Aqueous dispersion based on thermoplastic polymers

Abstract

An aqueous composition comprising a thermoplastic polymer, an inorganic thickening and / or stabilizing agent derived from a silicate, and a mineral dispersant, a method for producing said composition, a method for applying same to a substrate, and the substrates covered by this composition.

Description

[0001]AQUEOUS DISPERSION BASED ON THERMOPLASTIC POLYMERS Technical field The present invention relates to an aqueous formulation (composition) based on thermoplastic polymer, such as poly-aryl ether ketones, such as poly-ether ketone (PEK), poly-ether ether ketone (PEEK) or poly-ether ketone ketone (PEKK), stabilized by an inorganic thickening and / or stabilizing agent derived from a silicate and a mineral dispersant having a sheet structure. Prior art The class of poly-aryl ether ketones is known and offers interesting properties, such as temperature resistance, resistance to chemical agents or thermal conduction. Among these, poly-(ether ether ketone; PEEK) is known for its good performance at high temperatures, very good mechanical strength and very good chemical resistance.However, the melting temperature of such a molecule is high, which increases the costs and complexity of the application processes. In addition, having to work at high temperatures may affect other components of the formulation. Thus, a variety of basic polyaryl ether ketone molecules have been developed, such as other less crystalline molecules either substituted or having an alteration in the repetition of the aryl ethers, which allows either a simpler application mode or a modification of their properties. There have been various attempts to formulate these molecules. WO 2015 / 065710 describes the mixture of a particulate material, for example kaolinite, and a deformable polymer. These can be put in alkaline solution. There is also the description of fillers. EP3728401 describes a polymer comprising the poly-ether ether ketone having methylations on the aryl group.Fillers or reinforcing agents may be present. This polymer may be applied by molding onto the metal. EP3710517 describes the use of a sulfonated aryl ketone as a dispersing agent for an aqueous solution comprising a poly-aryl ether ketone. WO 2005 / 23893 describes an aqueous dispersion comprising a polymeric material and an organic surfactant according to a precise chemical structure. Thus, to some extent, aqueous poly aryl ether ketone compositions have been made. However, the inventors noticed that these compositions were either not stable over time, or during heat treatment, or were difficult to apply homogeneously to a surface, such as a vertical surface.Brief summary of the invention The object of the invention aims to solve the aforementioned drawbacks by providing an aqueous composition which comprises: - a water-insoluble thermoplastic polymer or a poly-aryl ether ketone, - an inorganic thickening and / or stabilizing agent derived from a silicate, and - a mineral dispersant having a sheet structure or graphene oxide or boron nitride, optionally functionalized. Thus, it is provided according to the invention that the water-insoluble thermoplastic polymer, such as PAEK, is dissolved in the presence of the inorganic thickening and / or stabilizing agent derived from a silicate and a mineral dispersant having a sheet structure. The composition according to the invention makes it possible to easily cover metal surfaces, either directly or on top of an internal ceramic layer (e.g.boron nitride and aluminum oxide), giving them, for example, resistance to chemical agents, mechanical strength, and / or impact resistance. In particular, this approach makes it possible to at least limit, when necessary, or even eliminate the presence of toxic compounds, such as chromium (VI) or additives used for the formulation of Teflon. Likewise, advantageously, the aqueous formulation developed does not use toxic, corrosive or dangerous products. The dependent claims refer to other advantageous embodiments. Preferably, the inorganic thickening and / or stabilizing agent derived from a silicate is talc or clay or an aluminosilicate, preferably a phyllosilicate, more preferably a smectite.Advantageously, the thermoplastic polymer is selected from the group comprising poly-aryl ether ketone, such as poly-ether ketone (PEK), poly-ether ether ketone (PEEK) or poly-ether ketone ketone (PEKK), polysulfone, polyethersulfone, polyetherimides, polyamide, polyimide, aramid, polyphenylene oxide (PPO), compounds comprising phenoxy groups, modified polyphenylene oxide (modified PPO), polyvinylpyrrolidone (PVP), poly(aryl)sulfide, polystyrene (PS), polycarbonate, polyarylether, polyaryletherketone, polyarylsulfide, polybenzimidazole, polyvinylidene fluoride (PVDF), ethylene tetrafluoroethylene (ETFE), perfluoroalkoxy, fluorinated ethylene-propylene (FEP), polychlorotrifluoroethylene (E-CTFE), ethylene vinyl alcohol (EVOH) and their mixtures.More preferably, the inorganic thickening and / or stabilizing agent derived from a silicate is a potassium and / or sodium silicate. In the context of the present invention, the thickening agent may also act as a stabilizer. The ratio between the maximum surface area of ​​the thickener and the thickness of the inorganic thickener derived from a silicate is advantageously greater than 100. The aqueous composition according to the invention is preferably a dispersion. According to a particularly preferred embodiment, the composition comprises at least 30% by weight of water relative to the total weight of the composition. Advantageously, the composition further comprises at least 10% by weight, preferably at least 30% by weight of a second polymer, preferably chosen from a fluoropolymer, nylon and natural polymers.Preferably, the composition comprises at least 5% by mass of an additive having a coefficient of friction of less than 0.3, preferably less than 0.2, more