JP6272898B2 - Enamel coating containing anisotropic particles and cooking utensils with such coating - Google Patents

Description

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

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

  The target field is mainly the field of heating products.

  A heated article, in the sense of the present invention, transfers the thermal energy that is delivered to a third material or object that is heated by and in contact with the article, either with its own heating system or with an external system. Means an article that can be made, or an article for receiving other pre-heated articles.

  Examples of heating utensils that can be used in accordance with the present invention include cooking utensils (such as saute frying pans, one-handed pans, woks, crepe frying pans, deep pans, goblet pans, cocot pans), heating lids, and food or Particular mention is made of heated mixing bowls of drink preparation equipment. However, the present invention is not limited to tableware such as dishware, iron bottoms, curling hair irons, and straight hair irons, radiators, towel racks or wood stoves, or barbecue plates, barbecue boxes. It can also relate to any other type of surface and article, such as a barbecue or a barbecue tank, a warmer hood.

  Enamel coatings are particularly appreciated in the field of heating articles, in particular cooking utensils, and more precisely in the field of irons and more precisely the bottom of irons.

  In the case of the bottom of the iron, the friction, heat and physicochemical properties of the coating are most important to ensure ease of ironing. Therefore, the enamel coating is an ideal compromise for coating the metal cover at the bottom of the iron because it has good heat resistance, low coefficient of friction that hardly changes with temperature, hydrophilic behavior, hydrolysis resistance It is. The disadvantage of enamel coatings for iron-type applications (including steam irons, dry irons, and steam generators in particular) is their low impact resistance. In fact, small fragments of enamel can appear at the level of the coated edge of the enameled cover (and especially around the coated cover), particularly when the coating is subjected to handling-induced impacts. Small pieces of enamel can also appear due to repeated contact with metal parts (button holes, snap buttons, fasteners ...) secured to the ironing fabric.

  Enamel coatings are colored coatings that they have not only good resistance to dishwashers, high flame resistance and scratch resistance, but also the most important decorative appearance, which is often decisive in consumer choice In the field of cooking utensils. However, they have the disadvantage that they easily peel off at the level of certain areas that are particularly fragile, which are areas of strong stress in cooking utensils. These areas are generally located in the curved area of the article or in the connection area with the handle.

  As a brittle area, for cooking utensils, the joint area between the bottom of the cap and the side wall of the utensil, or the top edge of the utensil that has been cut off (ground) to give a smooth, flat edge, or the handle clamp Particular mention may be made of the area supporting the tool (because it can undergo deformation resulting from the welding of the fixing element), the bottom in contact with the wire mesh of the burner.

  In addition, the enamel coating also has the disadvantage of having different thermal expansions at the bottom level of the article, depending on the location of the flame. However, it is important that the coating has a homogeneous thermal expansion, otherwise it will generate microcracks that impair resistance to the dishwasher.

  In order to avoid the above-mentioned problems, Applicants have developed an enameled coating comprising flakes and more generally anisotropically shaped particles oriented essentially perpendicular to the coating formed in the brittle region did.

  A particle essentially perpendicular to the coating means in the sense of the invention an angle α of 20 ° to 90 °, preferably 45 to 90 ° and better still 60 to 90 ° with respect to the average plane of the coating. Only the majority mean tilted particles.

  It is known to those skilled in the art to incorporate particles such as flakes in enamel type coatings. In this way, for example, US Pat. Nos. 5,098,086 and 5,037,059 describe enamel coatings for cooking utensils that incorporate mica or nacre flakes into the enamel coating.

  In addition, US Pat. Nos. 5,099,086 and 4,096,697 relate to the decoration of the bottom of an iron with an enamel coating containing pigments or filler materials.

French Patent No. 2,472,596 French Patent No. 813737 International Publication No. 2011/42886 Pamphlet U.S. Pat. No. 3,480,461

  However, none of these references describes any orientation of these particles (flakes, pigments or loading materials) in a particular area of the coating, especially for its strengthening, even if this orientation is applied at the level of this area. It also does not describe what can be done by.

  More particularly, the present invention is a heating article comprising a support having two opposing faces, at least one of which is coated with a protective coating, wherein the protective coating is at least dispersed with anisotropically shaped particles. Including a single enamel layer, the enamel layer is intended for a heating article characterized in that the anisotropic particles comprise at least one region essentially perpendicular to the enamel layer in the form of a membrane.

