Silica-free sol-gel finish with TMMS or tmes

Abstract

The present invention relates to the use of a sol-gel finishing layer to render non-stick or to improve the durability of the non-stick property of a coating free from fluorocarbon resin (3), applied to at least one face (2a) of a substrate (2) of a heating element for a household article, characterised in that the layer is free of silica and is obtained from a sol-gel composition comprising at least two polyalkoxysilane precursors, wherein the first is selected from the group of formula (I) RxSi(OR')4-x (I), where R is a (C1-C6)-alkyl, alkenyl-(C2-C6), (C3-C7)-cycloalkyl, (C4-C7)-cycloalkenyl, (C3-C7)-cycloalkyl-(C1-C6)-alkyl, aryl or aryl-(C1-C6) alkyl, optionally substituted. R' is a (C1-C8)-alkyl group; and x is 0, 1, 2 or 3; and the second is TMMS (trimethylmethoxysilane) or TMES (trimethylethoxysilane) or mixtures thereof.

Description

[0001] Silica-free sol-gel finish with TMMS or TMES

[0002] FIELD OF THE INVENTION

[0003] The present invention relates generally to the field of household articles comprising a surface covered with a non-stick coating. More specifically, the present invention applies to the field of non-stick coatings for cooking surfaces of kitchen articles and electrical cooking appliances. The present invention also relates to a method of manufacturing such articles.

[0004] The present invention addresses the technical problem of formulating solgel coatings with improved anti-adhesive durability.

[0005] STATE OF THE ART

[0006] In the field of cookware, coatings with non-stick properties are known, applied to metal substrates or supports (aluminum, aluminum casting, stainless steel, cast steel, etc.) which are of various chemical natures.

[0007] Specifically for the inner surfaces of these items, PTFE-type fluororesin coatings have been used for over 50 years, prized for their excellent non-stick properties. In recent years, so-called "ceramic" coatings, based on sol-gel chemistry, have also appeared on the market, offering superior thermal resistance and surface hardness to PTFE coatings, while retaining easy-to-clean properties.

[0008] It has been found that the non-stick properties of these sol-gel coatings decrease over time with the use of the cookware. It is known to those skilled in the art to add a silicone oil to compensate for this decrease in non-stick properties. However, the durability of these items, particularly their non-stick properties, remains limited and unsatisfactory for the user.

[0009] In addition, to obtain good mechanical properties, it is widely known, and all sol-gel coating manufacturers do it, to add colloidal silica to their coating formulations to obtain a coating several microns thick without cracks, with high mechanical resistance in all layers of the sol-gel coating, including the topcoat. Sol-gel formulations applied to cookware have been known for several years. Industrial formulations are based, in particular, on the hydrolysis and condensation of a silane MTES (MethylTriEthoxySilane) or MTMS (MethylTriMethoxySilane), with the addition of a non-reactive or reactive hydroxylated PDMS (polydimethylsiloxane) silicone oil in the primer and finish layers, always associated with colloidal silica.The role of silanes is to constitute a network which presents good mechanical characteristics, but also hydrophobic thanks to the presence of numerous methyl groups.

[0010] A hydrophobic compound, such as PDMS oil, is added to this network, which significantly increases the hydrophobic and non-stick properties. Unfortunately, the amount of PDMS oil cannot exceed a threshold beyond which the sol-gel coatings expel the excess oil. This results, at the end of condensation, in parts that are too greasy on the surface due to the seepage of the oil that is released.

[0011] STATEMENT OF THE INVENTION

[0012] The applicant has developed a finishing layer for sol-gel non-stick coatings making it possible to overcome the aforementioned drawbacks.

[0013] Surprisingly, the inventors have developed a ceramic coating that offers significant benefits to consumers. Cookware with this coating will retain its non-stick properties longer than other ceramic coatings.

[0014] The consumer will be able to use their item for several additional years. In addition to the obvious economic and environmental benefits, the consumer will achieve a significantly improved level of satisfaction during use, while potentially using less fat. In addition, another advantage of the invention is that the topcoat has optical properties compatible with the presence of visual attributes in the coating.

[0015] Furthermore, another advantage of the invention is that surprisingly satisfactory mechanical properties are retained and compatible with culinary use.

[0016] Furthermore, another advantage of the invention is that the topcoat can contain higher quantities of silicone oil than a standard coating, without surface release of this oil, which gives the coating longevity properties of its non-stick properties.

[0017] DESCRIPTION OF FIGURES

[0018] [Fig.1]: diagram of heating element according to the invention with layer (3b) is continuous and covers the entire layer (3a)

[0019] [Fig.2]: diagram of heating element according to the invention with layer (3b) not covering the entire layer (3a) and forming a decoration

[0020] [Fig.3]: diagram of heating element according to the invention with layer (3b) consisting of two decorations (i) and (j)

[0021] [Fig.4]: Pattern distribution diagram. 4A = adjacent non-overlapping patterns. 4B = partially overlapping patterns. 40 = overlapping patterns.

[0022] [Fig.5]: diagram of a culinary article according to the invention

[0023] [Fig.6]: diagram of an electrical cooking appliance according to the invention

[0024] DEFINITIONS

[0025] The term "coating" means all the layers adhering to the metal substrate and covering this substrate. The coating according to the invention obtained is advantageously solid, "solid" means the characteristic of a cohesive material insoluble in water, in common solvents, in food components such as aqueous or fatty mixtures, even if the material may have great hardness or great flexibility such as an elastomer.

[0026] The term "layer" is understood to mean, within the meaning of the present invention, a continuous or discontinuous layer. A continuous layer (or also called a monolithic layer) is a single whole forming a total flat area completely covering the surface on which it is placed. A discontinuous layer (or non-monolithic layer) may comprise several parts, thus not being a single whole.

[0027] The term "base coat", "primer coat", "bonding coat" or "bonding primer" refers to 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. The first layer of the coating is a primer coat.

[0028] The term "intermediate layer" means the layers inserted between the primary layer(s) and the finishing layer(s). The intermediate layer(s) may be "decorations" or "decorative layers". The intermediate layer(s) is / are not intended to come into contact with food.

[0029] The term "finish coat" or "finish" means a continuous surface layer applied after the intermediate layer(s) if the coating includes one or more intermediate layer(s) or after the primary layer(s). The last layer of the coating is a finishing coat. Usually, at least the last finishing coat, or even all finishing coats, is / are transparent to allow visibility of the underlying layers, in particular when the underlying layers are decorative layers. The finishing coat(s) protect the underlying layers from mechanical attack and give the coating its non-stick properties. Preferably, in the case of a cookware or electrical cooking appliance, the last finishing coat is intended to be in contact with food.

[0030] The term "decor" or "decorative layer" means one or more continuous or discontinuous layers comprising a pigment composition. The decor may be in the form of one or more patterns, or one or more colors. A decor is clearly visible to the user with the naked eye and at a normal distance from the household item.

[0031] Overlapping layers are defined as partially or completely overlapping layers. These layers may be in the form of partially overlapping patterns, for example concentric discs. Adjacent layers are defined as non-overlapping layers. These layers may be in the form of identical or different non-overlapping patterns, preferably uniformly distributed.

