Method for assembling an anti-adhesion film on a metal substrate by hot stamping

Abstract

A method for manufacturing a coated cooking element comprising the following steps: i. providing a metal substrate having a surface to be coated with a film; ii. providing a film, the film comprising a layer for contacting the surface of the metal substrate, the layer comprising 50 to 100% by weight of PTFE and 0 to 50% by weight of one or more thermoplastic polymers different from PTFE (% being relative to the total weight of PTFE and the one or more thermoplastic polymers); iii. heating the metal substrate; iv. positioning the film such that the layer faces the surface of the metal substrate heated in step iii; v. assembling the metal substrate and the film by hot stamping, the metal substrate being at a temperature of 350°C to 550°C during assembly, and a method such that when contacting the metal substrate during assembly in step (v), the film is heated essentially by conduction.

Description

Technical Field

[0001] The present invention relates to the field of methods for obtaining cooking elements coated with an anti-adhesion polymer film.

Background Art

[0002] In the industry of cooking utensils including anti-adhesive cooking surfaces, the development of the performance of anti-adhesive coatings and methods for obtaining such coatings is an important concern.

[0003] Conventionally, a metal substrate is first formed to form a kitchen utensil, and then the inner surface of the kitchen utensil is coated with a fluororesin having excellent heat resistance such as polytetrafluoroethylene (PTFE) or tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA) by a liquid spray coating method or a powder coating method. An alternative is to coat the substrate and then form the thus-coated substrate.

[0004] The liquid spray coating method has several drawbacks. When the metal substrate has a curved shape, it is difficult to obtain a uniform coating thickness. The liquid spray coating method also involves the use of solvents or volatile organic compounds that evaporate during the process and must be recovered and recycled. From an environmental perspective, a solvent-free and volatile organic compound-free method is preferred. On the other hand, the thickness of the coating is limited. If the coating film thickness is too thick, cracking is likely to occur.

[0005] The powder coating method also has drawbacks. The resulting coating has pinhead-type defects that can lead to a decrease in anti-adhesive properties.

[0006] The coatings obtained by these two methods may have a significant surface roughness that can cause cleaning problems, and some cooking residues may remain on the surface of the coating even after several washings.

[0007] To overcome the above drawbacks, the state of the art describes a metal substrate coated with a fluorinated film by lamination.

[0008] Patent Document 1 describes a kitchen utensil including a body containing a metal substrate laminated with a film of fluorinated resin. A method for obtaining the kitchen utensil is also described. In Example 1, a PTFE multilayer film is used without information on the properties of the layer. The operation of laminating the film onto the substrate is not described.

[0009] Patent Document 2 describes a method for obtaining a metal substrate coated with a fluorinated film (not including a primer layer containing an organic compound or an adhesive). The fluorinated film is a multilayer film obtained by continuously depositing an aqueous dispersion of components of a dried and sintered layer (fluorinated resin and optionally an inorganic filler) on a support. The multilayer film is then removed from its support and placed on a metal substrate before assembly. The layer of the fluorinated film in contact with the metal is made of a resin selected from PTFE and FEP, PFA, TFM, MFA (or a mixture thereof) having good flow characteristics, thus enabling good adhesion, which is not possible with PTFE. The metal substrate / fluorinated film assembly is carried out by thermocompression, either within a static press or between rollers (roll-to-roll method). In the static assembly method, both the substrate and the film are heated to a temperature of 300°C to 410°C with an applied pressure of 100 to 800 psi (0.7 MPa to 5.6 MPa). In the roll-to-roll assembly method (which is difficult to implement when the metal substrate has a considerable thickness), both the substrate and the film are heated to a temperature of 330°C to 420°C with an applied pressure of 2 to 15 MPa.

[0010] In both method variations, the pressure applied during assembly is several MPa, and the implementation temperature is limited by the decomposition temperature of the fluorinated film (especially PTFE starts at 420°C). Therefore, the assembly speed of the polymer film and the metal substrate is limited by the parameters of the assembly method.

Prior Art Documents

Patent Document

[0011]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0012] From an industrial perspective, there is still a need to develop a method for assembling a polymer film on a metal substrate that is more advantageous in terms of assembly time without causing a decrease in the quality of adhesion of the film to the substrate and without causing deterioration of the film.

[0013] Therefore, the applicant has developed a method for manufacturing a cooking element coated by hot stamping assembly of a metal substrate and a polymer film.

Means for Solving the Problems

[0014] The inventors have found that the method according to the present invention enables good adhesion of the polymer film to the substrate while achieving rapid assembly between the metal substrate and the polymer film mainly containing PTFE in the layer in contact with the metal substrate.

[0015] Unlike the usual methods for assembling a fluoropolymer film on a metal such as hot pressing, only the substrate is advantageously heated before assembling according to the method of the present invention. The polymer film is essentially heated by conduction when brought into contact with the substrate during assembly and is then cooled due to the thermal inertia of the assembly tool that remains at a temperature lower than the heating temperature of the metal substrate.

[0016] Therefore, during assembly, it is possible to heat very locally, especially at the substrate-film interface, and the film mainly contains PTFE in the layer that contacts the substrate at a temperature above its melting temperature for a very short time, without causing deterioration of the film.

[0017] By combining this high-temperature implementation with the pressure applied during stamping, the assembly of the polymer film and the metal substrate can be carried out in a much shorter time than the conventional method of assembling a polymer film on a metal substrate, such as hot pressing.

[0018] Therefore, the present invention relates to a method for manufacturing a coated cooking element (1) including the following steps. i. Providing a metal substrate (2) having a surface (2a) to be coated with a film (3); ii. Providing the film (3), wherein the film (3) includes a layer (3a) to be brought into contact with the surface (2a) of the metal substrate (2), and the layer (3a) contains 50 to 100% by weight of polytetrafluoroethylene (PTFE), 0 to 50% by weight of one or more thermoplastic polymers different from PTFE, (the percentages being relative to the total weight of PTFE and the one or more thermoplastic polymers); iii. Heating the metal substrate (2); iv. Positioning the film (3) such that the layer (3a) faces the surface (2a) of the metal substrate (2) heated in step iii; v. Assembling the metal substrate (2) and the film (3) by hot stamping, wherein the metal substrate (2) is at a temperature of 350°C to 550°C during assembly. A method such that when in contact with the metal substrate (2) during assembly in step (v), the film (3) is heated essentially by conduction.

