Sol-gel composition for providing a non-stick coating

Abstract

The invention relates to a sol-gel composition comprising a polymer matrix and ceramic particles trapped in the matrix and being selected from the group comprising silicon carbide, boron nitride, preferably cubic boron nitride, silicon nitride, boron carbide, titanium nitride, aluminium nitride, tungsten carbide, tungsten sulphide, molybdenum sulphide, diamond and combinations thereof, the polymer matrix comprising polysiloxanes.

Description

[0001] SOL-GEL COMPOSITION TO PROVIDE A NON-STICK COATING

[0002] The present invention relates to a composition for providing a non-stick coating comprising a polymer matrix which contains in its structure ceramic particles, a reaction mixture, and its applications, in particular as a non-stick coating.

[0003] Coatings can be used to cover a surface in order to give that surface non-stick properties, durability and abrasion resistance.

[0004] Such coatings are generally used in various industrial and domestic fields, typically to coat kitchen utensils, industrial equipment, and any other surfaces for which non-stick properties, high wear resistance, thermal conductivity, and low (or even non-)toxicity are required.

[0005] Per- and polyfluoroalkyl substances (PFAS) are a class of chemical compounds used for their non-stick and heat-resistant properties. However, due to their potential health and environmental effects, numerous regulations worldwide have been implemented to restrict their use, including in non-stick coatings for cookware, pans, and other items. PFAS-free non-stick coatings are currently undergoing significant development in the cookware industry. Therefore, it is essential for such items to have coatings that are resistant to temperature and abrasion during regular use.

[0006] One of the difficulties in developing alternative solutions that make it possible to do away with PFAS lies in the mechanical and thermal properties that the articles concerned must satisfy, which require the use of non-toxic coatings.

[0007] For example, in the case of cookware, some of the heat energy may dissipate in the insulating coating rather than being efficiently transferred to the cooking element. Furthermore, these coatings can cause hot spots to form at the points of contact with the heating element, thus compromising cooking quality.

[0008] Furthermore, it would be advantageous to have coatings capable of withstanding temperatures exceeding 200°C, conducting heat homogeneously and efficiently, while also being mechanically resistant to damage such as scratches and abrasion. Solutions exist that offer compositions obtained through a sol-gel process. A sol-gel composition is a chemical synthesis method used to produce solid materials from small molecules. The composition may include precursors, such as metal alkoxides, which, through hydrolysis and polycondensation, form a three-dimensional network that transforms into a gel. This gel is then dried and possibly heat-treated to obtain a solid material with specific properties.

[0009] Such compositions remain interesting because they do not release toxic compounds and are more environmentally friendly, unlike compositions that use PFAS.

[0010] Sol-gel compositions are known to exhibit adhesion to a variety of substrates, including metals, ceramics, and glasses.

[0011] US patent 2014-120-284 describes a ceramic coating obtained by a sol-gel process that provides scratch resistance and thermal conductivity. The ceramic coating is intended for application to a metallic substrate. This patent proposes a two-component composition, A and B, in which part A may include silicon carbide (SiC) or boron nitride in the presence of colloidal silica added separately to the mixture, and part B includes methyltrimethoxysilane (MTMS).

[0012] US patent 2012018433 describes a sol-gel coating covering a surface. The coating consists of a matrix formed from at least one metal polyalkoxylate and at least one colloidal metal oxide dispersed within said matrix. This patent focuses primarily on a functional decorative layer that coats the sol-gel coating.

[0013] There is also document EP 2 177 580 which concerns a single-layer sol-gel formulation. This is an organic-no-mineral hybrid system, where the network is predominantly inorganic (silica), and PDMS is incorporated as an anti-adherent surface modifier, via its -OH terminals which participate in condensation reactions.

[0014] Unfortunately, depending on the solubility of the PDMS chains in the water / alcohol sol-gel solvent, the hydroxyl groups can condense and form aggregates that are partially insoluble in the water / alcohol medium. Upon drying, these PDMS aggregates can create highly visible defects on the final coating (micro-cracks, inhomogeneous zones, loss of transparency, holes, etc.). This can significantly reduce the coating's anti-adhesion performance. US publication 2014 / 0220345 concerns a composite micropowder encapsulating PTFE with a polysiloxane formed in situ from silanes such as MTMS, TEOS, and phenyltrimethoxysilane. Thus, the released hydroxylated silicone oil is physically dispersed within the matrix, does not form a covalent network with the other components (silica, silanes), and can therefore be gradually leached or evaporated. Unfortunately, the use of fluorinated compounds is recommended.

[0015] However, the manufacturing processes for prior art sol-gel coatings are currently too complex. They require precise control of reaction conditions and heat treatment. Furthermore, ensuring a uniform and defect-free layer can be more difficult with sol-gel coatings, necessitating carefully controlled application and drying techniques.

[0016] It also became apparent that existing solutions are not sufficiently satisfactory in terms of non-stick properties. A test cooking an egg without fat did not yield good results.

[0017] There is therefore a real need to provide a sol-gel composition which allows for applications in which abrasion resistance, thermal conductivity, toxicity, implementation, and high temperature resistance (> 200 °C) are improved compared to current solutions in order to eliminate the use of PFAS.

[0018] The object of the invention is to resolve the aforementioned drawbacks by providing a sol-gel composition for providing an anti-stick coating comprising a polymer matrix and ceramic particles trapped in said matrix and being selected from the group comprising silicon carbide, boron nitride, preferably cubic boron nitride, silicon nitride, boron carbide, titanium nitride, aluminum nitride, tungsten carbide, tungsten sulfide, molybdenum sulfide, diamond and combinations thereof, said polymer matrix having at least one of the following structures (II, III) or combinations thereof:

[0019] Where A is between 1 and 60, preferably between 1 and 50, more preferably between 1 and 45, and wherein each Rn-Si(O-Ri2)- unit is repeated such that each Si atom of a given unit bonds to at least one oxygen atom of said corresponding Rn-Si(O-Ri2)- unit to have the polymer matrix which has a succession of said units which are linked to each other by Si- bonds

[0020] O (*), n is between 1 and 20, preferably between 1 and 15, more preferably between 1 and 10, The radicals Ri are identical or different and being independently chosen from an alkyl, preferably Ci-Cio, more preferably a methyl or an ethyl, Ru is an alkyl chain, preferably Ci-Cio, more preferably a methyl or an ethyl, or an oxygen atom ((O-)*) or a phenyl group,

[0021] R12 is an alkyl chain, preferably Ci-Cio, more preferably a methyl or an ethyl, or an oxygen atom ((O-)*) or a phenyl group.

