WO2014091166A2

WO2014091166A2 - Enamel coating comprising anisotropic particles and cooking item provided with such a coating

Info

Publication number: WO2014091166A2
Application number: PCT/FR2013/053054
Authority: WO
Inventors: Aurélien BERRUX; Michel Fontaine; Jean-Luc Perillon
Original assignee: Seb Sa
Priority date: 2012-12-12
Filing date: 2013-12-12
Publication date: 2014-06-19
Also published as: CN104854261B; EP2931940B1; CN104854261A; KR20150096476A; WO2014091166A3; JP2016501087A; EP2931940A2; KR102174186B1; FR2999171B1; JP6272898B2; FR2999171A1

Abstract

The invention relates to a protective coating including at least one layer of enamel (31), in which particles having an anisotropic shape (4) are dispersed, said layer including at least one area (5) in which said anisotropic particles (4) essentially include particles (41) that are perpendicular to the layer of enamel (31) in film form. The invention also relates to an item, for example a cooking item, including such a coating, and to a method for applying such a coating to a substrate.

Description

ENAMEL COATING COMPRISING ANISOTROPIC PARTICLES AND CULINARY ARTICLE PROVIDED WITH SUCH COATING

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

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

The target area is in the first place that of heating articles.

For the purposes of the present invention, a heating article is understood to mean an article which has its own heating system, or an article which is heated by an external system and which is capable of transmitting the heat energy brought by this system to a heating system. material or object third party in contact with said article, or an article which is intended to receive another previously heated article.

As examples of heating articles that can be used according to the present invention, mention may in particular be made of culinary articles (such as frying pans, saucepans, woks, pancakes, casseroles, pots, casseroles, etc.) or lids. heating and mixing bowls heating food preparation apparatus or beverage. But the present invention may also relate to any other type of surface and articles, such as tableware such as trivets, soles of an iron, curling irons, and straightening irons, radiators, towel racks or wood stoves, or barbecue plates, barbecue chests or barbecue vats, flat heating hoods.

Enamelled coatings are particularly popular in the field of heating articles, particularly culinary, and in that of irons, and more specifically iron soles.

In the case of iron soles, the tribological, thermal and physicochemical properties of the coating are paramount to ensure ease of ironing. An enamel coating is therefore an ideal compromise to coat the metal cap of an iron soleplate because it has a good thermal resistance, a low coefficient of friction that changes little with temperature, a hydrophilic behavior and resistance to wear. hydrolysis. The disadvantage of enamelled coatings for ironing applications (including steam irons, dry irons and steam plants) lies in their low impact resistance. Indeed, it may appear at the edge coated with the enameled cap (and more particularly on the periphery of the coated cap), small pieces of enamel, especially if the coating is subjected to shocks caused by handling. Small pieces of enamel may also appear by repeated contact on metal parts attached to the ironing textiles (buttonholes, snaps, zippers ...).

Enamel coatings are also particularly popular in the field of cookware because they provide colored coatings which not only have good dishwasher resistance, high flame and scratch resistance, but also decorative primordial, often decisive in the choice of the consumer. However, they have the disadvantage of flaking easily in some particularly sensitive areas, which are areas of high stress of the culinary article. These areas are generally located in the curvature areas of the article or in the connection areas with the handle or handles.

As a sensitive zone, there may be mentioned, for a culinary article, 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 and flat edge, or the area supporting the grip of the handle (because it may undergo deformation subsequent to the welding of the fastener), the bottom that contacts the grates of the burners. In addition, the enamelled 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 uniform thermal expansion, otherwise it generates microcracks that interfere with the behavior in the dishwasher.

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

By particles essentially perpendicular to the coating is meant, in the sense of the present invention, particles which are predominantly inclined at an angle of between 20 ° and 90 °, preferably between 45 and 90 °, and preferably between 60 and 90 ° with respect 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, French patents FR2472596 and FR813737 describe enamelled coatings for cookware, in which mica or mother-of-pearl flakes are incorporated in an enamelled coating.

Furthermore, the international application WO 2011/42886 and US Pat. No. 3,480,461 relate to the decoration of an iron soleplate using an enamelled coating comprising pigments or fillers.

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

More particularly, the present invention relates to 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 E-mail wherein particles of anisotropic form are dispersed, the enamel layer comprising at least one zone in which the anisotropic particles are substantially perpendicular to the film enamel layer.

The particles of anisotropic form can advantageously represent 0.05 to 10%, preferably 0.1 to 7%, and more preferably 1 to 5% by weight of the total weight of the enamel layer. Ideally, the particles of anisotropic form represent 2 to 3% by weight of the total weight of the enamel layer (31).