[0019] The present invention also relates to a method for forming the coated cooking element (1) described above, which includes a step (a) of press-forming the coated cooking element (1) obtained at the end of step (v).

[0020] Other aspects of the present invention are as described below and in the claims.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0022] Definition The term "film" is understood to mean, in the context of the present invention, a set consisting of one or more superimposed layers that are assembled with a metal substrate. The term "film" also corresponds to the said set once it has been assembled with a metal substrate.

[0023] The term "layer", as used in the context of the present invention, is understood to mean a continuous layer. A continuous layer (also referred to as a monolithic layer) is a single entity that forms a completely flat area that fully covers the surface on which it is placed or is intended to be placed.

[0024] For the purposes of the present invention, the term "hot stamping" means a method for assembling a pre-heated metal substrate (2) and a film (3) between a lower tool and an upper tool.

[0025] For the purposes of the present invention, the term "aluminum alloy" means aluminum alloys of series 1000, 2000, 3000, 4000, 5000, 6000, 7000 and 8000.

[0026] The inventors have developed a manufacturing method that meets the expressed needs.

[0027] The present invention relates to a method for manufacturing a coated cooking element (1) comprising the following steps. i. Providing a metal substrate (2) having a surface (2a) to be coated with a film (3); ii. Providing said film (3), said film (3) comprising a layer (3a) for contacting said surface (2a) of said metal substrate (2), said layer (3a) comprises 50 to 100% by weight of polytetrafluoroethylene (PTFE), 0 to 50% by weight of one or more thermoplastic polymers different from PTFE, (said percentages being relative to the total weight of PTFE and said one or more thermoplastic polymers (s)), iii. Heating said metal substrate (2); iv. Positioning said film (3) such that the layer (3a) faces said surface (2a) of the metal substrate (2) heated in step iii; v. a step of assembling the metal substrate (2) and the film (3) by hot stamping, wherein the metal substrate (2) is at a temperature of 350°C to 550°C during assembly, and when contacting the metal substrate (2) during the assembly of step (v), the film (3) is essentially heated by conduction.

[0028] Advantageously, steps i. to v. are executed continuously.

[0029] The metal substrate (2) used in step i of this method Advantageously, examples of the metal substrate (2) that can be used in the present invention include substrates made of aluminum, stainless steel, cast iron or aluminum, or titanium or copper.

[0030] For the purposes of the present invention, aluminum means a metal consisting of 100% aluminum or an aluminum alloy.

[0031] Advantageously, the metal substrate (2) is an aluminum substrate, a stainless steel substrate, or a multi-layer, particularly a two-layer or three-layer metal substrate, and these multi-layers can be obtained, for example, by co-lamination, thermal diffusion under load (solid bonding), or thermal or cold stamping (impact bonding).

[0032] Preferably, the metal substrate (2) includes alternating layers of metal and / or metal alloy.

[0033] According to one embodiment, the metal substrate (2) is an aluminum alloy substrate, a stainless steel substrate, or a multi-layer metal substrate whose surface (2a) is made of aluminum alloy or stainless steel.

[0034] Preferably, the metal substrate (2) is an aluminum substrate.

[0035] Advantageously, the thickness of the metal substrate (2) is configured to be between 0.5 mm and 10 mm, preferably between 2 mm and 10 mm, more preferably between 2.2 mm and 10 mm, more preferably between 2.5 mm and 10 mm, and even more preferably between 3 mm and 10 mm.

[0036] Advantageously, the surface (2a) of the metal substrate (2) has undergone a surface treatment before being assembled with the film (3), which can improve the adhesion of the film to the substrate.

[0037] According to one embodiment, the surface of the surface (2a) of the metal substrate (2) has undergone a surface treatment, and the surface treatment is a chemical attack, brushing, hydration, sandblasting, shot peening, plasma or corona or laser type physico-chemical treatment, chemical activation, or a combination of these different techniques.

[0038] Advantageously, the arithmetic mean roughness Ra of the surface of the surface (2a) of the metal substrate (2) is 1 μm or more, preferably 2 μm or more.

[0039] Advantageously, the arithmetic mean roughness Ra of the surface of the surface (2a) of the metal substrate (2) is 20 μm or less.

[0040] Advantageously, the arithmetic mean roughness Ra of the surface of the surface (2a) of the metal substrate (2) is in the range of 2 μm to 10 μm.

[0041] The arithmetic mean roughness Ra is measured using a roughness meter in accordance with standard ISO4287. Ra represents the arithmetic mean of the deviations from the mean. The surface topography can be studied, in particular, using a profilometer equipped with a probe with a fine stylus having a diamond tip, or an optical measuring device such as Altisurf (registered trademark) that enables non-contact measurement with a color confocal sensor. This study of the surface topography makes it possible to define the arithmetic mean roughness Ra.

[0042] The film (3) used in step ii of this method Adhesion of a fluorinated film to a metal substrate involves technical difficulties due to the inherent anti-adhesive properties of the fluorinated polymer. One solution consists of using a fluorinated undercoat of a tetrafluoroethylene and perfluoropropyl vinyl ether (PFA) copolymer or a tetrafluoroethylene and hexafluoropropene (FEP) copolymer that functions as a hot melt adhesive, thus enabling adhesion of the fluorinated film to the metal substrate.

[0043] Direct adhesion of PTFE to a metal substrate is limited not only by the poor flow properties of PTFE at high temperatures but also by its thermal decomposition that occurs at 420 °C.

[0044] The method according to the invention overcomes these difficulties and enables the assembly of a metal substrate (2) and a film (3) mainly containing PTFE as a polymer in a layer (3a) in contact with the metal substrate (2).

[0045] The film (3) used in the method according to the invention includes a layer (3a) arranged in contact with the face (2a) of the metal substrate (2), and the layer (3a) mainly contains PTFE as a polymer.

[0046] Thus, the layer (3a) contains 50 to 100% by weight of polytetrafluoroethylene (PTFE) and 0 to 50% by weight of one or more thermoplastic polymers different from PTFE, (the percentages being relative to the total weight of PTFE and the one or more thermoplastic polymers (s)).