[0022] Within the framework of the present invention, the proposed sol-gel composition is based on a three-dimensional polymer matrix, the basic skeleton of which is preferably a silicone which has, at its ends depending on the number of units A, a degree of (poly)condensation which allows to trap sufficiently the ceramic particles and which confers exceptional properties in terms of anti-adhesion, abrasion resistance and durability.

[0023] The following expression used in the invention: 'the R2 radicals are identical or different and being independently chosen from an alkyl, preferably C1-C10, more preferably a methyl or an ethyl, or an O-R3 group,' used above can thus advantageously be understood as follows:

[0024] When the R2 radicals are different, this means that at least one of the two R2 radicals present on the corresponding Si atom is equal to an O-CH3 group, or

[0025] When the R2 radicals are identical, this means that they correspond to the O-CH3 group on the corresponding Si atom. Preferably, said polymer matrix exhibits at least one of the following structures (II, III) or combinations thereof:

[0026] (II), or Or

[0027] A is between 1 and 60, preferably between 1 and 50, more preferably between 1 and 45, and wherein each Ru-Si(OO)- unit is repeated such that each Si atom of a given unit bonds to at least one oxygen atom of the corresponding Rn-Si(OO)- unit to have the polymer matrix which has a succession of said units which are linked to each other by Si-O bonds (*), n is between 1 and 20, preferably between 1 and 15, more preferably between 1 and 10,

[0028] The Ri radicals are identical or different and are independently chosen from an alkyl group, preferably Ci-Cio, more preferably a methyl or an ethyl group,

[0029] Ru is an alkyl chain, preferably Ci-Cio, more preferably a methyl or an ethyl, or an oxygen atom ((O-)*) or a phenyl group.

[0030] Preferably, the composition comprises metallic (or non-metallic) oxide particles selected from the group including zirconium oxide, titanium oxide, aluminum oxide, silica, and combinations thereof. The inclusion of metallic oxide particles as described above enhances the mechanical and chemical resistance of the polymer matrix, thereby improving its durability and anti-adhesion properties. Advantageously, the composition is substantially free of organic solvents. The absence of organic solvents reduces environmental and health risks, while minimizing volatility and increasing the chemical stability of the composition. This promotes better adhesion of the ceramic particles to the polymer matrix, thus improving its properties.

[0031] The expression 'substantially free of organic solvent' should be understood as meaning that the composition comprises less than 0.5% by mass of organic solvent, preferably less than 0.05% by mass, more preferably less than 0.005% by mass relative to the total mass of said composition.

[0032] According to an advantageous embodiment, metallic (or non-metallic) oxide particles, preferably silica, are present in an amount of between 2 and 10% by mass, preferably between 2 and 8% by mass, more preferably between 3 and 7.5% by mass, and more preferably between 5 and 7.5% by mass of dry silica relative to the total dry mass of the composition. The optimized amount of metallic (or non-metallic) oxide particles, particularly silica, in the specified proportions, ensures homogeneous dispersion within the polymer matrix. This significantly improves the mechanical properties, non-stick properties, and abrasion resistance of the composition, while maintaining the flexibility and ease of application of the sol-gel composition.

[0033] The composition for non-stick coating according to the invention can be obtained by a sol-gel process which comprises the following steps:

[0034] - To provide a component A which comprises ceramic particles selected from the group including silicon carbide, boron nitride, preferably cubic boron nitride, silicon nitride, boron carbide, titanium nitride, aluminium nitride, tungsten carbide, tungsten sulfide, molybdenum sulfide, diamond and combinations thereof,

[0035] - Provide a component B being the reaction product between a silicone and a silanization precursor: o the silicone comprising two terminal groups comprising at least two methoxy groups (-OCH3), and said silicone having the following structure (IV):

[0036] Or

[0037] The R2 radicals are identical or different and are independently chosen from an alkyl, preferably C1-C10, more preferably a methyl or an ethyl, or an O-R3 group.

[0038] R3 is an alkyl chain, preferably C1-C10, more preferably the methyl or ethyl radical, or a phenyl group, n is between 1 and 20, preferably between 1 and 15, more preferably between 1 and 10, and o The silanization precursor comprising at least two methoxy groups each bonded to a Si atom, and having the following structure (V):

[0039] R5

[0040] R4— Si-OCH3

[0041] OCH3

[0042] (V) Where

[0043] R4 and Rs are identical or different and are independently chosen from an alkyl, preferably C1-C10, more preferably a methyl or ethyl, or an O-R3 group,

[0044] R3 is an alkyl chain, preferably C1-C10, more preferably the methyl or ethyl radical, or a phenyl group,

[0045] - React components A and B to provide the sol-gel composition.

[0046] In a preferred embodiment, the silanization precursor is dimethoxydimethylsilane or (trimethoxymethyl)silane. The use of these specific precursors improves the chemical compatibility between the silicone and the silanization precursor, thus promoting a more efficient reaction and better polymer matrix formation. Preferably, a catalyst is added to the composition as component C. The addition of a catalyst accelerates the reaction process between the components, reducing production time and improving the efficiency of the sol-gel process.

[0047] More specifically, the X / Y molar ratio between silicone and precursor is between 1 / 4 and 1 / 60, preferably between 1 / 4 and 1 / 60. An optimized molar ratio ensures an adequate balance between the components, guaranteeing homogeneous crosslinking and improved mechanical and chemical properties.

[0048] Preferably, the reaction between components A and B, possibly with component C, is carried out via a hydrolysis mechanism followed by (poly)condensation. This reaction mechanism allows for controlled formation of the sol-gel structure, ensuring a homogeneous distribution of ceramic particles and improved matrix cohesion.

[0049] According to a preferred mode, said component A also comprises metallic (or non-metallic) oxide particles selected from the group comprising zirconium oxide, titanium oxide, aluminum oxide, silica and their combination, in colloidal form.

