EP2931940B1 - Enamel coating comprising anisotropic particles and cooking item provided with such a coating - Google Patents

Description

The present invention generally relates to an article provided with an enamel coating incorporating anisotropic particles (of flake or fiber type) and which can be used on any type of substrate, in particular metal.

The present invention also relates to a method for applying such a coating to a support.

The field targeted is primarily that of heating articles.

By heating article is meant, within the meaning of the present invention, an article which has its own heating system, or an article which is heated by an external system and which is able to transmit the calorific energy provided by this system to a third-party material or object in contact with said article, or else an article which is intended to receive another previously heated article.

By way of examples of heating articles that can be used according to the present invention, mention may in particular be made of culinary articles (such as sauté pans, saucepans, woks, crepe pans, stewpans, pots, casserole dishes, etc.), or lids heated bowls and mixing bowls of food or drink preparation appliances. But the present invention can also relate to any other type of surface and articles, such as table articles such as trivets, soleplates of an iron, curling irons, and straightening irons, radiators, towel rails or wood-burning stoves, or barbecue plates, barbecue chests or barbecue tubs, flat heater hoods.

Enamel coatings are particularly appreciated in the field of heating articles, in particular culinary articles, and in that of irons, and more specifically iron soleplates.

In the case of iron soleplates, the tribological, thermal and physicochemical properties of the coating are essential to ensure ease of ironing. An enamel coating is therefore an ideal compromise for coating the metal cap of an iron soleplate because it has good thermal resistance, a low friction coefficient that changes little with temperature, hydrophilic behavior and resistance to hydrolysis. The disadvantage of enamel coatings for applications of the iron type (including in particular steam irons, dry irons and steam generators) lies in their low resistance to shocks. Indeed, it may appear at the level of the coated edge of the enamelled cap (and more particularly on the periphery of the coated cap), small chips of enamel, in particular if the coating is subject to shocks caused by handling. Small chips of enamel may also appear through repeated contact on metal parts attached to textiles to be ironed (buttonholes, press studs, zippers, etc.).

Enamel coatings are also particularly appreciated in the field of cookware because they make it possible to obtain colored coatings which not only have good dishwasher resistance, high flame and scratch resistance, but also a primordial decorative element, very often decisive in the consumer's choice. However, they have the drawback of flaking off easily at certain particularly sensitive zones, which are the zones of high stress on the cooking utensil. These zones are generally located in the zones of curvature of the article or in the zones of connection with the handle or handles.

By way of sensitive zone, mention may in particular be made, for a culinary article, of the junction zone between the bottom of the cap and the side wall of the article or the upper edge of the article which is trimmed (rectified) to give a smooth, flat edge, or even the area supporting the grip of the handle (because it can undergo deformation following the welding of the fixing element), the bottom which is in contact with the grills of the burners.

In addition, enamel coatings also have the disadvantage of having a different thermal expansion depending on the position of the flame at the bottom of the article. However, it is important that the coating has a homogeneous thermal expansion, otherwise microcracks are generated which are detrimental to resistance to the dishwasher.

To avoid the aforementioned problems, the applicant has developed an enamel coating comprising flakes, and more generally particles of anisotropic shape, which are oriented essentially perpendicular to the coating formed in the sensitive areas.

By particles essentially perpendicular to the coating is meant, within the meaning of the present invention, particles which are mainly inclined at an angle α between 20° and 90°, preferably between 45 and 90°, and better still between 60 and 90 ° in relation to the average plane of the coating.

It is known to those skilled in the art to incorporate particles such as flakes into enamel-type coatings. Thus, for example, the French patents FR2472596 and FR813737 describe enamel coatings for cookware, in which mica or mother-of-pearl flakes are incorporated into an enamel coating.

Furthermore, the international application WO 2011/42886 and US patent US 3,480,461 relate to the decoration of an iron soleplate using an enamel coating comprising pigments or fillers.

However, none of these references describes any orientation of these particles (flakes, pigments or fillers) in a specific zone of the coating, in particular with a view to its reinforcement, nor a fortiori that this orientation can be achieved by applying a field magnetic in this area.

More particularly, the subject of the present invention is a heating article comprising a support having two opposite faces, at least one of which is covered with a protective coating, characterized in that said protective coating comprises at least one layer of enamel in which particles of anisotropic shape are dispersed, the enamel layer comprising at least one zone in which the anisotropic particles are essentially perpendicular to the enamel layer in the form of a film.

The particles of anisotropic shape can advantageously represent 0.05 to 10%, preferably 0.1 to 7%, and better still 1 to 5% by weight of the total weight of the enamel layer. Ideally, the particles of anisotropic shape represent 2 to 3% by weight of the total weight of the enamel layer.

In the area where the particles are essentially perpendicular, resistance to chipping and impact is significantly improved. In addition, this area does not exhibit a different thermal expansion from that of the rest of the coating.

By particles of anisotropic shape, is meant within the meaning of the present invention particles whose characteristic dimensions are not identical in all directions, such as for example fibers (of essentially one-dimensional shape) or flakes (of essentially two-dimensional or flat shape )

By particles essentially perpendicular to the film, is meant within the meaning of the present invention, particles which are mainly inclined at an angle α of between 20° and 90° relative to the mean plane of the film.

Such an orientation of the anisotropic particles can be obtained in different ways, depending on the type of anisotropic particles used.

Thus, in the case of particles capable of being oriented by a mechanical means (such as fibers), the orientation essentially perpendicular to the coating layer can for example result from a positioning linked to the method of application of the coating, as by example orientation through a one-way applicator such as a micro-nozzle.

In the case of particles able to be oriented by a physical means (for example electrical or magnetic), the essentially perpendicular orientation of the anisotropic particles with respect to the coating layer can result from a consecutive or simultaneous positioning with the application of the coating, such as for example the orientation of magnetizable particles under the effect of a magnetic field or electrisable particles under the effect of an electric field.

By magnetizable particles is meant, within the meaning of the present invention, particles capable of being oriented under the effect of a magnetic field.

The magnetizable particles can come in different natures.

In the context of the present invention, the magnetizable particles can advantageously be particles comprising at least one ferromagnetic metal.

They can be of a homogeneous nature, that is to say made up of the same material, or of a composite nature, that is to say that the magnetizable particles have a core-envelope structure, in which the ferromagnetic metal is in the core and/or in the envelope of said particles.

As examples of composite magnetizable particles, mention may in particular be made of mica flakes coated with a ferromagnetic material, such as for example mica flakes coated with a ferrite of the form (MO, Fe2O3) where M is a metal divalent, for example mica flakes coated with Fe ₃ O ₄ (magnetite) or Fe ₂ O ₃ , or FeO. Other materials with ferromagnetic properties can also be used: for example, mention may be made of cobalt, nickel, or the Heussler alloy consisting solely of non-ferromagnetic metals (61% Cu, 24% Mn, 15% Al) , or certain rare earths such as lanthanides, copper-manganese and aluminum oxides.