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

By particles of anisotropic shape, the meaning of the present invention is understood to mean 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 in the sense of the present invention, particles that are predominantly inclined at an angle 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 substantially perpendicular to the coating layer may, for example, result from positioning related to the coating application process, such as, for example the orientation through a monodirectional applicator as a micro ^¬ nozzle.

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

For the purposes of the present invention, the term "magnetizable particles" means particles capable of being oriented under the effect of a magnetic field.

Magnetizable particles can be of different natures.

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

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

As examples of composite magnetizable particles, particular mention may be made of mica flakes coated with a ferromagnetic material, such as, for example, mica flakes coated with a ferrite of the form (MO, Fe 2 O 3) 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 having ferromagnetic properties may also be used: mention may be made, for example, of cobalt, nickel, or Heussler alloy consisting solely of non-ferromagnetic metals (61% Cu, 24% Mn, 15% Al) , or some rare earths such as lanthanides, copper-manganese oxides and aluminum.

The advantage of coated mica flakes lies in the fact that they are particularly resistant to the high firing temperature of metal enamels, ie temperatures ranging from 550 ° C for enamels on aluminum to 850 ° C for enamels on steel or cast iron. In addition, these flakes made of mica offer better resistance to the alkalinity of the enamel slip 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 may further advantageously comprise non-magnetizable particles to improve the reinforcement of the coating.

For the purposes of the present invention, non-magnetizable particles are understood to mean non-magnetizable or weakly magnetizable particles having a zero or low magnetic moment (less than 1 emu / g).

These non-magnetizable particles may be of any shape (spherical, fiber or flake or

"Irregular"), of micrometric size, or even nanometric.

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

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

By particles essentially parallel to the enamelled coating layer is meant in the sense of the present invention, particles that are predominantly inclined at an angle between 0 ° and 20 ° with respect to the coating layer.

The alternation of areas in which the particles are arranged substantially parallel and / or random to the enamel layer and areas in which the particles are substantially perpendicular to the layer enamel allows to define a decoration, which can be perceived by the user as a three-dimensional decoration.

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 and intended to be arranged on a support.

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

a transparent undercoat free of magnetizable particles, which is continuous and is intended to be placed on a support, and

a finishing layer in which the magnetizable particles are dispersed, the finishing layer being continuous and partially or completely covering the underlayer.

For the purposes of the present invention, a finishing layer is intended to mean a layer which is intended to be in contact with the environment.

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

a colored and magnetisable particle-free undercoat, which is continuous and is intended to be arranged on a support, and

a topcoat in which the magnetizable particles are dispersed, the finishing layer being continuous and partially or completely covering the underlayer.

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

a transparent or colored undercoat and free of magnetizable particles, the underlayer being continuous and intended to be arranged on a support,

a first finishing layer in which magnetizable particles are dispersed, the first layer of finish being continuous and completely covering the underlayer, and

a second topcoat in which magnetizable particles are also dispersed, the second topcoat being continuous and partially or completely covering the first topcoat

According to a fifth particularly advantageous embodiment of the present invention, the enamel layer of the protective coating according to the invention can 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 topcoat, in which are also dispersed magnetizable particles, the topcoat is 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 embodiments with at least two layers (second to fifth embodiments), the sub-layer may have a thickness of between 5 and 30 μιη, and the finishing layer or layers may have a thickness of between between 20 and 60 μη.

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

an enamel layer comprising:

^■ a sub-layer free of magnetisable particles and is transparent or colored, this sub-layer being continuous and adapted to be disposed on a support, and

^■ at least one middle layer (313) which is either a colored layer, a magnetizable layer which in which are dispersed magnetizable particles (41), said middle layer (313) being continuous and covering partially or completely said underlayer (310), and

a first layer of magnetizable varnish, continuous and in which are dispersed magnetizable particles, this first layer of varnish partially or completely covering the enamel middle layer, and

- A second coat of clear, non-magnetizable, clear and continuous varnish completely covers the first layer of magnetizable varnish, so as to ensure chemical resistance and hold in the dishwasher.

Advantageously, for this sixth embodiment, the sub-layer may have a thickness of between 5 and 30 μιη, the middle enamel layer may have a thickness of between 20 and 60 μη. As regards the lacquer layers covering the enamel middle layer, the magnetizable lacquer layer may advantageously have a thickness of between 15 and 40 μτ, and the protective lacquer layer may have a thickness of between 10 and 20 μη.