[0050] Advantageously, colloidal silica is anionic. Anionic colloidal silica improves particle dispersion within the polymer matrix, thereby increasing film formation efficiency and composition stability.

[0051] In an advantageous embodiment, the colloidal silica has an average particle size between 10 and 700 nm, preferably between 10 and 500 nm. Optimized silica particle size ensures a high specific surface area, improving interaction with the polymer matrix and increasing mechanical and strength properties.

[0052] More advantageously, component A is dispersed in an aqueous medium. An aqueous dispersion facilitates the handling and mixing of the components, reducing the risks associated with the use of organic solvents and improving the safety and efficiency of the process.

[0053] Preferably, the ceramic particles of component A have an average particle size of between 1 and 10 microns, preferably between 1 and 5 microns, and even more preferably between 1 and 3 microns. Controlled-sized ceramic particles ensure homogeneous dispersion and optimal interaction with the polymer matrix, thus improving the anti-adhesive and mechanical properties of the composition. Preferably, component A includes the addition of a stabilizing and / or dispersing agent selected from an inorganic compound derived from a silicate or having a sheet or disc structure. The addition of specific stabilizing or dispersing agents improves the stability of the ceramic particle dispersion, reducing the tendency to agglomerate and ensuring uniform distribution within the matrix.One of the advantages related to the dispersing and / or stabilizing agent concerns the applicability of the composition according to the invention, which is improved.

[0054] Preferably, component A includes the addition of a stabilizing and / or dispersing agent selected from the group comprising graphene oxide, talc, clay, aluminosilicates, phyllosilicates, smectite, and combinations thereof. These stabilizing and dispersing agents improve the dispersion and stability of the ceramic particles within the polymer matrix, contributing to optimal mechanical and non-stick properties.

[0055] Advantageously, component A is added in an amount of between 5 and 40% by mass relative to the total mass of the composition. An optimized percentage of component A ensures a good balance between the mechanical properties and the flexibility of the composition, without compromising the non-stick performance.

[0056] Preferably, the catalyst is a weak acid catalyst chosen from the group including acetic acid, citric acid, formic acid, and mixtures thereof. The use of weak acid catalysts ensures a controlled and stable reaction, avoiding excessively rapid or uncontrolled reactions that could affect the quality of the polymer matrix.

[0057] In an advantageous configuration, the catalyst has a mass concentration between 25 and 65%, preferably between 35 and 60%, and more preferably between 40 and 60%. An optimized catalyst concentration ensures an efficient and homogeneous reaction, promoting the formation of a uniform and stable polymer matrix.

[0058] Preferably, the catalyst is added in an amount of 0.5 to 3% by mass, preferably 0.5 to 2.5% by mass, and more preferably 0.5 to 2% by mass, relative to the total mass of the composition. Controlled catalyst addition ensures an efficient reaction without excess, resulting in a high-quality polymer matrix with optimal properties. Advantageously, component B is added in an amount of 20 to 70% by mass, preferably 20 to 65% by mass, and more preferably 45 to 60% by mass, relative to the total mass of the composition. An adequate percentage of component B ensures proper formation of the polymer matrix, guaranteeing optimal mechanical and chemical properties.

[0059] Preferably, the stabilizing and / or dispersing agent is present in an amount between 0.1% and 1% by mass of the total composition. Precise addition of stabilizing and / or dispersing agents improves particle stability and dispersion, ensuring consistent and long-lasting performance of the composition.

[0060] More advantageously, ceramic particles are added in an amount of between 5 and 38% by mass, preferably between 10 and 35% by mass, relative to the total mass of the composition. An optimal percentage of ceramic particles ensures good non-stick performance and robust mechanical properties, while maintaining flexibility and ease of application.

[0061] Preferably, silicone has a molecular weight of less than 3000 g / mol, preferably less than 2500 g / mol, more preferably less than 1500 g / mol, and even more preferably less than 1000 g / mol. A silicone with a low molecular weight ensures better crosslinking and more homogeneous formation of the polymer matrix, improving its anti-adhesive and mechanical properties.

[0062] Preferably, the composition has a degree of (poly)condensation equal to Y / 2X, where X is the number of moles of silicone and Y is the number of moles of precursor. An optimized degree of (poly)condensation guarantees a stable and robust three-dimensional structure, ensuring exceptional mechanical and strength properties.

[0063] Other embodiments of the composition according to the invention are indicated in the attached claims.

[0064] The invention also relates to a sol-gel reaction mixture for a hydrolysis-(poly)condensation reaction to provide the sol-gel composition according to the invention comprising: a component A comprising ceramic particles selected from the group including silicon carbide, boron nitride, preferably cubic boron nitride, silicon nitride, boron carbide, titanium nitride, aluminum nitride, tungsten carbide, tungsten sulfide, molybdenum sulfide, diamond and combinations thereof,

[0065] A component B being the reaction product between a silicone and a silanization precursor: o the silicone comprising two terminal groups comprising at least two methoxy groups (-OCH3), and said silicone having the following structure (IV):

[0066] The R2 radicals are identical or different and are independently chosen from an alkyl, preferably C1-C10, more preferably a methyl or an ethyl, or an O-R3 group.

[0067] R3 is an alkyl chain, preferably C1-C10, more preferably the methyl or ethyl radical, or a phenyl group, n is between 1 and 20, preferably between 1 and 15, more preferably between 1 and 10, and o The silanization precursor comprising at least two methoxy groups each bonded to a Si atom, and having the following structure (V):

[0068] R5

[0069] R4 — Si- OCH3

[0070] OCH3

[0071] (V) Where

[0072] R4 and Rs are identical or different and being independently chosen from an alkyl, preferably C1-C10, more preferably a methyl or an ethyl, or an O-R3 group, Rs is an alkyl chain, preferably Ci-Cio, more preferably the methyl or ethyl radical, or a phenyl group.

[0073] All the characteristics mentioned above and in the rest of the description can be combined to specify certain elements included for the reaction mixture, in particular those mentioned for the composition and for the process characteristics.

[0074] Other embodiments of the reaction mixture according to the invention are indicated in the attached claims.

[0075] The invention also relates to a non-stick coating comprising the composition according to the invention.