[0047] According to one embodiment, the PTFE polymer is the only polymer in the layer (3a).

[0048] When the layer (3a) contains one or more thermoplastic polymers different from PTFE, this polymer or these polymers Tetrafluoroethylene and perfluoropropyl vinyl ether (PFA) copolymer, tetrafluoroethylene and hexafluoropropene (FEP) copolymer, polyvinylidene fluoride (PVDF), tetrafluoroethylene and polymethyl vinyl ether (MVA) copolymer, tetrafluoroethylene, polymethyl vinyl ether and fluoroalkyl vinyl ether (TFE / PMVE / FAVE) terpolymer, ethylene tetrafluoroethylene (ETFE), Polyaryletherketone (PAEK), polyetherketone (PEK), including polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetheretherketoneketone (PEEKK), polyetherketoneetherketoneketone (PEKEKK), preferably polyetheretherketone (PEEK), Polyamideimide (PAI), polyimide (PI), polyetherimide (PEI), polybenzimidazole (PBI), Poly(phenylene oxide) (PPO), poly(aryl ether sulfone) (PAES) polymer including polyether sulfone (PES), polyphenylene ether sulfone (PPSU), poly(arylene sulfide) (PAS) including polyphenylene sulfide (PPS), liquid crystal polymer, and mixtures thereof, selected from.

[0049] The film (3) can also be composed of a single layer (3a) forming the cooking surface (4).

[0050] According to another configuration, the film (3) can also include an additional layer disposed on top of the layer (3a) as described above. In this case, the film (3) thus further includes another layer (3b) forming the cooking surface (4), and the other layer (3b) is, Polytetrafluoroethylene (PTFE), tetrafluoroethylene and perfluoropropyl vinyl ether (PFA) copolymer, tetrafluoroethylene and hexafluoropropene (FEP) copolymer, polyvinylidene fluoride (PVDF), tetrafluoroethylene and polymethyl vinyl ether (MVA) copolymer, tetrafluoroethylene, polymethyl vinyl ether and fluoroalkyl vinyl ether (TFE / PMVE / FAVE) terpolymer, ethylene tetrafluoroethylene (ETFE), and mixtures thereof, preferably PTFE, Polyaryl ether ketone (PAEK), including polyether ketone (PEK), polyether ether ketone (PEEK), polyether ketone ketone (PEKK), polyether ether ketone ketone (PEEKK), polyether ketone ether ketone ketone (PEKEKK), preferably polyether ether ketone (PEEK), Polyamideimide (PAI), polyimide (PI), polyetherimide (PEI), polybenzimidazole (PBI), Poly(phenylene oxide) (PPO), poly(aryl ether sulfone) (PAES) polymers including polyether sulfone (PES), polyphenylene ether sulfone (PPSU), poly(arylene sulfide) (PAS) including polyphenylene sulfide (PPS), liquid crystal polymer, Silicone resin, And mixtures thereof, preferably a mixture of PTFE and PEEK, Comprising one or more polymers selected from

[0051] According to one embodiment, the film (3) further comprises at least one intermediate layer (3c) disposed between the layer (3a) and the other layer (3b), and the intermediate layer (3c) is Polytetrafluoroethylene (PTFE), tetrafluoroethylene and perfluoropropyl vinyl ether (PFA) copolymer, tetrafluoroethylene and hexafluoropropene (FEP) copolymer, polyvinylidene fluoride (PVDF), tetrafluoroethylene and polymethyl vinyl ether (MVA) copolymer, tetrafluoroethylene, polymethyl vinyl ether and fluoroalkyl vinyl ether (TFE / PMVE / FAVE) terpolymer, ethylene tetrafluoroethylene (ETFE), and mixtures thereof, preferably tetrafluoroethylene and perfluoropropyl vinyl ether (PFA) copolymer and PTFE, preferably PTFE, Polyaryletherketone (PAEK), including polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetheretherketoneketone (PEEKK), polyetherketoneetherketoneketone (PEKEKK), preferably polyetheretherketone (PEEK), Polyamideimide (PAI), polyimide (PI), polyetherimide (PEI), polybenzimidazole (PBI), Poly(phenylene oxide) (PPO), poly(aryl ether sulfone) (PAES) polymers including polyether sulfone (PES), polyphenylene ether sulfone (PPSU), poly(arylene sulfide) (PAS) including polyphenylene sulfide (PPS), liquid crystal polymer, Silicone resin And mixtures thereof, preferably a mixture of polyaryletherketone (PAEK) and PTFE, preferably a mixture of PEEK and PTFE; PTFE is particularly preferred, Comprising one or more polymers selected from

[0052] Silicone resin In the present disclosure, the expression "silicone resin" is used interchangeably to refer to silicone before or after crosslinking. In the present disclosure, the expression "silicone" refers to an organopolysiloxane material. Crosslinking is a process that enables the conversion of silicone into an insoluble material, for example, by polyaddition, polycondensation, or dehydrogenation. Crosslinking is generally carried out from a precursor, which is a silicone oil or resin, to obtain a three-dimensional array that forms a material called a silicone resin in the description.

[0053] This crosslinking can be carried out by thermal activation or chemical activation using a catalyst such as platinum.

[0054] The silicone resin may advantageously be obtained from a precursor soluble in a solvent or in an emulsion in water, for example, a crosslinkable oil or resin, particularly selected from a silicone hydride, a silicone oil resin containing at least one vinyl group (-CH=CH2), a silicone resin or a silicone-polyester resin (copolymer) containing at least one alkoxy group, for example, methoxy or ethoxy, and / or a silicone or a silicone-polyester resin (copolymer) containing at least one alkoxy group (particularly selected from ethoxy, or a hydroxy group, and mixtures thereof). These precursors have the ability to crosslink to obtain a silicone resin characterized by its insoluble and substantially solid form.

[0055] Advantageously, these precursors are polymers or oligomers, in the form of silicone oils having various degrees of branching, or silicone resins having various degrees of pre-crosslinking, or silicone resin copolymers such as silicone-polyester, silicone-alkyd, silicone-polyurethane, silicone-epoxy resins, or in the form of a mixture of silicone oil, silicone resin and silicone resin copolymers. The silicon atoms can be substituted by alkyl (especially methyl) or aryl (especially phenyl) groups or mixtures thereof. The oil or resin preferably contains, as substituents of the silicone atoms, one or more (two or more) hydroxy or alkoxy (especially methoxy, ethoxy, butoxy) functional groups.