[0032] For the purposes of the present invention, the term sol-gel coating is understood to mean a coating synthesized by sol-gel method from a sol-gel composition. The coating thus obtained may be either organo-mineral or entirely mineral. For the purposes of the present invention, the term sol-gel method means the synthesis principle comprising the transformation of a solution based on precursors in the liquid phase into a solid, by a set of chemical reactions (hydrolysis and condensation) at low temperature. The coating thus obtained may be either organo-mineral or entirely mineral.

[0033] For the purposes of the present invention, the term organo-mineral coating means a coating whose network is essentially inorganic, but which includes organic groups, in particular due to the precursors used and the baking temperature of the coating or due to the incorporation of organic fillers.

[0034] For the purposes of the present invention, the term “fully mineral coating” means a coating based on a fully inorganic material, free of any organic group. Such a coating can be obtained by sol-gel method, generally with a baking temperature of at least 400°C, or from precursors of the metal alkoxylate type and / or precursors of the metal polyalkoxylate type, generally with a baking temperature which can be lower than 400°C.

[0035] The expression "cooking article" is understood to mean, within the meaning of the present invention, an object intended for cooking and to be heated by an external heating system such as frying pans, saucepans, sauté pans, woks, barbecue grills. A cooking article is capable of transmitting the heat energy provided by this external heating system to a material or food in contact with said object.

[0036] The expression "electric cooking appliance" is understood to mean, within the meaning of the present invention, a heating object having its own heating system, such as an electric crepe maker, an electric raclette appliance, an electric fondue appliance, an electric grill, an electric griddle, an electric cooker, a bread maker, or an electric pressure cooking appliance.

[0037] In the present invention, the % by weight are expressed in dry weight, i.e. without solvent. By "(Ci-Ce)alkyl" or "(Ci-Ce)alkyl" group is meant, within the meaning of the present invention, a saturated, linear or branched monovalent hydrocarbon chain, comprising 1 to 6, preferably 1 to 4, carbon atoms. By way of example, mention may be made of methyl, ethyl, propyl groups.

[0038] For the purposes of the present invention, the term “(C3-C7)cycloalkyl” or “(C3-C7)cycloalkyl” group means a saturated cyclic hydrocarbon chain comprising 3 to 7 cyclic carbon atoms. A cycloalkyl may be monocyclic or bicyclic. Examples include cyclopropyl, cyclopentyl, cyclohexyl or cycloheptyl groups.

[0039] For the purposes of the present invention, the term “aromatic group” means an aryl or heteroaryl group.

[0040] For the purposes of the present invention, the term "aryl" means an aromatic hydrocarbon group, preferably comprising from 6 to 10 carbon atoms, and optionally comprising one or more fused rings, such as, for example, a phenyl or naphthyl group. Advantageously, this is phenyl.

[0041] For the purposes of the present invention, the term “(C2-C6) alkenyl” group means a monovalent, linear or branched hydrocarbon chain comprising at least one double bond and comprising 2 to 6 carbon atoms. By way of example, mention may be made of ethenyl, propenyl, allyl, butenyl, pentenyl or hexenyl groups.

[0042] By "optionally substituted" is meant, for the purposes of the present invention, that the group in question is optionally substituted by one or more, preferably 1 or 2 substituents chosen from the group consisting of a halogen atom, a C1-C6 alkyl group, NR a R b , COR C , CC>2R d , CONR e R f , and OR g , in which R a to R grepresent, independently of one another, H, (Ci-Ce)-alkyl, optionally substituted by a 3 to 6-membered heterocycle, which heterocycle is preferably saturated, preferably comprises only one heteroatom, preferably O or N, preferably O.

[0043] DETAILED DESCRIPTION OF THE INVENTION

[0044] The present invention therefore relates to the use of a sol-gel finishing layer to make non-stick or improve the durability of the non-stick of a coating free of fluorocarbon resin (3) applied to at least one face (2a) of a support (2) of a heating element for a household article, characterized in that said layer is free of silica and is obtained from a sol-gel composition comprising at least two polyalkoxysilane precursors,

[0045] - the first being chosen from the group of formula (I)

[0046] RxSi(OR')4-x (I) in which

[0047] R is (Ci-Ce)-alkyl, (C2-Ce)-alkenyl, (C3-C7)-cycloalkyl, (C4-C7)-cycloalkenyl, (C3-C7)-cycloalkyl-(Ci-C6)-alkyl, aryl or aryl-(Ci-Ce)alkyl, optionally substituted.

[0048] R' is a (Ci-Cs)-alkyl group; and x is 0, 1, 2 or 3; and

[0049] - the second being TMMS (TriMethylMethoxySilane) or TMES (TriMethylEthoxySilane) or their mixtures.

[0050] TMMS TMES

[0051] By grafting these two compounds to the network, we obtain a slightly different network:

[0052] • The amount of CH3 group is increased

[0053] • The quantity of SiO bonds is reduced => we create in a way more significant defects.

[0054] • It is possible to integrate more PDMS oil within this network.

[0055] In other words, TMMS and TMES make it possible to increase the levels of methyl groups in the network and the maximum level of silicone oil that can be incorporated, and therefore prolong the anti-adhesiveness of the coating.

[0056] Advantageously, the proportion between the first precursor and the second precursor is between 1:10 and 10:1, preferably between 5:1 and 1:5.

[0057] Advantageously, x is different from 0.

[0058] Advantageously, R is a (Ci-Ce)-alkyl group (for example methyl, ethyl), phenyl or vinyl. Advantageously, R' is a (Ci-Ce)-alkyl group, preferably a (Ci-C4)-alkyl group, more preferably methyl or ethyl.

[0059] Advantageously, the first precursor is chosen from the list consisting of methyltrimethoxysilane (MTMS), methyltriethoxysilane (MTES), dimethyldiethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-aminopropyltriethoxysilane, (3-glycidoxypropyl)trimethoxysilane, allyltrimethoxysilane and mixtures thereof.

[0060] Preferably, the first precursor is methyltrimethoxysilane (MTMS) or methyltriethoxysilane (MTES) or mixtures thereof.

[0061] Preferably, the first precursor is MTMS and the second precursor is TMMS.

[0062] Preferably, said sol-gel topcoat is free of colloidal silica or micronic silica or mixtures thereof.

[0063] Advantageously, said sol-gel finishing layer has a thickness of 1 to 15 μm, preferably 2 to 12 μm, more preferably 2 to 10 μm.

[0064] Alternatively, the sol-gel composition of the topcoat is free of colloidal metal oxide.

[0065] The sol-gel composition of the sol-gel topcoat may further comprise a solvent, in particular a solvent comprising at least one alcohol. A solvent comprising at least one alcohol is hereinafter referred to as an “alcoholic solvent”.

[0066] An alcohol is preferably a C1-C6 alcohol. A C1-C6 alcohol is understood to be a saturated, linear or branched hydrocarbon chain containing 1 to 6 carbon atoms and comprising a hydroxyl group (-OH) attached to a carbon atom. Examples include ethanol, n-propanol, isopropanol.

[0067] The finishing layer according to the invention may further comprise at least one functionalized or non-functionalized, reactive or non-functionalized silicone oil, preferably a PDMS oil. The linear PDMS silicone oils, pure or pre-emulsified in water, are characterized firstly by their molecular mass, which is a direct increasing function of the viscosity of the pure oil. They are then characterized by the presence or absence of reactive functions, for example hydroxyls on the silicon atoms (silanol), their number and their location on the molecular chain. For example, reactive oils with viscosities of between 50 and 20,000 mPa.s, and in particular between 300 and 5,000 mPa.s, may be used, having at least one reactive function, preferably at least 2, which may be placed at the end of the chain.