The anisotropically shaped particles can suitably account for 0.05 to 10% by weight, preferably 0.1 to 7% by weight and better still 1 to 5% by weight of the total weight of the enamel layer. . Ideally, the anisotropically shaped particles comprise 2 to 3 wt% of the total weight of the enamel layer.

  In areas where the particles are essentially vertical, the resistance to flaking and impact is clearly improved. In addition, this region does not have a thermal expansion different from that of the rest of the coating.

  An anisotropically shaped particle means in the sense of the present invention a characteristic size, for example a fiber (essentially one-dimensionally shaped) or a flake (essentially two-dimensionally or flatly shaped) flakes. , Meaning particles that are not the same in all directions.

  By particles that are essentially perpendicular to the membrane, in the sense of the present invention is meant particles that are mostly inclined by an angle α of 20 ° to 90 ° with respect to the average plane of the membrane.

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

  In this way, in the case of particles that can be oriented by mechanical means (like fibers), the orientation essentially perpendicular to the coating layer is passed through a unidirectional applicator such as, for example, a micro nozzle. As an orientation, it can occur, for example, as a result of positioning associated with the coating application method.

  In the case of particles that can be oriented by physical (eg electrical or magnetic) means, the essentially perpendicular orientation of the anisotropic particles relative to the coating layer is, for example, that of magnetizable particles or electric fields under the influence of a magnetic field. As with the orientation of the chargeable particles under influence, it can occur as a result of positioning continuously or simultaneously with the application of the coating.

  Magnetizable particles in the sense of the present invention mean particles that can be oriented under the influence of a magnetic field.

  Magnetizable particles can appear in a variety of properties.

  Within the framework of the present invention, the magnetizable particles can be particles that preferably comprise at least one ferromagnetic metal.

  They can be of a homogeneous nature, i.e. composed of the same material, or of a composite nature, i.e. magnetizable particles, in which the ferromagnetic metal is in the core and / or envelope of said particles , Having a core-sheath structure.

Examples of composite magnetizable particles include mica flakes, eg Fe ₃ O ₄ (magnetite), for example in the form of (MO, Fe ₂ O ₃ ), where M is a divalent metal. And mica flakes coated with a ferromagnetic material, such as mica flakes coated with Fe ₂ O ₃ or FeO. Other materials with ferromagnetism can also be used. That is, for example, Heusler alloys (61% Cu, 24% Mn, 15% Al) consisting of cobalt, nickel or exclusively non-ferromagnetic metals, or some rare earths such as lanthanides, copper oxide-manganese and aluminum. .

  The advantage exhibited by the coated mica flakes is that they withstand particularly well the high firing temperature of enamel for metals, ie temperatures ranging from 550 ° C. for enamels to aluminum to 850 ° C. for enamels for steel or cast steel. In addition, these mica flakes give better resistance to the alkalinity of enamel slurries obtained by hydrolysis (e.g. enamel slurries for aluminum having a pH of 13). Mention may also be made of stainless steel fibers coated with a sol-gel material as a corrosion protection during the coating implementation step, or flakes whose core is made of a ferromagnetic metal and whose jacket is made of a sol-gel material.

  The coating according to the invention may further preferably comprise non-magnetizable particles in order to improve the strengthening of the coating.

  By non-magnetizable particle is meant in the sense of the present invention a non-magnetizable or slightly magnetizable particle with a zero or slight (less than 1 emu / g) magnetic moment.

  These non-magnetizable particles may be of any (spherical, fiber or flake or “irregular”) shape of micrometer or even nanometer size.

  Non-magnetizable particles that can be used within the framework of the present invention include mica flakes and mica or silica flakes coated with titanium dioxide.

  The protective coating of the present invention further preferably has an enamel layer that takes the form of a membrane so that the particles reinforce the brittle regions adjacent to the regions where the particles are essentially perpendicular to the enamel coating layer. May include at least one region arranged essentially parallel to and / or randomly.

  By particles essentially parallel to the enamel coating layer is meant in the sense of the present invention particles which are mostly inclined by an angle α of 0 ° to 20 ° with respect to the coating layer.

  The alternating repetition of the regions where the particles are arranged essentially parallel and / or randomly to the enamel layer and the regions where the particles are essentially perpendicular to the enamel layer is a three-dimensional decoration by the user. Makes it possible to define decorations that can be perceived.

  According to a particularly preferred first embodiment of the invention, the enamel layer of the protective coating according to the invention may comprise a single layer which is continuous and is arranged on a support.

