Method for assembling anti-adhesion film onto metal base by hot stamping

Abstract

The invention relates to a method for producing a coated cooking element (1), comprising the following steps: i. Providing a metal base (2) and a metal mesh (3), the metal base (2) having a surface (2a) for contact with the metal mesh (3); ii. Attaching the metal mesh (3) to the face (2a) of the metal base (2); iii. Providing a film (4), said film (4) comprising a layer (4a) comprising one or more semi-crystalline or amorphous thermoplastic polymers, said layer (4a) being in contact with said face (2a) of said metal base (2) and with said metal mesh (3); iv. Heating the metal base (2) and the metal mesh (3); v. Positioning the film (4) such that the layer (4a) faces the face (2a) of the metal base (2) heated in step iv and the metal mesh (3); vi. Assembling the metal base (2) and the metal mesh (3) with the film (4) by hot stamping, the metal base (2) and the metal mesh (3) during assembly being at a temperature higher than the minimum of the melting point of the semi-crystalline thermoplastic polymer and the glass transition temperature (Tg) of the amorphous thermoplastic polymer of the layer (4a).

Description

Technical Field

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

[0002] In the industry of cookware comprising anti-stick cooking surfaces, the performance of anti-stick coatings and the development of methods for obtaining such coatings are of great interest.

[0003] Conventionally, a metal base is first molded into a kitchen utensil, and then a fluororesin having excellent heat resistance, such as polytetrafluoroethylene (PTFE) or tetrafluoroethylene-perfluoropropylvinyl ether (PFA), is coated on the inner surface of the kitchen utensil by a liquid spraying method or a powder coating method. An alternative is to coat the base and then mold the coated base.

[0004] Liquid spraying methods have many disadvantages. When the metal base has a curved shape, it is difficult to obtain a uniform coating thickness. Liquid spraying methods also involve the use of solvents or volatile organic compounds that evaporate during the process and must be recovered and recycled. From an environmental point of view, solvent-free, volatile organic compound-free methods are preferred. On the other hand, the coating thickness is limited. When the coating thickness is too thick, cracking may occur.

[0005] Powder coating methods also have disadvantages. The resulting coatings have pinhole-type defects, which can lead to reduced anti-adhesion properties.

[0006] The coatings obtained according to both methods may have a significant surface roughness, which may lead to cleaning problems, since some cooking residues may remain on the surface of the coating even after several washings.

[0007] Faced with the mechanical stresses inherent in cookware use, a loss of mechanical properties of the coating is observed and delamination of the coating may occur at the interface with the metal substrate.

[0008] In order to overcome the above mentioned drawbacks, the prior art describes metal substrates coated with fluorinated films by lamination.

[0009] Patent application KR20150030719 describes a kitchen utensil comprising a body comprising a metal base on which a fluorinated resin film is laminated. A method for obtaining the kitchen utensil is also described. In Example 1, a PTFE multilayer film is used, with no information on the nature of the layers. The operation of laminating the film on the base is not described.

[0010] Application KR20160099388 describes a method for obtaining a metal base coated with a fluorinated film (without 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 the components of the layer (fluorinated resin and optional inorganic filler) on a carrier, and the aqueous dispersion is dried and sintered. The multilayer film is then removed from its carrier and positioned on the metal base before assembly. The fluorinated film layer in contact with the metal is made of PTFE and a resin selected from FEP, PFA, TFM, MFA (or a mixture thereof), which has good flow properties and therefore has good adhesion that PTFE does not allow. The metal base / fluorinated membrane assembly is performed by hot pressing, in a static press or between rollers (roll-to-roll method). In the static assembly method, both the base and the membrane are heated to a temperature between 300°C and 410°C, and the pressure applied is 100-800psi (0.7MPa-5.6MPa). In a roll-to-roll assembly method (difficult to implement when the metal substrate has a significant thickness), both the substrate and the membrane are heated to a temperature between 330°C and 420°C, with an applied pressure between 2 and 15 MPa.

[0011] In both process variants, the pressure applied during assembly is several MPa and the implementation temperature is limited by the degradation temperature of fluorinated membranes, in particular PTFE, which starts at 420° C. Therefore, the assembly rate of the polymer membrane and the metal base is limited by the parameters of the assembly process.

[0012] Furthermore, although the process for obtaining a substrate coated with a laminated fluorinated film offers the possibility of having a thicker, and therefore more durable, anti-adhesive coating, the mechanical properties of such a film are not optimal. Summary of the invention

[0013] From an industrial point of view, there is still a need to develop methods for assembling polymer films onto metal substrates that are more advantageous in terms of assembly time and allow obtaining more effective coatings in terms of durability.

[0014] The Applicant has therefore developed a method for manufacturing a coated cooking element by hot stamping an assembly of a metal base and a polymer film, said assembly comprising a metal reinforcing element between the metal base and the polymer film.