The advantage of coated mica flakes lies in the fact that they are particularly resistant to the high firing temperature of enamels for metals, namely temperatures ranging from 550°C for enamels on aluminum to 850°C for enamels on steel or cast iron. In addition, these mica flakes offer better resistance to the alkalinity of the enamel slips obtained by hydrolysis (for example an enamel slip for aluminum has a pH of 13). Mention may also be made of stainless steel fibers coated with a sol-gel material, as protection against corrosion during the stages of implementation of the coating, or flakes whose core is made of ferromagnetic metal and the envelope is made of a sol-gel material.

The coating according to the invention can also advantageously comprise non-magnetizable particles to improve the reinforcement of the coating.

By non-magnetizable particles is meant, within the meaning of the present invention, non-magnetizable or weakly magnetizable particles having a zero or weak magnetic moment (less than 1 emu/g).

These non-magnetizable particles can be of any shape (spherical, fibers or flakes or “irregular”), of micrometric or even nanometric size.

As non-magnetizable particles that can be used in the context of the present invention, mention may in particular be made of mica flakes, and mica or silica flakes coated with titanium dioxide.

The protective coating of the present invention may further advantageously comprise, adjacent to the zone in which the particles are essentially perpendicular to the enamel coating layer, at least one zone in which the particles are arranged in an essentially parallel and/or random to the layer of enamel in the form of a film, so as to reinforce the sensitive areas.

By particles essentially parallel to the enamel coating layer, is meant within the meaning of the present invention, particles which are predominantly inclined at an angle α of between 0° and 20° with respect to the coating layer.

The alternation of the zones in which the particles are arranged in an essentially parallel and/or random manner to the enamel layer and the zones in which the particles are essentially perpendicular to the enamel layer makes it possible to define a decoration, which may be perceived by the user as a three-dimensional decor.

According to a first particularly advantageous embodiment of the present invention, the enamel layer of the protective coating according to the invention may comprise a single continuous layer intended to be placed on a support.

• une sous-couche transparente et exempte de particules magnétisables, qui est continue et est destinée à être disposée sur un support, et
• une couche de finition dans laquelle sont dispersées les particules magnétisables, la couche de finition étant continue et recouvrant partiellement ou complètement la sous-couche.

According to a second particularly advantageous embodiment of the present invention, the enamel layer of the protective coating according to the invention may comprise:

• a transparent underlayer free of magnetizable particles, which is continuous and is intended to be placed on a support, and
• a top coat in which the magnetizable particles are dispersed, the top coat being continuous and partially or completely covering the undercoat.

By finishing layer is meant, within the meaning of the present invention, a layer which is intended to be in contact with the environment.

• une sous-couche colorée et exempte de particules magnétisables, qui est continue et est destinée à être disposée sur un support, et
• une couche de finition dans laquelle sont dispersées les particules magnétisables, la couche de finition étant continue et recouvrant partiellement ou complètement la sous-couche.

According to a third particularly advantageous embodiment of the present invention, the enamel layer of the protective coating according to the invention may comprise:

• a colored underlayer free of magnetizable particles, which is continuous and is intended to be placed on a support, and
• a top coat in which the magnetizable particles are dispersed, the top coat being continuous and partially or completely covering the undercoat.

• une sous-couche transparente ou colorée et exempte de particules magnétisables, la sous-couche étant continue et destinée à être disposée sur un support,
• une première couche de finition dans laquelle sont dispersées des particules magnétisables, la première couche de finition étant continue et recouvrant complètement la sous-couche, et
• une deuxième couche de finition dans laquelle sont également dispersées des particules magnétisables, la deuxième couche de finition étant continue et recouvrant partiellement ou complètement la première couche de finition.

According to a fourth particularly advantageous embodiment of the present invention, the enamel layer of the protective coating according to the invention may comprise:

• a transparent or colored underlayer free of magnetizable particles, the underlayer being continuous and intended to be placed on a support,
• a first topcoat in which magnetizable particles are dispersed, the first topcoat being continuous and completely covering the undercoat, and
• a second topcoat in which magnetizable particles are also dispersed, the second topcoat being continuous and partially or completely covering the first topcoat.

• une sous-couche colorée, dans laquelle sont dispersées des particules magnétisables, la sous-couche colorée étant continue et destinée à être disposée sur un support, et
• une couche de finition transparente, dans laquelle sont également dispersées des particules magnétisables, la couche de finition étant continue et recouvrant partiellement ou complètement la sous-couche colorée.

According to a fifth particularly advantageous embodiment of the present invention, the enamel layer of the protective coating according to the invention may comprise:

• a colored underlayer, in which magnetizable particles are dispersed, the colored underlayer being continuous and intended to be placed on a support, and
• a transparent top coat, in which magnetizable particles are also dispersed, the top coat being continuous and partially or completely covering the colored undercoat.

Such an embodiment has the advantage of mechanically reinforcing each layer and the mechanical connection between each layer.

Advantageously, for the embodiments with at least two layers (second to fifth embodiments), the underlayer can have a thickness of between 5 and 30 μm, and the topcoat or layers may have a thickness of between 20 and 60 μm.

• une couche d'émail comprenant :
  • ▪ une sous-couche exempte de particules magnétisables et qui est transparente ou colorée, cette sous-couche étant continue et destinée à être disposée sur un support, et
  • ▪ au moins une couche médiane qui est soit une couche colorée, soit une couche magnétisable laquelle dans laquelle sont dispersées des particules magnétisables, ladite couche médiane étant continue et recouvrant partiellement ou complètement ladite sous-couche, et
• une première couche de vernis magnétisable, continue et dans laquelle sont dispersées des particules magnétisables, cette première couche de vernis recouvrant partiellement ou complètement la couche médiane en émail, et
• une deuxième couche de vernis incolore et transparente, non magnétisable, continue et recouvrant complètement la première couche de vernis magnétisable, de manière à garantir la tenue chimique et la tenue au lave-vaisselle.

According to a sixth particularly advantageous embodiment of the present invention, the protective coating according to the invention may comprise:

• an enamel layer comprising:
  • ▪ a sub-layer free of magnetizable particles and which is transparent or colored, this sub-layer being continuous and intended to be placed on a support, and
  • ▪ at least one middle layer which is either a colored layer or a magnetizable layer in which magnetizable particles are dispersed, said middle layer being continuous and partially or completely covering said sub-layer, and
• a first layer of magnetizable varnish, continuous and in which magnetizable particles are dispersed, this first layer of varnish partially or completely covering the middle enamel layer, and
• a second layer of colorless and transparent varnish, non-magnetizable, continuous and completely covering the first layer of magnetizable varnish, so as to guarantee chemical resistance and resistance to the dishwasher.