For all of these embodiments, a colored layer (whether it is an underlayer, a topcoat or a layer of varnish) is understood to mean the present invention. a layer comprising at least one opaque pigment chosen from thermostable pigments, for example spinels, ceramic pigments, oxides, organometallics such as ultramarine blue, micaceous or siliceous flake pigments (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 furthermore comprise a discontinuous outer enamel layer, which is screen printed or padprinted.

In the case where the heating article according to the invention is a culinary article, the outer layer of enamel can also comprise rounded charges, which are advantageously spherical with a diameter of between 5 and 40 μιη, and preferably between 15 and 20 μιτι, the thickness of the outer layer (32) varying between 10 and 30 μιη. These beads protrude from the surface of the outer layer of enamel.

As rounded fillers (or balls) used in the outer enamel layer according to the invention include stainless steel balls, copper, bronze or refractory steel.

Preferably, stainless steel balls are used.

The rounded fillers are advantageously present in the outer layer of enamel in a proportion of 1 to 5% by weight relative to the total weight of the outer layer. These rounded loads make it possible both to increase the wear resistance of the enamel coating and to reduce (when the loads 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 hob and the lesser hardness of the beads compared to that of the enamel layer. Thus, the coating is easily cleaned and does not present a risk of scratching sensitive surfaces such as glass-ceramic or induction plates.

Regarding the nature of the support of the article, it can be made of a material selected from metals, glass and ceramics.

As metal supports according to the invention, there may be mentioned supports having a structure:

- monolayer aluminum, or polished, brushed or micro-blasted aluminum alloy, sandblasted, chemically treated, or cast aluminum, or polished, brushed or micro-blasted stainless steel, or cast iron or aluminum,

or a multilayer metal support, in part or in whole, comprising from outside to inside the following layers ferritic stainless steel / aluminum / austenitic stainless steel or stainless steel / aluminum / copper / aluminum / austenitic stainless steel, or another aluminum casting cap, 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 culinary articles, heating lids or hot mixing bowls of apparatus for preparing food or drink, or iron soles, tableware such as trivets, radiators or wood-burning stoves, curling irons, hair straighteners, towel rails or barbecue plates, barbecue chests or bowls, barbecue.

Finally, the subject of the present invention is also a method of manufacturing, on a heating article support, a coating comprising at least one enamel layer in which particles of anisotropic form are dispersed, characterized in that comprises a step of orienting said anisotropic particles by a physical means (for example by applying an electric or magnetic field) or mechanically (for example during the application of the coating using a monodirectional applicator such as a ^micro¬¬ nozzle) in at least one zone of the enamel layer.

The support and the anisotropic particles are as defined above.

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

a) the supply of support;

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;

c) the magnetization orientation 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 said applying step b); then

d) optionally a drying step, preferably at a temperature between room temperature and 150 ° C, followed (e) cooking at a temperature of not less than

500 ° C.

The magnetizable particles are as defined above.

In this embodiment of the process according to the invention, particles of magnetizable anisotropic form 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 performed either during the application of the enamel composition, or after this application step d), but in any case prior to step e) cooking.

After drying and baking, a protective coating is obtained which simultaneously has a high resistance to chipping and shocks and a homogeneous thermal expansion throughout the coating.

In this embodiment of the process according to the invention in which the anisotropic particles are magnetizable and oriented by magnetization, the step b) of applying the enamel layer may advantageously comprise the following substeps:

bl) spraying on one of the faces of the support a sub-layer enamel composition free of magnetizable particles, said enamel composition being transparent or colored to form an uncured underlayer; then

- b2) spraying on this uncured underlayer of at least one finishing enamel composition in which are dispersed magnetizable particles, to form an uncured enamel finish layer.

Preferably, the step b) of applying the enamel layer may further comprise after step b2) but before cooking e), a step b3) of spraying on the non-enamel finish layer. baking at least a second finishing enamel composition in which magnetizable particles are also dispersed to form a second uncovered enamel coating layer (312).