[0068] Advantageously, the composition of the finishing layer is obtained by hydrolysis of the sol-gel precursors by adding water and an acid or basic catalyst, then by condensation reaction leading to the production of a sol-gel coating composition.

[0069] The composition of the sol-gel topcoat may include an acid catalyst such as, for example, acetic acid, formic acid, citric acid, hydrochloric acid, tartaric acid or mixtures thereof.

[0070] The composition of the sol-gel topcoat may include a basic catalyst such as sodium hydroxide NaOH, potassium hydroxide KOH, ammonia NHL or mixtures thereof.

[0071] The composition of the sol-gel topcoat may further comprise a coloring agent as defined in the list below.

[0072] The composition of the sol-gel topcoat may further comprise at least one filler as defined in the list below.

[0073] Coated heating element

[0074] Another subject of the invention relates to a method for manufacturing a coated heating element (1) for a household article comprising a coated support (2) comprising the following steps: a) Providing a support (2) having at least one face to be coated (2a); b) Applying a coating (3) to said support (2a) on this at least one face to be coated (2a); c) Applying a sol-gel finishing layer as described above to said coating (3). Advantageously, the sol-gel finishing layer is applied during step c) by electrostatic powdering, spray spraying, screen printing, spray gun, doctor blade, coating cylinder, brush, roller application or digital printing, preferably by spraying.

[0075] Another object of the invention relates to a coated heating element (1) for a household article capable of being obtained according to the above method.

[0076] COATING

[0077] The coating (3) is of a nature suitable for heating elements for household articles.

[0078] The person skilled in the art will know how to choose the appropriate coating depending on the household item and its use(s).

[0079] Advantageously, the coating (3) comprises one or more layers. Conventionally, the coating (3) comprises in this order from the substrate (2) one or more primer layer(s) (3a), optionally one or more intermediate layer(s) (3b) and one or more finishing layer(s) (3c).

[0080] The coating (3) does not comprise fluorocarbon resin, also called fluoropolymer or fluoropolymer. In other words, said coating (3) is free of fluorocarbon resin. Thus, the coating (3) does not comprise or emit perfluoroalkyl and polyfluoroalkyl compounds.

[0081] When the coating (3) comprises several layers, they may be identical or different in nature of the components, in percentage by weight of the components, in thickness, etc.

[0082] The coating (3) may comprise: one or more additive(s), and / or one or more coloring agent(s), and / or one or more filler(s).

[0083] The coating (3) may be of organic, inorganic or hybrid nature. The coating (3) may be of ceramic nature, for example sol-gel type, polymeric, for example based on thermoplastic polymers, based on silicone resin or based on enamel.

[0084] THERMOPLASTIC POLYMERS

[0085] 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.

[0086] PAEK

[0087] 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.

[0088] Other aromatic thermoplastic polymers

[0089] As aromatic thermoplastic polymer(s), examples suitable according to the invention are poly(phenylene oxide) (PPO), poly(arylethersulfone) polymer (PAES), and in particular polyethersulfone (PES), polyphenylene ether sulfone (PPSll), poly(arylene sulfides) (PAS) and in particular polyphenylene sulfide (PPS), liquid crystal polymers and mixtures thereof.

[0090] Heterocyclic thermoplastic polymers

[0091] Examples of heterocyclic thermoplastic polymers suitable according to the invention are polyetherimides (PEI), polyimides (PI), polyamideimides (PAI) and polybenzymidazole (PBI), or mixtures thereof.

[0092] Advantageously, the thermoplastic polymer(s) is / are chosen from the group consisting of polyethersulfone (PES), polyphenylene ether sulfone (PPSll), polyamideimide (PAI), polyimide (PI), poly(phenylene oxide) (PPO), poly(arylene sulfide) (PAS), polyetherimide (PEI), polybenzymidazole (PBI), liquid crystal polymers (LCP), polyphenylene sulfide (PPS), polyarylether ketone (PAEK) including polyether ketone (PEK), polyether ether ketone (PEEK), polyether ketone ketone (PEKK), polyether ether ketone ketone (PEEKK), polyether ketone ether ketone ketone (PEKEKK) and mixtures thereof.

[0093] Alternatively, the PAEK is implemented in the form of a suspension and the PAEK particles in the PAEK suspensions have a particle size with a d50 of about 10 pm to 15 pm.

[0094] SILICONE RESINS

[0095] In the text of the description, the expression "silicone resin" is used interchangeably to refer to the silicone before its crosslinking or after its crosslinking. In the text of the description, the expression "silicone" designates an organopolysiloxane material. Crosslinking is the step which makes it possible to transform the silicone into an insoluble material, for example by polyaddition, polycondensation or dehydrogenation. Crosslinking is carried out from precursors which are generally silicone oils or resins, which crosslink to obtain a three-dimensional network forming a material called silicone resin, in the description.

[0096] This crosslinking can be done by thermal activation, or chemical activation using a catalyst, such as platinum.

[0097] The silicone resins can be obtained from precursors, advantageously soluble in a solvent or in emulsion in water, such as oils or crosslinkable resins, in particular chosen from: a silicone hydride, a silicone oil resin comprising at least one vinyl group (-Ch ChL), a silicone or silicone-polyester resin (copolymer) comprising at least one alkoxy group, for example methoxy or ethoxy, and / or a silicone or silicone-polyester resin (copolymer) comprising at least one alkoxy group, in particular ethoxy, or a hydroxy group and mixtures thereof. These precursors have the capacity to crosslink in order to obtain a silicone resin which is characterized by its insolubility and its substantially solid form.

[0098] Advantageously, these precursors are polymeric or oligomeric, either in the form of silicone oils with a variable degree of branching, or in the form of silicone resins with a variable degree of pre-crosslinking or copolymers of silicone resins such as silicone-polyester, silicone-alkyd, silicone-polyurethane, silicone-epoxy resins, or in the form of a mixture of silicone oils, silicone resins and copolymers of silicone resins. The silicon atoms may be substituted by alkyl (in particular methyl) or aryl (in particular phenyl) groups or mixtures thereof. The oils or resins preferably comprise one or more (2, 3 or more) hydroxy or alkoxy (in particular methoxy, ethoxy, butoxy) functional groups as substituents of silicon atoms.

[0099] Advantageously, the silicone resin(s), obtained after crosslinking their precursors, i.e. crosslinked, is / are chosen from the group consisting of methyl silicone and / or phenyl silicone and / or methyl-phenyl-silicone resins, methyl silicone-polyester resin (copolymers), phenyl silicone-polyester resin (copolymers), methyl-phenyl silicone-polyester resin (copolymers), silicone-alkyd resin (copolymers), modified silicone resin and mixtures thereof.

[0100] Advantageously, the silicone resin(s) is / are chosen from the group consisting of methyl silicone and / or phenyl silicone and / or methyl-phenyl-silicone resins, methyl silicone-polyester resin (copolymers), phenyl silicone-polyester resin (copolymers), methyl-phenyl silicone-polyester resin (copolymers), silicone-alkyd resin (copolymers), modified silicone resin and mixtures thereof.