Advantageously, for this sixth embodiment, the underlayer can have a thickness of between 5 and 30 μm, the middle enamel layer can have a thickness of between 20 and 60 μm. As regards the layers of varnish covering the middle layer of enamel, the layer of magnetizable varnish can advantageously have a thickness of between 15 and 40 μm, and the layer of protective varnish can have a thickness of between 10 and 20 μm.

For all of these embodiments, by colored layer (whether it is an undercoat, a finishing coat or a varnish coat), it is meant within the meaning of the present invention a layer comprising at least one opaque pigment chosen from thermostable pigments such as for example spinels, ceramic pigments, oxides, organometallics such as ultramarine blue, pigments in micaceous or silicon flakes (non-magnetizable), metal salts , thermochromic semiconductor pigments and mixtures thereof.

Advantageously, whatever the embodiment envisaged, the enamel layer of the protective coating of the heating article according to the invention may also comprise a discontinuous outer enamel layer, which is screen-printed or pad-printed.

In the case where the heating article according to the invention is a culinary article, the external enamel layer can also comprise rounded fillers, which are advantageously spherical with a diameter of between 5 and 40 μm, and preferably between 15 and 20 µm, the thickness of the outer layer varying between 10 and 30 µm. These beads protrude from the surface of the outer enamel layer.

As rounded fillers (or balls) that can be used in the outer enamel layer according to the invention, mention may in particular be made of balls made of stainless steel, copper, bronze or refractory steel.

Preferably, stainless steel balls are used. The rounded fillers are advantageously present in the outer layer of enamel at a rate of 1 to 5% by weight relative to the total weight of the outer layer. These rounded fillers make it possible both to increase the wear resistance of the enamel coating and to reduce (when the fillers are flush with the surface of the enamel layer) the coefficient of friction due to the decrease the contact surface between the article and the cooking plate and the lesser hardness of the balls compared to that of the enamel layer. Thus, the coating is easily cleanable and presents no risk of scratching sensitive surfaces such as ceramic or induction hobs.

As regards the nature of the support of the article, the latter can be made of a material chosen from among metals, glass and ceramics.

• monocouche en aluminium ou alliage d'aluminium poli, brossé ou microbillé, sablé, traité chimiquement, ou en fonte d'aluminium, ou en acier inoxydable poli, brossé ou microbillé, ou en fonte d'acier ou d'aluminium,
• soit un support métallique multicouches, en partie ou en totalité, comprenant de l'extérieur vers l'intérieur les couches suivantes acier inoxydable ferritique / aluminium/acier inoxydable austénitique ou encore acier inoxydable / aluminium / cuivre / aluminium / acier inoxydable austénitique, ou encore une calotte d'aluminium de fonderie, d'aluminium ou d'alliages d'aluminium doublée d'un fond extérieur en acier inoxydable.

By way of metal supports in accordance with the invention, mention may be made of supports having a structure:

• monolayer in polished, brushed or microblasted aluminum or aluminum alloy, sandblasted, chemically treated, or in cast aluminum, or in polished, brushed or microblasted stainless steel, or in cast steel or aluminium,
• either a multi-layer metal support, in part or in whole, comprising from the outside towards the inside the following layers ferritic stainless steel/aluminum/austenitic stainless steel or even stainless steel/aluminum/copper/aluminum/austenitic stainless steel, or else a cap of cast aluminium, aluminum or aluminum alloys lined with a stainless steel outer bottom.

By way of examples of articles according to the invention, mention may in particular be made of cookware, heated lids or heated mixer bowls of food or drink preparation appliances, or even the soles of iron, table items such as trivets, radiators or wood-burning stoves, or even curling irons and straightening irons, towel racks or barbecue plates, barbecue or barbecue tubs.

Finally, another subject of the present invention is a process for the manufacture, on a support of a heating article, of a coating comprising at least one layer of enamel in which particles of anisotropic shape are dispersed,
characterized in that it comprises a step of orienting said anisotropic particles by a physical means (for example by application of an electric or magnetic field) or mechanical means (for example during the application of the coating using one-way applicator such as a micro-nozzle) in at least one area of the enamel layer.

The support and the anisotropic particles are as defined above.

1. a) la fourniture du support ;
2. b) l'application par pulvérisation sur l'une des faces du support d'au moins une composition d'émail dans laquelle sont dispersées des particules anisotropes comprenant des particules magnétisables ;
3. c) l'orientation par aimantation des particules magnétisables en appliquant un champ magnétique, l'aimantation c) étant réalisée soit au cours de l'application b) de la composition d'émail sur le support, soit immédiatement après ladite étape d'application b) ; puis
4. d) de manière optionnelle une étape de séchage, de préférence à une température comprise entre la température ambiante et 150°C, suivie
5. e) d'une cuisson réalisée à une température d'au moins 500°C.

Advantageously, the method according to the invention may comprise the following steps:

1. a) the provision of the medium;
2. b) the application by spraying on one of the faces of the support of at least one enamel composition in which are dispersed anisotropic particles comprising magnetizable particles;
3. c) the orientation by magnetization of the magnetizable particles by applying a magnetic field, the magnetization c) being carried out either during the application b) of the enamel composition on the support, or immediately after the said application step b); then
4. d) optionally a drying step, preferably at a temperature between room temperature and 150°C, followed
5. e) firing carried out at a temperature of at least 500°C.

The magnetizable particles are as defined above.

In this embodiment of the method according to the invention, magnetizable particles of anisotropic shape are used: step d) of orientation of the magnetizable particles is therefore a magnetization step carried out by application of a magnetic field, which is carried out either during the application of the enamel composition, or after this application step d), but in any event prior to the baking step e).

After drying and curing, a protective coating is obtained which simultaneously exhibits high resistance to chipping and impact and homogeneous thermal expansion throughout the coating.

• b1) la pulvérisation sur l'une des faces du support d'une composition d'émail de sous-couche exempte de particules magnétisables, ladite composition d'émail étant transparente ou colorée pour former une sous-couche non cuite ; puis
• b2) la pulvérisation sur cette sous-couche non cuite d'au moins une composition d'émail de finition dans laquelle sont dispersées des particules magnétisables, pour former une couche d'émail de finition non cuite.

In this embodiment of the method according to the invention in which the anisotropic particles are magnetizable and oriented by magnetization, step b) of applying the enamel layer can advantageously comprise the following sub-steps:

• b1) the spraying on one of the faces of the support of an undercoat enamel composition free of magnetizable particles, said enamel composition being transparent or colored to form an unfired undercoat; then
• b2) the spraying on this unbaked underlayer of at least one finishing enamel composition in which magnetizable particles are dispersed, to form an unbaked finishing enamel layer.

