickness of the (3c 1) layer thus obtained is 4 µm.

[0364] Counterexample 2: Preparation of a coating different from the present invention

[0365] The coating of counterexample 2 comprises: - a base layer (3a') different from that of the invention and identical to that of counterexample 1, and - a topcoat (3c2) identical to that of example 2.

[0366] BOILING WATER TEST

[0367] In order to simulate aging due to aqueous cooking, we carry out a boiling water aging test.

[0368] The test procedure is as follows#:

[0369] - Washing the pan before testing# with warm water, yellow side of the sponge and detergent.

[0370] - Fill with tap water and heat until boiling.

[0371] - When boiling occurs, maintain heating and start the timer.

[0372] - After a 2-hour boiling period: wash the item with warm water and a sponge yellow side and detergent to remove surface limescale.

[0373] - Evaluation of anti-stickiness by cooking an egg.

[0374] - Cleaning and restarting a boiling cycle if the egg comes loose.

[0375] We thus carry out as many boiling cycles as necessary until the egg no longer comes off.

[0376] The higher the number of cycles, and therefore the number of hours, the more durable the coating is considered to be in terms of anti-stick performance.

[0377] Comparative results

[0378] The table below summarizes the tests carried out and the results in terms of durability of the anti-sticking through a cyclic boiling test described above.

[0379] [Tables4] Boiling Water Test Result (e in hours) Example 1: 50 Example 2: 50 Counter-example 1: 15 Counter-example 2: 15

[0380] The coating according to the invention exhibits durable anti-stick properties while being adherent to the substrate.

Claims

Demands

1. Coated cooking element (1) for a cooking article or electrical cooking appliance, comprising a metallic substrate (2) coated on at least one face (2a) by a coating (3) consisting of the following layers and in this order from the metallic substrate (2): (3a) a sol-gel base layer obtained from at least one sol-gel mixture (SG) comprising a metal alkoxide precursor having an aliphatic chain comprising at least one unsaturation and / or substituted by a thiol group, (3b) optionally one or more discontinuous intermediate layer(s) which may be decorations, and (3c) a top layer at least partially in contact with layer (3a) and comprising a silicone elastomer obtained from at least one organopolysiloxane bearing reactive vinyl functions (-CH=CH2) and at least one other organopolysiloxane bearing reactive silyl hydride functions (-Si-H) or reactive thiol functions (-SH),in which, when the silicone elastomer of layer (3c) is obtained from at least one organopolysiloxane bearing reactive thiol (-SH) functions, the metal alkoxide-type precursor of layer (3a) has an aliphatic chain comprising at least one unsaturation and which may further be substituted by a thiol (-SH) group.

2. Coated cooking element (1) according to claim 1 characterized in that the metal alkoxide-type precursor of the sol-gel mixture for layer (3a) is an alkoxysilane selected from the group consisting of: - a trialcoxysilane bearing an aliphatic chain comprising at least one unsaturation and / or substituted by a thiol group, - a dialcoxysilane bearing one or two aliphatic chains comprising at least one unsaturation and / or substituted by a thiol group, - a monoalkoxysilane bearing one, two or three aliphatic chains comprising at least one unsaturation and / or substituted by a thiol group, and - their mixtures.

3. Coated cooking element (1) according to claim 1 or claim 2 characterized in that the sol-gel mixture for layer (3a) further comprises a metal alkoxide type precursor not carrying unsaturation.

4. Coated cooking element (1) according to claim 3 characterized in that the metal alkoxide type precursor not carrying unsaturation is selected from the group consisting of methyltrimethoxysilane (MTMS), tetraethoxysilane (TEOS), methyltriethoxysilane (MTES), dimethyldimethoxysilane, and mixtures thereof.

5. Coated cooking element (1) according to any one of the preceding claims characterized in that the layer (3a) comprises at least one metal oxide, preferably a colloidal metal oxide selected from colloidal silica and / or colloidal alumina and / or colloidal zirconia and / or colloidal titanium.

6. Coated heating element (1) according to any one of the preceding claims, characterized in that the organopolysiloxanes bearing reactive functions of layer (3c) are silicone oils.

7. Coated cooking element (1) according to any one of the preceding claims, characterized in that: • the thickness of layer (3a) is between 1 pm and 100 pm, preferably between 30 pm and 60 pm, and • the thickness of layer(s) (3b), when present, is between 1 pm and 100 pm, preferably between 3 pm and 10 pm, and • the thickness of the finishing layer (3c) is between 0.1 pm and 10 pm, preferably between 1 pm and 2 pm.

8. A method for manufacturing a coated cooking element (1) according to any one of the preceding claims comprising the following successive steps: i. supplying a metallic substrate (2) comprising at least one face (2a) intended to be coated, ii. optionally, pre-treatment of the face (2a), iii. application of the sol-gel base coat (3a) on the face (2a), iv. optionally, drying and / or baking of the layer (3a), v. where applicable, application of the layer(s) (3b), vi. optionally, drying of the layer(s) (3b) and / or baking of the layer(s) (3b) and where applicable of the layer (3a), vii. application of the topcoat (3c), viii. baking of the layers and obtaining the element (1).

9. A method according to claim 8, characterized in that step viii is carried out at a temperature ranging from 150°C to 350°C for a duration of 1 min to 45 min.

10. Cooking article (100) or electric cooking appliance (200) comprising a coated cooking element (1) conforming to any one of claims 1 to 7 or capable of being obtained according to claim 8 or claim 9.

11. Culinary article (100) according to claim 10, selected from the group consisting of saucepan, frying pan, fondue or raclette pan, stockpot, wok, sauté pan, crepe pan, grill, griddle, pot, casserole dish, cooker or bread machine bowl, cooking mold, molds and baking trays, barbecue trays and grills, preparation bowls.

12. Electric cooking appliance (200) according to claim 10, selected from the group consisting of electric crepe maker, electric raclette grill, electric fondue set, electric grill, electric griddle, electric cooker, bread maker, electric appliance pressure cookers, waffle makers, rice cookers and jam makers.

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