preferably less than 0.1 and preferably chosen from the group comprising tungsten sulfide, molybdenum sulfide, boron nitride, tungsten carbide, silicon carbide, inorganic oxides (titanium oxide, silicon oxide, zirconium oxide), and mixtures thereof. Other embodiments of the composition are included in the set of claims.The present invention also relates to a method for formulating a composition according to the invention, comprising the steps of adding to an aqueous solution with mechanical stirring the following elements: - an inorganic thickener and / or stabilizer being a silicate or a derivative of a silicate, then - a mineral dispersant or graphene oxide and / or boron nitride, - particles of a water-insoluble thermoplastic polymer or of a polyaryl ether ketone, said mechanical stirring being preferably carried out at at least 2000 rpm and / or for at least 1 hour. The thickener acts as a stabilizer. This characteristic is already present in the thickener disclosed within the scope of the present invention.The invention preferably relates to a method for applying the composition according to the invention, comprising the step of spraying, optionally at room temperature, said composition onto a substrate, then baking the coated substrate, so as to fix a coating thereon, preferably for at least 5 minutes and / or at a temperature above the melting temperature of the thermoplastic polymer, preferably between 170 and 450°C, preferably between 400 and 430°C, such as approximately 420°C. More advantageously, the substrate is a metal or a ceramic. According to an advantageous embodiment, the substrate is chosen from a metal and a ceramic, covered with a coating comprising a polyaryl ether ketone. Other embodiments of the method are included in the set of claims.The present invention also relates to a substrate selected from a metal and a ceramic, covered by a coating comprising a water-insoluble thermoplastic polymer or a polyaryl ether ketone and which is capable of being obtained by the method according to the invention. Even more preferably, the invention targets a substrate covered according to the method described above, in which the coating comprises at least 30% by mass of water-insoluble thermoplastic polymer or a polyaryl ether ketone and / or at least 0.01%, preferably at least 1% of a silicate derivative and / or at least 0.01%, preferably at least 0.1% of a mineral dispersant or graphene oxide and / or boron nitride.Preferably, the substrate comprises either at least 60% by weight of the water-insoluble thermoplastic polymer or polyaryl ether ketone, or at least 30% by weight of the water-insoluble thermoplastic polymer or polyaryl ether ketone and at least 30% by weight of another polymer, preferably selected from fluoropolymers, natural fibers and nylon. The present invention also covers any product that comprises the composition according to the invention. Other embodiments of the product are available in the set of claims.The invention may also relate to a kitchen utensil which comprises a coating which comprises a water-insoluble thermoplastic polymer or a polyaryl ether ketone, a silicate derivative (preferably an aluminosilicate and / or a sodium or potassium silicate) and mineral dispersant or graphene oxide and / or boron nitride, said water-insoluble thermoplastic polymer or said polyaryl ether ketone being present in the coating in an amount of at least 30% by mass. Advantageously, the coating further comprises a fluoropolymer, preferably in an amount of at least 30% by mass or an inorganic substance with a low coefficient of friction selected from the group consisting of boron nitride, tungsten sulfide, molybdenum sulfide, silicon carbide, tungsten carbide, preferably in an amount of at least 30% by mass.More advantageously, the kitchen utensil according to the invention does not comprise perfluorooctanoic acid (PFOA) and / or per- and polyfluoroalkyl substances (PFAS). Other embodiments of the utensil are available in the set of claims. Brief description of the drawings Figure 1 shows the application of different aqueous compositions comprising PEEK on surfaces. Detailed description of the invention The composition according to the invention uses water-insoluble thermoplastic polymers. The person skilled in the art knows that the poly-aryl ether ketone family of polymers is part of the water-insoluble thermoplastics.In the context of the present invention, the water-insoluble thermoplastic polymer is advantageously chosen from the group comprising poly-aryl ether ketone, such as poly-ether ketone (PEK), poly-ether ether ketone (PEEK) or poly-ether ketone ketone (PEKK), polysulfone, polyethersulfone, polyetherimides, polyamide, polyimide, aramid, polyphenylene oxide (PPO), compounds comprising phenoxy groups, modified polyphenylene oxide (modified PPO), polyvinylpyrrolidone (PVP), poly(aryl)sulfide, polystyrene (PS), polycarbonate, polyarylether, polyaryletherketone, polyarylsulfide, polybenzimidazole, polyvinylidene fluoride (PVDF), ethylene tetrafluoroethylene (ETFE), perfluoroalkoxy, fluorinated ethylene-propylene (FEP), polychlorotrifluoroethylene (E-CTFE), ethylene vinyl alcohol (EVOH) and mixtures thereof.Advantageously, the thermoplastic polymer is PEEK or a polyamide or polyimide. Even more advantageously, the thermoplastic polymer can be combined with EVOH, a preferred combination will be a polyamide (or polyimide) with EVOH. Thus, the inventors have discovered that these thermoplastic polymers can be formulated stably in the presence of a mineral dispersant having a sheet structure, for example graphene oxide or boron nitride, optionally functionalized. Thus, a first aspect of the present invention relates to an aqueous composition comprising: - a water-insoluble thermoplastic polymer or a poly-aryl ether ketone, - an inorganic thickening and / or stabilizing agent derived from a silicate, and - a mineral dispersant having a sheet