[0101] Silicone resins can be obtained from precursors, notably chosen from: a silicone hydride, a silicone resin comprising at least one vinyl group (-CH=CH2), a silicone-polyester resin (copolymer) comprising at least one methoxy group, and / or a silicone-polyester resin (copolymer) comprising at least one ethoxy group, and mixtures thereof.

[0102] The silicone resin forms a network which can be made up of a combination of 4 simple organosiloxane units named M, D, T and Q depending on the degree of substitution by oxygen of the silicon atom, as described in the following table, where R is an organic substituent described below. The organopolysiloxane material or polymer is obtained by crosslinking from precursors which can be monomeric or polymeric, or intermediately which can be oligomeric. The organopolysiloxane polymer can also be obtained from a mixture of these different kinds of precursors. When the network contains a higher number of T and Q units, than D, the crosslinking density is higher. The distribution between the M, D, T and Q units depends on the chemical structure of the precursors, in particular on this M, D, T, Q distribution within the precursors.

[0103] The polymeric precursors are organopolysiloxanes. These macromolecules are formed from 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.

[0104] Organopolysiloxanes can be either linear or slightly branched (majority of D groups), or branched or highly branched (majority of T and Q groups). Linear or lightly 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 a network at the level of the individual macromolecule and are called silicone resins. At room temperature, the resins are substantially in solid form, or in liquid form, provided in particular that they have a fairly low molecular weight, in the form of a solution in a solvent or in the form of an aqueous emulsion. They can be copolymerized with organic polymers or oligomers not containing silicon, chosen in particular from polyesters, acrylics, alkyds, polyurethanes, epoxy resins.

[0105] When the crosslinking is a hydrolysis-polycondensation: it is carried out thanks to the reactive hydroxy or alkoxy functions, in particular methoxy, ethoxy or butoxy, present on the organopolysiloxane.

[0106] When the crosslinking is a polyaddition (or hydrosilylation): it is carried out by reaction between the reactive vinyl functions (-Ch ChL) present on one of the organopolysiloxanes and the reactive silyl hydride functions (Si-H) present on the other organopolysiloxane mixed with the first.

[0107] All these reactive functions are present on each organopolysiloxane in number of at least one and can be present in number of 2, 3, or more ... as much as the molecular structure allows. Silicone oils containing at least one reactive function are called "reactive oils". The reactive functions can be found either at the end of the macromolecular chain (termination), or distributed over the chain.

[0108] Silicone-polyester resins in particular have silicone / polyester mass ratios of, 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.

[0109] Linear PDMS silicone oils, pure or pre-emulsified in water, are characterized firstly by their molecular mass, which is a direct increasing function of the viscosity of the pure oil. They are then characterized by the presence or absence of reactive functions, for example hydroxyls on the silicon atoms (silanol), their number and their location on the molecular chain. For example, reactive oils with viscosities between 50 and 20,000 mPa.s, and in particular between 300 and 5,000 mPa.s, can be used, having at least one reactive function, preferably at least 2, which can be placed at the end of the chain.

[0110] Polymer precursors reacting by polyaddition may include, for example, polymethylhydrosiloxane, vinylmethylsiloxane, vinyl-terminated polydimethylsiloxane (PDMS), in particular linear, vinyl-terminated diphenylsiloxane-dimethylsiloxane copolymers, hydride-terminated polydimethylsiloxanes, hydride-terminated polyphenylmethylsiloxanes, cyclic vinylmethylsiloxane, vinyl-MQ resin, trimethylsilyl-terminated polymethylhydrosiloxane, trimethylsiloxane-terminated dimethylsiloxane copolymer, MQ resin hydride, and the like, as well as combinations thereof.

[0111] Polymeric precursors reacting by hydrolysis-polycondensation, whether silicone resins or silicone oils, may include, for example, poly(methylsilsesquioxanes), poly(propylsilsesquioxanes), poly(phenylsilsesquioxanes), 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-acetoxyethylsilsesquioxanes), organo-modified alkoxy-silanes and their oligomers, and all similar macromolecules and their mixtures.

[0112] The organopolysiloxane material or polymer may also be obtained by crosslinking a mixture of one or more monomeric precursors and one or more polymeric precursors as described above, as well as one or more oligomeric precursors which may be linear, branched or cyclic. These oligomeric precursors have a lower molecular weight than the polymeric precursors. Polymeric and / or oligomeric precursors comprising a number of reactive functions as described above greater than 2, advantageously much greater than 2, may be added to the mixture as a “co-binder” in order to promote a high crosslinking density of the organopolysiloxane polymer finally obtained.

[0113] Monomeric, oligomeric and / or polymeric precursors, in particular silicone resins, copolymerized or not with an organic polymer, act as a polymeric binder in order to obtain the solid organopolysiloxane polymer combined with the thermoplastics of each layer.

[0114] Silicone oil-type organopolysiloxane precursors can be considered additives if they are added in small amounts (typically between 0.1 and 5% dry) to the overall formulation of a layer, independently of other components for the formation of the solid organopolysiloxane polymer.

[0115] Crosslinking may require a catalyst:

[0116] - In the case of crosslinking of organopolysiloxanes by hydrolysis-polycondensation, the formula may include a metal catalyst, such as, for example, metal complexes based on platinum, tin, zinc, zirconium and cerium, in particular platinum-cyclovinylmethyl-silxane complexes, tin ethylhexanoate, zinc ethylhexanoate, zirconium ethylhexanoate, cerium ethylhexanoate, and tin dibutyl laurate.

[0117] - In the case of crosslinking of organopolysiloxanes by hydrosylilation, the addition of a catalyst may be necessary: ​​this may be, for example, platinum or a suitable platinum-based catalyst such as the Karstedt catalyst or the Ashbys catalyst.

[0118] A crosslinking agent, for example carrying Si-H bonds, may be present.

[0119] Sol-gel

[0120] According to one embodiment, the primary layer(s) and the possible intermediate layer(s) are one or more sol-gel layers.

[0121] Advantageously, the composition of these layers may comprise a solution based on liquid-phase precursors comprising sol-gel precursors of the metal alkoxylate type and / or sol-gel precursors of the metal or metalloid polyalkoxylate type. Preferably, a metal or metalloid alkoxylate chosen from the group consisting of:

[0122] - precursors corresponding to the general formula Mi(ORi)n,

[0123] - precursors corresponding to the general formula M2(OR2)(n-1)R2', and

[0124] - precursors corresponding to the general formula M3(OR3)(n-2)R3'2, with:

[0125] Ri, R2, R3 or R3' denoting an alkyl group,

[0126] R2' denoting an alkyl or phenyl group, n being an integer corresponding to the maximum valence of the metals Mi, M2 or M3, Mi M2 or M3 denoting a metal or metalloid chosen from Si, Zr, Ti, Sn, Al, Ce, V, Nb, Hf, Mg, B or Ln.

[0127] Advantageously, the metal alkoxylate of the sol-gel solution of the sol-gel composition is an alkoxysilane. Mention may in particular be made, as alkoxysilanes which may be used in the sol-gel solution, of methyltrimethoxysilane (MTMS), tetraethoxysilane (TEOS), methyltriethoxysilane (MTES), dimethyldimethoxysilane, and mixtures thereof.