Preferably, step b) of applying the enamel layer may further comprise, after step b2) but prior to firing e), a step b3) of spraying on the non baked of at least a second finish enamel composition in which are also dispersed magnetizable particles, to form a second layer of unbaked finish enamel.

Finally, the method according to the invention may further comprise, after carrying out a drying step d) of the finished enamel layer(s) formed (the drying step then no longer being optional but necessary for this embodiment), a step of application by screen printing on said finishing enamel layer of a layer of enamel paste, which may or may not include rounded fillers.

These rounded charges (or balls) are as defined above.

• la figure 1 représente une vue schématique en coupe d'une portion de support d'article conforme à l'invention selon une première variante de réalisation ;
• la figure 2 représente une vue schématique en coupe d'une portion de support d'article conforme à l'invention selon une deuxième variante de réalisation (montrant deux sous-variantes 2a et 2b) ;
• la figure 3 représente une vue schématique en coupe d'une portion de support d'article conforme à l'invention selon une troisième variante de réalisation (montrant deux sous-variantes 3a et 3b) ;
• la figure 4 représente une vue schématique en coupe d'une portion de support d'article conforme à l'invention selon une quatrième variante de réalisation ;
• la figure 5 représente une vue schématique en coupe d'une portion de support d'article conforme à l'invention selon une cinquième variante de réalisation (montrant quatre sous-variantes 5a à 5d) ;
• la figure 6 représente une vue schématique en coupe d'une portion de support d'article culinaire conforme à l'invention selon une sixième variante de réalisation ;
• la figure 7 représente une vue schématique en coupe d'une portion de semelle de fer à repasser conforme à l'invention selon une septième variante de réalisation ;
• la figure 8 représente une vue de dessous de la semelle de fer à repasser représentée sur la figure 7 ;
• la figure 9 représente une vue schématique en coupe de la disposition des aimants sous un support d'article revêtu pour réaliser l'étape d'aimantation ;
• la figure 10 est une vue détaillée de la figure 9 au niveau de la zone Z (définie par les bords de deux aimants et l'entrefer) ;
• la figure 11 est une vue de dessus (photographie) d'une portion de semelle d'un fer à repasser sous laquelle on a disposé des aimants permanents sous forme de bandes à contour triangulaire ;
• la figure 12 est une vue détaillée de la figure 1 au niveau d'une zone spécifique Z (définie par les bords de deux aimants et l'entrefer) ;
• la figure 13 représente une série de trois images 13a à 13c de microscopie électronique à balayage (MEB) d'une coupe de semelle de fer à repasser figure 3 réalisées au niveau de la zone spécifique Z.

Other advantages and features of the present invention will result from the following description, given by way of non-limiting example and made with reference to the appended figures:

• the figure 1 shows a schematic sectional view of an article support portion according to the invention according to a first variant embodiment;
• the figure 2 represents a schematic sectional view of an article support portion according to the invention according to a second variant embodiment (showing two sub-variants 2a and 2b);
• the picture 3 shows a schematic sectional view of an article support portion according to the invention according to a third variant embodiment (showing two sub-variants 3a and 3b);
• the figure 4 shows a schematic sectional view of an article support portion according to the invention according to a fourth variant embodiment;
• the figure 5 represents a schematic sectional view of an article support portion according to the invention according to a fifth variant embodiment (showing four sub-variants 5a to 5d);
• the figure 6 shows a schematic sectional view of a cooking utensil support portion according to the invention according to a sixth variant embodiment;
• the figure 7 shows a schematic cross-sectional view of a portion of an iron soleplate according to the invention according to a seventh variant embodiment;
• the figure 8 shows a bottom view of the iron soleplate shown on the figure 7 ;
• the figure 9 shows a schematic sectional view of the arrangement of the magnets under a coated article support to carry out the magnetization step;
• the figure 10 is a detailed view of the figure 9 at the level of zone Z (defined by the edges of two magnets and the air gap);
• the figure 11 is a top view (photograph) of a sole portion of an iron under which permanent magnets have been placed in the form of strips with a triangular outline;
• the figure 12 is a detailed view of the figure 1 at the level of a specific zone Z (defined by the edges of two magnets and the air gap);
• the figure 13 shows a series of three scanning electron microscopy (SEM) images 13a to 13c of an iron soleplate section picture 3 carried out at the level of the specific zone Z.

On the figure 1 , there is shown an article support portion according to the invention according to a first variant embodiment. One of the faces 21 of the support 2 is provided with a continuous and monolayer film 31 of an enamel coating in which particles of anisotropic shape 4, 41 are dispersed.

The figure 1 shows that the film 31 comprises at least one zone 5 in which the particles of anisotropic shape 41 are essentially perpendicular to the film 31.

This specific orientation of the anisotropic particles 41 in the zone 5 can for example be obtained by magnetization if the anisotropic particles 4, 41 comprise magnetizable particles. In practice, the procedure is as follows: there is placed under the support 2, on the side of the uncoated face 22, a permanent magnet, in particular of the elastomer type (which limits the magnetization conditions to a temperature below 80°C) or an electromagnet. It is also possible to use a permanent magnet of the Ferrite or Neodymium type, or even an electro-induced magnet. In this case, the maximum temperature value of the conditions under which the magnetization takes place can then be greater than 80° C., but must remain below the curie temperature of the magnets used. To obtain a specific holographic image, a magnet having the desired shape will be used, which will be cut and/or machined in a permanent ferromagnetic or electro-induced material.

Preferably, a magnet is used emitting a magnetic field whose intensity is between 40 and 100 mT, and preferably of the order of 70 mT.

The figure 1 clearly shows that the magnetizable particles 41 of the monolayer enamel film 31 are oriented perpendicular to this film in the specific zone 5, according to the field lines produced by the permanent magnet located just below this zone 5.

The figure 2 represents a schematic sectional view of a support portion 2 of an article in accordance with the invention according to a second variant embodiment, showing two sub-variants illustrated respectively on the figures 2a and 2b . The two sub-variants illustrated on the figures 2a and 2b differ from the alternative embodiment illustrated in the figure 1 in that the enamel coating 31 in the form of a film is two-layered.

For the two sub-variants illustrated on the figures 2a and 2b , the two-layer coating 31 comprises a sub-layer 310 placed on one of the faces 21 of the support 2 (free of particles of anisotropic shape) and a finishing layer 311 in the form of a continuous film of enamel covering the underlayer 310, the anisotropic particles 4, 41 being included in the finishing layer 311. The underlayer 310 can be colored, as shown in the figure 2a , or transparent, as shown in figure 2b . The orientation of the anisotropic particles 41 can, in the same way as for the first variant embodiment, be carried out by magnetization if these anisotropic particles 41 comprise magnetic particles.