structure or graphene oxide or boron nitride, optionally functionalized.The inventors noticed, to their great surprise, that the mineral dispersant (for example graphene oxide or boron nitride) makes it possible to stabilize an aqueous composition of water-insoluble thermoplastic polymer or a poly-aryl ether ketone, such as PAEK or polyamide or polyimide. The inventors consider that, in the formulation they developed, graphene oxide (or boron nitride) acts advantageously as a dispersing agent. According to a preferred embodiment, the inorganic thickening and / or stabilizing agent derived from a silicate may have a sheet structure and may be chosen for specific applications. Furthermore, the mineral dispersant which has a sheet structure may for example be graphene oxide, boron nitride or any other functional equivalent known to those skilled in the art.Furthermore and advantageously, the graphene oxide or boron nitride can be provided in multilayers, which makes it possible to have several sheets, preferably at least 2 sheets parallel to each other, more preferably at least 5 sheets, even more preferably at least 10 sheets. This also extends to any other mineral dispersant which has a sheet structure. Advantageously, the mineral dispersant which has a sheet structure is graphene oxide (mono- or multi-layer) or boron nitride (mono- or multi-layer). Advantageously, a combination between graphene oxide and boron nitride is also possible. According to a particularly preferred embodiment of the invention, it is possible to functionalize the mineral dispersant by adding functional groups.When the dispersant (e.g. boron nitride) is functionalized, it may or may not be in the form of a sheet. Preferably, the functionalized boron nitride will be in the form of a sheet. The inorganic thickener and / or stabilizer derived from a silicate provides a slight stabilizing effect to the PAEK composition, when present without graphene oxide (or boron nitride). On the other hand, surprisingly, the formulation of the thermoplastic polymer (PAEK, polyamide or polyimide) in the presence of both the mineral dispersant (preferably graphene oxide or boron nitride) and the inorganic thickener and / or stabilizer derived from a silicate, provides very good stability, and allows the composition to be applied easily, even on vertical surfaces. This may also apply to other mineral thickeners and / or stabilizers in sheet form (besides phyllosilicates).Preferably, the inorganic thickening and / or stabilizing agent derived from a silicate is talc or an aluminosilicate, preferably a phyllosilicate, preferably selected from the group of a smectite, (e.g. hectorite, or laponite). In the context of the present intention, bentonite is advantageously considered to be a smectite. Alternatively, or additionally, the inorganic thickening and / or stabilizing agent (e.g. aluminosilicate, phyllosilicate, smectite) is a potassium and / or sodium silicate, i.e. at least 10%, preferably at least 20%, or even at least 40% (by mole) of the alkali or alkaline earth cations of a molecule of the inorganic thickener and / or stabilizer being a silicate is potassium or sodium. The inventors noticed that these cations provide better stabilization of the composition.Advantageously, the inorganic thickener and / or stabilizer has a sheet structure, for example rectangular in shape or in the form of a flat disc (e.g. laponite). Preferably, the inorganic thickener and / or stabilizer is a mineral whose sheet thickness is less than 10 nm, preferably less than 5 nm, or even a thickness of between approximately 0.2 nm and 1 nm. The inventors have noted that this type of structure exhibits synergy with the mineral dispersant, preferably graphene oxide or boron nitride. For the sheet structures of the organic thickener and / or stabilizer, preferably the dimensions of the largest surface vary between 25 and 300 nm, preferably the sheet has a rectangular (largest) surface, for example with a length between 200 and 400 (or 300) nm, for example about 250 nm, and a width between 30 and 75 nm, preferably about 50 nm.For example, the sheet has a (largest) substantially square surface, for example with a side size of between 200 and 400 nm, for example about 300 nm. Alternatively, the sheet has a disc-shaped surface, the diameter of which is advantageously between 10 and 50 nm, for example about 25 nm. In the context of the present invention, the thickening and / or stabilizing agent may relate to the same compound which has both a thickening and stabilizing effect. In other words, the ratio between the largest surface area and the thickness of the thickener and / or stabilizer is preferably greater than 100, preferably greater than 1000. The inventors have noticed that an incorporation of the thickener and / or stabilizer (silicate, aluminosilicate) at a content of between 0.1 and 5% (by weight), preferably between 0.5 and 2, such as about 0.8% or about 1% by weight (weight of silicate: total weight of the aqueous composition) works well.In other words, an advantageous weight ratio between the water-insoluble thermoplastic polymer, such as a PAEK (PEK, PEEK, PEKK) or a polyamide or polyimide and the thickener and / or stabilizer (silicate, aluminosilicate) is between 10 and 100, preferably between 20 and 75, such as between 40 and 50 (weight of PAEK: weight of thickener and / or stabilizer). In the context of the present invention, graphene oxide (CAS, 1034343-98-0) preferably means a two-dimensional layered structure (read, mono- or multi-layer sheet(s)) composed of carbon atoms arranged in a hexagon shape and substituted by -OH, carbonyl, epoxy and carboxyl residues. Advantageously, the graphene oxide of the present invention consists of a superposition of sheets, preferably parallel to each other, of less than 20, preferably less than 15, more preferably less than 10 layers.Graphene oxide may comprise 1, 2, 3, 4, 5, 6 or 7 