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

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

Other advantages and features of the present invention will result from the description which follows, given by way of nonlimiting example and with reference to the appended figures:

Figure 1 shows a schematic sectional view of an article support portion according to the invention according to a first embodiment;

FIG. 2 represents a schematic sectional view of an article support portion according to the invention according to a second variant embodiment (showing two subvariants 2a and 2b);

FIG. 3 represents a schematic sectional view of an article support portion according to the invention according to a third variant embodiment (showing two subvariants 3a and 3b);

FIG. 4 represents a schematic sectional view of an article support portion according to the invention according to a fourth variant embodiment;

- Figure 5 shows a schematic sectional view of an article support portion according to the invention according to a fifth embodiment (showing four sub-variants 5a to 5d);

- Figure 6 shows a schematic sectional view of a culinary article support portion according to the invention according to a sixth embodiment; Figure 7 shows a schematic sectional view of a sole portion of iron according to the invention according to a seventh embodiment;

- Figure 8 shows a bottom view of the iron soleplate shown in Figure 7;

Figure 9 shows a schematic sectional view of the arrangement of the magnets under a coated article carrier to perform the magnetization step;

Figure 10 is a detailed view of Figure 9 at the zone Z (defined by the edges of two magnets and the air gap);

- Figure 11 is a top view (photograph) of a sole portion of an iron under which permanent magnets have been arranged in the form of triangular contour strips;

Figure 12 is a detailed view of Figure 1 at a specific area Z (defined by the edges of two magnets and the gap);

FIG. 13 represents a series of three images 13A to 13B of scanning electron microscopy (SEM) of an iron sole plate section 3 made at the level of the specific zone.

Z.

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

FIG. 1 shows that the film 31 comprises at least one zone 5 in which the particles of anisotropic shape 41 are substantially 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 41 comprise magnetizable particles. In practice, we proceed in the same way following: there is placed under the support 2, on the side of the uncoated side 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 type Ferrite or Neodymium, or an electrically-induced magnet. In this case, the maximum temperature value of the conditions in which the magnetization takes place may then be greater than 80 ° C., but must remain below the curie temperature of the magnets used. To obtain a specific holographic image, use will be made of a magnet having the desired shape, which will be cut and / or machined in a permanent or electro-induced ferromagnetic material.

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

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

FIG. 2 represents a schematic cross-sectional view of an article support portion 2 according to the invention according to a second variant embodiment, showing two sub-variants illustrated respectively in FIGS. 2a and 2b. The two-sub-variants illustrated in FIGS. 2a and 2b differ from the variant embodiment illustrated in FIG. 1 in that the enamel coating in the form of film 31 is bilayered.

For the two sub-variants shown in the figures

2a and 2b, the bilayer coating 31 comprises an underlayer 310 disposed 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 41 being included in the topcoat 311. The underlayer 210 may be colored, as shown in Figure 2a, or transparent, as shown in Figure 2b. The orientation of the anisotropic particles 41 may, in the same way as for the first embodiment variant, be made by magnetization if these anisotropic particles 41 comprise magnetic particles.

FIG. 3 represents a schematic sectional view of an article support portion according to the invention according to a third embodiment variant, also showing two sub-variants illustrated respectively in FIGS. 3a) and 3b). Each of these sub-variants 3a) and 3b) differs from the embodiments illustrated in FIGS. 2a and 2b respectively in that the enamel coating 31 bilayer a second topcoat 312 in which anisotropic particles 41 are also dispersed.

FIG. 3 also shows that the two-layer enamel coating of FIG. 3 comprises a three-dimensional pattern formed by alternating zones 6 with anisotropic particles 41 essentially parallel to the coating 31 and zones 5 with essentially perpendicular anisotropic particles 41. 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 elastomer, which emit a magnetic field of the same intensity or different intensities, for example of the order of 80 mT measured independently. These concentric magnets may advantageously be in the form of a central disk of small diameter (for example equal to or less than 15 mm) and a plurality of concentric rings arranged around this central disk of a width of the order from 10 to 15 mm. These magnets can advantageously be arranged on a substrate (for example a stainless steel tray) which can be move perpendicular to the support of the article. This movement can be done by means of a jack which causes the substrate (or plate) close to the article to be magnetized, so as to define a gap.

In the case of an iron soleplate having a substantially triangular shaped cap to be coated, there are for example strips of magnets (for example elastomer under the zones to be reinforced support 22, on the side of the These strips may 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 perpendicularly to the support 2 (or to the film 31) at the zones 5 under which a magnet has been arranged (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.

FIG. 4 represents a schematic sectional view of an article support portion according to the invention according to a fourth variant embodiment, which is different from the sub-variant embodiment illustrated in FIG. 2a, in that the sub-layer 310 comprises anisotropic particles 41. As for the third embodiment illustrated in FIGS. 3a) and 3b), the two-layer enamel coating 31 of FIG. 3 comprises a three-dimensional pattern formed by the alternation of zones 6 with anisotropic particles 41 substantially parallel to the coating 31, and zones 5 with anisotropic particles 41 substantially perpendicular to the film. If the anisotropic particles 41 comprise or are magnetic particles, the orientation of the particles in the zones 5 can be obtained by placing magnets under the support 2.