The picture 3 represents a schematic sectional view of an article support portion according to the invention according to a third variant embodiment, also showing two sub-variants illustrated respectively on the figures 3a and 3b . Each of these sub-variants 3a and 3b differs from the variant embodiments illustrated in the figures 2a and 2b respectively in that the enamel coating 31 further comprises a second finishing layer 312 in which anisotropic particles 4, 41 are also dispersed.

The picture 3 also shows that the two-layer enamel coating 31 of the picture 3 comprises a three-dimensional pattern formed by the alternation of zones 6 with anisotropic particles 4 essentially parallel to the coating 31 and zones 5 with anisotropic particles 41 essentially perpendicular to the film.

Here too, the specific orientation of the anisotropic particles 41 in the zones 5 will be achieved by magnetization if the anisotropic particles are magnetizable.

Thus, in the case of a culinary article whose bottom of the support intended to be coated has a substantially circular shape, this magnetization can for example be achieved by placing under the support (of substantially circular shape), on the side of the face 22 uncoated, a plurality of concentric permanent magnets made of elastomer, which emit a magnetic field of the same intensity or of different intensities, for example of the order of 80 mT measured (s) independently. These concentric magnets can advantageously be in the form of a central disc of small diameter (for example equal to or less than 15 mm) and of a plurality of concentric rings arranged around this central disc with a width of the order from 10 to 15 mm. These magnets can advantageously be arranged on a substrate (for example a stainless steel plate) which can move perpendicularly to the support of the article. This movement can be done by means of a jack which brings the substrate (or plate) close to the article to be magnetized, so as to define an air gap.

In the case of an iron soleplate having a cap of substantially triangular shape intended to be coated, there are for example strips of magnets (for example made of elastomer) under the zones to be reinforced of the support 22, on the side of the face 22 uncoated. These bands can be continuous or discontinuous and have the substantially triangular shape of the cap. They emit a magnetic field of the same intensity or of different intensities, for example of the order of 80 mT measured independently.

The magnetizable anisotropic particles will then orient themselves along the field lines, that is to say perpendicular to the support 2 (or to the film 31) at the level of the zones 5 under which a magnet has been placed (the field lines being perpendicular to the enamel coating 31, and parallel to the support 2 (and therefore to the coating 31) in the zones 6 where the field lines are parallel to the support 2, with a continuum of progressive orientation of the magnetizable anisotropic particles between these two zones.

The figure 4 shows a schematic sectional view of an article support portion according to the invention according to a fourth embodiment variant, which differs from the sub-variant embodiment illustrated in the figure 2a , in that the sub-layer 310 comprises anisotropic particles 4, 41. As for the third alternative embodiment illustrated in the figures 3a and 3b , the two-layer enamel coating 31 of the picture 3 comprises a three-dimensional pattern formed by the alternation of zones 6 with anisotropic particles 4 essentially parallel to the coating 31, and zones 5 with anisotropic particles 41 essentially perpendicular to the film. If the anisotropic particles 41 include or are magnetic particles, the orientation of the particles in the zones 5 can be obtained by arranging magnets under the support 2.

• ▪ une sous-couche 310 exempte de particules magnétisables 4, 41, et qui est transparente (comme illustré sur les figures 5a et 5b) ou colorée (comme illustré sur les figures 5c et 5d),
• ▪ une couche médiane 313 qui est soit une couche colorée (comme illustrée sur les figures 5b et 5d), soit une couche magnétisable laquelle dans laquelle sont dispersées des particules anisotropes 4, 41 de préférence magnétisables (comme illustrée sur les figures 5a et 5c), la couche médiane 313 étant continue et recouvrant la sous-couche 310.

The figure 5 represents a schematic sectional view of an article support portion according to the invention according to a fifth variant embodiment, showing four sub-variants illustrated respectively on the figures 5a to 5d . These figures show a support 2, one of the faces 21 of which is coated with a layer of enamel 31 comprising:

• ▪ an underlayer 310 free of magnetizable particles 4, 41, and which is transparent (as illustrated in the figures 5a and 5b ) or colored (as shown in the figures 5c and 5d ),
• ▪ a middle layer 313 which is either a colored layer (as illustrated on the figures 5b and 5d ), or a magnetizable layer in which are dispersed anisotropic particles 4, 41 preferably magnetizable (as illustrated on the figures 5a and 5c ), the middle layer 313 being continuous and covering the underlayer 310.

• ▪ une première couche de vernis transparente ou colorée 321, continue et dans laquelle sont dispersées des particules anisotropes 4, 41, qui sont de préférence magnétisables, et
• ▪ une deuxième couche de vernis incolore 322 continue et recouvrant complètement et/ou partiellement la première couche de vernis 321.

The middle layer 313 is itself covered by:

• ▪ a first layer of transparent or colored varnish 321, continuous and in which are dispersed anisotropic particles 4, 41, which are preferably magnetizable, and
• ▪ a second layer of clear varnish 322 continues and completely and/or partially covering the first layer of varnish 321.

Here too, the specific orientation of the anisotropic particles 41 in the zones 5 will be achieved by magnetization if the anisotropic particles are magnetizable.

• ▪ une couche d'émail 31 continue, qui est pigmentée et comporte des particules magnétisables 4, 41,
• ▪ une couche de vernis incolore 32, continue et dans laquelle sont dispersées des particules magnétisables 4, 41, et
• ▪ une couche d'émail externe 33 discontinue, qui est obtenue par sérigraphie ou tampographie, comportant des billes métalliques 34 (en cuivre, en bronze ou en acier réfractaire).

The figure 6 shows a schematic sectional view of a cooking utensil support portion according to the invention according to a sixth variant embodiment. In this variant specific to a culinary item such as a frying pan 1, the support 2 comprises an inner face 22 which is the face facing the side of the food likely to be received in the frying pan 1, and an outer face 21 which is intended to be placed towards an external heat source. The support 2 comprises, on its inner face 22, a non-stick coating 7 (for example in sol-gel material or in fluorocarbon resin), and on its outer face 21 a coating 3 comprising:

• ▪ a continuous layer of enamel 31, which is pigmented and comprises magnetizable particles 4, 41,
• ▪ a layer of colorless varnish 32, continuous and in which are dispersed magnetizable particles 4, 41, and
• ▪ a discontinuous external enamel layer 33, which is obtained by screen printing or pad printing, comprising metal balls 34 (in copper, bronze or refractory steel).

The figure 7 shows a schematic cross-sectional view of a portion of an iron soleplate according to the invention according to a seventh variant embodiment, and the figure 8 represents a bottom view of the sole illustrated on the figure 7 .