layer(s) (sheets), as well as mixtures of these structures. This also advantageously applies to boron nitride or any other mineral dispersant which has a sheet structure. Graphene oxide may be obtained by treating graphite with a strong oxidant, followed by separation into sheets in an alkaline solution. The person skilled in the art knows methods for producing sheet-like boron nitride. In the context of the present invention, the boron nitride will preferably always be in sheet form (mono- or multi-layer). The inventors have noted that an incorporation of graphene oxide in a weight content of between 0.1% and 2% by weight, preferably between 0.2 and 1%, for example about 0.4%, works well (weight of graphene oxide: weight of the aqueous composition). This applies to the mineral dispersant as defined within the scope of the present invention.In other words, an advantageous weight ratio between the water-insoluble thermoplastic polymer, such as PAEK (PEK, PEEK, PEKK) and the mineral dispersant (preferably graphene oxide or boron nitride) is between 20 and 500, preferably between 50 and 200, such as between 100 and 150 (weight of PAEK: weight of graphene oxide). Alternatively, the incorporation of boron nitride as a mineral dispersant is in an amount of up to 5% by mass. When boron nitride is used as an additive, it may be present in an amount of at least 5% by mass. In other words, an advantageous weight ratio between the water-insoluble thermoplastic polymer, such as PAEK (PEK, PEEK, PEKK) and graphene oxide and between 2 and 500, preferably between 5 and 200, such as between 10 and 150 (weight of PAEK: weight of graphene oxide).Advantageously, the aqueous composition is a dispersion (stabilized by the mineral dispersant (graphene oxide or boron nitride) and the silicate). In the context of the present invention, preferably, the PAEK is a polymer consisting (essentially) of the units of formula (-Ar-X-) as well as the units of formula (-Ar'-Y-), in which: - Ar and Ar' each denote a divalent aromatic radical; - Ar and Ar' are preferably chosen from 1,3-phenylene, 1,4-phenylene, 4,4'-biphenylene, 1,4-naphthylene, 1,5-naphthylene and 2,6-naphthylene, optionally substituted; - X denotes an electron-withdrawing group, which may preferably be chosen from the carbonyl group (more preferred) and the sulfonyl group; - Y denotes a group chosen from an oxygen atom (more preferred), a sulfur atom, an alkylene group, such as in particular -CH2- and isopropylidene. Among the X units, at least 50 mol.%, preferably at least 70 mol.% and more particularly, at least 80 mol.% of the X units represent a carbonyl group. Advantageously, all the X units denote a carbonyl group. Among the Y units, preferably, at least 50 mol.%, preferably at least 70 mol.% and more particularly at least 80 mol.% of the Y units represent an oxygen atom. Advantageously, all the Y units denote an oxygen atom. Preferably, the PAEK is a poly-ether-ether-ketone (PEEK), comprising a succession of repeating units of the type –(Ar-O- Ar2-O-Ar3-CO)n -, each Ar, Ar2 and Ar3 independently representing a divalent aromatic radical, preferably a phenylene. The bonds on either side of each Ar, Ar2 and Ar3 unit (e.g. the groups forming the -O- or -CO- chain) may be of the para, or meta, or ortho type (preferably of the para type).Alternatively, PAEK is a poly-ether-ketone-ketone (PEKK), comprising a succession of repeating units of the type –(Ar-O- Ar2-CO-Ar3-CO)n-, each Ar, Ar2 and Ar3 independently representing a divalent aromatic radical, preferably a phenylene. Preferably this PAEK is substantially composed of the monomers according to formulas (i), (ii), (iii), (iiii) and (v) below. (iii) Advantageously, the PAEK of the aqueous composition consists substantially of the monomer of formula (I), the monomer of formula (ii), the monomer of formula (iii), the monomer of formula (iiii) or the monomer of formula (v), preferably the PAEK of the aqueous composition consists essentially of the monomer of formula (ii), Poly-ether ether ketone (PEEK). According to a preferred alternative, the PAEK of the aqueous composition consists essentially of the monomer of formula (iii), Poly ether ketone ketone (PEKK); PEEK (CAS No. 29658-26-2) being more preferred than PEKK. Preferably, in the context of the present invention, in addition to PAEK, the water-insoluble thermoplastic polymer is selected from the group consisting of poly-aryl ether ketone, such as poly-ether ketone (PEK), poly-ether ether ketone (PEEK) or poly-ether ketone ketone (PEKK), polysulfone, polyethersulfone, polyetherimides, polyamide,polyimide, aramid, polyphenylene oxide (PPO), compounds comprising phenoxy groups, modified polyphenylene oxide (modified PPO), polyvinylpyrrolidone (PVP), poly(aryl)sulfide, polystyrene (PS), polycarbonate, polyarylether, polyaryletherketone, polyarylsulfide, polybenzimidazole, polyvinylidene fluoride (PVDF), ethylene tetrafluoroethylene (ETFE), perfluoroalkoxy, fluorinated ethylene-propylene (FEP), polychlorotrifluoroethylene (E-CTFE), ethylene vinyl alcohol (EVOH) and mixtures thereof. Preferably, the water-insoluble thermoplastic polymer, such as PAEK (e.g., PEK, PEEK, or PEKK), is inserted in the form of particles, preferably substantially spherical particles. Advantageously, these particles have a known size, and not too large. In the context of the present invention, preferably,d50 means that 50% of the particles have a size less than the value given below. In the context of the present invention, preferably, d90 means that 90% of the particles have a size less than the value given below. In the context of the present invention, preferably, d99 means that 99% of the particles have a size less than the value given below. The preferred d50 value for the water-insoluble thermoplastic polymer, such as PAEK (PEEK) of the present invention is 50 µm, preferably 40 µm, preferably 30 µm, preferably 20 µm, or even 10 µm or 5 µm. Alternatively, or in