According to a particularly preferred second embodiment of the invention, the enamel layer of the protective coating according to the invention comprises:
A transparent and magnetizable particle-free underlayer for continuous and disposition on the support;
A finishing layer in which magnetizable particles are dispersed, which may be continuous and may cover the underlying layer partially or completely.

  The finishing layer means a layer for contacting the surroundings in the meaning of the present invention.

According to a particularly preferred third embodiment of the invention, the enamel layer of the protective coating according to the invention comprises
-An underlying layer without colored and magnetizable particles to be continuous and disposed on a support;
A finishing layer in which magnetizable particles are dispersed, which may be continuous and may cover the underlying layer partially or completely.

According to a particularly preferred fourth embodiment of the invention, the enamel layer of the protective coating according to the invention comprises
A transparent or colored and magnetizable particle-free underlayer, which is continuous and is arranged on a support;
A first finishing layer in which magnetizable particles are dispersed, the first finishing layer being continuous and completely covering the lower layer;
A second finishing layer, in which the magnetizable particles are likewise dispersed, and may be continuous and a second finishing layer partially or completely covering the first finishing layer;

According to a particularly preferred fifth embodiment of the invention, the enamel layer of the protective coating according to the invention comprises
A colored underlayer in which magnetizable particles are dispersed, continuous and arranged for placement on a support;
A transparent finish layer in which the magnetizable particles are likewise dispersed, and may comprise a continuous and a finish layer partially or completely covering the colored underlayer.

  Such embodiments have the advantage of mechanically strengthening each layer and the mechanical connection between each layer.

  Preferably, for embodiments having at least two layers (second to fifth embodiments), the lower layer may have a thickness of 5 to 30 μm and the finish layer is 20 to 60 μm thick. You may have.

According to a particularly preferred sixth embodiment of the invention, the protective coating according to the invention comprises
-An enamel layer,
A magnetizable particle-free and transparent or colored underlayer, which is continuous and is arranged on a support;
· Colored or a layer, a layer of at least one central magnetizable particles are magnetizable layer dispersed, and a central layer continuous and covers the lower layer partially or completely Including enamel layers,
A first magnetizable varnish layer in which continuous and magnetizable particles are dispersed, the first varnish layer partially or completely covering the central enamel layer;
A second varnish layer which is colorless and transparent, non-magnetizable, continuous and completely covers the first magnetizable varnish layer so as to ensure chemical resistance and resistance to dishwashers ; May be included.

  Suitably, for this sixth embodiment, the lower layer may have a thickness of 5 to 30 μm and the central enamel layer may have a thickness of 20 to 60 μm. With respect to the varnish layer covering the central enamel layer, the magnetizable varnish layer may preferably have a thickness of 15 to 40 μm and the protective varnish layer has a thickness of 10 to 20 μm. Also good.

  For these embodiments as a whole, the colored layer (which is the lower layer, the finishing layer or the varnish layer) means in the sense of the invention a heat-stable pigment such as spinel, a ceramic pigment, an oxide, At least selected from organometallic compounds such as ultramarine blue, (non-magnetizable) mica or siliceous palate pigments, metallic salts, thermochromic semiconductor pigments and mixtures thereof It means a layer containing one kind of opaque pigment.

  Preferably, whatever the contemplated embodiment, the enamel layer of the protective coating of the heating article according to the present invention may further comprise a discontinuous outer enamel layer that is silkscreen printed or pad printed.

When the heating article according to the invention is a cooking utensil, the outer enamel layer may also comprise a rounded charge material, preferably spherical, having a diameter of 5 to 40 μm, and preferably 15 to 20 μm. the thickness of the layer, varies between 10 and 30 [mu] m. These balls overhang on the surface of the outer enamel layer.

  Rounded charge materials (or balls) that can be used in the outer enamel layer according to the invention include in particular stainless steel, copper, bronze or heat resistant steel balls.

  Preferably, stainless steel balls are used. The rounded charge material is preferably present in the outer enamel layer in a proportion of 1 to 5% by weight relative to the total weight of the outer layer. These rounded loading materials increase the wear resistance of the enamel coating and its coefficient of friction because of the reduced contact area between the article and the calcined plate and the smaller hardness of the ball relative to the hardness of the enamel layer. At the same time (when the charge material appears on the surface of the enamel layer). In this way, the coating is easily cleanable and has no risk of scratching fragile surfaces such as glass ceramic plates or induction cookers.