[0076] Advantageously, the coating according to the invention has a cycle number of at least 500 according to the abrasion resistance test carried out according to the description.

[0077] Preferably, the coating according to the invention has a thickness of between 10 and 100 microns, preferably between 20 and 80 microns, more preferably between 25 and 60 microns, more preferably still between 25 and 55 microns.

[0078] The invention also relates to a metal or ceramic substrate equipped with the coating according to the invention.

[0079] Advantageously, the coating is obtained by carrying out the following steps:

[0080] Application of the composition according to any one of claims 1 to 24, preferably by spraying, onto a substrate. Curing of said composition, preferably by applying a temperature between 100 and 400 °C, more preferably between 150 and 350 °C, more preferably still between 150 and 300 °C. Preferably, the curing step is carried out over a period of time between 1 and 300 minutes, preferably between 1 and 120 minutes, more preferably between 1 and 60 minutes, more preferably still between 15 and 35 minutes.

[0081] Even more preferably, the coating or composition according to the invention is free from per- and polyfluoroalkylated compounds, PFAS types.

[0082] The expression 'substantially free of per- and polyfluoroalkylated compounds' should be understood as meaning that the composition comprises less than 0.001% by mass of per- and polyfluoroalkylated compounds, preferably less than 0.0001% by mass of per- and polyfluoroalkylated compounds, relative to the total mass of said composition.

[0083] Other embodiments of the coating and substrate according to the invention are indicated in the attached claims.

[0084] The invention also relates to a multilayer and its manufacturing and application process on a metal or ceramic substrate.

[0085] The multilayer comprises the coating according to the invention and a primary layer arranged to be disposed on a substrate, said primary layer comprising: ceramic particles trapped in a polymer matrix and being selected from the group including silicon carbide, boron nitride, preferably cubic boron nitride, silicon nitride, boron carbide, titanium nitride, aluminum nitride, tungsten carbide, tungsten sulfide, molybdenum sulfide and their combination, colloidal silica, a polymer matrix formed of a polysiloxane obtained from the hydrolysis-polycondensation of a siloxane selected from the group including di-methoxydimethylsilane, (trimethoxymethyl)silane.

[0086] Advantageously, the multilayer has a thickness of between 20 and 200 m, preferably between 20 and 150 m, more preferably between 20 and 100 pm.

[0087] The manufacturing process for the multilayer according to the invention and its application to a metal or ceramic substrate comprises the following steps: o Formation of the primary layer composition by mixing and reacting:

[0088] ■ ceramic particles selected from the group comprising silicon carbide, boron nitride, preferably cubic boron nitride, silicon nitride, boron carbide, titanium nitride, aluminum nitride, tungsten carbide, tungsten sulfide, molybdenum sulfide and combinations thereof, with

[0089] ■ a polysiloxane selected from the group comprising dimethoxydimethylsilane, (trimethoxymethyl)silane and their combinations, and

[0090] ■ of colloidal silica, Formation of the anti-stick coating composition by reacting the reaction mixture according to the invention,

[0091] Application of the primary layer composition to the substrate, preferably preheated, followed by application of the anti-adhesive coating composition to the primary layer.

[0092] Curing of the multilayer, preferably by applying a temperature between 100 and 400 °C, more preferably between 150 and 350 °C, more preferably still between 150 and 300 °C. Preferably, the curing step is carried out for a period of time between 1 and 300 minutes, preferably between 1 and 120 minutes, more preferably between 1 and 60 minutes, more preferably still between 15 and 35 minutes.

[0093] Other embodiments of the multilayer and associated process according to the invention are indicated in the attached claims.

[0094] The invention also relates to a non-stick kitchen article comprising the composition or coating according to the invention.

[0095] Other embodiments of said article according to the invention are indicated in the attached claims.

[0096] The invention also relates to the use of a non-stick mold comprising the composition according to the invention or the coating according to the invention, to allow the flow and molding of plastic materials.

[0097] Other embodiments of the mold according to the invention are indicated in the attached claims.

[0098] Figure 1 is a photo of a device that allows an abrasion resistance test to be performed.

[0099] Figure 2 is a photograph illustrating abrasion resistance test results according to an example of the invention and according to a comparative example.

[0100] Component B is the reaction product between a silicone and a silanization precursor.

[0101] Silicone comprises two terminal groups, each of which comprises at least two methoxy groups (-OCH3), preferably at least 2 methoxy groups, and has the following structure (IV):

[0102] Or

[0103] The R2 radicals are identical or different and are independently chosen from an alkyl, preferably C1-C10, more preferably a methyl or an ethyl, or an O-R3 group.

[0104] R3 is an alkyl chain, preferably C1-C10, more preferably the methyl or ethyl radical, or a phenyl group, n is between 1 and 20, preferably between 1 and 15, more preferably between 1 and 10.

[0105] Silicone can be obtained by reacting silicone with a compound chosen from the group including (methoxy)trimethylsilane, dimethoxydimethylsilane, (trimethoxymethyl)silane and their combination.

[0106] The silicone according to the invention, which has at each of its ends a Si(R2-R2)-OCH3 group, has end groups which are functional in the context of a hydrolysis-(poly)condensation reaction of the sol-gel processes.

[0107] Preferably, silicone which has at each of its ends a group comprising at least two methoxy groups can be chosen from the following structures IV: The R2 radicals are identical or different and are independently chosen from an alkyl, preferably C1-C10, more preferably a methyl or an ethyl, or an O-R3 group.

[0108] It should be noted that each CH3 group of said silicone included in the structures above can be replaced by a C1-C10 alkyl chain. The methyl or ethyl group being preferred.

[0109] The silanization precursor of the invention comprises at least two methoxy groups, each linked to a Si atom, and having the following structure (V): Or

[0110] R4 and Rs are identical or different and are independently chosen from an alkyl, preferably C1-C10, more preferably a methyl or ethyl, or an O-R3 group,

[0111] R3 is an alkyl chain, preferably C1-C10, more preferably the methyl or ethyl radical, or a phenyl group.

[0112] Preferably, the silanization precursor is the following structure (V):

[0113] OCH3

[0114] R4-S1-OCH3

[0115] OCH3d (V)

[0116] In which R4 is chosen from an alkyl, preferably Cl-ClO, more preferably a methyl or an ethyl.