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

^■ a sublayer 310 free of magnetizable particles 41, and which is transparent (as shown in Figures 5a and 5b) or colored (as shown in Figures 5c and 5d),

^■ a middle layer 313 that is a color layer (as illustrated in Figures 5b and 5d), a magnetizable layer which in which are dispersed particles preferably anisotropic magnetizable 41, the middle layer 313 being continuous and covering the sub layer 310).

The middle layer 313 is itself covered by:

^■ a first layer of transparent or colored varnish 321, continuous and dispersed therein anisotropic particles 41, which are preferably magnetizable and

^■ a second coat of clearcoat 322 continuous and completely and / or partially covering the first layer of varnish 321.

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

^■ an enamel layer 31 continues, which is pigmented and contains magnetizable particles 41,

A layer of clear varnish 32, continuous and in which magnetizable particles 41 are dispersed, and

^■ an outer enamel layer 33 discontinuous, which is obtained by screen printing or pad printing, comprising metallic balls 34 (of copper, bronze or heat resisting steel).

FIG. 7 represents a schematic cross-sectional view of a sole portion of an iron according to the invention according to a seventh embodiment variant, and FIG. 8 represents a bottom view of the soleplate illustrated in FIG. 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 in Figure 6: it does not It differs only in the absence of rounded charges in the discontinuous outer enamel layer 33.

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

In these examples, unless otherwise indicated, all percentages and parts are expressed in percentages by weight.

EXAMPLES

Chipping Resistance Test The ability to resist scaling of different protective coatings of the same thickness (between 70 and 80 μιη) and applied to identical metal substrates is evaluated as follows. These coatings are subjected to a scratch of 10 mm in length, which is induced by a calibrated diamond tip of 50 μm in diameter, which is applied with a force gradually increasing from 0 to 5 Newtons. For this, we use a device marketed under the name "Microscratch tester" from CSM Instruments.

After formation of the scratch, it is determined under a microscope from which force a peeling of the coating to the metal is visible (see table 3 of results).

products

brackets

aluminum alloy foodstuff holder (eg alloy 4917),

cap of an iron soleplate made of aluminum alloy (for example alloy 3003),

culinary article holder made of cast iron and sheet steel.

Ferromagnetic flakes

As ferromagnetic flakes that can be used in the context of the present invention, it will be possible to use in compositions Bl and VI:

the mica flakes coated with iron oxide sold by ECKART under the name STAPA TA Ferricon 200 (magnetizable flakes),

the mica flakes coated with iron oxide marketed by MERCK under the name Colorona Blackstar blue or green (magnetizable flakes),

uncoated mica flakes marketed by MERCK under the name Iriodin 119

(non-magnetizable flakes). loads

stainless steel balls. compositions

Porous pigmented Bl enamel slip composition with magnetizable charges for aluminum substrates (culinary articles, insoles of irons made of aluminum or cast aluminum ...).

An enamel frit slip B 1 is prepared, the composition of which is given below in Table 1 below.

Table 1

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

The composition of the enamel frit F1 is given in Table 2 below. Table 2

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

B2 enamel slip composition for cast iron culinary article holders

An enamel frit slip B2 is prepared, the composition of which is given below in Table 3 below.

Table 3

Components of slip B2 Quantity (parts by weight)

Enamel frit F2 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%

Zr0 ₂ 0 to 2% The contents indicated are parts by weight per 100 parts by weight of frit (reference amount in the composition of the slip). The composition of the enamel frit F2 is given in Table 4 below.

Table 4

Varnished VI varnish composition with magnetizable fillers

A varnish composition VI is prepared, the composition of which is given below in Table 5 below. Table 5

B3 white enamel slip composition for cast iron (with magnetizable charges) s

A pigmented enamel frit slip B3 is prepared to form a white cover enamel. Its composition is given in Table 6 below.

Table 6

Table 7 shows the composition of the F3 frit used for the white cover enamel.

Table 7

Silkscreen paste compositions (with and without rounded fillers)

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

A second composition of screen printing paste P4 is prepared with fillers, the composition of which is also given below in Table 8 below. Table 8

EXAMPLE 1 Production of a Protective Coating According to the Invention on the External Face of an Aluminum Alloy Foodstuff Holder

The slurry B1, the composition of which is given in Table 1, is applied by spraying on the outer face of the aluminum alloy culinary support to form an enamel layer 31 (35 μm thick). Then, on this enamel layer 31, the varnish composition VI, the composition of which is given in Table 2, is applied to form a layer of varnish 32 (thickness 35 μιη).