[0056] Advantageously, after crosslinking of these precursors, i.e., after being crosslinked, the silicone resin obtained is selected from the group consisting of methyl silicone resin and / or phenyl silicone resin and / or methylphenyl silicone resin, methyl silicone polyester resin (copolymer), phenyl silicone polyester resin (copolymer), methylphenyl silicone polyester resin (copolymer), silicone alkyd resin (copolymer), modified silicone resin and mixtures thereof.

[0057] Advantageously, the silicone resin is selected from the group consisting of methyl silicone resin and / or phenyl silicone resin and / or methylphenyl silicone resin, methyl silicone polyester resin (copolymer), phenyl silicone polyester resin (copolymer), methylphenyl silicone polyester resin (copolymer), silicone alkyd resin (copolymer), modified silicone resin and mixtures thereof.

[0058] The silicone resin can be obtained from precursors selected in particular from hydrogenated silicones, silicone resins containing at least one vinyl group (-CH=CH2), silicone-polyester resins (copolymers) containing at least one methoxy group, and / or silicone-polyester resins (copolymers) containing at least one ethoxy group, and mixtures thereof.

[0059] The single layer (3) of silicone resin can form a network composed of a combination of four simple organosiloxane units denoted as M, D, T, and Q, depending on the degree of substitution of silicon atoms by oxygen, as described in the following table, where R is an organic substituent as described below.

[0060] [Table 1]

[0061] The organopolysiloxane material or polymer can be obtained by crosslinking from a monomer or a precursor that can be a polymer, or by crosslinking from an intermediate that can be an oligomer. The organopolysiloxane polymer can also be obtained from a mixture of these different types of precursors. When the sequence contains more units T and Q than D, the crosslink density is higher. The distribution between the units M, D, T, and Q depends on the chemical structure of the precursor, in particular on this M, D, T, Q distribution within the precursor.

[0062] The polymeric precursor is an organopolysiloxane. These macromolecules are formed from M, D, T, and / or Q units, as described in the table, where R is independently an alkyl group, in particular methyl, or an aryl group, in particular phenyl, and R of different natures can be present on the same macromolecule.

[0063] The organopolysiloxanes can be either linear or slightly branched (most of the D groups), or branched or highly branched (most of the T and Q groups). Linear or slightly branched organopolysiloxanes are generally liquids, more or less viscous at room temperature, and are called silicone oils. Branched or highly branched (pre-crosslinked) organopolysiloxanes form networks on the scale of individual macromolecules and are called silicone resins. At room temperature, the resins are in a substantially solid form or, provided they have a fairly low molecular weight, in a liquid form, in particular in the form of a solution in a solvent or in the form of an aqueous emulsion. They can be copolymerized with organopolymers or oligomers that do not contain silicon, especially those selected from polyesters, acrylics, alkyds, polyurethanes, epoxy resins.

[0064] When the crosslinking is by hydrolysis polycondensation: it is carried out thanks to the reactive hydroxy or alkoxy, in particular methoxy, ethoxy or butoxy functional groups present on the organopolysiloxane.

[0065] When the crosslinking is by polyaddition (or hydrosilylation), it is carried out by reaction between the reactive vinyl functional group (-CH=CH2) present on one of the organopolysiloxanes and the reactive silyl - hydride functional group (Si - H) present on another organopolysiloxane mixed with the first.

[0066] All these reactive functional groups are present in at least one number on each organopolysiloxane and can be present in numbers of 2, 3 or more as long as the molecular structure allows it. A silicone oil containing at least one reactive function is called a "reactive oil". The reactive functional groups can be found at the ends (terminals) of the macromolecular chains or can be distributed along the chains.

[0067] The silicone polyester resin, in particular, has a silicone / polyester mass ratio, for example, 90 / 10, 80 / 20, 70 / 30, 60 / 40, 50 / 50, 40 / 50, 30 / 70, 20 / 80, 10 / 90, and is preferably between 80 / 20 and 50 / 50.

[0068] Pure or pre-emulsified in water linear PDMS silicone oils are characterized by a molecular weight which is a direct increasing function of the viscosity of the pure oil. They are then characterized by the presence or absence of reactive functional groups, such as hydroxyl groups on silicon atoms (silanols), their number, and their position on the molecular chain. For example, reactive oils having a viscosity of 50 to 20,000 mPa·s, particularly 300 to 5000 mPa·s, can be used, having at least one reactive functional group, preferably at least two reactive functional groups, which can be located at the ends of the chain.

[0069] Examples of polymer precursors that react by addition polymerization include polymethylhydrosiloxane, vinylmethylsiloxane, (especially linear) vinyl-terminated polydimethylsiloxane (PDMS), vinyl-terminated diphenylsiloxane-dimethylsiloxane copolymer, hydride-terminated polydimethylsiloxane, hydride-terminated polyphenylmethylsiloxane, cyclic vinylmethylsiloxane, vinyl-MQ resin, trimethylsilyl-terminated polymethylhydrosiloxane, dimethylsiloxane, terminated methylhydrosiloxane and trimethylsiloxane copolymer, hydrogenated MQ resin, etc., as well as combinations thereof.

[0070] The polymeric precursors that react by hydrolysis-condensation can be silicone resins or silicone oils, such as, for example, poly(methylsilsesquioxane), poly(propylsilsesquioxane), poly(phenylsilsesquioxane), polydimethylsiloxane (PDMS), trimethylsilyl-terminated polydimethylsiloxane (PDMS), hydroxyl-terminated polydimethylsiloxane (PDMS), silanol-terminated polydimethylsiloxane (PDMS), silanol-terminated polyphenylsiloxane (PDMS), silanol-terminated diphenylsiloxane-dimethylsiloxane copolymer, poly(2-acetoxyethylsilsesquioxane), organically modified alkoxysilanes and their oligomers, and all similar macromolecules thereof, and mixtures thereof can be included.