  With regard to the nature of the article support, it can be made of a material selected from metal, glass and ceramic.

As a metal support suitable for the present invention, the following structure:
-Polished, frosted or bead blasted (microbill), sandblasted, chemically treated aluminum or aluminum alloy, or cast aluminum, or polished, frosted, Or bead blasted stainless steel, or a single layer of cast steel or cast aluminum,
Or alternatively, from the outside to the inside, the next layer, ferritic stainless steel / aluminum / austenite stainless steel, or stainless steel / aluminum / copper / aluminum / austenite stainless steel, or the outer bottom of the stainless steel is doubled Also included are supports having partially or wholly multilayered metal supports, including cast product aluminum, aluminum or aluminum alloy caps.

  Examples of articles according to the present invention include cooking utensils, heated lids, or heated mixing bowls in food or drink preparation equipment, or iron bottoms, tableware such as dishclothes, radiators or wood stoves, or curling hair irons And hair straighteners, towel racks, or barbecue plates, barbecue boxes or barbecue tanks.

Finally, the present invention is a method for producing a coating comprising at least one enamel layer in which anisotropically shaped particles are dispersed on a support of a heating article, comprising:
During application of the coating within at least one region of the enamel layer by physical means (eg by applying an electric or magnetic field) or by mechanical means (eg by using a unidirectional applicator such as a micro nozzle) ) A method further comprising the step of orienting said anisotropic particles.

  The support and anisotropic particles are as defined above.

Preferably, the method according to the invention comprises
a) a support supplying step;
b) spraying the one of the surfaces of the support of at least one enamel composition, in which anisotropic particles containing magnetizable particles are dispersed,
c) an orientation step by magnetization of magnetizable particles applying a magnetic field, wherein the magnetization c) takes place during or immediately after the application step b) of the enamel composition to the support. And d) optionally, preferably a drying step, preferably at a temperature between ambient temperature and 150 ° C., followed by e) a calcination step performed at a temperature of at least 500 ° C.

  Magnetizable particles are as defined above.

  In this embodiment of the method according to the invention, magnetizable anisotropically shaped particles are used. That is, the orientation step d) of the magnetizable particles is therefore carried out by application of a magnetic field, either during application of the enamel composition or after this application step d), but in any case prior to the firing step e). Magnetization step.

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

In this embodiment of the method according to the invention, in which the anisotropic particles are magnetizable and oriented by magnetization, the enamel layer application step b) preferably comprises the following:
B1) a sub-step of spraying a lower layer enamel composition free of magnetizable particles onto one of the faces of the support, said enamel composition being transparent to form an unfired lower layer Or b2) at least one finished enamel composition with magnetizable particles dispersed therein to form a non-fired finished enamel layer. And a sub-step of spraying on the lower layer of firing.

Preferably, the enamel layer application step b) is after step b2), but prior to firing e), the magnetizable particles are similar to form a non-fired second finished enamel layer. Spraying at least one second finish enamel composition dispersed in the non-fired finish enamel layer may further comprise step b3).

  Finally, after the method according to the invention has performed the drying step d) of the finished enamel layer formed (in which case the drying step is no longer optional and is necessary for this embodiment), the rounded filling An application step by silk screen printing of the enamel paste layer to the finished enamel layer, which may or may not include materials, may be further included.

  These rounded filling materials (or balls) are as defined above.

  Other advantages and characteristics of the invention will arise as a result of the description which follows, given by way of non-limiting example and made with reference to the accompanying drawings.