[0128] Preferably, the primary layer(s) and the optional intermediate layer(s) comprise methyltrimethoxysilane (MTMS) as a sol-gel precursor.

[0129] Advantageously, the composition of the sol-gel layers comprises at least one sol-gel precursor of the metal alkoxylate type as described above and at least 2% by mass relative to the total mass of the composition of at least one colloidal metal oxide dispersed in said composition.

[0130] Advantageously, the composition of the sol-gel layers is obtained by hydrolysis of the sol-gel precursor by adding water and an acid or basic catalyst, then by condensation reaction leading to the production of a sol-gel non-stick coating composition.

[0131] The composition of the sol-gel layers may include an acid catalyst such as, for example, acetic acid, formic acid, citric acid, hydrochloric acid, tartaric acid or mixtures thereof.

[0132] The composition of the sol-gel layers may comprise a basic catalyst such as sodium hydroxide NaOH, potassium hydroxide KOH, ammonia NH4 or mixtures thereof. The composition of the sol-gel layers may further comprise a coloring agent as defined in the list below.

[0133] The composition of the sol-gel layers may further comprise at least one filler as defined in the list below.

[0134] The composition of the sol-gel layers may further comprise at least one functionalized or non-functionalized, reactive or non-reactive silicone oil, for example a polydimethylsiloxane oil (PDMS oil).

[0135] ADDITIVES

[0136] Advantageously, said additives are chosen from the group consisting of antifoaming agents, dispersing agents, wetting agents, thickeners, pH adjusters, reactive silicone oils.

[0137] Said anti-foaming agent(s) are preferably chosen from the group consisting of mineral oils, diols, hydrocarbons, glycerides, oxyrane, emulsified fatty acids.

[0138] The surfactant(s) is (are) preferably chosen from the group consisting of glycol ether, ethoxylated alcohol excluding alkyl phenol ethoxylates (APE), gemini surfactants.

[0139] The dispersing agent(s) is (are) preferably chosen from the group consisting of anionic dispersants such as fatty acid derivatives.

[0140] Said thickeners are preferably chosen from the group consisting of acrylic-based or polyurethane-based copolymer, cellulose, pyrogenic silica.

[0141] The said pH adjusters are preferably chosen from the group consisting of Bronsted bases: ammonia, amines (triethylamine, triethanolamine, etc.), hydroxides (soda, potash, etc.), carbonates.

[0142] Advantageously, the proportion of additives in the finishing layer according to the invention is less than 20% by weight relative to the total weight of said layer. COLOURING AGENTS

[0143] A "coloring agent" has the function of changing or providing a color.

[0144] Advantageously, the coloring agent(s) is / are chosen from the group consisting of thermochromic pigments, thermostable pigments, soluble dyes, glitter, preferably hologram glitter, and mixtures thereof.

[0145] Advantageously, the proportion of coloring agents in the finishing layer according to the invention, when they are present, is less than 10% by weight relative to the total weight of said layer.

[0146] Advantageously, the finishing layer according to the invention is transparent. In this case, if it comprises coloring agents, these coloring agents are glitters.

[0147] Thermochromic pigments

[0148] Preferably, the thermochromic pigment(s) is / are chosen from the group consisting of Bi2O3, Fe2Os, V2O5, WO3, CeO2, ln2Os, Yi i 84Cao,ieTii i 84Vo,i60i,84, Agi, (Bii-xAx)(Vi.yMy)O4, BiOCi-zD z with :

[0149] - x is equal to 0 or x is between 0.001 and 0.999,

[0150] - y is equal to 0 or y is between 0.001 and 0.999,

[0151] - z is equal to 0 or z is between 0.001 and 0.999,

[0152] - C and D are chosen from the group consisting of iodine, fluorine, chlorine and bromine and C and D are different from each other,

[0153] - A and M are chosen from the group consisting of nitrogen, phosphorus, an alkali metal, an alkaline earth metal, a transition metal, a poor metal, a metalloid or a lanthanide,

[0154] - A and M are different from each other.

[0155] Knowing that A and M are different from each other, when:

[0156] - A is an alkali metal, it can be chosen from Li, Na, K, Rb, Cs,

[0157] - M is an alkali metal, it can be chosen from Li, Na, K, Rb, Cs,

[0158] - A is an alkaline earth metal, it can be chosen from Be, Mg, Ca, Sr, Ba,

[0159] - M is an alkaline earth metal, it can be chosen from Be, Mg, Ca, Sr, Ba,

[0160] - A is a transition metal, it can be chosen from Sc, Ti Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Ta, W, Ir,

[0161] - M is a transition metal, it can be chosen from Sc, Ti Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Ta, W, Ir, - A is a poor metal, it can be chosen from Al, Zn, Ga, In, Sn,

[0162] - M is a poor metal, it can be chosen from Al, Zn, Ga, In, Sn,

[0163] - A is a metalloid, it can be chosen from B, Si, Ge, Sb,

[0164] - M is a metalloid, it can be chosen from B, Si, Ge, Sb,

[0165] - A is a lanthanide, it can be chosen from La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu,

[0166] - M is a lanthanide, it can be chosen from La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu.

[0167] Preferably, A and M different from each other are B and / or Mg.

[0168] Preferably, the pigment (Bii- xAx)(Vi-yMy)O4 exhibits a monoclinic scheelite crystallographic form at room temperature.

[0169] Preferably, x and y are 0, i.e. the pigment (Bii- x Ax)(Vi-yMy)O4 is Bismuth Vanadate (BiVO4). Advantageously, a BiVO4 with a monoclinic scheelite crystallographic structure at room temperature is used.

[0170] Bismuth Vanadate is a yellow inorganic compound with the formula BiVO4, widely used for its color properties and lack of toxicity. Registered in the Colour Index International database as QI Pigment Yellow 184, it is marketed by Heubach (Vanadur®), BASF (Sicopal®), FERRO (Lysopac) and Bruchsaler Farbenfabrik (Brufasol®).

[0171] Thermostable pigments

[0172] Preferably, the thermostable pigment(s) is / are chosen from the group consisting of:

[0173] - Yellow titanium rutile pigment,

[0174] - Yellow pigment derived from bismuth, for example selected from stabilized bismuth vanadates (Pyi84)

[0175] - Red pigment, for example selected from perylene red (for example PR149, PR178 and PR224), iron oxide,

[0176] - Orange pigment of bismuth oxyhalides type (POss),

[0177] - Bismuth vanadate orange pigment (POse)

[0178] - Zinc tin titanium orange pigment (PO82)

[0179] - Cerium sulfide orange pigment (PO75; PO?s) - Antimony titanium chrome rutile orange-yellow pigment (PBr24)

[0180] - Orange-yellow pigment of tin and zinc rutile type (Py2ie)

[0181] - Orange-yellow pigment of niobium oxide tin zinc sulfide (Py22?)

[0182] - Orange-yellow pigment of double oxides of tin and niobium

[0183] - CO3(PO4)2

[0184] - UCOPO4

[0185] - COAI2O4

[0186] - O2O3

[0187] - TiO2

[0188] - Black pigment PBk28 (Copper chromite black spinel)

[0189] - and their mixtures.

[0190] Decors

[0191] According to one embodiment, the layer(s) (3b) is (are) continuous and covers the entire layer (3a) (see Figure 1).

[0192] According to another embodiment, the layer(s) (3b) do(es) not cover the entire layer (3a) and form(s) at least one decoration (see Figure 2).