[0071] Organic polysiloxane materials or polymers can also be obtained by crosslinking one or more of the above monomer precursors and mixtures of one or more polymer precursors, and one or more oligomer precursors that can be linear, branched or cyclic. These oligomer precursors have a lower molecular weight than the polymer precursors. In order to promote the high crosslink density of the finally obtained organic polysiloxane polymer, polymers and / or oligomer precursors containing several reactive functional groups above 2, preferably far above 2, can be added to the mixture as "cocondensing agents".

[0072] Whether copolymerizing with an organic polymer or not, monomers, oligomers and / or polymer precursors, especially silicone resins, serve as polymer binders to obtain a solid organic polysiloxane polymer in combination with the thermoplastic resin of each layer.

[0073] Organopolysiloxane precursors can be regarded as additives when added in small amounts (generally 0.1 - 5% dry) to the overall formulation of the layer, independently of the other components for the formation of the solid organopolysiloxane polymer.

[0074] Catalysts may be required for crosslinking: · In the case of crosslinking of organopolysiloxanes by hydrolysis-polycondensation, the formulation may include metal catalysts such as platinum, tin, zinc, zirconium and cerium-based metal complexes, in particular platinum-cyclovinylmethyl-siloxane complexes, tin ethylhexanoate, zinc ethylhexanoate, zirconium ethylhexanoate, cerium ethylhexanoate and tin dibutyl laurate. · When crosslinking an organopolysiloxane by hydrosilylation, the addition of a catalyst may be necessary: this may be a suitable platinum-based catalyst such as, for example, a platinum or Karstedt catalyst or an Ashby catalyst.

[0075] A crosslinking agent may be present, for example, a crosslinking agent having an Si-H bond.

[0076] The film (3) may further comprise at least one filler and / or at least one reinforcing material.

[0077] Examples of fillers that can be used in the present invention include, in particular, metal oxides, metal carbides, metal oxynitrides, metal nitrides, silica, and mixtures thereof.

[0078] These fillers may be present in one or more layers of the film (3) or in each layer of the film (3).

[0079] Examples of reinforcing materials that can be used under the present invention include fibrous mineral or metal reinforcing materials, metal meshes, glass fiber materials or cloths. The reinforcing material can also consist of a non-fluorinated polymer having high thermomechanical properties of the polyaryletherketone (PEAK) type such as, for example, polyetheretherketone (PEEK) or polyamideimide (PAI). The reinforcing material may be in the form of a layer of the film (3) disposed between the layer (3a) and the layer (3b) forming the cooking surface.

[0080] In order to improve the adhesion between the film (3) and the metal substrate (2), the layer (3a) of the film (3) that contacts the surface (2a) of the metal substrate (2) in step (v) may be subjected to mechanical or chemical surface treatment. This prior surface treatment can be a chemical attack, brushing, hydration, sandblasting, shot peening, plasma or corona or laser type physicochemical treatment, chemical activation, or a combination of these different techniques.

[0081] According to one embodiment, the thickness of the film (3) is configured to be between 5 μm and 500 μm, preferably between 25 μm and 150 μm.

[0082] The thickness of the layer(s) of the film (3) is measured at 20 random points on the cross-section of the film. The average thickness of the film (3) is obtained by averaging these 20 measured values.

[0083] The total thickness of the film (3) of the coated cooking element (1) according to the present invention, i.e., as measured on the cooking element after being coated with the film (3), is configured to be between 5 μm and 500 μm, preferably between 25 μm and 150 μm.

[0084] The measurement of the thickness of the film (3) of the coated cooking element (1) according to the present invention is performed at 20 random points on the section of the coated substrate. The average thickness of the film (3) is obtained by averaging these 20 measured values.

[0085] The film (3) can be obtained by depositing a first layer on a support before assembling it with the metal substrate (2), then by successive deposition of other layers, and then separating it from the support by peeling the film. The layers of the film (3) can also be assembled together by any other assembly method such as lamination, for example.

[0086] Generally, the film (3) of the coated cooking element (1) can be considered to completely cover the surface (2a) of the metal substrate (2), although only a part of the metal substrate (2) is covered.

[0087] In the exemplary embodiments shown in FIGS. 1 and 2, the film (3) comprises three layers (3a, 3b, 3c).

[0088] Step iii The metal substrate (2) is heated in step iii before steps iv and v of the method. The metal substrate can be heated in a furnace or, for example, by induction using any suitable apparatus.

[0089] The metal substrate (2) is heated to a temperature such that the temperature during assembly in step v is between 350°C and 550°C.

[0090] Thus, the metal substrate can be heated to a temperature between 400°C and 600°C.

[0091] Step iv Before assembly in step v, the film (3) is placed on the metal substrate (2) such that its layer (3a) faces the surface (2a) of the metal substrate (2) preheated in step iii.

[0092] The film (3) is arranged during the assembly step v such that the entire surface of the layer (3a) is in simultaneous contact with the surface of the surface (2a) of the metal substrate (2).

[0093] To ensure this contact between the layer (3a) of the film (3) and the surface (2a) of the metal substrate (2), the film (3) can be attached to an upper tool or stretched between two rollers.

[0094] Step v When assembling the metal substrate (2) and the film (3) by hot stamping, the metal substrate (2) is at a temperature of 350°C to 550°C during assembly.

[0095] When the temperature is less than 350 °C, the adhesion of the film (3) to the metal substrate (2) is insufficient.

[0096] When the temperature exceeds 550 °C, deterioration of the film (3) is observed.

[0097] Advantageously, the metal substrate (2) is at a temperature of 400 °C to 500 °C, preferably 420 °C to 480 °C.

[0098] The temperature of the metal substrate (2) can also be between 440 °C and 480 °C.

[0099] The temperature of the metal substrate (2) during assembly corresponds to the temperature of the metal substrate (2) when the pressing process is started, that is, when the pressing of the metal substrate (2) / film (3) set is started.

[0100] According to one embodiment, the assembly by hot stamping in step v is performed by a hydraulic or mechanical press including a lower tool and an upper tool assembled between the metal substrate (2) and the film (3), the metal substrate (2) preferentially contacts the lower tool, and the film (3) preferentially contacts the upper tool.

[0101] The surface of the lower tool is advantageously flat and can be surface-treated to avoid the adhesion of the metal substrate to the tool.