[0117] Thus, and in a particularly preferred manner, the reaction between silicone equipped with two groups corresponding to structure IV (see below) reacts with structure V below: This allows us to provide a three-dimensional polymer matrix with the following structure:

[0118] It is evident that all other combinations between the different variants set out above are included within the scope of the present invention.

[0119] A person in the trade will be able to make these combinations if necessary from the restricted lists of compounds indicated.

[0120] Metallic (or non-metallic) oxide particles are preferably chosen from the group including zirconium oxide, titanium oxide, aluminum oxide, silica and their combination, in colloidal form.

[0121] The expression 'in colloidal form' means that the metallic (or non-metallic) oxide particles, for example colloidal silica, are a stable suspension of very fine particles, for example silicon dioxide (SiO2) in a liquid.

[0122] It should be noted that, in the context of the invention, metallic (or non-metallic) oxide particles are advantageous but not essential to the realization of the invention. Their presence is preferred to obtain better effects.

[0123] Regarding the presence of the stabilizing and / or dispersing agent, this is also preferred within the framework of the invention.

[0124] The preparation of the composition according to the invention includes two main components, component A and component B, optionally in the presence of component C. Component C relates to the catalyst as described in the invention. Component B is the reaction product between silicone, which has at each of its ends a functional group endowed with at least two methoxy groups, and the silanization precursor.

[0125] Silicone which has a functional group at each of its ends is preferably provided with two methoxy groups, more preferably 3 methoxy groups.

[0126] During the preparation of the composition, component A is obtained by mixing the ceramic particles advantageously with metallic (or non-metallic) oxide particles and optionally with the stability / dispersion agent as described in the invention.

[0127] Components B and C can be supplied separately or mixed together. The resulting mixture can then be mixed with component A.

[0128] Component B can be mixed with component A and then the resulting mixture of components B and A (or vice versa) added to component C.

[0129] All combinations of mixtures are possible within the scope of the invention.

[0130] According to the invention, the notion linked to the expression 'to react' is that commonly understood by a person skilled in the art and means that the mixture allows the indicated compounds to react in a preliminary manner and that in the event of drying and / or heating a hardening is obtained resulting from the reaction between the compounds.

[0131] The invention also relates to a multilayer comprising the non-stick coating according to the invention and a primer layer. It can thus be a bilayer applied to a substrate.

[0132] Thus, and according to a preferred method, it is possible to further improve the durability of the non-stick coating's performance according to the invention through the two-layer system. This allows for more effective stabilization of the coating's surface when it is part of a multi-layer system.

[0133] The multilayer according to the invention can thus comprise two layers, i.e. a primary layer as described in the invention which ensures adhesion, mechanical and thermal resistance and the non-stick coating according to the invention.

[0134] The primary layer according to the invention comprises:

[0135] Polysiloxane compounds selected from the group including di-methoxydimethylsilane, (trimethoxymethyl)silane and their combinations (crosslinkable matrix), colloidal silica, and a ceramic such as silicon carbide which provides the mechanical reinforcement effect.

[0136] The non-stick coating according to the invention maximizes non-stick properties with a more suitable structure for improved durability. It comprises the composition as described in the invention and may, for example, include PDMS as the functional silicone and MT MS in the presence of colloidal silica and diamond particles.

[0137] Within the framework of the invention, it should be noted that the diamond particles of the anti-stick coating according to the invention are not essential but preferred. The table below illustrates, in a preferred manner, the components of the multilayer according to the invention and characteristics related to the manufacturing process of a multilayer as described within the framework of the invention and exemplified below. The table illustrates a preferred embodiment with preferred data to illustrate the invention.

[0138] The abrasion resistance test described in the present invention, particularly in the examples section, is performed on a coating using a 2803 linear abrasive tester (reference 1 in Figure 1) with a weight of 1 kg (reference 2 in Figure 1) and a speed of 99 cycles / minute (see Figure 1, which illustrates the device used). To achieve an abrasive effect, a Scotch-Brite® abrasive belt (or equivalent) made of aluminum oxide is bonded to the axis of the abrasive tester. Thanks to its 1 kg weight, the linear abrasive tester can apply an abrasion force to the coating with a number of cycles ranging from 100 to 10,000.

[0139] The method for evaluating the non-stick properties of coatings is based on the 'egg test' according to the AFNOR NF D21-51 1 standard. The test is carried out according to the following procedure:

[0140] • Cleaning the surface of the sample (coated pans)

[0141] • Drying of coated pans

[0142] • The pan is then placed on a hob with a temperature between 140 and 170°C

[0143] • A 60 / 65 gauge egg is cracked and poured into the center of the pan until the egg coagulates

[0144] • Next, the egg is removed using a spatula

[0145] • And, the coating is cleaned using a damp vegetable sponge.

[0146] The non-stick performance of the coating can be evaluated according to the following ratings:

[0147] — Rating of 100: The egg is completely and very easily removed from the pan using the spatula,

[0148] — Rating of 75: The egg does not come off completely and the coating is very easy to clean with a damp sponge

[0149] — Rating of 50: The egg does not come off completely and the coating can be cleaned with a damp sponge

[0150] — Rating of 25: The egg does not come off completely and the coating can hardly be cleaned with a damp sponge

[0151] — Rating of 0: The egg does not come off completely but the coating cannot be cleaned with a damp sponge.

[0152] EXAMPLES

[0153] Example 1

[0154] Example 1 relates to a first embodiment of a single-layer coating on an aluminum pan. The single-layer coating composition is prepared by stirring silicon carbide with colloidal silica and a stabilizing and / or dispersing agent dispersed in water (component A) using a mechanical disperser for 30 minutes. A mixture (component B) of MTMS and functional PDMS 1 is prepared, to which a catalyst (component C) of formic acid at 50% by mass in water is added. The resulting mixture (components B + C) is added to component A (silicon carbide, colloidal silica, and dispersing agent) and stirred for 1 to 2 hours.

[0155] The resulting mixture is then filtered with a 50-micron filter before being sprayed onto a sandblasted and degreased aluminum pan.

[0156] The coating is hardened by baking between 200 and 300°C for 30 minutes and has a dry thickness of 30 to 50 microns.