[0015] Summary of the invention

[0016] The inventors have found that the method according to the invention allows to achieve a rapid assembly between a metal base and a polymer film comprising one or more semi-crystalline or amorphous thermoplastic polymers, while ensuring good adhesion of the polymer film to said metal base.

[0017] Unlike conventional methods of assembling fluoropolymer films on metals, such as hot pressing, only the base is advantageously heated prior to assembly according to the method of the invention. When in contact with the base during assembly, the polymer film is heated substantially by conduction and then cools due to the thermal inertia of the assembly tool, which is maintained at a temperature lower than the heating temperature of the metal base.

[0018] Thus, during the assembly process, a polymer film comprising one or more semi-crystalline or amorphous thermoplastic polymers can be heated very locally, particularly at the base-film interface, to a temperature above the melting temperature or glass transition temperature of all or a portion of the thermoplastic polymer, and the heating can be done for a very short time, which will not cause degradation of the film.

[0019] The implementation of such high temperature in combination with the pressure applied during stamping allows the assembly of the polymer membrane and the metal substrate to be carried out in a much shorter time compared to conventional methods of assembling a polymer membrane on a metal substrate, such as hot pressing.

[0020] Furthermore, a metal reinforcement in the form of a metal mesh is attached to the metal base before assembly with the polymer film. The presence of this reinforcement allows the mechanical properties of the coated metal base to be improved. The cohesion between the metal base and the polymer film is thereby enhanced. The metal reinforcement in particular allows the properties of the anti-stick cooking surface to be improved, in particular by increasing the scratch resistance of the anti-stick coating.

[0021] Therefore, the present invention relates to a method for producing a coated cooking element (1), comprising the following steps:

[0022] i. Providing a metal base (2) and a metal mesh (3), wherein the metal base (2) has a surface (2a) for contacting the metal mesh (3);

[0023] ii. attaching the metal mesh (3) to the surface (2a) of the metal base (2);

[0024] iii. providing a film (4), said film (4) comprising a layer (4a) containing one or more semi-crystalline or amorphous thermoplastic polymers, said layer (4a) being in contact with said face (2a) of said metal base (2) and with said metal mesh (3);

[0025] iv. heating the metal base (2) and the metal mesh (3);

[0026] v. Positioning the film (4) so ​​that the layer (4a) faces the face (2a) of the metal base (2) and the metal mesh (3) heated in step iv.

[0027] vi. Assembling the metal base (2) and the metal mesh (3) with the film (4) by hot stamping, wherein during the assembly, the metal base (2) and the metal mesh (3) are at a temperature higher than the lowest value of the melting point of the semi-crystalline thermoplastic polymer of the layer (4a) and the glass transition temperature (Tg) of the amorphous thermoplastic polymer.

[0028] The invention also relates to a method for shaping a coated cooking element as described above, comprising a step (a) of press-shaping the coated cooking element (1) obtained at the end of step (vi).

[0029] Other aspects of the invention are described below and in the claims.

[0030] definition

[0031] Within the meaning of the present invention, the term "film" is understood to mean a set consisting of one or more superimposed layers intended to be assembled with a metal base. The term "film" also corresponds to said set once assembled with a metal base.

[0032] Within the meaning of the present invention, the term "layer" is understood to mean a continuous layer. A continuous layer (or also called integral layer) is a single integral body forming a total flat area that completely covers the surface on which it is placed or to be placed.

[0033] For the purposes of the present invention, the term "hot stamping" refers to a method for assembling a pre-heated metal substrate (2) and a membrane (4) between a lower tool and an upper tool.

[0034] For the purposes of the present invention, the term "aluminum alloy" refers to the 1000, 2000, 3000, 4000, 5000, 6000, 7000 and 8000 series aluminum alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A cross-sectional view of an exemplary embodiment of a coated cooking element (1) comprising a metal base (2), a metal mesh (3) and a membrane (4) is shown before assembly according to the method of the invention.

[0036] Figure 2 A metal mesh (3) made of woven metal which can be used according to the method of the invention is shown.

[0037] Figure 3 A metal mesh (3) made of expanded metal which can be used according to the method of the invention is shown.

[0038] FIG. 4 shows a cross-sectional view of an exemplary embodiment of a coated cooking element ( 1 ), comprising a metal base ( 2 ), a metal mesh ( 3 ) and a membrane ( 4 ).

[0039] exist Figure 4a In the embodiment, the metal mesh (3) is completely pressed into the metal base (2).

[0040] exist Figure 4b In the embodiment, the metal mesh (3) is only partially pressed into the metal base (2), and the surface of the metal mesh (3) appears on the surface of the film (4), that is, the film (4) does not cover the entire metal mesh (3).

[0041] exist Figure 4c In the embodiment, the metal mesh (3) is only partially pressed into the metal base (2), and the surface of the metal mesh (3) is completely covered by the film (4). DETAILED DESCRIPTION

[0042] The inventors have developed a manufacturing method that can meet the described needs.