addition, the preferred d90 value is 60 µm, preferably 50 µm, preferably 40 µm, preferably 25 µm, or even 15 µm or 10 µm. Alternatively, or in addition, the preferred d99 value is 80 µm, preferably 70 µm, preferably 60 µm, preferably 50 µm, or even 20 µm. In the context of the present invention,when the water-insoluble thermoplastic polymer particle, such as PAEK, is not spherical, preferably the diameter is the equivalent diameter, such as the volume equivalent diameter dv (V= ^ / 6.dv³). Preferably, the aqueous composition (dispersion) comprises at least 30% by weight of water. Preferably, the aqueous composition (dispersion) comprises at least 30% by weight of water-insoluble thermoplastic polymer, such as PAEK (PEK, PEEK, PEKK), for example between 40 and 50% by weight, such as about 45% by weight. Alternatively, the aqueous composition further comprises a fluoropolymer or nylon fibers, to the detriment (in part) of the PAEK (PEK, PEEK, PEKK). Such a composition comprises between 10 and 30% by weight of PAEK (such as PEEK) and between 10 and 30% by weight of fluoropolymer or nylon microbeads. According to another preferred alternative, the aqueous composition further comprises an additive,selected from the group consisting of tungsten sulfide (WS2), molybdenum sulfide (MoS2), boron nitride, tungsten carbide, silicon carbide, inorganic oxides (titanium oxide, silicon oxide, zirconium oxide), and mixtures thereof. The incorporation of the fluoropolymer, boron nitride (also listed as a dispersant), tungsten sulfide or molybdenum sulfide provides good non-stick properties to a coating produced from this aqueous composition, for example the coating of a kitchen utensil, such as a cooking utensil: the incorporation of PAEK (PEEK) provides chemical, thermal and mechanical resistance, and the fluoropolymer or the additives listed above provide the non-stick character. On the other hand, carbides or metal oxides are advantageously incorporated for increasing mechanical resistance, for example resistance to abrasion or scratching,for example when the thermoplastic polymer is not a PAEK. The additives are advantageously incorporated at a weight content of at least 5%, preferably between 5 and 20%, more preferably between 10 and 15%. Preferably the fluoropolymer or the additive is incorporated, during the process described below, in the form of powder or an emulsion. In the context of the present invention, the fluoropolymer referenced in the present application can be replaced as desired by an inorganic substance with a low coefficient of friction chosen from the group comprising boron nitride, tungsten sulfide, molybdenum sulfide, silicon carbide, tungsten carbide, preferably in an amount of at least 30% by mass. This is applicable to each paragraph which provides for the addition of fluoropolymer. Preferably this fluoropolymer (or the composition comprising this fluoropolymer) is free of toxic or potentially toxic compounds,such as perfluorooctanoic acid (PFOA) and / or per- and polyfluoroalkyl substances (PFAS). Advantageously, this fluoropolymer is compatible with culinary (food) use. A favorable fluoropolymer is polytetrafluoroethylene (PTFE), preferably free of PFOA and / or per- and polyfluoroalkyl substances (PFAS). Thus, the above additives (not being a fluoropolymer) are advantageous because they allow a complete freedom from fluoropolymers when necessary. The incorporation of nylon microbeads allows for a reduction in costs, but this somewhat reduces mechanical strength and thermal stability. A related aspect of the present invention relates to a method for formulating this composition, comprising the steps of: 1- Putting the demineralized water under mechanical stirring 2- Adding the silicate or a silicate derivative (clay) in small portions and under strong mechanical stirring (2000 – 5000 rpm),advantageously so as to obtain the clay in sheet form (if the incorporated silicate is clay) 3- Addition of the mineral dispersant (graphene oxide and / or boron nitride for example) 4- Addition of the water-insoluble thermoplastic polymer powder such as PAEK (PEEK) 5- Optionally add the second polymer or additive (chosen from tungsten sulfide, molybdenum sulfide, tungsten carbide, silicon carbide, inorganic oxides, and mixtures thereof) 6- Leave stirring for 1 to 2 hours to thoroughly disperse the water-insoluble thermoplastic polymer powder, such as PAEK (PEK, PEEK, PEKK), advantageously until a fluid liquid is obtained. Preferably, the decrease in viscosity of the composition is monitored over time. A related aspect of the present invention relates to a method of applying this composition, which comprises the step of spraying this composition described above onto a substrate,then baking the coated substrate. A preferred substrate of this method is a metal or a ceramic. Advantageously, the metal is included among nickel, iron, aluminum, cobalt and their alloys. Thus, preferably, the substrate is a metal, and this method advantageously comprises the preliminary step of adding a primer layer consisting essentially of (i) an aluminum oxide (hereinafter sometimes referred to as "first particle"), (ii) boron nitride (or beryllium oxide or aluminum nitride; hereinafter, sometimes referred to as "second particle") and (iii) aluminum (tri)phosphate (before spraying the composition described above onto this primer layer), this primer layer being advantageously baked onto the substrate,for example before applying the composition comprising PAEK (PEEK). An advantageous temperature for curing the primer layer is about 370°C. An advantageous temperature for curing the composition comprising PAEK (preferably PEEK) is about 420°C (e.g. between 350°C and 450°C). An advantageous time is between 5 and 30 minutes, for example about 10 minutes. In particular, Al2O3 particles (e.g. with a diameter between 1 and 10 µm, preferably 3 to 5 µm), BN particles (e.g. with a diameter between 1 and 20 