[0157] Functional PDMS 1 is a silicone (n=2) which includes two (methoxy)trimethylsilane groups as terminal groups.

[0158] The stabilizing and / or dispersing agent is not essential in the composition and could be omitted.

[0159] Table 1

[0160] Example 2

[0161] Example 2 relates to a second embodiment of a single-layer coating on an aluminum pan.

[0162] The single-layer coating composition is prepared by stirring silicon carbide in the presence of colloidal silica and the stabilizing and / or dispersing agent in water (component A) with a mechanical disperser for 30 minutes. A mixture (component B) of MTMS and functional PDMS 2 is prepared, to which a catalyst (component C) of formic acid at 50% by mass in water is added. The resulting mixture (components B + C) is added to component A (silicon carbide, colloidal silica, and the stabilizing and / or dispersing agent) and stirred for 1 to 2 hours.

[0163] The resulting mixture is then filtered with a 50-micron filter before being sprayed onto a sandblasted and degreased aluminum pan.

[0164] The coating is hardened by baking between 200 and 300°C for 30 minutes and has a dry thickness of 30 to 50 microns.

[0165] Functional PDMS 2 is a silicone (n=2) which includes two dimethoxydimethylsilane groups as terminal groups.

[0166] Table 2

[0167] The stabilizing and / or dispersing agent is not essential in the composition and could be omitted.

[0168] Example 3

[0169] Example 3 relates to a third embodiment of a single-layer coating on an aluminum pan.

[0170] The single-layer coating composition is prepared by stirring silicon carbide with colloidal silica and a stabilizing and / or dispersing agent in water (component A) using a mechanical disperser for 30 minutes. A mixture (component B) of MTMS and functional PDMS 3 is prepared, to which a catalyst (component C) of formic acid at 50% by mass in water is added. The resulting mixture (components B + C) is added to component A (silicon carbide, colloidal silica, and the stabilizing and / or dispersing agent) and stirred for 1 to 2 hours.

[0171] The resulting mixture is then filtered through a 50-micron filter before being sprayed onto a sandblasted and degreased aluminum pan. The coating is hardened by baking at 200-300°C for 30 minutes and has a dry thickness of 30-50 microns.

[0172] Functional PDMS 3 is a silicone (n=2) which includes two trimethoxymethylsilane groups as terminal groups.

[0173] Table 3

[0174] The stabilizing and / or dispersing agent is not essential in the composition and could be omitted.

[0175] Example 4 Example 4 relates to the evaluation, called the 'egg test', of the non-stick properties of coatings of examples 1 to 3 of the invention.

[0176] Table 4

[0177] Example 5 Example 5 relates to the abrasion resistance properties of a pan coated with the composition according to example 3.

[0178] The results were repeated for abrasion tests with a number of cycles of 100, 200, 300, 500, 1000 and 10000, as illustrated in Figure 2.

[0179] The coating of example 3 according to the invention withstands up to 10,000 cycles.

[0180] The results of the abrasion resistance tests show that the control coating withstands up to 300 cycles (from 500 cycles the metal begins to show).

[0181] Example 6

[0182] Example 6 relates to a first embodiment of a two-layer coating (multilayer according to the invention) on an aluminum pan.

[0183] Table 6

[0184] The A+B+C mixture for each layer is prepared separately. The composition of the two-layer coating is prepared by stirring component A (from the first and second layers) with a mechanical disperser for 30 minutes. Component B is then prepared and a formic acid catalyst (50% by mass in water) is added. This mixture is added to component A and stirred for 1 to 2 hours. Both mixtures are then filtered through a 50-micron filter before being sprayed onto a sandblasted and degreased aluminum pan.

[0185] The first layer mixture is applied to a pan preheated to 40°C, then the second layer mixture is applied to the first while still wet (no drying time between the two layers).

[0186] The coating is hardened by baking between 200 and 300°C for 30 minutes and has a total thickness of 50 to 80 microns.

[0187] Example 7

[0188] Example 7 relates to another embodiment of a two-layer coating (multilayer according to the invention) on an aluminum pan in which the coating notch comprises diamond powder.

[0189] Table 7

[0190] The A+B+C mixture for each layer is prepared separately.

[0191] The two-layer coating composition is prepared by stirring component A (from the first and second layers) with a mechanical disperser for 30 minutes. Component B is then prepared and a formic acid catalyst (50% by mass in water) is added. This mixture is added to component A and stirred for 1 to 2 hours. Both mixtures are then filtered through a 50-micron filter before being sprayed onto a sandblasted and degreased aluminum pan.

[0192] The first layer mixture is applied to a pan preheated to 40°C, then the second layer mixture is applied to the first while still wet (no drying time between the two layers).

[0193] The two-layer coating is hardened by baking between 200 and 300°C for 30 minutes and has a total thickness of 50 to 80 microns.

[0194] Example 8 - Egg test

[0195] Example 8 concerns the evaluation, known as the 'egg test', of the non-stick properties of Examples 6 and 7 of the invention after several dishwasher wash cycles. The pans are washed in the dishwasher using a quick program lasting 1 hour and 15 minutes at a temperature of 60°C. Several wash cycles are performed, and after each cycle an egg test is carried out to evaluate the non-stick properties of the coating (according to AFNOR standard NF D 21-51 1).

[0196] Table 8

[0197] Comparative example 1

[0198] The comparative example concerns a coating known from the prior art and corresponds to a commercially available sol-gel coated pan which includes colloidal silica in the presence of MTMS, silicone and ceramic particles.

[0199] Table 5 illustrates the results of the non-stick tests of comparative example 1.

[0200] Table 5

[0201] Comparative example 2

[0202] Comparative example 2 concerns the abrasion resistance properties of a pan coated with the composition according to comparative example 1.

[0203] The results were repeated for abrasion tests with a number of cycles of 100, 200, 300, 500, 1000 and 10000, as illustrated in Figure 2.

[0204] The results of the abrasion resistance tests show that the control coating withstands up to 300 cycles. Indeed, after 500 cycles, the metal of the pan begins to show through.

[0205] The articles "a" and "an" are used here to refer to one or more of one (i.e., at least one) of the grammatical objects of the article and can be replaced by an article that denotes a plural such as "at least 2", "at least 3", "several", etc.