[0102] Advantageously, the plane of the surface of the upper tool has an angle of 0.01° to 0.5°, preferably 0.15° to 0.25° with respect to the plane of the surface of the lower tool. This angle makes it possible to limit the entrapment of air during the assembly process.

[0103] Advantageously, the assembly tool is not heated before the assembly step v.

[0104] Optionally, the lower tool can be heated. Optionally, the upper tool can be cooled.

[0105] According to one embodiment, the lower tool is heated to a temperature configured between 25°C and the temperature of the metal substrate (2) during assembly, and / or the upper tool is brought to a temperature configured between 15°C and 120°C in step v.

[0106] Unless otherwise specified, the temperature values shown in this application correspond to the measured temperature values and are not setpoint temperatures.

[0107] The temperature values are measured by any suitable means, for example, by temperature probes arranged on the surface or mass of the heated or cooled element.

[0108] The temperature of the metal substrate (2) during assembly (step v) is 350°C to 550°C. The temperature of the metal substrate (2) during assembly corresponds to the temperature of the surface (2a) of the metal substrate (2) at the start of stamping, i.e., at the start of pressurization of the metal substrate (2) / film (3) set.

[0109] Next, the temperature of the metal substrate (2) may decrease during the stamping operation, especially if the lower tool is not heated before the assembly process.

[0110] During the stamping operation in step v, a pressure of 100 MPa or more, preferably several hundred MPa, is advantageously used.

[0111] According to one embodiment, the metal substrate (2) and the film (3) are maintained under a pressure configured between 100 MPa and 800 MPa, preferably between 350 MPa and 500 MPa, in step v.

[0112] The pressure applied during the pressing operation is considerably higher than the pressure applied in conventional metal substrate / polymer film assembly methods such as hot pressing, which is only a few MPa.

[0113] According to one embodiment, the duration for maintaining the metal substrate (2) and the film (3) under pressure is 1 minute or less, preferably 15 seconds or less, in step v.

[0114] Stamping can be performed by applying a sharp impact with a duration of less than 5 seconds.

[0115] According to another embodiment, the duration for maintaining the metal substrate (2) and the film (3) under pressure is composed of between 1 second and 1 minute, preferably between 2 seconds and 15 seconds, in step v.

[0116] When the film (3) comes into contact when assembled with the heated substrate, it is essentially heated by conduction. Next, it is cooled during stamping due to the thermal inertia of the assembly tool, which has a lower temperature than the heating temperature of the metal substrate (2). Therefore, the temperature of the film (3) can rapidly decrease during the stamping operation, especially when the lower tool has not been heated before the assembly process.

[0117] The film (3) is preferably not heated before the assembly step v.

[0118] Therefore, according to the method of the present invention, it is possible to heat the film (3) very locally, particularly at the metal substrate (2)-film (3) interface, to a temperature exceeding its melting temperature for a very short time, which does not cause deterioration of the film.

[0119] Advantageously, the temperature of the film (3) at the end of the step v of assembling the film (3) and the metal substrate (2), that is, the temperature when the assembly of the film (3) and the metal substrate (2) is no longer maintained under pressure, is lower than the melting temperature of PTFE.

[0120] As described above, by combining temperature and pressure during assembly by stamping, it is possible to ensure reliable adhesion of the film (3) on the metal substrate (2) in a very short time.

[0121] After assembly, the metal substrate (2) coated with the film (3) is cooled to room temperature to obtain maximum adhesion between the film (3) and the metal substrate (2).

[0122] Next, the metal substrate (2) coated with the film (3) can be shaped at the end of step (v).

[0123] The second object of the present invention thus relates to a method of shaping the coated cooking element described above, comprising a step (a) of press - shaping the coated cooking element (1) obtained at the end of step (v).

[0124] The shaping method may further comprise a step (b) of stretching the coated cooking element (1) obtained at the end of step (a).

[0125] The adhesion of the film (3) to the metal substrate (2) before shaping must be sufficient to avoid loss of adhesion during and after the shaping operation.

[0126] The coated cooking element (1) according to the method of the present invention can form a cooking container in a cooking utensil selected from the group consisting of a saucepan (pot), a frying pan, a skillet, or a fondue or raclette pot, a stew pot, a wok, a sauté pan, a crepe pan, a grill, a griddle, a cooking pot, a cocotte, and a molded cooking article.

[0127] The coated cooking element (1) according to the method of the present invention can form a cooking container in an electric cooking appliance selected from the group consisting of an electric crepe maker, an electric raclette, an electric fondue appliance, an electric grill, an electric griddle, an electric cooker, a cooking robot, and a bread maker. Thus, the cooking utensil can form a cooking accessory for an electric cooking appliance.

[0128] The following examples are presented for illustrative purposes and should in no way be construed as limiting the present invention.

[0129] Examples: Equipment used -For assembly test: Hydraulic press SGM 160 T equipped with an upper flat punch and a lower flat punch. The flat surface of the upper punch has an angle of 0.15° with respect to the flat surface of the lower punch so as not to trap air during the assembly process. -For rapid press forming test: Zwick BPU 400 press forming machine

[0130] The metal substrate used: A metal substrate (2) made of aluminum 1200 (condition 0) is used for the test. The metal substrate (2) is used as it is or after surface treatment.

[0131] The following three configurations are tested. ·A metal substrate (2) made of unprocessed aluminum with an arithmetic mean roughness Ra of less than 1 μm, and ·A metal substrate (2) made of hydrated and polished aluminum having an arithmetic mean roughness Ra between 2 μm and 3 μm, and ·A metal substrate (2) having an arithmetic mean roughness Ra between 3 μm and 4 μm.

[0132] The arithmetic mean roughness Ra is measured using an optical measuring device such as Altisurf (registered trademark).

[0133] The polymer film used: The following films (3) supplied by Saint-Gobain were used: ·Film (3) Chemfilm (registered trademark) Skyve PTFE 0001: A colorless PTFE film having a thickness of 100 μm; ·Film (3) Chemfilm (registered trademark) black skived PTFE 0167: A black PTFE film having a thickness of 100 μm.

[0134] Example 1: Assembly test Experimental conditions: The metal substrate (2) is cut into disks with a diameter of 340 mm.