[0043] The invention therefore relates to a method for producing a coated cooking element (1), comprising the following steps:

[0044] i. Providing a metal base (2) and a metal mesh (3), wherein the metal base (2) has a surface (2a) for contacting the metal mesh (3);

[0045] ii. attaching the metal mesh (3) to the surface (2a) of the metal base (2);

[0046] iii. providing a film (4), said film (4) comprising a layer (4a) containing one or more semi-crystalline or amorphous thermoplastic polymers, said layer (4a) being in contact with said face (2a) of said metal base (2) and with said metal mesh (3);

[0047] iv. heating the metal base (2) and the metal mesh (3);

[0048] v. Positioning the film (4) so ​​that the layer (4a) faces the face (2a) of the metal base (2) and the metal mesh (3) heated in step iv.

[0049] vi. Assembling the metal base (2) and the metal mesh (3) with the film (4) by hot stamping, wherein during the assembly, the metal base (2) and the metal mesh (3) are at a temperature higher than the lowest value of the melting point of the semi-crystalline thermoplastic polymer of the layer (4a) and the glass transition temperature (Tg) of the amorphous thermoplastic polymer.

[0050] Advantageously, steps i to v are performed continuously.

[0051] The metal base (2) used in step i of the method

[0052] As metal base (2) that can be used in the present invention, there may advantageously be mentioned bases made of aluminum, stainless steel, cast iron or aluminum, or titanium or copper.

[0053] For the purposes of the present invention, aluminum refers to a metal consisting of 100% aluminum or an aluminum alloy.

[0054] Advantageously, the metal base (2) is an aluminum base, a stainless steel base or a multilayer (particularly two-layer or three-layer) metal base, which can be obtained, for example, by co-lamination, by thermal diffusion under load (solid-state bonding) or by hot stamping or cold stamping (impact bonding).

[0055] Preferably, the metal base (2) comprises alternating layers of metal and / or metal alloy.

[0056] According to one embodiment, the metal base (2) is an aluminum base, a stainless steel base or a multi-layer metal base whose surface (2a) is made of an aluminum alloy or stainless steel.

[0057] Preferably, the metal base (2) is an aluminum base.

[0058] Advantageously, the thickness of the metal base (2) is between 0.5 mm and 10 mm.

[0059] Advantageously, the face ( 2 a ) of the metal base ( 2 ) has undergone a surface treatment before being assembled with the membrane ( 4 ), allowing the adhesion of said membrane to said base to be improved.

[0060] According to one embodiment, the surface of the face (2a) of the metal base (2) has undergone a surface treatment which is chemical etching, brushing, hydration, sandblasting, shot blasting, physicochemical treatment of the plasma or corona or laser type, chemical activation or a combination of these different techniques.

[0061] The metal mesh (3) used in step i of the method

[0062] Metal mesh refers not only to metal mesh made of intersecting wires, but also to perforated metal sheets or expanded metal mesh with holes.

[0063] Advantageously, the metal mesh (3) is a woven metal mesh or an expanded metal mesh, preferably made of stainless steel.

[0064] The thickness of the metal mesh (3) may be between 50 μm and 800 μm, preferably between 150 μm and 500 μm.

[0065] Thus, in the case of a woven metal mesh (3), the diameter (or thickness) of the wires may be between 50 μm and 800 μm, preferably between 150 μm and 500 μm.

[0066] When the metal mesh (3) is made of expanded metal, the thickness of the mesh may be between 50 μm and 800 μm, preferably between 150 μm and 500 μm.

[0067] In the case of a woven metal mesh (3), the metal wires woven in the same direction are advantageously spaced 0.2 mm to 8 mm from each other.

[0068] The patterns, ie the empty areas in the woven metal mesh or in the expanded metal mesh, may be all identical or, on the contrary, all different.

[0069] Figure 2 and Figure 3 Woven metal mesh and expanded metal mesh are shown separately as being useful in the context of the present invention.

[0070] The size of the metal mesh (3) is smaller than or equal to the size of the metal base (2).

[0071] According to one embodiment, the metal mesh (3) has undergone a surface treatment which is chemical etching, brushing, hydration, sandblasting, shot blasting, physicochemical treatment of the plasma or corona or laser type, chemical activation or a combination of these different techniques.

[0072] Step (ii) of attaching the metal mesh (3) to the surface (2a) of the metal base (2)

[0073] A metal mesh (3) is applied to the face (2a) of the metal base (2).

[0074] The metal mesh (3) is attached to the face (2a) by means of attachment points or by moulding so as to embed it at least partially into the surface of the metal base (2).

[0075] Attaching the metal mesh (3) by attachment points means that the metal mesh (3) is pre-crimped on the metal base (2) at a few points rather than over its entire surface in contact with the metal base (2). This connection allows the metal mesh (3) to be positioned on the metal base (2) for the subsequent steps of the method.