2 is a schematic cross-sectional view of a part of a support of an article according to the invention according to a first embodiment. FIG. 6 is a schematic cross-sectional view of a part of a support of an article according to the invention according to a second embodiment variant (showing the former of two sub-variants 2a and 2b). Fig. 4 is a schematic cross-sectional view of a part of a support of an article according to the invention according to a second embodiment variant (showing the latter of two sub-variants 2a and 2b). FIG. 6 is a schematic cross-sectional view of a part of a support of an article according to the invention according to a third embodiment variant (showing the former of two sub-variants 3a and 3b). Fig. 6 is a schematic cross-sectional view of a part of a support of an article according to the invention according to a third embodiment variant (showing the latter of two sub-variants 3a and 3b). FIG. 6 is a schematic cross-sectional view of a part of a support of an article according to the invention according to a fourth embodiment. FIG. 6 is a schematic sectional view of a part of a support of an article according to the invention according to a fifth embodiment variant (showing 5a which is one of four sub-variants 5a to 5d). FIG. 6 is a schematic cross-sectional view of a part of a support of an article according to the invention according to a fifth embodiment (showing 5b which is one of four sub-variants 5a to 5d). FIG. 7 is a schematic cross-sectional view of a part of a support of an article according to the invention according to a fifth embodiment variant (showing 5c which is one of four sub-variants 5a to 5d). FIG. 6 is a schematic cross-sectional view of a part of a support of an article according to the invention according to a fifth embodiment variant (showing 5d which is one of four sub-variants 5a to 5d). It is a schematic sectional drawing of a part of the support body of the cooking utensil according to the present invention according to the sixth embodiment. FIG. 9 is a schematic cross-sectional view of a part of the bottom of an iron according to the present invention according to a seventh embodiment. FIG. 8 is a bottom view of the bottom of the iron illustrated in FIG. 7. FIG. 2 is a schematic cross-sectional view of the placement of a magnet under a support of a coated article to perform a magnetization step. FIG. 10 is a detailed view of FIG. 9 at the level of region Z (defined by the edges of the two magnets and the pole gap). It is a top view (photograph) of a part of the bottom of an iron which has arranged a strip-shaped permanent magnet which has a triangular outline under it. FIG. 2 is a detailed view of FIG. 1 at a particular zone Z level (defined by the edges of two magnets and the pole gap). It was performed at the level of a particular region Z, which is a diagram of 13a of 13 c from a series of three images 13a of a scanning electron microscopy of the cross section of the iron in the bottom of FIG. 3 (MEB). It was performed at the level of a particular region Z, which is a diagram of 13b of the 13 c from a series of three images 13a of a scanning electron microscopy of the cross section of the iron in the bottom of FIG. 3 (MEB). It was performed at the level of a particular region Z, which is a diagram of 13c of the 13 c from a series of three images 13a of a scanning electron microscopy of the cross section of the iron in the bottom of FIG. 3 (MEB).

FIG. 1 shows a part of a support for an article according to the invention according to a first embodiment variant. One of the faces 21 of the support 2 comprises a continuous and enamel-coated single-layer membrane 31 in which anisotropically shaped particles 4, 41 are dispersed.

  FIG. 1 shows that the membrane 31 comprises at least one region 5 in which the anisotropically shaped particles 41 are essentially perpendicular to the membrane 31.

This particular orientation of the anisotropic particles 41 in the region 5 can be obtained, for example, by magnetization when the anisotropic particles 4, 41 comprise magnetizable particles. In practice, this is done as follows: on the side of the uncoated surface 22 under the support 2, a permanent magnet, in particular an elastomer-type permanent magnet (this limits the magnetization conditions to temperatures below 80 ° C. ) Or an electromagnet. It is also possible to use ferrite or neodymium type permanent magnets or electrically induced magnets. In this case, the maximum temperature value under which magnetization is performed may exceed 80 ° C., but it must remain below the Curie temperature of the magnet used. To obtain a specific holographic image, a magnet having the desired shape is cut and / or processed in a permanent ferromagnetic material or an electrically induced material.

  Preferably, a magnet is used that emits a magnetic field with an intensity of 40 to 100 mT and preferably about 70 mT.

  FIG. 1 shows that the magnetizable particles 41 of a single-layer enamel film 31 are in this film along a line of magnetic field generated in a particular region 5 by a permanent magnet placed just below this region 5. Clearly shown to be vertically oriented.

FIG. 2 represents a schematic cross-sectional view of a part of a support 2 of an article according to the invention according to a second embodiment, showing the two sub-variations illustrated in FIGS. 2a and 2b respectively. Two sub variant illustrated in Figure 2a and 2b, in that the enamel coating 31 in the form of film is double-layered, different from the exemplified variant in Figure 1.

With respect to the two sub-variants illustrated in FIGS. 2 a and 2 b, the bilayer coating 31 comprises a lower layer 310 disposed on one of the faces 21 of the support 2 (without anisotropically shaped particles), and a lower layer 310. And a finishing layer 311 having the shape of a continuous enamel film covering the same, and the anisotropic particles 4 and 41 are included in the finishing layer 311. Lower layer 3 10, or may be colored as shown in Figure 2a, or may be transparent, as shown in FIG. 2b. The orientation of the anisotropic particles 41 may be performed by magnetization when these anisotropic particles 41 include magnetic particles as in the first embodiment.