In this variant specific to an iron soleplate, the support 2 comprises, on its outer face 21 intended to be in contact with the laundry to be ironed, a coating 3 which is substantially identical to that illustrated on the figure 6 : it differs from it only by the absence of rounded fillers in the discontinuous outer enamel layer 33 .

The figures 9 to 13 are described in more detail in the following examples, which illustrate the invention without limiting its scope.

In these examples, unless otherwise indicated, all the percentages and parts are expressed in mass percentages.

EXAMPLES Chip resistance test

The ability to resist chipping of different protective coatings, of the same thicknesses (between 70 and 80 µm) and applied on identical metallic substrates, is evaluated as follows.

These coatings are subjected to a 10 mm long scratch, which is induced by a calibrated diamond tip 50 µm in diameter, which is applied with a gradually increasing force from 0 to 5 Newtons. For this, a device marketed under the name “ Microscratch tester ” from the company CSM Instruments is used.

After formation of the scratch, the strength from which a peeling of the coating down to the metal is visible is determined under a microscope (see table 9 of results).

Products Brackets

• aluminum alloy cookware holder (e.g. 4917 alloy),
• cap with an aluminum alloy iron soleplate (for example alloy 3003),
• cast iron and sheet steel cookware rack.

Ferromagnetic flakes

• les paillettes de mica enrobées d'oxyde de fer commercialisées par la société ECKART sous la dénomination STAPA TA Ferricon 200 (paillettes magnétisables),
• les paillettes de mica enrobées d'oxyde de fer commercialisées par la société MERCK sous la dénomination Colorona Blackstar blue ou green (paillettes magnétisables),
• les paillettes de mica non enrobées commercialisées par la société MERCK sous la dénomination Iriodin 119 (paillettes non magnétisables).

As ferromagnetic flakes that can be used in the context of the present invention, the following may be used in compositions B1 and V1:

• mica flakes coated with iron oxide marketed by ECKART under the name STAPA TA Ferricon 200 (magnetizable flakes),
• mica flakes coated with iron oxide marketed by the company MERCK under the name Colorona Blackstar blue or green (magnetizable flakes),
• uncoated mica flakes marketed by the company MERCK under the name Iriodin 119 (non-magnetizable flakes).

Expenses

• stainless steel balls.

Compositions

Composition of pigmented B1 enamel slip with magnetizable fillers for aluminum substrate (cookware, aluminum or cast aluminum iron soleplates, etc.).

A slip of enamel frit B1 is prepared, the composition of which is given below in Table 1 below. <u>Table 1</u> B1 Slip Components Quantity (parts by weight) F1 enamel frit 100 Water 45 to 60 Boric acid 0 to 4 Molybdic Acid 0 to 4 Potassium Hydroxide 0 to 2 Carbonate; Silicate or metasilicate of soda 0 to 5 Pigments 0 to 30 Ferromagnetic flakes 0.1 to 10

The contents indicated are parts by weight per 100 parts by weight of frit (reference quantity in the composition of the slip).

The composition of the enamel frit F1 is given in Table 2 below. <u>Table 2</u> Components of the F1 frit Quantity (mass percentages) SiO ₂ 33.8 V ₂ O ₅ 6.31 SbO 3.64 _Na2O 20.42 BaO ₂ 3.7 _K2O 15.23 TiO ₂ 15.21 WO 1.69 Total 100

The contents indicated are mass percentages relative to the weight of the frit.

B2 enamel slip composition for cast iron cookware supports

A slip of enamel frit B2 is prepared, the composition of which is given below in Table 3 below. <u>Table 3</u> B2 slip components Quantity (parts by weight) F2 enamel frit 100 Water 35 to 50 Clay 6 to 9 bentonite 0.1 to 0.4 Boric acid 0.2 to 0.4 Quartz 200 8 to 15 _ZrO2 0 to 2

The contents indicated are parts by weight per 100 parts by weight of frit (reference quantity in the composition of the slip).

The composition of the enamel frit F2 is given in Table 4 below. <u>Table 4</u> Components of the F2 frit Quantity (mass percentages) SiO ₂ 50-60% Al ₂ O ₃ 5-15% _{B2O3 _} 8-14% _Na2O 6-12% CaO 3-7% ZnO 3-5% CoO 0-4% _MnO2 0-4% NiO 0-4% Total 100%

The contents indicated are mass percentages relative to the weight of the frit.

Varnish composition V1 pigmented with magnetizable fillers

A varnish composition V1 is prepared, the composition of which is given below in Table 5 below. <u>Table 5</u> Varnish Components V1 Quantities (parts by weight) Enamel Frit F 100 Water 40 to 60 Carbomethylcellulose 0 to 10 xanthan gum 0 to 10 Ferromagnetic flakes 0.1 to 10

Composition B3 of white enamel coating slip for cast iron (with magnetizable fillers)

A pigmented slurry of B3 enamel frit intended to constitute a white covering enamel is prepared. Its composition is given in Table 6 below. <u>Table 6</u> B3 Slip Components Quantity (parts by weight) F3 enamel frit 100 Water 30 to 55 Clay 6 to 9 bentonite 0.1 to 0.4 Quartz 3 to 6 organic gum 0 to 0.5 Boric acid 0.2 to 0.4 Mineral pigment for tint shade (ex: yellow ZrSiPr, blue CoO.) 0 to 5 Ferromagnetic flakes 0.1 to 7

Table 7 shows the composition of the F3 frit used for the white covering enamel. <u>Table 7</u> Components of the F3 frit Quantity (mass percentages) SiO ₂ 40-50% Al ₂ O ₃ 0-5% TiO ₂ 13-20% _{B2O3 _} 8-14% _Na2O 6-12% K20 3-8% CaO 3-7% ZnO 3-5% MgO 0-2% _{P2O5 _} 0-4% Total 100%

Screen printing paste compositions (with and without rounded fillers)

A first screen-printing paste composition P3 is prepared with fillers, the composition of which is given below in Table 8 below.

A second filler-free P4 screen-printing paste composition is prepared, the composition of which is also given below in Table 8 below. <u>Table 8</u> Components of P3 and P4 screen-printing pastes Quantity (parts by weight) P3 paste with steel balls Quantity (parts by weight) P4 paste without steel balls Frit F 100 100 black iron oxide 20 20 Oil (terpene) 35 35 steel balls 20 0

EXAMPLE 1 Production of a protective coating in accordance with the invention on the external face of a culinary article support made of aluminum alloy.

The slip B1, the composition of which is given in Table 1, is sprayed onto the outer face of the aluminum alloy cookware support, to form an enamel layer 31 (thickness 35 μm). Then, the varnish composition V1, the composition of which is given in Table 5, is applied to this enamel layer 31 to form a varnish layer 32 (thickness 35 μm).