[0076] Advantageously, the metal mesh (3) is attached to the face (2a) of the metal base (2) by stamping so as to embed said metal mesh (3) at least partially in said face (2a).

[0077] Embossing refers to the operation of stamping (eg using a hammer or punch of a press) or forcing (eg by a surface device or rollers) the metal mesh (3) to embed it at least partially into the surface of the metal base (2).

[0078] Unlike attachment via anchor points, the embossing operation is performed over the entire surface of the metal mesh (2).

[0079] Advantageously, the molding operation is carried out at room temperature using a press.

[0080] The depth of the metal mesh (3) depends on the force applied during embossing, the relative hardness of the metals of the metal mesh (3) and the metal base (2) and properties such as the diameter of the wires of the metal mesh (3).

[0081] According to one embodiment, the metal mesh (3) is only partially embedded in the surface of the metal base (2) and constitutes a protrusion.

[0082] According to another embodiment, the metal mesh (3) is completely embedded in the surface of the metal base (2).

[0083] When the metals of the metal mesh (3) and the metal base (2) are different, embossing can produce a composite base having properties resulting from the properties of both metals. Thus, if the metal mesh (3) is made of a harder metal than the metal base (2), the mechanical properties of the base metal will be altered, for example its tendency to deform when hot will be reduced.

[0084] The metal mesh ( 3 ) can generate a structuring of the surface after being attached to the metal base ( 2 ), thereby increasing the contact surface with the membrane ( 4 ) and thus improving the cohesion of the assembly.

[0085] The set of metal base (2) and metal mesh (3) may undergo a surface treatment after the attachment step, which surface treatment is chemical etching, brushing, hydration, sandblasting, shot blasting, physicochemical treatment of plasma or corona or laser type, chemical activation or a combination of these different techniques.

[0086] Advantageously, the surface of the face ( 2 a ) of the metal base ( 2 ) has an arithmetic mean roughness Ra greater than or equal to 1 μm, preferably greater than or equal to 2 μm.

[0087] Advantageously, the surface of the face ( 2 a ) of the metal base ( 2 ) has an arithmetic mean roughness Ra less than or equal to 20 μm.

[0088] Advantageously, the arithmetic mean roughness Ra of the surface of the face (2a) of the metal base (2) is in the range of 2 μm to 10 μm.

[0089] The arithmetic mean roughness Ra is measured using a roughness meter according to standard ISO 4287. Ra represents the arithmetic mean of the deviations from the mean. The surface topography can be studied, in particular using a profilometer with a probe equipped with a fine needle with a diamond tip, or using An optical metrology instrument of the type in which a confocal color sensor enables contactless measurement. By studying this surface topography data, the arithmetic mean roughness Ra can be determined.

[0090] The membrane (4) used in step iii of the process

[0091] The film (4) comprises a layer (4a) comprising one or more semi-crystalline or amorphous thermoplastic polymers, said layer (4a) being placed in contact with said face (2a) of said metal base (2) and with said metal mesh (3).

[0092] The melting point of the semicrystalline thermoplastic polymer and the glass transition temperature (Tg) of the amorphous thermoplastic polymer in the film (4) can be determined by thermal analysis methods such as differential thermal analysis (or differential scanning calorimetry (DSC)) or by dynamic mechanical analysis (DMA).

[0093] According to one embodiment, the film (4) comprises a single layer (4a) forming the cooking surface (5), the single layer comprising one or more semi-crystalline or amorphous thermoplastic polymers.

[0094] According to another configuration, the film (4) further comprises one or more layers, each layer comprising one or more semi-crystalline or amorphous thermoplastic polymers.

[0095] According to one embodiment, the semi-crystalline or amorphous thermoplastic polymer of the layer (4a) and, where appropriate, the same or different polymer of the additional layers of the film (4) are chosen from:

[0096] - polytetrafluoroethylene (PTFE), copolymers of tetrafluoroethylene and perfluoropropyl vinyl ether (PFA), copolymers of tetrafluoroethylene and hexafluoropropylene (FEP), polyvinylidene fluoride (PVDF), copolymers of tetrafluoroethylene and polymethyl vinyl ether (MVA), terpolymers of tetrafluoroethylene, polymethyl vinyl ether and fluoroalkyl vinyl ether (TFE / PMVE / FAVE), ethylene tetrafluoroethylene (ETFE) and mixtures thereof;

[0097] - polyaryletherketone (PAEK), including polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetheretherketoneketone (PEEKK), polyetherketoneetherketoneketone (PEKEKK), preferably polyetheretherketone

[0098] Ketone (PEEK);

[0099] - polyphenylene oxide (PPO), poly(arylether sulfone) (PAES) polymers, including polyethersulfone (PES), polyphenylene ether sulfone (PPSU), poly(arylene sulfide) (PAS) including polyphenylene sulfide (PPS), liquid crystal polymers;

[0100] - Polyamideimide (PAI), polyimide (PI), polyetherimide (PEI), polybenzimidazole (PBI);

[0101] - and mixtures thereof.