[0135] The metal substrate (2) is heated in a furnace having a heating set point temperature of 550 °C.

[0136] After heating for 15 minutes, the temperature of the metal substrate (2) measured using a contact probe is 520 °C.

[0137] After heating for 15 minutes, the metal substrate (2) is placed on the unheated lower punch of a hydraulic press.

[0138] The unheated film (3) is brought into contact with the metal substrate (2) immediately before assembly.

[0139] The metal substrate (2) and the film (3) are assembled by sharp blow stamping with a stamping force of 3000 T (i.e., 33 kg / mm corresponding to a pressure of 330 Mpa), and the temperature of the metal substrate (2) during stamping is 420 °C. 2 )

[0140] Results: After cooling, the quality of the adhesion of the film (3) to the metal substrate (2) is evaluated.

[0141] The PTFE film (3) adheres strongly to the metal substrate (2) made of hydrated matte aluminum and the chemically etched aluminum metal substrate (2).

[0142] The adhesiveness of the raw aluminum metal substrate (2) is insufficient.

[0143] Example 2: Rapid press forming test The hydrated, etched, and coated aluminum disk according to Example 1 is subjected to a Swift press forming test.

[0144] Experimental conditions: · Cut the disk to a diameter of 64 mm · 33 mm punch (drawing limit ratio = 1.9) · Press forming die: 40 mm

[0145] Results Figure 3 shows a metal substrate (2) made of hydrated satin-finished aluminum coated with a PTFE0167 film (3) according to Example 1 and subjected to a press forming operation.

[0146] When the film (3) is on the outside of the substrate, no peeling of the film (3) is observed after forming.

[0147] Similar results are obtained with etched aluminum metal substrates (2) coated with a PTFE0001 film (3) and a PTFE0167 or PTFE0001 film film (3).

[0148] Example 3 : Press forming a frying pan The hydrated satin-finished, etched, and coated aluminum disks according to Example 1 are formed by press forming in the form of a frying pan with a diameter of 26 cm.

[0149] Results Figure 4 shows a metal substrate (2) made of hydrated satin-finished aluminum coated with a PTFE0167 film according to Example 1 and subjected to a press forming operation.

[0150] Next, the frying pan was subjected to a thermal shock test. After heating the shell (La calotte) to 300 °C with a gas burner, the frying pan was immersed in water at room temperature, and this process was repeated 25 times.

[0151] No problem of film peeling (3) on the aluminum metal substrate (2) was observed.

[0152] Similar results are obtained with the PTFE0001 film (3) and the etched aluminum metal substrate (2) coated with the PTFE0167 or PTFE0001 film (3).

[0153] Example 4 : Press-forming the source pan (pot) The hydrated satin-finished, etched, and coated aluminum disks according to Example 1 are formed by press-forming and drawing in the form of a 20-cm diameter pot.

[0154] Results Figure 5 shows the metal substrate (2) made of hydrated satin-finished aluminum coated with the PTFE0167 film (3) according to Example 1 and subjected to a press-forming - stretching operation.

[0155] The pot was then subjected to a thermal shock test. After heating the shell to 300 °C with a gas burner, the pot was immersed in water at room temperature, and this process was repeated 25 times.

[0156] No problem of peeling of the film (3) on the aluminum metal substrate (2) was observed.

[0157] Similar results are obtained with the PTFE0001 film (3) and the etched aluminum metal substrate (2) coated with the PTFE0167 or PTFE0001 film (3).

[0158] These examples show the excellent adhesion between the film (3) and the metal substrate (2) after assembly, as well as the suitability of the coated metal substrate (2) obtained according to the invention for press-forming.

Claims

1. A method for manufacturing a coated cooking element (1) comprising the following steps: i. providing a metal substrate (2) having a surface (2a) to be coated with a film (3); ii. providing said film (3), said film (3) comprising a layer (3a) for contacting said surface (2a) of said metal substrate (2), said layer (3a) comprising 50 to 100% by weight of polytetrafluoroethylene (PTFE), 0 to 50% by weight of one or more thermoplastic polymers different from PTFE, (said percentages being relative to the total weight of PTFE and said one or more thermoplastic polymers); iii. heating said metal substrate (2); iv. positioning said film (3) such that said layer (3a) faces said surface (2a) of said metal substrate (2) heated in step iii; v. assembling said metal substrate (2) and said film (3) by hot stamping, said metal substrate (2) being at a temperature of 350°C to 550°C during assembly. A method for manufacturing a coated cooking element (1), wherein during assembly in step (v), said film (3) is essentially heated by conduction when contacting said metal substrate (2).

2. The hot stamping assembly in step v is performed by a hydraulic or mechanical press comprising a lower tool and an upper tool assembled between said metal substrate (2) and said film (3), said metal substrate (2) preferentially contacting said lower tool and said film (3) preferentially contacting said upper tool. The method for manufacturing a coated cooking element (1) according to Claim 1.

3. Said metal substrate (2) and said film (3) are maintained under a pressure of 100 MPa to 800 MPa, preferably 350 MPa to 500 MPa, during step v. The method for manufacturing a coated cooking element (1) according to Claim 2.

4. The duration of maintaining said metal substrate (2) and said film (3) under pressure is 1 minute or less, preferably 15 seconds or less, during step v. The method for manufacturing a coated cooking element (1) according to Claim 2 or 3.

5. The duration for maintaining the metal substrate (2) and the film (3) under pressure is, in step v, composed of between 1 second and 1 minute, preferably between 2 seconds and 15 seconds, for the method of manufacturing the coated cooking element (1) according to any one of claims 2 to 4.

6. The plane of the surface of the upper tool has an angle composed of between 0.01° and 0.5°, preferably between 0.15° and 0.25°, for the method of manufacturing the coated cooking element (1) according to any one of claims 2 to 5.

7. The lower tool is heated to a temperature composed of between 25 °C and the temperature of the metal substrate (2) during assembly, and / or the upper tool is brought to a temperature composed of between 15 °C and 120 °C in step v, for the method of manufacturing the coated cooking element (1) according to any one of claims 2 to 6.