The magnetizable flakes contained in the layers of enamel 31 and varnish 32 are oriented by magnetization in certain areas of the protective coating, immediately after the application of these layers, by application of a magnetic field of 70 mT by means of two permanent magnets 51, 52 arranged under the substrate (in this case under the face of the support opposite to that which is coated), as is schematically illustrated in the figures 9 and 10 . Under the action of the magnetic field, the mica flakes, thanks to their coating of magnetic iron oxide, are oriented along the field lines, i.e. in line with the magnet, and in particular substantially vertically in areas P1 and P2 shown on the figure 9 .

To promote this orientation of the flakes, it is preferable that the viscosity of the layers applied be as low as possible. For this, the introduction of a small quantity of a non-VOC heavy solvent such as hexylene glycol makes it possible to reduce evaporation on spraying and provides a longer application time for the magnets, allowing orientation after spraying. facilitated. Any drying of the enamel layer before to have oriented the magnetic charges. However, the magnets can be applied until the final drying of the coating, to consolidate the orientation. This mode is particularly recommended if you want to obtain a decor with a clear perception of relief.

These layers are then dried at a temperature below 150°C, and preferably between 60 and 80°C, to obtain a dry biscuit on which a P3 enamel paste (comprising steel balls) is applied by screen printing. whose composition is given in Table 8 to form a discontinuous outer layer of enamel 33. Then the article is baked in conventional convection or radiation ovens at 500 to 1000° C. for 5 to 30 minutes in depending on the support to be coated.

• ▪ les paillettes tendent à s'orienter perpendiculairement au support (c'est-à-dire qu'une majorité d'entre elles présentent un angle d'inclinaison par rapport au support compris entre 45 et 90°) à l'endroit où les lignes de champs sont perpendiculaires au support 2, c'est-à-dire dans la zone C, correspondant à la zone 5 (figure 13c),
• ▪ les paillettes tendent à s'orienter parallèlement au support (c'est-à-dire qu'une majorité d'entre elles présentent un angle d'inclinaison par rapport au support inférieur à 20°), à l'endroit où les lignes de champs sont perpendiculaires au support 2 (figure 13b montrant spécifiquement la zone B, correspondant à la zone 6).

The observations of this coating under the Scanning Electron Microscope (SEM) at the level of the Z zone correspond to the SEM images represented in the figure 13 (for the iron soleplate), which show that:

• ▪ the flakes tend to be oriented perpendicular to the support (that is to say that a majority of them have an angle of inclination with respect to the support of between 45 and 90°) at the place where the field lines are perpendicular to support 2, i.e. in zone C, corresponding to zone 5 ( figure 13c ),
• ▪ the flakes tend to be oriented parallel to the support (that is to say that a majority of them have an angle of inclination with respect to the support of less than 20°), at the place where the lines of fields are perpendicular to the support 2 ( figure 13b specifically showing zone B, corresponding to zone 6).

EXAMPLE 2 Production of a protective coating in accordance with the invention on the cap of an iron soleplate.

The same coating as in Example 1 is applied to the cap of the iron soleplate, except for the absence of steel balls in the outer layer of enamel (this outer layer of enamel being obtained from P4 silkscreen paste without steel balls).

The orientation of the magnetizable particles is carried out, as for example 1, by applying a magnetic field of 70 mT by means of two permanent magnets 51, 52 arranged under the substrate (in this case under the face of the support opposite to that which is clothed), as shown schematically on the figures 9 and 10 and really on the figure 11 . Under the action of the magnetic field, the mica flakes, thanks to their coating of magnetic iron oxide, are oriented along the field lines, i.e. in line with the magnet substantially vertically (zone C) .

The observations of this coating with the Scanning Electron Microscope (SEM) at the level of the zone Z are represented by the SEM images represented at the figure 13 (figures 13a to 13c showing areas A to C respectively).

• ▪ la zone C (correspondant à la référence 5 sur les figures 1 à 7), qui est la zone entre les deux aimants 51 et 52 où les lignes de champs magnétiques sont perpendiculaires au support, est une zone de couleur noire, car on ne perçoit que peu, voire pas du tout le reflet des particules magnétisables (du fait de leur position verticale par rapport au support) ;
• ▪ la zone B (correspondant à la référence 6 sur les figures 1 à 7), qui est située au bord de l'aimant 51 à l'endroit où les lignes de champs sont parallèles au support, est une zone claire et brillante, car c'est dans cette zone que le reflet des particules magnétisables est le plus intense ;
• ▪ la zone A, qui est essentiellement définie comme la partie centrale de l'aimant 51, présente une brillance moyenne (comprise entre celle observée dans la zone B et celle observée dans la zone C), car les particules magnétisables sont orientées par rapport au support d'un angle intermédiaire (supérieur à 20° mais moindre que celui observé dans la zone C).

The observation of this coating under an optical microscope at the level of zone Z are represented on the figure 12 , where it is possible to view the succession of the different zones A, B and C. In this figure:

• ▪ zone C (corresponding to reference 5 on the figures 1 to 7 ), which is the zone between the two magnets 51 and 52 where the lines of magnetic fields are perpendicular to the support, is a black zone, because one perceives only little, if at all, the reflection of the magnetizable particles (because their vertical position relative to the support);
• ▪ zone B (corresponding to reference 6 on the figures 1 to 7 ), which is located at the edge of the magnet 51 at the place where the field lines are parallel to the support, is a clear and brilliant zone, because it is in this zone that the reflection of the magnetizable particles is the most intense ;
• ▪ zone A, which is essentially defined as the central part of magnet 51, has an average brightness (between that observed in zone B and that observed in zone C), because the magnetizable particles are oriented with respect to the support of an intermediate angle (greater than 20° but less than that observed in zone C).

EXAMPLE 3 Production of a protective coating in accordance with the invention on the internal and/or external face of a cookware support made of cast iron.

This item will generally be treated in 2 coats with 2 firings.

A first coat of enamel slip B2 (see Tables 3 and 4) which is generally opaque, is applied by spraying to the interior and exterior wall of a cast iron cookware support previously shot-blasted and degreased. This layer will be baked between 800°C and 850°C for 4 to 12 minutes.

Note that it is possible from the first layer to use ferromagnetic flakes: if this is the case, their orientation will be facilitated if the magnets are applied when the enamel is still liquid, ie before drying and firing. Drying will maintain the orientation of the flakes subjected to the magnetic fields of the magnets.

After baking and cooling the enamelled article with a first layer, the coating enamel slip B3 is applied.

The thickness of this second layer will be 100 to 200 μm. This layer will make it possible to obtain the mechanical reinforcement linked to the orientation of the flakes during the application of the magnetic field. This step will be favored and facilitated when the enamel slip is still liquid (promoted mobility). This second firing will take place between 750°C and 820°C for 4 to 12 minutes.