µm) and aluminum phosphate Al(H2PO4)3 are suspended in water with stirring, then applied by spraying onto the metal layer before curing (e.g. involving a step at 95°C and / or 370°C). The inventors obtained good results with Al2O3:BN mass ratios between 1:20 and 1:5,preferably between 1:10 and 1:6. The preferred BN is of hexagonal structure. Another related aspect of the present invention relates to a substrate selected from, a metal and a ceramic, covered by a coating comprising this water-insoluble thermoplastic polymer, such as PAEK (e.g. PEEK); this coating further comprising a graphene oxide (or boron nitride) and a silicate and may further comprise one of the additives listed above, if incorporated. Preferably, the coating of this substrate has a thickness of between 5 and 200 µm, advantageously, between 20 and 150 µm, such as between 50 and 120 µm, or between 70 and 100 µm. Advantageously, this coating comprises at least 30% by mass of water-insoluble thermoplastic polymer, such as PAEK (e.g. PEEK) and / or at least 0.5% of a silicate derivative (typically about 1%) and / or at least 0.3% of a graphene oxide or boron nitride. Alternatively, preferably,the coating of this substrate comprises at least 10% by mass of PAEK (e.g. PEEK) and at least 10% by mass of nylon microbeads. Preferably, the coating of this substrate does not comprise chromium (VI) and / or fluoropolymers, such as perfluorooctanoic acid (PFOA) and / or per- and polyfluoroalkyl substances (PFAS). Another related aspect of the present invention relates to a kitchen utensil comprising a coating comprising a PAEK (e.g. PEEK), a silicate derivative and a graphene oxide and, preferably a non-stick fluoropolymer, advantageously polytetrafluoroethylene (PTFE) or at least 5% by mass of an additive having a coefficient of friction of less than 0.3, preferably less than 0.2, more preferably less than 0.1, preferably selected from the group comprising tungsten sulfide, molybdenum sulfide, boron nitride, tungsten carbide, silicon carbide, inorganic oxides (titanium oxide,silicon, zirconium), and mixtures thereof. Preferably, the additive is not a fluoropolymer. This cookware coating preferably does not comprise perfluorooctanoic acid (PFOA) and / or per- and polyfluoroalkyl substances (PFAS). Another related aspect of the present invention relates to a metal surface coated with a primary (ceramic) layer consisting essentially of - aluminum oxide particles, - second particles selected from boron nitride, beryllium oxide or aluminum nitride and - a binder (preferably an aluminum phosphate), and a surface layer comprising a poly-aryl ether ketone, a silicate derivative (preferably an aluminosilicate and / or a sodium or potassium silicate) and a graphene oxide, this poly-aryl ether ketone being present in the surface layer in an amount of at least 30% by mass. Preferably, in this primary layer,the mass ratio between the aluminum oxide and the second particles chosen from boron nitride, beryllium oxide or aluminum nitride (Al, 2 O 3 :BN or Al 2 O 3 :BeO or Al 2 O 3:AlN) is between 1:20 and 1:5, preferably between 1:10 and 1:6. This allows good thermal conductivity while maintaining sufficient mechanical strength. The second preferred particle is boron nitride, preferably hexagonal boron nitride. This allows maximum thermal conductivity. The preferred binder for this primer layer is aluminum triphosphate. Preferably the primer layer comprises between 20 and 50% by weight of the binder (aluminum triphosphate), preferably between 30 and 40% by weight of the binder. This ensures good cohesion of the particles and good mechanical strength, as well as good thermal conductivity. In the context of the present invention, preferably, the poly-aryl ether ketone of the surface layer is as described above for the aqueous composition; the preferred poly-aryl ether ketone is poly-ether ether ketone (PEEK), or poly-ether ketone ketone (PEKK). In the context of the present invention,the expression "water-insoluble" means that the thermoplastic polymer has a solubility in water of less than 100 mg / L of water at room temperature (20°C). Preferably, the thermoplastic polymer of the invention is semi-crystalline with a crystallinity level of between 10 and 90%, preferably between 20 and 80%, measured by DSC. The coefficient of friction used in the context of the present invention is measured according to the horizontal plane method with equipment conforming to standard ISO 8295 (plastic, sheet and film). Overall, the measuring apparatus (Thwing-Albert FP-2260 Friction / Peel Tester) essentially comprises a horizontal test table,a sled and a traction mechanism capable of producing a relative movement between the sled and the test table regardless of which of the two constitutes the moving part. The coatings to be tested are placed in plane contact and under uniform contact pressure. The contact pressure force must be produced by a sled whose square-shaped contact base has an area of ​​40 cm* (edge ​​length: 63 mm). The total mass of the sled must be 200 g (exerts a pressure force equal to 1.96 N). The force necessary to move the surfaces relative to each other is recorded. This force recorded during sliding makes it possible to calculate the coefficient of friction. Other characteristics and advantages of the present invention will be drawn from the non-limiting description which follows,and with reference to the drawings and examples. Examples: It is understood that the present invention is in no way limited to the embodiments described above and that many modifications may be made thereto without departing from the scope of the appended claims. Example 1: Composition of the PEEK-based dispersion: - PEEK powder: 45% - Smectite group clay: 1% - Graphene oxide 1.5% (in the form of a paste at 25 wt% in water) - Demineralized water: 52.5 Preparation of the dispersion: 1- Put the demineralized water under mechanical stirring 2- Add the