8. The metal substrate (2) is an aluminum alloy substrate, a stainless steel substrate, or a multi-layer metal substrate whose surface (2a) is made of aluminum alloy or stainless steel, for the method of manufacturing the coated cooking element (1) according to any one of claims 1 to 7.

9. The surface of the surface (2a) of the metal substrate (2) has undergone a surface treatment, and the surface treatment is chemical attack, brushing, hydration, sandblasting, shot peening, plasma or corona or laser type physicochemical treatment, chemical activation, or a combination of these different techniques, for the method of manufacturing the coated cooking element (1) according to any one of claims 1 to 8.

10. The PTFE polymer is the only polymer in the layer (3a), for the method of manufacturing the coated cooking element (1) according to any one of claims 1 to 9.

11. The one or more thermoplastic polymers different from the PTFE of the layer (3a) are ・ Tetrafluoroethylene and perfluoropropyl vinyl ether (PFA) copolymer, tetrafluoroethylene and hexafluoropropene (FEP) copolymer, polyvinylidene fluoride (PVDF), tetrafluoroethylene and polymethyl vinyl ether (MVA) copolymer, tetrafluoroethylene, polymethyl vinyl ether and fluoroalkyl vinyl ether (TFE / PMVE / FAVE) terpolymer, ethylene tetrafluoroethylene (ETFE), - Polyaryletherketone (PAEK), polyetherketone (PEK), including polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetheretherketoneketone (PEEKK), polyetherketoneetherketoneketone (PEKEKK), preferably polyetheretherketone (PEEK), - Polyamideimide (PAI), polyimide (PI), polyetherimide (PEI), polybenzimidazole (PBI), - Poly(phenylene oxide) (PPO), poly(aryl ether sulfone) (PAES) polymers including polyether sulfone (PES), polyphenylene ether sulfone (PPSU), poly(arylene sulfide) (PAS) including polyphenylene sulfide (PPS), liquid crystal polymers, and mixtures thereof, A method for producing the coated cooking element (1) according to any one of claims 1 to 9, selected from

12. The method for producing a coated cooking element (1) according to any one of claims 1 to 11, wherein the film (3) is also composed of a single layer (3a) forming a cooking surface (4).

13. The film (3) further includes another layer (3b) forming a cooking surface (4), and the other layer (3b) is - Polytetrafluoroethylene (PTFE), tetrafluoroethylene and perfluoropropyl vinyl ether (PFA) copolymer, tetrafluoroethylene and hexafluoropropene (FEP) copolymer, polyvinylidene fluoride (PVDF), tetrafluoroethylene and polymethyl vinyl ether (MVA) copolymer, tetrafluoroethylene, polymethyl vinyl ether and fluoroalkyl vinyl ether (TFE / PMVE / FAVE) terpolymer, ethylene tetrafluoroethylene (ETFE), and mixtures thereof, preferably PTFE, - Polyaryletherketone (PAEK), polyetherketone (PEK), including polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetheretherketoneketone (PEEKK), polyetherketoneetherketoneketone (PEKEKK), preferably polyetheretherketone (PEEK), - Polyamideimide (PAI), polyimide (PI), polyetherimide (PEI), polybenzimidazole (PBI), - Poly(phenylene oxide) (PPO), poly(aryl ether sulfone) (PAES) polymers including polyether sulfone (PES), polyphenylene ether sulfone (PPSU), poly(arylene sulfide) (PAS) including polyphenylene sulfide (PPS), liquid crystal polymers, - Silicone resins, - And mixtures thereof, preferably a mixture of PTFE and PEEK, A method for producing the coated cooking element (1) according to any one of claims 1 to 11, comprising one or more polymers selected from

14. The film (3) further includes at least one intermediate layer (3c) disposed between the layer (3a) and the other layer (3b), and the intermediate layer (3c) - Polytetrafluoroethylene (PTFE), tetrafluoroethylene and perfluoropropyl vinyl ether (PFA) copolymer, tetrafluoroethylene and hexafluoropropene (FEP) copolymer, polyvinylidene fluoride (PVDF), tetrafluoroethylene and polymethyl vinyl ether (MVA) copolymer, tetrafluoroethylene, polymethyl vinyl ether and fluoroalkyl vinyl ether (TFE / PMVE / FAVE) terpolymer, ethylene tetrafluoroethylene (ETFE), and mixtures thereof, preferably tetrafluoroethylene and perfluoropropyl vinyl ether (PFA) copolymer and PTFE, preferably PTFE, - Polyaryl ether ketone (PAEK), polyether ether ketone (PEEK) including polyether ketone (PEK), polyether ketone ketone (PEKK), polyether ether ketone ketone (PEEKK), polyether ketone ether ketone ketone (PEKEKK), preferably polyether ether ketone (PEEK), - Polyamideimide (PAI), polyimide (PI), polyetherimide (PEI), polybenzimidazole (PBI), - Poly(phenylene oxide) (PPO), poly(aryl ether sulfone) (PAES) polymers including polyether sulfone (PES), polyphenylene ether sulfone (PPSU), poly(arylene sulfide) (PAS) including polyphenylene sulfide (PPS), liquid crystal polymers, - Silicone resins - And mixtures thereof, preferably a mixture of polyaryl ether ketone (PAEK) and PTFE, preferably a mixture of PEEK and PTFE; PTFE is particularly preferred, A method for producing the coated cooking element (1) according to claim 13, comprising one or more polymers selected from

15. The method for producing a coated cooking element (1) according to any one of claims 1 to 14, wherein the film (3) further comprises at least one filler and / or at least one reinforcing material.

16. The method for producing a coated cooking element (1) according to any one of claims 1 to 15, wherein in the step (v), the layer (3a) of the film (3) in contact with the surface (2a) of the metal substrate (2) is subjected to a mechanical or chemical surface treatment.

17. The method for producing a coated cooking element (1) according to any one of claims 1 to 16, wherein the thickness of the film (3) is configured to be between 5 μm and 500 μm, preferably between 25 μm and 150 μm.

18. A method for molding the coated cooking element (1) according to any one of claims 1 to 17, comprising a step (a) of press-molding the coated cooking element (1) obtained at the end of the step (v).

19. The method for molding the coated cooking element (1) according to claim 18, further comprising a step (b) of stretching the coated cooking element (1) obtained at the end of the step (a).

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