The magnetizable flakes contained in the layers of enamel 31 and varnish 32 are oriented by magnetization in certain zones 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 disposed under the substrate (in this case under the face of the support opposite to that which is coated), as is schematically illustrated in FIGS. 9 and 10. Under the action of the magnetic field, the flakes of mica, thanks to their coating of magnetic iron oxide, are oriented along the field lines, that is to say the right of the magnet, and in particular substantially vertically in the areas P1 and P2 shown in FIG. 9 . To promote this orientation flakes, it is preferable that the viscosity of the layers applied is as low as possible. For this purpose, the introduction of a small amount of a non-VOC heavy solvent such as hexylene glycol makes it possible to reduce the evaporation on spraying and offers a longer duration of application of the magnets, allowing an orientation after easier spray. Avoid any drying of the enamel layer before orienting 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 get 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 is applied by screen printing a P3 enamel paste (comprising steel balls) the composition of which is given in Table 4 to form a discontinuous outer layer of enamel 33. Then the article is baked in conventional convection or radiation furnaces of 500 to 1000 ° C. for 5 to 30 minutes in function of the support to be coated.

The observations of this scanning electron microscope (SEM) coating at zone Z correspond to the SEM images shown in FIG. 13 (for the soleplate of the iron), which show that:

^■ the flakes tend to orient themselves perpendicular to the support (that is to say, a majority of them have an angle of inclination relative to the support between 45 and 90 °) where the field lines are perpendicular to the support 2, that is to say in the zone C, corresponding to the zone 5 (FIG. 13C),

^■ the flakes tend to orient parallel to the support (that is to say, a majority of them have an angle of inclination relative to the lower bracket 20 °), where the lines of fields are perpendicular to the support 2 (Figure 13b specifically showing the zone B, corresponding to the zone 6).

EXAMPLE 2: Production of a protective coating according to the invention on the cap of an iron soleplate.

Is made on the cover of the iron soleplate the same coating as in Example 1, except the absence of steel balls in the outer layer of enamel (this outer layer of enamel being obtained from P4 screen-printing 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 opposite support to that which is coated), as schematically illustrated in Figures 9 and 10 and actually in Figure 11. Under the action of the magnetic field, mica flakes, thanks to their magnetic iron oxide coating, s 'orient according to the field lines, ie to the right of the magnet substantially vertically (zone C).

The observations of this scanning electron microscope (SEM) coating at the zone Z are represented by the SEM images shown in FIG. 13 (FIGS. 13a to 13c respectively showing the zones A to C).

The observation of this coating with an optical microscope at zone Z is shown in FIG. 12, where it is possible to visualize the succession of the different zones A, B and C. In this figure:

^■ zone C (corresponding to reference 5 in Figures 1 to 7), which is the area between the two magnets 51 and 52 where the magnetic field lines are perpendicular to the support, is a black area, since it is perceives that little or no reflection of magnetizable particles (because of their vertical position relative to the support); zone B (corresponding to reference numeral 6 in FIGS. 1 to 7), which is situated at the edge of magnet 51 at the point where the field lines are parallel to the support, is a bright and clear zone, because 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), since the magnetizable particles are oriented relative to the support an intermediate angle (greater than 20 ° but less than that observed in zone C).

EXAMPLE 3: Production of a Protective Coating According to the Invention on the Internal and / or External Face of a Cast Iron Culinary Object Holder

This article will usually be processed in 2 layers with 2 firings.

Spray is applied on the inner and outer wall of a culinary article support cast steel previously blasted and degreased a first layer of glaze enamel B2 (see Tables 5 and 6) generally opaque. This layer will be fired 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, or before drying and baking. Drying will maintain the orientation of the flakes subjected to the magnetic fields of the magnets.

After firing and cooling of the enamelled article of a first layer, the slip of enamel cover 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 related to the orientation of the flakes during the application of the magnetic field. This step will be preferred and facilitated when the slip of enamel is still liquid (favored mobility). This second firing will take place between 750 ° C and 820 ° C for 4 to 12 minutes.

It will be appreciated that the enamels described above in the case of cast iron metals for culinary applications or small household appliances can be applied either within the article or outside the article. Their strengthening of the mechanical properties can take place inside the article (multiple contact with utensils: whip, knife, spatula ...) or outside the article (hob, sink, grill). oven ...).

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

An increase in strength is observable by a non-standard test using a hammer of mass 300 g dropping from a height of 15 cm in less than 1 second on the surface of the enamelled cast iron article. The impact is without peeling in the case of the slush loaded with flakes while one is observed in the absence of flakes.