[0206] The expressions "in one embodiment," "according to one embodiment," and similar terms generally mean that the particular feature, structure, or characteristic referred to in the expression is included in at least one embodiment of this disclosure, and may be included in more than one embodiment of this disclosure. It is important to note that such expressions do not necessarily refer to the same embodiment.

[0207] If the text indicates that a component or feature "may" or "could" be included or have a feature, it is not necessary that this particular component or feature be included or have the feature.

[0208] If it appears here, the term "comprising" or "containing" and derivatives thereof are not intended to exclude the presence of any additional component, step, or procedure, whether or not disclosed herein. For the avoidance of doubt, the term "comprising" may include any additional element / additive, adjuvant, or compound unless otherwise specified. By contrast, the term "essentially consisting of," if it appears here, excludes from the scope of any subsequent quotation any other component, step, or procedure, except those not essential to operability, and the term "consisting of," if used, excludes any component, step, or procedure not specifically defined or indicated. The terms "or" and "and / or," unless otherwise specified, refer to the members indicated individually as well as in any combination. For example, the expression A and / or B refers to A alone, B alone, or A and B.Furthermore, the term and any equivalent to "comprising" can be replaced by "consisting of".

[0209] Also, the terms "obtainable" or "can be obtained" or any similar or derived expression may be replaced by "directly obtained".

[0210] It is understood that the present invention is in no way limited to the embodiments described above and that many modifications can be made to it without departing from the scope of the attached claims.

Claims

DEMANDS 1. Sol-gel composition for providing a non-stick coating comprising a polymer matrix and ceramic particles trapped in said matrix and being selected from the group comprising silicon carbide, boron nitride, preferably cubic boron nitride, silicon nitride, boron carbide, titanium nitride, aluminium nitride, tungsten carbide, tungsten sulfide, molybdenum sulfide, diamond and combinations thereof, said polymer matrix having at least one of the following structures (II, III) or combinations thereof: Or A is between 1 and 60, preferably between 1 and 50, more preferably between 1 and 45, and wherein each Ru-Si(O-Ri2)- unit is repeated such that each Si atom of a given unit bonds to at least one oxygen atom of said corresponding Ru-Si(O-Ri2)- unit to have the polymer matrix which exhibits a succession of said units which are linked to each other by Si-O links (*), n is between 1 and 20, preferably between 1 and 15, more preferably between 1 and 10, The Ri radicals are identical or different and are independently chosen from an alkyl group, preferably Ci-Cio, more preferably a methyl or an ethyl group, Ru is an alkyl chain, preferably Ci-Cio, more preferably a methyl or ethyl group, or an oxygen atom ((O-)*) or a phenyl group, R12 is an alkyl chain, preferably Ci-Cio, more preferably a methyl or an ethyl, or an oxygen atom ((O-)*) or a phenyl group.

2. Composition according to claim 1 comprising metallic (or non-metallic) oxide particles selected from the group comprising zirconium oxide, titanium oxide, aluminium oxide, silica and combinations thereof.

3. Composition according to claim 1 or 2, being substantially free of organic solvent.

4. Composition according to any one of the preceding claims, wherein said metallic (or non-metallic) oxide particles, preferably silica, are present in an amount of between 2 and 10% by mass, preferably between 2 and 8% by mass, more preferably between 3 and 7.5% by mass, more preferably still between 5 and 7.5% by mass of dry silica matter relative to the total dry mass of said composition.

5. Composition for non-stick coating according to any one of the preceding claims being obtained by a sol-gel process comprising the following steps: - To provide a component A which comprises ceramic particles selected from the group including silicon carbide, boron nitride, preferably cubic boron nitride, silicon nitride, boron carbide, titanium nitride, aluminium nitride, tungsten carbide, tungsten sulfide, molybdenum sulfide, diamond and their combinations, - Provide a component B being the reaction product between a silicone and a silanization precursor: o silicone comprising two terminal groups comprising at least two methoxy groups (-OCH3), and said silicone having the following structure (IV): Or The R2 radicals are identical or different and are independently chosen from an alkyl, preferably C1-C10, more preferably a methyl or an ethyl, or an O-R3 group. R3 is an alkyl chain, preferably C1-C10, more preferably the methyl or ethyl radical, or a phenyl group, n is between 1 and 20, preferably between 1 and 15, more preferably between 1 and 10, and o The silanization precursor comprising at least two methoxy groups each bonded to a Si atom, and having the following structure (V): Or R4 and Rs are identical or different and are independently chosen from an alkyl, preferably C1-C10, more preferably a methyl or ethyl, or an O-R3 group, R3 is an alkyl chain, preferably C1-C10, more preferably the methyl or ethyl radical, or a phenyl group, - React components A and B to provide the sol-gel composition.

6. Composition according to claim 5, wherein said precursor is di-methoxydimethylsilane or (trimethoxymethyl)silane.

7. Composition according to claim 5 or 6, wherein a catalyst is added as component C of said composition.

8. Composition according to any one of claims 5 to 7, wherein the molar ratio X / Y is between - and — , preferably between - and — , where X corresponds to the number of moles of said silicone and Y to the number of moles of said precursor.

9. Composition according to any one of claims 5 to 8, wherein the reaction step between components A, B and optionally with component C is carried out by a hydrolysis mechanism followed by (poly)condensation.

10. Composition according to any one of claims 5 to 9, wherein said component A also comprises metallic (or non-metallic) oxide particles selected from the group comprising zirconium oxide, titanium oxide, aluminium oxide, silica and combinations thereof, in colloidal form.

1. Composition according to any one of claims 5 to 10, wherein the colloidal silica is anionic.

12. Composition according to any one of claims 5 to 11, wherein the colloidal silica has an average particle size of between 10 and 700 nm, preferably between 10 and 500 nm.

13. Composition according to any one of claims 5 to 12, wherein said component A is in dispersion in an aqueous medium.

14. Composition according to any one of claims 5 to 13, wherein said ceramic particles of component A have an average particle size of between 1 and 10 microns, preferably between 1 and 5 microns, more preferably between 1 and 3 microns.

15. Composition according to any one of claims 5 to 14, wherein component A comprises the addition of a stabilizing and / or dispersing agent being selected from an inorganic compound derived from a silicate or having a sheet or disc structure.