clay in small portions and under strong mechanical stirring (2000 – 5000 rpm) 3- Add the graphene oxide (in the form of a paste at 25 wt% in water) 4- Add the PEEK powder 5- Leave stirring for 1 to 2 hours to thoroughly disperse the PEEK powder (obtaining a fluid liquid) Example 2: Composition of the PEEK-based dispersion: - PEEK powder: 45% - Graphene oxide 1,5% (in the form of a 25 wt% paste in water) - Demineralized water: 53.5 Preparation of the dispersion: 1- Put the demineralized water under mechanical stirring 2- Addition of the graphene oxide under strong mechanical stirring (2000 – 5000 rpm) 3- Addition of the PEEK powder 4- Leave under stirring for 1 to 2 hours to properly disperse the PEEK powder (obtaining a fluid liquid) Example 3: Composition of the PEEK-based dispersion: - PEEK powder: 45% - Smectite group clay: 1% - Demineralized water: 54% Preparation of the dispersion: 1- Put the demineralized water under mechanical stirring 2- Addition of the clay in small portions and under strong mechanical stirring (2000 – 5000 rpm) 3- Addition of the PEEK powder 4- Leave under stirring for 1 to 2 hours to properly disperse the PEEK powder (obtaining a fluid liquid) 2 hours to properly disperse the PEEK powder (obtaining a fluid liquid) Dispersion stability test: The 3 three dispersions (example 1,2 and 3) are stored in test tubes and left to stand for a period of one month. Dispersion of example 1 is very stable; the PEEK powder remains homogeneously dispersed. Dispersion of example 2: beginning of sedimentation of the PEEK powder. Dispersion of example 3: Strong sedimentation of the PEEK powder. Method of applying PEEK in dispersion: The 3 different PEEK dispersions are applied by spraying using a pneumatic gun (nozzle: 1 to 1,5 mm). Substrate preparation: The surface of the metal substrates is prepared by sandblasting (obtaining a surface roughness Ra of 2 to 4 microns). Application conditions: Gun: 1 mm nozzle Air pressure: 2 to 4 bar The metal substrates are placed vertically to measure the effect of the dispersion flow on the application Thickness applied wet: 100 to 200 microns Thickness applied dry: 50 to 100 microns. Baking conditions: Baking at 420°C for 10 minutes Figure 1 shows that the composition of Example 1 is by far the best. The composition of Example 2, which seemed quite good following the sedimentation test, does not allow for a homogeneous application. Example 4: PEEK + fluoropolymer Composition of the PEEK-based dispersion: - PEEK powder: 22.5% - Fluoroplymer powder (PFA): 22.5% - Smectite group clay: 1% - Graphene oxide 1.5% (in the form of a paste at 25 wt% in water) - Demineralized water: 52.5 Preparation of the dispersion: 1- Put the demineralized water under mechanical stirring 2- Addition of the clay in small portions and under strong mechanical stirring (2000 – 5000 rpm) 3- Addition of the graphene oxide 4- Addition of the PEEK powder 5- Addition of the fluoropolymer powder 6- Leave stirring for 1 to 2 hours to properly disperse the PEEK powder (obtaining a fluid liquid). Application and cooking similar to the PEEK-based dispersion (Ex 1). Contact angle measurement Ex 1 (PEEK alone): contact angle between 30 and 40° (hydrophilic surface and low anti-adhesion) Ex 4 (PEEK + PFA): contact angle between 90 and 100° (hydrophobic surface and good anti-adhesion). Example 5: PEEK + inorganic anti-adhesive additives Composition of the PEEK-based dispersion: - PEEK powder: 25 to 35% - Additive powder 1 (WS2 particles with a D50 between 0.5 and 8 microns): 1 to 5% - Additive powder 2 (BN particles with a D50 between 0.5 to 8 micron): 1 to 5% - Additive powder 3 (SiC particles with a D50 between 0.5 to 8 micron): 1 to 5% - Smectite group clay: 0.5 to 1% - Graphene oxide 0.1 to 1% (in the form of a paste at 25 wt% in water) - Demineralized water: 60 to 70% Preparation of the dispersion: 1- Put the demineralized water under mechanical stirring 2- Addition of the clay in small portions and under strong mechanical stirring (2000 – 5000 rpm) 3- Addition of the graphene oxide 4- Addition of the PEEK powder 5- Addition of the powder of additives 1, 2 and 3 6- Leave under stirring for 1 to 2 hours to properly disperse the PEEK powder + additives (obtaining a fluid liquid). Application and curing similar to PEEK-based dispersion (Ex 1). Contact angle and anti-adhesion measurement Ex 5 (PEEK + additives 1,2 and 3): contact angle between 90 and 100° (hydrophobic surface and good anti-adhesion). Example 6: Polyamide 11 (powder with D50 between 10 and 50 microns) Composition of the dispersion based on polyamide 11: - Polyamide 11 powder: 35 to 45% - Smectite group clay: 0.5 to 1% - Graphene oxide 0.1 to 1% (in the form of a paste at 25 wt% in water) - Demineralized water: 55 to 67% Preparation of the dispersion: 1- Put the demineralized water under mechanical stirring 2- Add the clay in small portions and under strong mechanical stirring (2000 – 5000 rpm) 3- Add the graphene oxide 4- Add the polyamide 11 powder 5- Leave stirring for 1 to 2 hours to properly disperse the polyamide 11 powder (obtaining a fluid liquid). Similar application to PEEK-based dispersion (Ex 1). Baking conditions: Baking at 250°C for 10 minutes Example 7: Polyimide (powder with D50 between 10 and 50 microns,Tg = 245°C and Tm = 388°C) Composition of the polyimide-based dispersion: - Polyimide powder 11: 35 to 45% - Smectite group clay: 0.5 to 1% - Graphene oxide 0.1 to 1% (in the form of a paste at 25 wt% in water) - Demineralized water: 55 to 67% Preparation of the dispersion: 1- Put the demineralized water under mechanical stirring 2- Add the clay in small portions and under strong mechanical stirring (2000 – 5000 rpm) 3- Add the graphene oxide 4- Add the polyimide powder 5- Leave stirring for 1 to 2 hours to thoroughly disperse the polyimide powder (obtaining a fluid liquid). Similar application to the PEEK-based dispersion (Ex 1). Cooking conditions: Cook at 440°C for 10 minutes,