[0193] Advantageously, the layer(s) (3b) compose several decorations, one (i) comprising one or more thermochromic pigment(s) and the other (j) comprising at least one temperature reference pigment composition (see Figure 3).

[0194] According to one embodiment, each of the two decorations (i) and (j) is presented in the form of adjacent non-overlapping patterns. For example, each decoration is represented by different geometric patterns distributed uniformly over the entire surface and alternating with respect to each other (see Figure 4A).

[0195] According to another embodiment, the two decorations (i) and (j) are partially overlapping. For example, each decoration is represented by different geometric patterns distributed uniformly over the entire surface and partially overlapping (see Figure 4B).

[0196] Preferably, the two decorations (i) and (j) are overlapping, either because one of the two decorations is a continuous layer and the other decoration covers it in the form of patterns, or because the two decorations (i) and (j) are in the form of overlapping patterns (see Figure 4C). Sequins

[0197] The flakes usable in the context of the present invention may be independently chosen from mica flakes, coated or not, silica flakes, coated or not, aluminum flakes, coated or not, iron oxide flakes, coated or not. Mica or silica flakes coated with titanium dioxide. The flakes usable in the context of the present invention may be treated to give a particular color effect.

[0198] Advantageously, the flake(s) is / are particles chosen from the group consisting of particles of mica, aluminum, mica coated with titanium dioxide or mixtures thereof.

[0199] Hologram sequins

[0200] Advantageously, the glitter(s) is / are hologram glitter, i.e. a mixture of magnetizable particles and non-magnetizable particles.

[0201] The magnetizable particles may advantageously be particles comprising at least one ferromagnetic metal. These magnetizable particles may be of a homogeneous nature, i.e. made of the same material, or of a composite nature, i.e. these magnetizable particles have a core-shell structure, in which the ferromagnetic metal is found in the core and / or in 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 protection against corrosion during the steps of implementing the coating, or else plastic flakes coated with iron oxide Fe2O3, or flakes whose core is made of ferromagnetic metal and the shell is formed of a plastic material or a sol-gel material.

[0202] According to one embodiment, a portion of said magnetizable particles is oriented so as to form a three-dimensional decoration.

[0203] Advantageously, the mixture of magnetizable particles and non-magnetizable particles represents between 1% and 5% by weight of the weight of the layer, preferably between 2% and 3% by weight. Advantageously, the percentage of non-magnetizable particles in the mixture of magnetizable particles and non-magnetizable particles is between 15% and 40% by weight relative to the total weight of the mixture of magnetizable particles and non-magnetizable particles.

[0204] Advantageously, the magnetizable particles have a dimension D50 less than or equal to 23 pm.

[0205] The term “D50” means, within the meaning of the present invention, the maximum dimension presented by 50% of the particles by number.

[0206] Advantageously, the non-magnetizable particles have a dimension D90 of between 20% and 250% of the dimension D90 of the magnetizable particles.

[0207] The term “D90” means, within the meaning of the present invention, the maximum dimension presented by 90% of the particles by number.

[0208] Advantageously, the magnetizable particles and / or the non-magnetizable particles are colored on the surface.

[0209] Advantageously, the non-magnetizable particles are made of mica, aluminum, or mica coated with titanium dioxide.

[0210] Advantageously, the magnetizable particles consist of iron, iron oxide, iron-coated aluminum, or iron-coated mica, the iron being in ferritic form.

[0211] CHARGES

[0212] The fillers within the meaning of the invention provide mechanical reinforcement and can also provide hydrophobic properties, while improving the mechanical resistance and thermal conductivity of the coating.

[0213] The fillers do not only have the function of providing color to the coating, but can contribute to it. Advantageously, the filler(s) is / are chosen from the group consisting of ceramic fillers (SiC>2, etc.) and / or mineral and / or metallic fillers (AI2O3, "IIO2, etc.) and / or silicas and / or diamond particles.

[0214] Preferably, the filler(s) is / are chosen from the group consisting of metal oxides, metal carbides, metal oxynitrides, metal nitrides, and mixtures thereof.

[0215] Advantageously, said metal is a transition metal, such as at least one of the elements chosen from B, Ni, Ti, Zr or Hf.

[0216] More preferably, the charge(s) is / are chosen from the group consisting of:

[0217] - fillers for reinforcement: organic or inorganic hard fillers; the inorganic hard fillers are preferably particles of silicon carbide or alumina or zirconia or graphite, or ceramics, or carbonate, or hydrated alumina, aluminum trihydroxide or one or more metal oxide(s), graphite, graphene;

[0218] - other fillers for reinforcement chosen from metal oxides: silica, micas, lamellar fillers, clays such as montmorillonite, sepiolite, gypsite, kaolinite and laponite, zinc dioxide, quartz, and zirconium phosphate, alumina, zirconia, zinc oxide, copper oxide, iron oxide;

[0219] - fillers chosen from reinforcing fibers: glass fiber, carbon fiber, or aramid fiber;

[0220] - conductive fillers comprising a transition metal carbide and / or a transition metal nitride: characterized in that the transition metal is at least one of the elements chosen from B, Ni, Ti, Zr or Hf, for example: cubic boron nitride, diamond particles, metallic particles;

[0221] - lamellar fillers that can provide lubricating properties, such as clays, graphene or graphite.

[0222] More preferably, the filler(s) is / are chosen from the group consisting of alumina, silicon carbide, tungsten carbide, boron nitride, quartz, and mixtures thereof.

[0223] Some inorganic hard fillers such as silicon carbide, in addition to their mechanical reinforcement performance, also have the advantage of being conductive fillers and therefore provide excellent thermal conductivity. The addition of this type of filler improves the culinary rendering with better diffusion of heat from the metal substrate to the food in contact with the coating.

[0224] Advantageously, the average diameter d50 of the charges is between 0.1 and 50 pm, advantageously still between 5 and 15 pm.

[0225] Advantageously, the proportion of fillers in a layer of the coating (3), when it comprises them, is between 0.5 and 30% by dry weight relative to the total weight of said layer after cooking, preferably between 5 and 20%.

[0226] Support

[0227] The support (2) is of a nature suitable for heating elements for household items.

[0228] The person skilled in the art will know how to choose the appropriate support depending on the household item and its use(s).

[0229] For example, the support (2) is made of terracotta, glass, ceramic, pottery or a metal substrate.

[0230] When the support (2) is a metal substrate, it is advantageously a substrate made of aluminum, stainless steel, cast iron or aluminum, iron, titanium or copper. For the purposes of the present invention, aluminum means a metal consisting of 100% aluminum or an aluminum alloy.

[0231] Advantageously, the support (2) when it is a metal substrate is an aluminum substrate, a stainless steel substrate or a multi-layer metal substrate. The metal substrate (2) can be a two-layer or three-layer substrate, these multi-layers being able to be obtained for example by co-lamination, by hot diffusion under load (solid state bonding) or by hot or cold impact bonding.

[0232] Preferably, the metal substrate comprises alternating layers of metal and / or metal alloy.

[0233] According to one embodiment, the support (2) when it is a metal substrate is a substrate made of aluminum alloy, stainless steel or a multilayer metal substrate whose face (2a) is made of aluminum alloy or stainless steel. Preferably, the support (2) when it is a metal substrate is an aluminum substrate.