16. Composition according to any one of claims 5 to 15, wherein component A comprises the addition of a stabilizing and / or dispersing agent selected from the group comprising graphene oxide, talc, clay, aluminosilicates, phyllosilicates, smectite and combinations thereof.

17. Composition according to any one of claims 5 to 16, wherein component A is added in an amount of between 5 and 40% by mass relative to the total mass of the composition.

18. Composition according to any one of claims 7 to 17, wherein said catalyst is a weak acid catalyst selected from the group comprising acetic acid, citric acid, formic acid and mixtures thereof.

19. Composition according to any one of claims 7 to 18, wherein said catalyst has a mass concentration of between 25 and 65%, preferably between 35 and 60%, more preferably between 40 and 60%.

20. Composition according to any one of claims 7 to 19, wherein said catalyst is added in an amount of between 0.5 and 3% by mass, preferably between 0.5 and 2.5% by mass, more preferably between 0.5 and 2% by mass, relative to the total mass of the composition.

21. Composition according to any one of claims 5 to 20, wherein said component B is added in an amount of between 20 and 70% by mass, preferably between 20 and 65% by mass, more preferably between 45 and 60% by mass, relative to the total mass of the composition.

22. Composition according to any one of claims 15 to 21, wherein the stabilizing and / or dispersing agent is present in an amount between 0.1 and 1% relative to the total mass of the composition.

23. Composition according to any one of claims 5 to 22, wherein said ceramic particles are added in an amount of between 5 and 38% by mass, preferably between 10 and 35% by mass, relative to the total mass of the composition 24. Composition according to any one of claims 5 to 23, wherein said silicone has a molecular mass of less than 3000 g / mol, preferably less than 2500 g / mol, more preferably less than 1500 g / mol, more preferably still less than 1000 g / mol.

25. Composition according to any one of claims 5 to 24, exhibiting a degree of (poly)condensation equal to , where X corresponds to the number of moles of said silicone and Y to the number of moles of said precursor.

26. Sol-gel reaction mixture for a hydrolysis-(poly)condensation reaction to provide the sol-gel composition according to any one of the preceding claims, comprising: a component A comprising ceramic particles selected from the group including silicon carbide, boron nitride, preferably cubic boron nitride, silicon nitride, boron carbide, titanium nitride, aluminium nitride, tungsten carbide, tungsten sulfide, molybdenum sulfide, diamond and combinations thereof, A component B being the reaction product between a silicone and a silanization precursor: o the silicone comprising two terminal groups comprising at least two methoxy groups (-OCH3), and said silicone having the following structure (IV): Or The R2 radicals are identical or different and are independently chosen from an alkyl, preferably C1-C10, more preferably a methyl or an ethyl, or an O-R3 group. R3 is an alkyl chain, preferably C1-C10, more preferably the methyl or ethyl radical, or a phenyl group, n is between 1 and 20, preferably between 1 and 15, more preferably between 1 and 10, and o The silanization precursor comprising at least two methoxy groups each bonded to a Si atom, and having the following structure (V): R5 R4 — Si- OCH3 OCH3 (V) Or R4 and Rs are identical or different and are independently chosen from an alkyl, preferably Ci-Cio, more preferably a methyl or an ethyl, or an O-R3 group, R3 is an alkyl chain, preferably C1-C10, more preferably the methyl or ethyl radical, or a phenyl group.

27. Non-stick coating comprising the composition according to any one of claims 1 to 25 and having a cycle number of at least 500 according to the abrasion resistance test.

28. Coating according to claim 27 or 28 having a thickness of between 10 and 100 microns, preferably between 20 and 80 microns, more preferably between 25 and 60 microns, more preferably still between 25 and 55 microns.

29. Coating according to claim 27 or 28 being free from per- and polyfluoroalkylated compounds, PFAS types.

30. Metal or ceramic substrate provided with the coating according to any one of claims 27 to 29.

31. Multilayer comprising the coating according to any one of claims 27 to 29 and a primary layer arranged to be disposed on a substrate, said primary layer comprising: ceramic particles trapped in a polymer matrix and being selected from the group comprising silicon carbide, boron nitride, preferably cubic boron nitride, silicon nitride, boron carbide, titanium nitride, aluminium nitride, tungsten carbide, tungsten sulfide, molybdenum sulfide and their combination, colloidal silica, a polymer matrix formed of a polysiloxane obtained from the hydrolysis-polycondensation of a siloxane selected from the group comprising di-methoxydimethylsilane, (trimethoxymethyl)silane.

32. Multilayer according to claim 31 having a thickness of between 20 and 200 m, preferably between 20 and 150 m, more preferably between 20 and 100 pm.

33. A method for manufacturing the multilayer according to claim 30 or 31 and applying it to a metal or ceramic substrate, comprising the following steps: o Formation of the primary layer composition by mixing and reacting: ■ ceramic particles selected from the group comprising silicon carbide, boron nitride, preferably cubic boron nitride, silicon nitride, boron carbide, titanium nitride, aluminum nitride, tungsten carbide, tungsten sulfide, molybdenum sulfide and combinations thereof, with ■ a polysiloxane obtained by the hydrolysis-polycondensation of a siloxane selected from the group comprising dimethoxydimethylsilane, (trimethoxymethyl)silane and their combinations, and ■ colloidal silica, Formation of the anti-stick coating composition by reacting the reaction mixture according to claim 26, Application of the primary layer composition to the substrate, preferably preheated, followed by application of the anti-adhesive coating composition to the primary layer. Curing of the multilayer, preferably by applying a temperature between 100 and 400 °C, more preferably between 150 and 350 °C, more preferably still between 150 and 300 °C.

34. A method according to claim 33, wherein the hardening step is carried out over a period of time of between 1 and 300 minutes, preferably between 1 and 120 minutes, more preferably between 1 and 60 minutes, more preferably still between 15 and 35 minutes.

35. Non-stick kitchen article comprising the composition according to any one of claims 1 to 25 or the coating according to any one of claims 27 to 29 or the multilayer according to claim 31 or 32.

36. Use of a non-stick mold comprising the composition according to any one of claims 1 to 25 or the coating according to any one of claims 27 to 29 to enable the flow and molding of plastic materials.

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