[0102] Furthermore, the membrane (4) may further comprise at least one filler and / or at least one reinforcement.

[0103] As fillers that can be used in the present invention, mention may in particular be made of metal oxides, metal carbides, metal oxynitrides, metal nitrides, silicon dioxide and mixtures thereof.

[0104] These fillers may be present in one or more layers of the film (4) or in the layers of the film (4).

[0105] As reinforcements that can be used in the invention, mention may be made of mineral or metal reinforcements of the fiber type, metal meshes, glass fiber materials or fabrics. The reinforcement may also consist of a non-fluorinated polymer with high thermodynamic properties of the polyaryletherketone (PEAK) type, such as polyetheretherketone (PEEK) or polyamideimide (PAI). The reinforcement may be in the form of a layer of the membrane (4) situated between the layer (4a) and the layer (4) forming the cooking surface.

[0106] In order to improve the adhesion of the film (4) and the metal base (2), the face (2a) of the film (4) in contact with the metal base (2) and with the metal mesh (3) during step (vi) may have undergone a mechanical or chemical surface treatment. This surface treatment may be chemical etching, brushing, hydration, sandblasting, shot blasting, physicochemical treatment of the plasma or corona or laser type, chemical activation or a combination of these different techniques.

[0107] According to one embodiment, the thickness of the film (4) is between 5 μm and 500 μm, preferably between 25 μm and 150 μm.

[0108] The thickness of the layer of the film (4) was measured at 20 random points on the film cross section. The average thickness of the film (4) was obtained by averaging these 20 measurements.

[0109] The total thickness of the film (4) of the coated cooking element (1) according to the invention, i.e. the total thickness measured on the cooking element after it has been coated with the film (4), is between 5 μm and 500 μm, preferably between 25 μm and 150 μm.

[0110] The thickness of the film (4) of the coated cooking element (1) according to the invention is measured at 20 random points on the cross section of the coated base. The average thickness of the film (4) is obtained by averaging these 20 measurements.

[0111] Before being assembled with the metal base (2), the membrane (4) can be obtained by depositing a first layer on a support, then possibly by successively depositing the other layers, and then by peeling off the membrane to separate it from the support. The layers of the membrane (4) can also be assembled together by any other assembly method, for example by lamination.

[0112] Typically, the film (4) of the coated cooking element (1) completely covers the face (2a) of the metal base (2), but may be considered to cover only a portion of the metal base (2).

[0113] exist Figure 1 In the embodiment shown, the membrane (4) comprises 2 layers (4a, 4b).

[0114] Step iv

[0115] Prior to steps v and vi of the method, the metal base (2) and metal mesh (3) from step (ii) are heated in step iv. The metal base (2) and metal mesh (3) may be heated by any suitable means, for example in a furnace or by induction heating.

[0116] step v

[0117] Prior to assembly in step vi, the membrane (4) is positioned above the metal base (2) so that its layer (4a) faces the face (2a) of the metal base (2) and the metal mesh (3) preheated in step iii.

[0118] The film ( 4 ) is positioned so that during the assembly step vi the entire surface of the layer ( 4 a ) is in contact simultaneously with the surface of the face ( 2 a ) of the metal base ( 2 ) and with the metal mesh ( 3 ).

[0119] To ensure this contact, the film (4) can be attached to an upper tool or stretched between 2 rollers.

[0120] Step vi

[0121] When the metal base (2) and the metal mesh (3) are assembled with the film (4) by hot stamping, the metal base (2) and the metal mesh (3) are at a temperature higher than the lowest value of the melting point of the semi-crystalline thermoplastic polymer and the glass transition temperature (Tg) of the amorphous thermoplastic polymer of the layer (4a) when assembled.

[0122] When the temperature during assembly is below the lowest of the melting point of the semi-crystalline thermoplastic polymer and the glass transition temperature (Tg) of the amorphous thermoplastic polymer of the layer (4a), the adhesion of the film (4) to the metal base (2) and the metal mesh (3) is insufficient.

[0123] When the temperature is higher than 550°C, degradation of the membrane (4) is observed.

[0124] When the layer (4a) consists mainly of PTFE by weight, in the semi-crystalline or amorphous thermoplastic polymer constituting it, the metal base (2) and the metal mesh (3) are at a temperature between 350°C and 550°C, preferably between 400°C and 450°C when assembled with the membrane (4).

[0125] The temperature of the metal base (2) and the metal mesh (3) during assembly corresponds to the temperature of the metal base (2) and the metal mesh (3) at the start of stamping, that is, at the start of pressurization of the metal base (2) and the metal mesh (3) / film (4).