COMPARATIVE EXAMPLE 4: Production of a Protective Coating on the External Face of an Iron Sole Free of Magnetizable Particles In the same manner as in Example 2, a protective coating comprising an enamel layer 31, on which is deposited a layer of varnish 32, then a layer of screen-printed enamel 33. The protective coating of comparative example 1 differs from that of example 1 in the absence of magnetizable flakes in the layers of enamel 31, varnish 32, and serigraphic enamel layer 33.

EXAMPLE 5 Evaluation of Resistance to Chipping on an Aluminum Culinary Object

The ability to resist peeling of the protective coatings of Example 2 at zones B and C, as well as in Comparative Example 2 (no particular zone because no magnetization) was evaluated according to the test indicated previously. The results obtained are shown in Table 9 below.

Table 9

Thickness of the coating delamination (in μm) metal (in N)

Example 1

(with oriented flakes)

70-80 μπι 27, 22 ± 1.41

Measurement at a level

zone C

Example 1

(with non-oriented flakes)

70-80 μπι 21.39 ± 0.76

Measurement at a level

zone B

Example 2

(with oriented flakes)

70-80 μπι 26,79 ± 1,33 Measured at the level of the

zone C in FIGS. 11 and 12

Example 2

(with non-oriented flakes)

70-80 μπι 21.76 ± 0, 82 Measured at the level of the

zone B in FIGS. 11 and 12

Comparative Example 4

70-80 μπι 23.04 ± 0.44

(without glitter) The delamination values shown in Table 5 correspond to a mean metal flash value for 4 measurements per sample.

The comparison of the delamination value measured at zone B of Example 1 or 2 with that of Comparative Example 2 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, if there is no magnetizable flakes, because horizontal flakes are likely to facilitate delamination.

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

Claims

1. Heating article (1) characterized in that it comprises a support (2) having two opposite faces (21, 22), at least one of which (21) is covered with a protective coating (3),

characterized in that said protective coating (3) comprises at least one enamel layer (31) in which particles of anisotropic form (4) are dispersed, said layer comprising at least one zone (5) in which said anisotropic particles (4) essentially comprise perpendicular particles (41) to the enamel layer (31) in the form of a film.

2. Article according to claim 1, wherein said particles (4) represent 0.05 to 10 by weight relative to the total weight of the enamel layer (31).

3. Article according to claim 2, wherein said particles (4) represent 0.1 to 7% by weight relative to the total weight of the enamel layer (31).

4. Article according to claim 3, wherein said particles represent 1 to 5%, and preferably 2 to 3% by weight of the total weight of the enamel layer (31).

An article according to any one of claims 1 to 4, wherein said particles comprise particles capable of being oriented (41) by mechanical or physical means.

The article of claim 5, wherein said orientable particles (41) are magnetizable particles.

An article according to claim 6, wherein said magnetizable particles (41) comprise at least one ferromagnetic metal.

8. Article according to one of claims 6 or 7, wherein said enamel layer (31) further comprises non-magnetizable particles.

9. Article according to any one of claims 6 to 8, wherein the magnetizable particles (41) and optionally non-magnetizable particles, have a core-envelope structure.

The article of claim 9, wherein the ferromagnetic metal of the magnetizable particles (41) is in the core and / or envelope of said particles (41).

An article according to claim 10, wherein the magnetizable particles (41) are mica flakes coated with iron oxide Fe ₃ O ₄ or Fe ₂ O 3 or FeO.

12. Article according to any one of claims 1 to 11, further comprising, adjacent to the zone (5), at least one zone (6) in which the particles (4) of anisotropic form are arranged in a random manner or essentially parallel to the enamel layer (31).

13. Article according to claim 12, wherein the alternation of the zones (5) and (6) defines a decoration.

14. Article (3) according to any one of claims 6 to 13, wherein the enamel layer (31) comprises:

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

at least one finishing layer (311) in which the magnetizable particles (41) are dispersed, said finishing layer (311) being continuous and partially or completely covering said underlayer (310).

15. Article (3) according to any one of claims 13, wherein the enamel layer (31) comprises:

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

- A topcoat (311) in which are dispersed the magnetizable particles (41), said topcoat (311) being continuous and partially or completely covering said undercoat (310).

16. Article (3) according to any one of claims 13, wherein the enamel layer (31) comprises:

an undercoat (310) that is transparent or colored and free of magnetizable particles (41), said underlayer (310) being continuous and intended to be placed on a support,

a first finishing layer (311) in which magnetizable particles (41) are dispersed, said first finishing layer (311) being continuous and completely covering said underlayer (310), and

a second finishing layer (312) in which magnetizable particles (41) are also dispersed, said second finishing layer (311) being continuous and partially or completely covering said first finishing layer (311).