FIG. 3 represents a schematic cross-sectional view of a part of a support of an article according to the invention according to a third embodiment, which likewise shows the two sub-variations illustrated in FIGS. 3a and 3b respectively. Each of these sub-variants 3a and 3b is illustrated in FIGS. 2a and 2b, respectively, in that the enamel coating 31 further includes a second finishing layer 312 in which anisotropic particles 4, 41 are similarly dispersed. This is different from the modified embodiment.

FIG. 3 shows a region 5 in which the two-layer enamel coating 31 of FIG. 3 has an anisotropic particle 4 essentially parallel to the coating 31 and an anisotropic particle 41 essentially perpendicular to the film. It also shows that it includes a three-dimensional pattern formed by alternating repetitions of.

  Again, the specific orientation of the anisotropic particles 41 in the region 5 is effected by magnetization if the anisotropic particles are magnetizable.

  In this way, in the case of cooking utensils where the bottom of the support to be coated has a substantially circular shape, this magnetization is for example on the side of the uncoated surface 22 under the (substantially circular) support. This can be done by placing a plurality of concentric permanent magnets of the same or different strength, e.g. about 80 mT measured independently, made of an elastomer that emits a magnetic field. These concentric magnets preferably take the form of a short diameter central disk (e.g., 15 mm or less) and a plurality of concentric rings disposed about this central disk about 10 to 15 mm wide. obtain. These magnets are preferably placed on a substrate (eg, a stainless steel tray) that can move vertically to the support of the article. This movement can be done with a jack that carries the substrate (or tray) in the vicinity of the article to be magnetized so as to define a pole gap.

In the case of an iron bottom having a generally triangular cover to be coated , a strip of magnet (eg an elastomer) is placed on the side of the uncoated surface 22 , for example under the area to be reinforced of the support 22. These bands may be continuous or discontinuous and may have a generally triangular shape of the cover. They emit a magnetic field of about 80 mT of the same or different intensity, for example measured independently.

  The magnetizable anisotropic particles are then oriented along the lines of the magnetic field, ie perpendicular to the support 2 (or film 31) at the level of the region 5 under which the magnet is placed (the magnetic field lines are In the region 6 where the magnetic field lines are parallel to the support 2 and parallel to the support 2 (and thus the coating 31), the magnetizable difference between these two regions. Oriented with a continual gradual orientation of isotropic particles.

FIG. 4 shows a support for an article according to the invention according to a fourth embodiment, which differs from the sub-variation of the embodiment illustrated in FIG. 2a in that the lower layer 310 comprises anisotropic particles 4, 41. FIG. Similar to the third embodiment illustrated in FIGS. 3 a and 3 b , the two-layer enamel coating 31 of FIG. 3 has regions 6 with anisotropic particles 4 essentially parallel to the coating 31. And a three-dimensional pattern formed by alternating repetitions of regions 5 having anisotropic particles 41 essentially perpendicular to the film. When the anisotropic particles 41 include magnetic particles or are magnetic particles, the particle orientation in the region 5 can be obtained by placing a magnet under the support 2.

FIG. 5 represents a schematic cross-sectional view of a part of a support of an article according to the invention according to a fifth embodiment, showing the four sub-variations illustrated in FIGS. 5a to 5d, respectively. These figures show that one of the surfaces 21 of the support 2 is
A lower layer 310 that is free of magnetizable particles 4, 41 and is transparent (as illustrated in FIGS. 5a and 5b) or colored (as illustrated in FIGS. 5c and 5d);
A colored layer ( as illustrated in FIGS. 5b and 5d) or anisotropic particles 4, 41, preferably magnetizable anisotropy (as illustrated in FIGS. 5a and 5c) It is shown that the particles are coated with an enamel layer 31 comprising a central layer 313 , which is a dispersible magnetizable layer, continuous and covering the lower layer 310.

The middle layer 313 is itself:
A first transparent or colored varnish layer 321 in which anisotropic particles 4, 41 which are continuous and preferably magnetizable are dispersed;
And a second colorless varnish layer 322 which is continuous and completely and / or partially covers the first varnish layer 321.

  Again, the specific orientation of the anisotropic particles 41 in the region 5 is effected by magnetization if the anisotropic particles are magnetizable.