[0126] According to one embodiment, the assembly by hot stamping during step vi. is performed with the aid of a hydraulic or mechanical press, comprising a lower tool and an upper tool, between which the metal base (2) and the metal mesh (3) are assembled with the membrane (4), the metal base (2) preferably being in contact with the lower tool, and the membrane (4) preferably being in contact with the upper tool.

[0127] The surface of the lower tool, advantageously flat, may undergo a surface treatment in order to avoid any adhesion of the metal base to said tool.

[0128] Advantageously, the plane of the surface of the upper tool has an angle of between 0.01° and 0.5°, preferably between 0.15° and 0.25° relative to the plane of the surface of the lower tool.This angle allows limiting the entrapment of air during the assembly step.

[0129] Advantageously, the assembly tool is not heated prior to assembly step v.

[0130] Optionally, the lower tool may be heated. Optionally, the upper tool may be cooled.

[0131] According to one embodiment, during step vi, the lower tool is heated to a temperature between 25°C and the temperature of the metal base (2) when assembled, and / or the upper tool is heated to a temperature between 15°C and 120°C.

[0132] Unless otherwise stated, the temperature values ​​indicated in this application correspond to measured temperature values ​​and not set temperatures.

[0133] The temperature value is measured by any suitable means, for example by a temperature probe located on the surface or in the body of the heating or cooling element.

[0134] The temperature of the metal base (2) and the metal mesh (3) during assembly corresponds to the temperature of the surface (2a) of the metal base (2) when pressurization of the metal base (2) and the metal mesh (3) / film (4) begins.

[0135] The temperature of the metal base (2) and the metal mesh (3) then decreases during the punching operation, in particular when the lower tool is not heated prior to the assembly step.

[0136] During the punching operation of step vi, a pressure greater than or equal to 100 MPa, preferably several hundred MPa, is advantageously used.

[0137] According to one embodiment, during step vi, the metal base (2), the metal mesh (3) and the membrane (4) are maintained at a pressure between 100 MPa and 800 MPa, preferably between 350 MPa and 500 MPa.

[0138] The pressure applied during the stamping operation is significantly higher than the pressure applied in conventional metal substrate / polymer membrane assembly processes such as hot pressing, which is only a few Pa.

[0139] According to one embodiment, during step vi, the metal base (2), the metal mesh (3) and the membrane (4) are kept under pressure for a duration less than or equal to 1 minute, preferably less than or equal to 15 seconds.

[0140] Punching may be performed by applying sharp blows of a duration of less than 5 seconds.

[0141] According to another embodiment, during step vi, the metal base (2), the metal mesh (3) and the membrane (4) are kept under pressure for a duration between 1 second and 1 minute, preferably between 2 seconds and 15 seconds.

[0142] When the membrane (4) is in contact with the heated metal base (2) and the heated metal mesh (3) during assembly, it is heated substantially by conduction. It then cools during stamping due to the thermal inertia of the assembly tool, which has a lower temperature than the heating temperature of the metal base (2). Therefore, during the stamping operation, especially when the lower tool is not heated before the assembly step, the temperature of the membrane (4) can drop rapidly.

[0143] Prior to assembly step vi, the membrane ( 4 ) is advantageously not heated.

[0144] According to the method of the invention, it is thus possible to heat the film (4), in particular at the metal base (2) - film (4) interface, very locally to a temperature higher than the lowest of the melting point of the semi-crystalline thermoplastic polymer of the layer (4a) and the glass transition temperature (Tg) of the amorphous thermoplastic polymer for a very short time, without causing any degradation of the film (4).

[0145] Advantageously, at the end of step vi. of assembling the membrane (4) with the metal base (2) and the mesh (3), i.e. when the assembly of the membrane (4), the metal base (2) and the mesh (3) is no longer held under pressure, the temperature of the membrane (4) is lower than the lowest of the melting point of the semi-crystalline thermoplastic polymer of the layer (4a) and the glass transition temperature (Tg) of the amorphous thermoplastic polymer.

[0146] During assembly by punching, the combination of temperature and pressure as described above allows ensuring the adhesion of the membrane (4) to the metal base (2) and the metal mesh (3) in a very short time.

[0147] In step ii, the metal mesh (3) is attached to the surface (2a) via attachment points or is at least partially embedded in the surface of the metal base (2).

[0148] Step vi of assembling the metal base ( 2 ) and the metal mesh ( 3 ) with the membrane ( 4 ) by hot stamping may also result in the metal mesh ( 3 ) being partially embedded in the surface of the metal base ( 2 ).

[0149] The presence of the metal mesh (3) helps to improve the anti-stick properties of the cooking surface, in particular by increasing the scratch resistance of the anti-stick coating.

[0150] The metal mesh (3) can help limit the penetration of the metal tool into the anti-adhesion coating, thereby limiting the formation of scratches.