17. Article (3) according to any one of claims 13, wherein the enamel layer (31) comprises:

a colored underlayer (310) in which magnetizable particles (41) are dispersed, said underlayer (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 sub-layer (310).

18. Article (3) according to any one of claims 17, wherein:

the underlayer (310) has a thickness of between

- The finishing layer or layers (311, 312) have a thickness of between 20 and 60 μιη.

19. Article (3) according to any one of claims 13, wherein:

the enamel layer (31) comprises:

^■ an underlayer (310) free from magnetizable particles (41) and which is transparent or colored, said underlayment (310) being continuous and adapted to be disposed on a support, ■ a central layer (313) which is either a colored layer or a magnetizable layer in which are dispersed magnetizable particles (41), said middle layer (313) being continuous and partially or completely covering said underlayer (310), and

said middle layer (313) is completely or partially covered by:

^■ a first layer of magnetizable varnish (321), continuous and in which are dispersed magnetizable particles (41), and

^■ a second layer of clear and transparent varnish (322), continuous and completely covering said first layer of magnetizable varnish (321).

20. Article (3) according to claim 19, wherein: the underlayer (310) has a thickness between 5 and 30 μιτι,

the middle layer (313) has a thickness of between 20 and 60 μιτι,

the magnetizable lacquer layer (321) has a thickness of between 15 and 40 μm, and the protective varnish layer (322) has a thickness of between 10 and 20 μη.

21. Article (3) according to any one of claims 14 to 20, wherein the enamel layer (31) further comprises a discontinuous outer enamel layer (33), which is screen printed or stamped.

22. Article (3) according to claim 21, wherein the outer layer of enamel (33) comprises rounded charges, which are preferably balls of stainless steel, copper, bronze or refractory steel.

23. Article according to any one of claims 1 22, characterized in that the support (2) is made of a material selected from metals, glass, and ceramics.

24. Article according to claim 23, characterized in that the support (2) is:

a single-layer metal support made of aluminum or polished, brushed or micro-blasted aluminum alloy, sand-blasted, chemically treated, or cast aluminum, or polished, brushed or micro-blasted stainless steel, or cast steel or aluminum ,

or a multilayer metal support, in part or in whole, comprising from outside to inside the following layers ferritic stainless steel / aluminum / austenitic stainless steel or stainless steel / aluminum / copper / aluminum / austenitic stainless steel, or a cap of aluminum foundry, aluminum or aluminum alloys lined with a stainless steel outer bottom.

25. An article according to any one of the preceding claims, which is a culinary article, or a heating lid, or a food blender of a food or beverage preparation apparatus, or an iron soleplate. ironing, a table item such as a table top, or a radiator, or a towel rack or a wood stove, or a barbecue plate, or a chest or a barbecue tub.

26. A method of producing, on a support (2) of a heating article (1), a protective coating (3) comprising at least one layer of enamel (31) in which particles (4) of anisotropic form,

characterized in that said method comprises a step of orienting said anisotropic particles (4) by physical or mechanical means in at least one area (5) of the enamel layer (31).

The method of claim 26, comprising the steps of:

a) providing the support (2);

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

c) the magnetization orientation of said magnetizable particles (41) by applying a magnetic field, said magnetization c) being carried out either during the application b) of the enamel composition on the support, or immediately after said step d application b); then

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

(e) cooking at a temperature of not less than

500 ° C.

The method of claim 27, wherein the applying step b) comprises:

bl) the spraying on one of the faces of the support (2) of a sub-layer enamel composition free of magnetizable particles, said enamel composition being transparent or colored to form an underlayer (310) uncooked ; then b2) spraying said uncured undercoat (310) with at least one finishing enamel composition in which magnetizable particles (41) are dispersed, to form a finishing enamel layer (311); cooked.

The method of claim 28, wherein step b) further comprises between steps b2) and d) of drying or e) cooking, a step b3) of spraying on said finishing enamel layer (311). ) uncured of at least a second finishing enamel composition in which magnetizable particles (41) are also dispersed, to form a second uncured enamel finish layer (312).

30. Method according to any one of claims 27 to 29, characterized in that it comprises, after performing a drying step d) of the finish enamel layer or layers (311, 312), a step applying serigraphically to said enamel finish layer (311, 312) an enamel paste layer (33), which may or may not include rounded fillers.