Claims

CLAIMS 1. An aqueous composition comprising: - a water-insoluble thermoplastic polymer or a poly-aryl ether ketone, - an inorganic thickening and / or stabilizing agent derived from a silicate, and - a mineral dispersant having a sheet structure or graphene oxide or boron nitride, optionally functionalized.

2. The aqueous composition according to claim 1 in which the inorganic thickening and / or stabilizing agent derived from a silicate is talc or clay or an aluminosilicate, preferably a phyllosilicate, more preferably a smectite. 3.The composition according to claim 1 or 2, wherein the thermoplastic polymer is selected from the group consisting of poly-aryl ether ketone, such as poly-ether ketone (PEK), poly-ether ether ketone (PEEK) or poly-ether ketone ketone (PEKK), polysulfone, polyethersulfone, polyetherimides, polyamide, polyimide, aramid, polyphenylene oxide (PPO), compounds comprising phenoxy groups, modified polyphenylene oxide (modified PPO), polyvinylpyrrolidone (PVP), poly(aryl)sulfide, polystyrene (PS), polycarbonate, polyarylether, polyaryletherketone, polyarylsulfide, polybenzimidazole, polyvinylidene fluoride (PVDF), ethylene tetrafluoroethylene (ETFE), perfluoroalkoxy, fluorinated ethylene-propylene (FEP), polychlorotrifluoroethylene (E-CTFE), ethylene vinyl alcohol (EVOH) and their mixtures. 4.The composition according to any one of the preceding claims, wherein the inorganic thickening and / or stabilizing agent derived from a silicate is a potassium and / or sodium silicate.

5. The aqueous composition according to any one of the preceding claims, wherein the ratio between the maximum surface area and the thickness of the inorganic thickening and / or stabilizing agent derived from a silicate is greater than 100.

6. The aqueous composition according to any one of the preceding claims being a dispersion.

7. The aqueous composition according to any one of the preceding claims comprising at least 10%, preferably at least 30% by mass of the water-insoluble thermoplastic polymer, relative to the total weight of the composition, preferably poly-aryl ether ketone, preferably poly-aryl ether ketone being substantially consisting of monomers according to formulae (i), (ii), (iii), (iiii) and (v) below 20 (v). and / or wherein the poly-aryl ether ketone consists essentially of the monomers of formula (ii).

8. The aqueous composition according to any one of the preceding claims comprising at least 30% by weight of water relative to the total weight of the composition.

9. The aqueous composition according to any one of the preceding claims further comprising at least 10% by weight, preferably at least 30% by weight of a second polymer, preferably chosen from a fluoropolymer, nylon and natural polymers or at least 5% by weight of an additive having a coefficient of friction of less than 0.3, preferably less than 0.2, more preferably less than 0.1 and preferably chosen from the group comprising tungsten sulfide, molybdenum sulfide, boron nitride, tungsten carbide, silicon carbide, inorganic oxides (titanium oxide, silicon oxide, zirconium oxide), and mixtures thereof. 10.A method for formulating a composition according to any one of the preceding claims, comprising the steps of adding to an aqueous solution with mechanical stirring the following elements: - an inorganic thickener and / or stabilizer being a silicate or a derivative of a silicate, then - a mineral dispersant or graphene oxide and / or boron nitride, - particles of a water-insoluble thermoplastic polymer or of a polyaryl ether ketone, said mechanical stirring being preferably carried out at at least 2000 rpm and / or for at least 1 hour.

11. A method of applying the composition according to any one of claims 1 to 9 comprising the step of spraying, optionally at room temperature, said composition onto a substrate, then baking the coated substrate, so as to fix a coating thereon, preferably for at least 5 minutes and / or at a temperature above the melting temperature of the thermoplastic polymer, preferably between 170 and 450°C, preferably between 400 and 430°C, such as approximately 420°C.

12. A method according to claim 11, wherein the substrate is a metal or a ceramic.

13. A substrate selected from a metal and a ceramic, covered with a coating comprising a water-insoluble thermoplastic polymer or a polyaryl ether ketone and obtainable by the method according to any one of claims 10 to 12. 14.The coated substrate according to claim 11 or 12 or 13, wherein the coating comprises at least 30% by weight of water-insoluble thermoplastic polymer or polyaryl ether ketone and / or at least 0.01%, preferably at least 1% of a silicate derivative and / or at least 0.01%, preferably at least 0.1% of an inorganic dispersant or graphene oxide and / or boron nitride.

15. The substrate according to claim 14 comprising either at least 60% by weight of the water-insoluble thermoplastic polymer or polyaryl ether ketone, or at least 30% by weight of the water-insoluble thermoplastic polymer or polyaryl ether ketone and at least 30% by weight of another polymer, preferably selected from fluoropolymers, natural fibers and nylon.

16. Product comprising the composition according to any one of claims 1 to 9.A kitchen utensil comprising a coating comprising a water-insoluble thermoplastic polymer or polyaryl ether ketone, a silicate derivative (preferably an aluminosilicate and / or a sodium or potassium silicate) and mineral dispersant or graphene oxide and / or boron nitride, said water-insoluble thermoplastic polymer or polyaryl ether ketone being present in the coating at a level of at least 30% by mass.

17. The kitchen utensil of claim 16, wherein the coating further comprises a fluoropolymer or a low friction inorganic substance selected from the group consisting of boron nitride, tungsten sulfide, molybdenum sulfide, silicon carbide, tungsten carbide, preferably in an amount of at least 30% by mass.

18. The kitchen utensil of claim 16 or 17 not comprising perfluorooctanoic acid (PFOA) and / or per- and polyfluoroalkyl substances (PFAS).

Images