[0151] Due to the presence of the metal mesh (2), the cooking surface (5) of the coated cooking element (1) may also have a surface texture, for example forming protrusions in the form of reliefs.

[0152] These elevations may make it possible to increase the resistance of the anti-adhesive coating to scratches, in particular when using metal tools which would come into contact mainly with the elevated peaks of the cooking surface (5).

[0153] Figure 4, purely for illustrative and non-limiting purposes, shows a cross-sectional view of an exemplary embodiment of a coated cooking element (1) according to the present invention, comprising a metal base (2), a metal mesh (3) and a membrane (4).

[0154] exist Figure 4a In the embodiment, the metal mesh (3) is completely pressed into the metal base (2).

[0155] exist Figure 4b In the embodiment, the metal mesh (3) is only partially pressed into the metal base (2), and the surface of the metal mesh (3) appears on the surface of the film (4), that is, the film (4) does not cover the entire metal mesh (3).

[0156] exist Figure 4cIn the embodiment, the metal mesh (3) is only partially pressed into the metal base (2), and the surface of the metal mesh (3) is completely covered by the film (4).

[0157] According to a variant not shown, the metal mesh (3) is only partially pressed into the metal base (2) and the surface of the metal mesh (3) is completely covered by the film (4). Due to the presence of the metal mesh, the surface of the assembled film (4) is not flat and has protrusions in the form of floating.

[0158] The coated cooking element (1) may also have a configuration of the assembly of the metal base (2), the metal mesh (3) and the film (4) that is different in different areas of the coated cooking element (1). Thus, the metal mesh (3) may be completely pressed into the metal base (2) in some areas of the coated cooking element (1) and partially pressed into the metal base (2) in other areas of the coated cooking element (1).

[0159] After assembly, the metal base (2) and the metal mesh (3) coated with the film (4) are left to cool to room temperature in order to obtain maximum adhesion between the metal base (2), the metal mesh (3) and the film (4).

[0160] Then, at the end of step (vi), the metal substrate (2) coated with the film (4) can be shaped.

[0161] Therefore, a second object of the present invention relates to a method for shaping a coated cooking element as described above, comprising a step (a) of press-shaping the coated cooking element (1) obtained at the end of step (vi).

[0162] The forming process may also comprise a step (b) of stretching the coated cooking element (1) obtained at the end of step (a).

[0163] The adhesion of the film (4) to the metal substrate (2) must be good enough before forming to avoid any loss of adhesion during and after the forming operation.

[0164] The coated cooking element (1) according to the method of the invention can form a cooking container in a cooking article, wherein the cooking article is selected from a frying pan, a frying pan, a casserole dish with a handle for cheese fondue or raclette, a frying pan, a wok, a frying pan, a griddle pan, a grill, a broiler, a cooking pot, a casserole dish, a cooking mold.

[0165] The coated cooking element (1) according to the method of the invention can form a cooking vessel in an electric cooking appliance selected from an electric pancake maker, an electric raclette maker, an electric fondue maker, an electric grill, an electric frying pan, a cooking robot, a bread maker. Thus, the cooking device can form a cooking accessory of an electric cooking appliance.

Claims

1. A method for producing a coated cooking element (1), comprising the following steps: i. Providing a metal base (2) and a metal mesh (3), wherein the metal base (2) has a surface (2a) for contacting the metal mesh (3); ii. attaching the metal mesh (3) to the surface (2a) of the metal base (2); iii. providing a film (4), said film (4) comprising a layer (4a) containing one or more semi-crystalline or amorphous thermoplastic polymers, said layer (4a) being in contact with said face (2a) of said metal base (2) and with said metal mesh (3); iv. heating the metal base (2) and the metal mesh (3); v. positioning the film (4) so ​​that the layer (4a) faces the surface (2a) of the metal base (2) and the metal mesh (3) heated in step iv; vi. Assembling the metal base (2) and the metal mesh (3) with the film (4) by hot stamping, wherein during the assembly, the metal base (2) and the metal mesh (3) are at a temperature higher than the lowest value of the melting point of the semi-crystalline thermoplastic polymer of the layer (4a) and the glass transition temperature (Tg) of the amorphous thermoplastic polymer.

2. Method for producing a coated cooking element (1) according to claim 1, characterized in that The assembly by hot stamping during step vi. is performed with the aid of a hydraulic or mechanical press comprising a lower tool and an upper tool between which the metal base (2) and the metal mesh (3) are assembled with the membrane (4), the metal base (2) preferably being in contact with the lower tool and the membrane (4) preferably being in contact with the upper tool.

3. Method for producing a coated cooking element (1) according to claim 2, characterised in that During step vi, the metal base ( 2 ), the metal mesh ( 3 ) and the membrane ( 4 ) are maintained at a pressure between 100 MPa and 800 MPa, preferably between 350 MPa and 500 MPa.