FIG. 6 shows a schematic cross-sectional view of a part of a support of a cooking utensil according to the present invention according to a sixth embodiment. In this variant specific to cooking utensils such as the frying pan 1, the support 2 is directed to an inner surface 22, which is a side oriented on the side of food that may be received in the frying pan 1, and to an external heat source. And an outer surface 21 for placement. The support 2 includes an anti-adhesion coating 7 (for example made of sol-gel material or fluorocarbon resin) on its inner surface 22 and on its outer surface 21.
A continuous enamel layer 31 comprising pigmented and magnetizable particles 4, 41;
A continuous colorless varnish layer 32 in which the magnetizable particles 4, 41 are dispersed;
Silk obtained by screen printing or pad printing, comprising (copper, steel bronze or heat resisting steel) containing a metal ball 34, a discontinuous outer enamel layer 33, a coating 3 comprising a.

  FIG. 7 represents a schematic cross-sectional view of a part of the bottom of an iron according to the invention according to a seventh embodiment, and FIG. 8 represents a bottom view of the bottom illustrated in FIG.

  In this variant specific to the bottom of the iron, the support 2 comprises a coating 3 which is substantially identical to that illustrated in FIG. 6 on the outer surface 21 for contacting the ironing fabric. That is, it differs only by the lack of rounded charge material in the discontinuous outer enamel layer 33.

  9-13 are described in further detail at the level of the examples that follow, which illustrate the invention without limiting its scope.

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

Examination of resistance to peeling The suitability to withstand peeling of various protective coatings of the same thickness (70 to 80 μm) and applied to the same metal substrate was evaluated as follows.

  These coatings were scratched 10 mm in length, calibrated with a diameter of 50 μm, induced by a diamond tip and applied by a force gradually increasing from 0 to 5 Newtons. For this purpose, a device marketed under the name “Microscratch tester” from CSM Instruments is used.

After the formation of the scratch, it is determined under a microscope which strength to metal coating is visible (see Table 9 of the results).

Product
Support-Support for cooking utensils of aluminum alloy (eg alloy 4917),
-A cover on the bottom of the iron of an aluminum alloy (eg alloy 3003),
-Supports for cookware of steel and steel plates.

Ferromagnetic flakes As ferromagnetic flakes that can be used within the framework of the present invention, in compositions B1 and V1,
-Mica flakes (magnetizable flakes) coated with iron oxide, marketed under the name STAPA TA Ferricon 200 by the company ECKART,
-Mica flakes (magnetizable flakes) coated with iron oxide sold under the name Colorona Blackstar blue or green by the company MERCK.
-Uncoated mica flakes (non-magnetizable flakes) sold under the name Iriodin 119 by the company MERCK
Can be used.

Loading material -stainless steel balls

Composition Composition of slurry B1 of pigmented enamel B1 with magnetizable loading material for an aluminum substrate (aluminum or cast aluminum cookware, iron bottom ...).

  An enamel frit slurry B1 is prepared, the composition of which is given below in Table 1 below.

  The indicated content is parts by weight per 100 parts by weight frit (a reference amount in the composition of the slurry).

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

The indicated content is a mass percentage with respect to the weight of the frit.
Enamel Slurry B2 Composition for Cast Steel Cookware Supports An enamel frit slurry B2 is prepared, the composition of which is given below in Table 3 below.

  The indicated content is parts by weight per 100 parts by weight frit (a reference amount in the composition of the slurry).

  The composition of the enamel frit F2 is given in Table 4 below.

The indicated content is a mass percentage with respect to the weight of the frit.
Composition of Varnish V1 Pigmented with Magnetizable Charge Material A composition of varnish V1 is prepared, the composition of which is given below in Table 5 below.

Coated white enamel slurry composition B3 for cast steel (with magnetizable charge)
A slurry B3 colored with enamel frit pigment to make up the coated white enamel is prepared. Its composition is given in Table 6 below.

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

Silk screen printing paste composition (with and without rounded charge)
A first composition of silk screen printing paste P3 with charge material is prepared, the composition of which is given below in Table 8 below.

A second composition of silk screen printing paste P4 without charge is prepared, the composition of which is also given below in Table 8 below.

Example 1 : Production of a protective coating according to the invention on the outer surface of an aluminum alloy cooking utensil support.

In order to form an enamel layer 31 (thickness 35 μm) on the outer surface of an aluminum alloy cooking utensil support, a slurry B1 whose composition is given in Table 1 is applied by spraying. Next, in order to form a varnish layer 32 (having a thickness of 35 μm) on the enamel layer 31, a composition of varnish V1 whose composition is given in Table 5 is applied.