It will be noted that the enamels described above in the case of cast steel metals for culinary applications or small household appliances can be applied either inside the article or outside the article. Their reinforcement of the mechanical properties can take place inside the article (multiple contact with utensils: whisk, knife, spatula...) or outside the article (cooking plate, sink, grid of oven...).

The coating described above shows a significant improvement over the same coating lacking oriented magnetizable flakes in slip B3. The optimization of the resistance to chipping is beneficial for example by the impact of a metal utensil during conventional use.

An increase in resistance is observable by a non-standard test using a 300 g hammer falling from a height of 15 cm in less than 1 second on the surface of the enameled cast iron article. The impact takes place without flaking in the case of the slip loaded with flakes, whereas one is observed in the absence of flakes.

COMPARATIVE EXAMPLE 4 Production of a protective coating on the outer face of an iron soleplate free of magnetizable particles.

In the same way as in Example 2, a protective coating is produced comprising a layer of enamel 31, on which is deposited a layer of varnish 32, then a layer of serigraphic enamel 33. The protective coating of comparative example 4 differs from that of example 1 by the absence of magnetizable flakes in the layers of enamel 31, varnish 32, and screen-printed enamel layer 33.

EXAMPLE 5: Evaluation of resistance to chipping on an aluminum cookware

The ability to resist chipping of the protective coatings of Examples 1 and 2 in areas B and C, as well as in Comparative Example 4 (no particular area because no magnetization) is evaluated in accordance with the test previously indicated. The results obtained are shown in Table 9 below. <u>Table 9</u> Coating thickness (in µm) Metal delamination (in N) Example 1 (with oriented spangles) Measurement carried out at the level of a zone C 70-80µm 27.22 ± 1.41 Example 1 (with non-oriented flakes) Measurement carried out at the level of a zone B 70-80µm 21.39 ± 0.76 Example 2 (with oriented flakes) Measurement carried out at the level of zone C on the figures 11 and 12 70-80µm 26.79 ± 1.33 Example 2 (with non-oriented flakes) Measurement carried out at the level of zone B on the figures 11 and 12 70-80µm 21.76 ± 0.82 Comparative Example 4 (without flakes) 70-80µm 23.04 ± 0.44

The delamination values indicated in table 9 correspond to an average metal chipping value for 4 measurements per sample.

The comparison of the delamination value measured at the level of zone B of example 1 or 2 with that of comparative example 4 shows that the force to be applied during the test to obtain delamination to the metal is lower when the particles are oriented parallel to the coating, only if there are no magnetizable flakes, because horizontal flakes are likely to facilitate delamination.

The comparison of the delamination value measured at the level of zone C of example 1 or 2 with that measured at the level of zone B of the same example clearly shows that the force to be applied during the test to obtain delamination to the metal is greater when the particles are oriented perpendicular to the coating, than when they are parallel, which means that the chipping resistance is better when the coating comprises oriented particles. In this case, they have a reinforcing role.

Claims (15)

1. A heating article (1) characterized in that it comprises a support (2) having two opposite sides (21, 22), at least one (21) of which is covered with a protective coating (3),
   characterized in that said protective coating (3) comprises at least one enamel layer (31) in film form in which anisotropically shaped particles (4, 41) are dispersed, said layer comprising at least one zone (5) in which said anisotropic particles (4, 41) substantially comprise particles whose axis along the largest dimension is perpendicular (41) to the support (2).
2. The article as claimed in claim 1, wherein said particles (4, 41) represent 0.05 to 10% by weight based on the total weight of the enamel layer (31).
3. The article as claimed in any one of claims 1 to 2, wherein said particles (4, 41) comprise mechanically or physically orientable particles (41).
4. The article as claimed in claim 3, wherein said orientable particles (41) are magnetizable particles.
5. The article as claimed in claim 4, wherein said magnetizable particles (41) comprise at least one ferromagnetic metal.
6. The article as claimed in one of claims 4 or 5, wherein said enamel layer (31) further comprises non-magnetizable particles.
7. The article as claimed in any one of claims 1 to 6, further comprising, adjacent to the zone (5), at least one zone (6) in which the anisotropically shaped particles (4) are arranged randomly or substantially parallel to the enamel layer (31).
8. The article as claimed in claim 7, wherein the alternating zones (5) and (6) define a decoration.
9. The article as claimed in any one of claims 4 to 8, wherein the enamel layer (31) comprises:

   - an undercoat (310), transparent or colored, and free of magnetizable particles (41), which is continuous and is intended to be arranged on a support, and

   - at least one topcoat (311) in which the magnetizable particles (41) are dispersed, said topcoat (311) being continuous and partially or completely covering said undercoat (310).
10. The article as claimed in any one of claims 4 to 8, wherein the enamel layer (31) comprises:

    - a colored undercoat (310), in which magnetizable particles (41) are dispersed, said undercoat (310) being continuous and intended to be arranged on a support, and

    - at least one transparent topcoat (311), in which magnetizable particles (41) are also dispersed, said topcoat (311) being continuous and partially or completely covering said undercoat (310).
11. The article as claimed in any one of claims 1 to 10, characterized in that the support (2) is made of a material selected from metals, glass, and ceramics.
12. The article as claimed in any one of the preceding claims, which is a culinary article, or a heating lid, or a heating mixing bowl of a food or beverage preparation appliance, or a soleplate of an iron, a table article such as a table mat, or a radiator, or a towel holder or a wood stove, or a barbecue plate, or a barbecue housing or pan.
13. A process for producing, on a support (2) of a heating article (1) according to any one of claims 1-12, a protective coating (3) comprising at least one enamel layer (31) in which anisotropically shaped particles (4, 41) are dispersed,
    characterized in that said process comprises a step of orienting said anisotropic particles (41) by physical or mechanical means in at least one zone (5) of the enamel layer (31).
14. The process as claimed in claim 13, comprising the following steps:

    a) providing the support (2);

    b) applying by spraying onto one side of the support (2) at least one enamel composition in which anisotropic particles comprising magnetizable particles (41) are dispersed;

    c) orienting by magnetization said magnetizable particles (41) by applying a magnetic field so as to orient the axis along the largest dimension of the magnetizable particles perpendicularly to the support (2), said magnetization c) being carried out either during the application b) of the enamel composition to the support or immediately after said application step b); then

    d) optionally, a drying step, preferably at a temperature comprised between room temperature and 150°C, followed by

    e) firing at a temperature of at least 500°C.
15. The process as claimed in claim 14, wherein step b) of applying comprises:

    - b1) spraying onto one side of the support (2) an undercoat enamel composition free of magnetizable particles, said enamel composition being transparent or colored to form an unfired undercoat (310); then

    - b2) spraying onto said unfired undercoat (310) at least one topcoat enamel composition in which magnetizable particles (41) are dispersed, to form an unfired topcoat enamel (311).

Images