[0234] Advantageously, the thickness of the support (2) is between 0.5 mm and 10 mm.

[0235] Advantageously, the face (2a) of the support (2) has previously undergone a surface treatment making it possible to improve the adhesion of the coating to said substrate.

[0236] According to one embodiment, the support (2) when it is a metal substrate has undergone a surface treatment, said surface treatment being a chemical attack, brushing, hydration, sandblasting, shot blasting, a physicochemical treatment of the plasma or corona or laser type, a chemical activation or a combination of these different techniques.

[0237] Advantageously, the face of the substrate (2a) on which the coating (3) according to the invention will be applied can be treated so as to increase its specific surface area; for an aluminum substrate, this treatment can be done by anodization (creation of a tubular alumina structure), by chemical attack, by sandblasting, by brushing, by shot blasting or by adding material by means of a technology such as thermal projection (flame, plasma or arc spray). Other metal substrates can also be polished, sandblasted, brushed, micro-blasted or receive an addition of material by means of a technology such as thermal projection (flame, plasma or arc spray).

[0238] As metallic substrates which can be used in the present invention, mention may advantageously be made of anodized or non-anodized aluminum substrates, optionally polished, brushed, sandblasted, shot-blasted or micro-blasted, anodized or non-anodized aluminum alloy substrates, optionally polished, brushed, sandblasted or micro-blasted, steel substrates, optionally polished, brushed, sandblasted, shot-blasted or micro-blasted, stainless steel substrates, optionally polished, brushed, sandblasted or micro-blasted, cast steel, aluminum or iron substrates, and copper substrates, optionally hammered or polished.

[0239] Advantageously, the support (2) when it is a metal 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, aluminum or aluminum alloy caps lined with an outer stainless steel base, metal co-laminated substrates, for example two-layer co-laminated substrates comprising a stainless steel layer (for example intended to constitute the inner face of the article) and a layer of aluminum or aluminum alloy, anodized or not (for example intended to constitute the outer face of the article).

[0240] Advantageously, the average arithmetic roughness Ra of the surface of the face (2a) of the support (2) when it is a metal substrate is greater than or equal to 1 pm.

[0241] The arithmetic mean roughness Ra is measured using a roughness meter according to ISO 4287. Ra represents the arithmetic mean of the deviations from the mean. The surface topography can be studied in particular with a profilometer with a probe equipped with a fine stylus equipped with a diamond tip, or with an optical metrology device such as Altisurf®, in which a chromatic confocal sensor allows a contactless measurement. The study of this surface topography makes it possible to define the arithmetic mean roughness Ra.

[0242] Advantageously in the case of a culinary article or electrical cooking appliance, the support is a hollow metal cap which comprises a base and a side wall rising from the base, said cap having a concave inner face adapted to receive food and a convex outer face intended to be arranged towards the heating means or a heat source.

[0243] Process

[0244] The invention also relates to a method for manufacturing a household article comprising a coated heating element (1) for a household article comprising a coated support (2) characterized by the following steps: a) a step of providing a support (2) in the form of a substantially flat support comprising two opposite faces or a support (2) of convex or hollow shape defining a concave inner face (21) and a convex outer face (22);a') where appropriate, when a support (2) in the form of a substantially flat support is provided during step (a), a step of shaping said substrate to give it the shape of a support (2) of convex or hollow shape defining a concave inner face (21) and a convex outer face (22), said step (a') being carried out either before step (a), or before step (b) of applying the coating (3), or after step (b) and before step (c) of applying the finishing layer or after step (c); b) Application of the coating (3); c) Application on said coating (3) of a sol-gel finishing layer as described above. The implementation of this method makes it possible to obtain a household article whose support is coated with a non-stick coating.;

[0245] The support implemented in steps (a) and (a') is that described above.

[0246] Advantageously, the method according to the invention may further comprise, prior to step a), a step of surface treatment of the face of the support intended to be coated. This surface treatment may consist of a physicochemical treatment (in particular by plasma) or even a chemical treatment (chemical stripping in particular) and / or a mechanical treatment (sandblasting, brushing, emery, shot blasting for example), in order to create a roughness of the surface of the support which will be favorable to the adhesion of the primary coating layer. The surface treatment may also advantageously be preceded by a degreasing operation intended to clean the surface.

[0247] Advantageously, the support is optionally cleaned and heated before applying the composition according to step (b). The heating temperature can be between 40 and 80°C, this preheating prevents dripping during application.

[0248] Advantageously, step (b) of the method according to the invention may comprise an intermediate drying step which takes place after the application of the coating composition and before the application of the finishing layer.

[0249] The coating composition may be applied to the substrate by spraying or by any other application method, such as dipping, pad coating, brush coating, roller coating, inkjet coating, curtain coating, spin coating, or screen printing. However, spraying, for example by means of a gun, has the advantage of forming a homogeneous and continuous layer, which, after curing, forms a continuous, uniformly thick, waterproof coating on a concave or convex substrate.

[0250] The application to the support, in step (b) of the method according to the invention, can take place by screen printing, roller, inkjet, spraying or curtain.

[0251] In the case of a sol-gel coating (3), the application to the support, in step (b) of the method according to the invention, can take place by spraying comprising spraying or nebulization in the form of droplets of solution of the sol-gel coating composition. The application to the support, in step (b) of the method according to the invention, can also take place by flat coating techniques, which allow on the one hand a significant saving in coating consumption from an industrial point of view, and on the other hand the elimination of the problem of spraying outside the article (or "over spray" in English).

[0252] Advantageously, step (c) of the process according to the invention can take place at a temperature of 200 to 400°C, in particular at a temperature of 220 to 350°C, more particularly at a temperature of 250 to 320°C, preferably at 300°C.

[0253] A drying step may be considered between step (b) and step (c). Any means of drying may be considered, oven drying, drying by ultraviolet or infrared radiation, plasma drying, open air drying or a combination of these heating means.

[0254] This optional drying step can allow solvents to evaporate and avoid the stresses associated with densification / baking of the coating.

[0255] The total thickness of the coating after implementing the method according to the invention may be between 1 and 200 μm, in particular between 2 and 100 μm, preferably between 2 and 80 μm.

[0256] Household item

[0257] The present invention also relates to a household article comprising a coated heating element (1) according to the invention or capable of being obtained according to the above method.

[0258] According to one embodiment, the household article according to the invention is a culinary article (100) or an electric cooking appliance (200) and the sol-gel finishing layer forms the cooking face.

[0259] In this case, the finishing layer according to the invention is advantageously transparent.

[0260] In this case, the coloring agent of the finishing layer according to the invention is advantageously glitter.

[0261] Said culinary article (100) is preferably chosen from the group consisting of saucepan, frying pan, skillets or pots for fondue or raclette, stewpot, wok, sauté pan, crepe maker, grill, griddle, pot, casserole dish, cooker or bread machine bowl, culinary mold, molds and plates for pastry, barbecue plates and grills, preparation bowls. According to one embodiment, the culinary article (100) comprises a heating face (6) intended to be placed in contact with an external heating source, the heating face (6) being opposite the cooking face (5) intended to be placed in contact with the food during cooking.