4. Method for producing a coated cooking element (1) according to claim 2 or 3, characterized in that During step vi, the metal base (2), the metal mesh (3) and the membrane (4) are kept under pressure for a duration less than or equal to 1 minute, preferably less than or equal to 15 seconds.

5. Method for producing a coated cooking element (1) according to any one of claims 2 to 4, characterized in that During step vi, the metal base (2), the metal mesh (3) and the membrane (4) are kept under pressure for a duration between 1 second and 1 minute, preferably between 2 seconds and 15 seconds.

6. Method for producing a coated cooking element (1) according to any one of claims 2 to 5, characterized in that The plane of the surface of the upper tool has an angle with respect to the plane of the surface of the lower tool of between 0.01° and 0.5°, preferably between 0.15° and 0.25°.

7. Method for producing a coated cooking element (1) according to any one of claims 2 to 6, characterized in that In step vi, the lower tool is heated to a temperature between 25°C and the temperature of the metal base (2) when assembled, and / or the upper tool is heated to a temperature between 15°C and 120°C.

8. Method for producing a coated cooking element (1) according to any one of the preceding claims, characterized in that The metal base (2) is an aluminum base, a stainless steel base or a multi-layer metal base whose surface (2a) is made of aluminum alloy or stainless steel.

9. Method for producing a coated cooking element (1) according to any one of the preceding claims, characterized in that The surface of the face (2a) of the metal base (2) has undergone a surface treatment which is chemical etching, brushing, hydration, sandblasting, shot blasting, physicochemical treatment of the plasma or corona or laser type, chemical activation or a combination of these different techniques.

10. Method for producing a coated cooking element (1) according to any one of the preceding claims, characterized in that The metal mesh (3) is a woven metal mesh or an expanded metal mesh, preferably made of stainless steel.

11. Method for producing a coated cooking element (1) according to any one of the preceding claims, characterized in that The thickness of the metal mesh (3) is between 50 μm and 800 μm.

12. Method for producing a coated cooking element (1) according to any one of the preceding claims, characterized in that The metal mesh (3) is attached to the face (2a) of the metal base (2) by embossing to embed the metal mesh (3) at least partially into the face (2a).

13. Method for producing a coated cooking element (1) according to any one of the preceding claims, characterized in that The film (4) comprises a single layer (4a) forming a cooking surface (5), the single layer comprising one or more semi-crystalline or amorphous thermoplastic polymers.

14. Method for producing a coated cooking element (1) according to any one of claims 1 to 12, characterized in that The film (4) further comprises one or more layers, each layer comprising one or more semi-crystalline or amorphous thermoplastic polymers.

15. Method for producing a coated cooking element (1) according to any one of the preceding claims, characterized in that The semi-crystalline or amorphous thermoplastic polymer of the layer (4a) and, where appropriate, the same or different polymers of the additional layers of the film (4) are selected from: - polytetrafluoroethylene (PTFE), copolymers of tetrafluoroethylene and perfluoropropyl vinyl ether (PFA), copolymers of tetrafluoroethylene and hexafluoropropylene (FEP), polyvinylidene fluoride (PVDF), copolymers of tetrafluoroethylene and polymethyl vinyl ether (MVA), terpolymers of tetrafluoroethylene, polymethyl vinyl ether and fluoroalkyl vinyl ether (TFE / PMVE / FAVE), ethylene tetrafluoroethylene (ETFE) and mixtures thereof; - polyaryletherketone (PAEK), including polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetheretherketoneketone (PEEKK), polyetherketoneetherketoneketone (PEKEKK), preferably polyetheretherketone (PEEK); - polyphenylene oxide (PPO), poly(arylether sulfone) (PAES) polymers, including polyethersulfone (PES), polyphenylene ether sulfone (PPSU), poly(arylene sulfide) (PAS) including polyphenylene sulfide (PPS), liquid crystal polymers; - Polyamideimide (PAI), polyimide (PI), polyetherimide (PEI), polybenzimidazole (PBI); - and mixtures thereof.

16. Method for producing a coated cooking element (1) according to any one of the preceding claims, characterized in that The membrane (4) further comprises at least one filler and / or at least one reinforcement.

17. Method for producing a coated cooking element (1) according to any one of the preceding claims, characterized in that During step (vi), the face (2a) of the metal base (2) and the layer (4a) of the membrane (4) in contact with the metal mesh (3) have been subjected to a mechanical or chemical surface treatment.

18. Method for producing a coated cooking element (1) according to any one of the preceding claims, characterized in that The thickness of the film (4) is between 5 μm and 500 μm, preferably between 25 μm and 150 μm.

19. A method for shaping a coated cooking element (1) according to any one of the preceding claims, comprising a step (a) of press-shaping the coated cooking element (1) obtained at the end of step (vi).

20. Method for forming a coated cooking element (1) according to claim 19, further comprising a step (b) of stretching the coated cooking element (1) obtained at the end of step (a).

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