[0262] The culinary article according to the present invention may in particular be a culinary article of which one of the two opposite faces of the substrate is an inner face, possibly concave, intended to be arranged on the side of food likely to be introduced into or onto said article, and of which the other face of the substrate is an outer face, possibly convex, intended to be arranged towards a heat source.

[0263] Said electric cooking appliance (200) is preferably chosen from the group consisting of electric crepe maker, electric raclette appliance, electric fondue appliance, electric grill, electric griddle, electric cooker, bread maker, electric pressure cooking appliance, waffle makers, rice cookers and jam makers.

[0264] The electrical cooking appliance (200) comprises a coated cooking element (1) according to the invention and a heating source (210) configured to heat said coated cooking element (1).

[0265] According to one embodiment, the household item according to the invention is heating household equipment in the fields of laundry or personal care.

[0266] Advantageously, the household article according to the invention is an iron and the sol-gel finishing layer coats the soleplate of the iron or a hair care article and the sol-gel finishing layer coats one of the heating plates of said article.

[0267] EXAMPLES

[0268] The aims, aspects and advantages of the present invention will be better understood from the description given below of a particular embodiment of the invention presented by way of non-limiting example.

[0269] Of course, the invention is in no way limited to the embodiment described and illustrated, which has been given only as an example. Modifications remain possible, in particular from the point of view of the composition of the various elements or by substitution of technical equivalents, without departing from the scope of protection of the invention. Formulation of the initial finishing layer

[0270] Finish = top coat Formulation of the primer coat

[0271] Boiling water test

[0272] In order to simulate aging due to aqueous cooking, we carry out a boiling water aging test. The test procedure is as follows:

[0273] - Wash the pan before testing with lukewarm water, yellow side sponge and detergent.

[0274] - Fill with tap water and heat until boiling

[0275] - When boiling, maintain heating and start the stopwatch

[0276] - After a period of 2 hours of boiling: wash the item in lukewarm water, sponge yellow side and detergent to remove surface limescale.

[0277] - Evaluation of non-stick properties by cooking eggs.

[0278] - cleaning and restarting a boiling cycle if the egg comes loose.

[0279] This is how you carry out as many boiling cycles as necessary until the egg no longer comes loose.

[0280] The higher the number of cycles, and therefore the number of hours, the more the coating is considered capable of resisting boiling water.

[0281] Comparative results

[0282] In order to go even further in terms of anti-adhesion and hydrophobicity, part of the MTMS is replaced in the starting formulas above by TMMS (TriMethylMethoxySilane).

[0283] Several types of prototypes were made, combining variations in the ratio of TMMS / MTMS and PDMS oil in the topcoat. The primer coat is identical for all prototypes and is described above. The coating consists of a primer coat and a topcoat, which topcoat varies between prototypes. The topcoat varies in terms of the MTMS / TMMS ratio. The topcoat also varies in terms of the amount of PDMS oil (in the finish formula above, the amounts of isopropanol and butyl glycol solvents are thus adjusted according to the amount of PDMS oil to arrive at a total of 100).

[0284] The table below summarizes the tests carried out and the results in terms of durability of the non-stick coating through a cycled boiling test described above.

[0285] Precursor rates are given relative to the total precursor rate. Full data / all configurations:

[0286] MTMS / TMMS formulas achieve remarkable performance.

Claims

CLAIMS 1. Use of a sol-gel finishing layer for making non-stick or improving the durability of the non-stick of a coating free of fluorocarbon resin (3) applied to at least one face (2a) of a support (2) of a heating element for a household article, characterized in that said layer is free of silica and is obtained from a sol-gel composition comprising at least two polyalkoxysilane precursors, - the first being chosen from the group of formula (I) RxSi(OR')4-x (I) in which R is (Ci-Ce)-alkyl, (C2-Ce)-alkenyl, (C3-C7)-cycloalkyl, (C4-C7)-cycloalkenyl, (C3-C7)-cycloalkyl-(Ci-C6)-alkyl, aryl or aryl-(Ci-Ce)alkyl, optionally substituted. R' is a (Ci-Cs)-alkyl group; and x is 0, 1, 2 or 3; and - the second being TMMS (TriMethylMethoxySilane) or TMES (TriMethylEthoxySilane) or their mixtures.

2. Use of a sol-gel finishing layer according to claim 1, characterized in that the proportion between the first precursor and the second precursor is between 1:10 and 10:1, preferably between 5:1 and 1:

5.

3. Use of a sol-gel topcoat according to claim 1 or 2, the first precursor being methyltrimethoxysilane (MTMS) or methyltriethoxysilane (MTES) or mixtures thereof.

4. Use of a sol-gel topcoat according to claim 3, characterized in that the first precursor is MTMS and the second precursor is TMMS.

5. Use of a sol-gel finishing layer according to one of the preceding claims, characterized in that it further comprises at least one functionalized or non-functionalized, reactive or non-reactive silicone oil.

6. Method for manufacturing a coated heating element (1) for a household article comprising a coated support (2) comprising the following steps: a) Providing a support (2) having at least one face to be coated (2a); b) Applying a coating (3) to this at least one face to be coated (2a) of said support; c) Application to said coating (3) of a sol-gel finishing layer as described in any one of claims 1 to 5.

7. Method according to claim 6 characterized in that the sol-gel finishing layer is applied during step c) by electrostatic powdering, spray spraying, screen printing, spray gun, doctor blade, coating cylinder, brush, roller application or digital printing, preferably by spraying.

8. Coated heating element (1) for a household article obtainable according to any one of claims 6 to 7.

9. Method of manufacturing a household article comprising a coated heating element (1) according to claim 8 for a household article comprising a coated support (2) characterized by the following steps: a) a step of providing a support (2) in the form of a substantially flat support comprising two opposite faces or a support (2) of convex or hollow shape defining a concave inner face (21) and a convex outer face (22); a') where appropriate, when a support (2) in the form of a substantially flat support is provided during step (a), a step of shaping said substrate to give it the shape of a support (2) of convex or hollow shape defining a concave inner face (21) and a convex outer face (22), said step (a') being carried out either before step (a), or before step (b) of applying the coating (3), or after step (b) and before step (c) of applying the finishing layer or after step (c);b) Application of the coating (3); c) Application on said coating (3) of a sol-gel finishing layer as described in any one of claims 1 to 5.; 10. Household article comprising a coated heating element (1) according to claim 8 or obtainable according to claim 9.

11. Household article according to claim 10, characterized in that it is a culinary article or an electrical cooking appliance and in that the sol-gel finishing layer forms the cooking face.

12. Culinary article (100) according to claim 11, chosen from the group consisting of saucepan, frying pan, skillets or pots for fondue or raclette, stewpan, wok, sauté pan, crepe pan, grill, griddle, pot, casserole dish, cooker or bread machine bowl, mold culinary, baking tins and trays, barbecue trays and grills, preparation bowls.

13. Electric cooking appliance (200) according to claim 11, chosen from the group consisting of electric crepe maker, electric raclette appliance, electric fondue appliance, electric grill, electric griddle, electric cooker, bread maker, electric pressure cooking appliance, waffle makers, rice cookers and jam makers.

14. Household article according to claim 10, characterized in that it is a heating household appliance in the fields of laundry care or personal care.

15. Household article according to claim 14, characterized in that it is an iron and the sol-gel finishing layer coats the soleplate of the iron or a hair care article and the sol-gel finishing layer coats one of the heating plates of said article.

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