  As schematically illustrated in FIGS. 9 and 10, two permanent magnets 51, 52 disposed under the substrate (in this case, under the surface of the support opposite the coated surface) Immediately after the application of the enamel layer 31 and the varnish layer 32, the magnetizable flakes contained in these layers are orientated by magnetization in several areas of the protective coating by the application of the magnetic field of 70 mT used. Due to the action of the magnetic field, the mica flakes, due to their magnetic iron oxide coating, are aligned along the magnetic field lines, i.e. perpendicular to the magnet, and in particular substantially perpendicular within the regions P1 and P2 represented in FIG. Oriented.

  In order to promote this orientation of flakes, it is preferred that the viscosity of the applied layer be as low as possible. To this end, the introduction of a small amount of non-VOC heavy solvent such as hexylene glycol allows for reduced evaporation on the spray, and higher magnet application time that allows easy post-spray orientation. Bring. Thus, any drying of the enamel layer before orienting the magnetic charge material is avoided. However, the magnets can be applied until the final drying of the coating in order to harden the orientation. This form is particularly recommended if it is desired to obtain a decoration with a clear perception of irregularities.

These layers are then dried biscuit coated with silk screen printing enamel paste P3 (including steel balls) whose composition is given in Table 8 to form a discontinuous outer enamel layer 33. sec) to obtain a temperature of less than 150 ° C., preferably 60 to 80 ° C. The article is then fired in a conventional convection or radiant furnace at 500 to 1000 ° C. for 5 to 30 minutes, depending on the support to be coated.

At the level of region Z, observation of this coating with a scanning electron microscope (MEB) corresponds to the image MEB represented in FIG.
The flakes tend to be oriented perpendicular to the support where the lines of magnetic field are perpendicular to the support 2, ie in region C corresponding to region 5 (FIG. 13c) (ie most of them are Having an inclination angle with respect to the support of 45 to 90 °),
The flakes tend to be oriented parallel to the support (ie most of them) where the magnetic field lines are perpendicular to the support 2 (FIG. 13b specifically shows a region B corresponding to region 6) Has a tilt angle with respect to the support of less than 20 °)
It shows that.

Example 2 : Production of a protective coating according to the invention on the cover of the bottom of the iron.

  The same coating as in Example 1 is made on the bottom cover of the iron except that there is no steel balls in the outer enamel layer (this outer enamel layer is obtained from a silk screen printing paste P4 without steel balls). .

  The orientation of the magnetizable particles is under the substrate (in this case the coated surface, as schematically shown in FIGS. 9 and 10 as in Example 1 and as actually illustrated in FIG. 11). This is done by applying a magnetic field of 70 mT using two permanent magnets 51, 52 (under the surface of the support opposite to). Under the action of the magnetic field, the mica flakes are oriented substantially perpendicular (region C) along the magnetic field lines, ie perpendicular to the magnet, due to their magnetic iron oxide coating.

  At the level of region Z, the observation of this coating with a scanning electron microscope (MEB) is represented by the image MEB represented in FIG. 13 (FIGS. 13a to 13c show regions A to C, respectively).

At the level of region Z, the observation of this coating with an optical microscope is represented in FIG. 12, and it is possible to visualize the succession of various regions A, B and C. In this figure,
The region C (corresponding to reference numeral 5 in FIGS. 1 to 7), which is the region between the two magnets 51 and 52, whose magnetic field lines are perpendicular to the support, is its vertical position relative to the support Because the magnetizable particles perceive the reflection only slightly, and not at all, so that they are black areas,
The region B (corresponding to reference numeral 6 in FIGS. 1 to 7) placed at the edge of the magnet 51 where the magnetic field lines are parallel to the support has the strongest reflection of magnetizable particles. Because this is this area, it is a bright and shining area,
• Region A, essentially defined as the center of magnet 51, is oriented with respect to the support at an intermediate angle where the magnetizable particles (greater than 20 ° but smaller than the angle observed in region C). Thus, it has a moderate luminance (between the luminance observed in region B and the luminance observed in region C).

Example 3 : Fabrication of a protective coating according to the invention on the inner and / or outer surface of a cast steel cookware support.

  This article is processed in two layers, typically by two firings.

A first layer of enamel slurry B2 (see Table 3 and Table 4 ), generally opaque, on the inner and outer walls of a pre-shot and defatted cast steel cookware support Is applied by spraying. This layer is fired at 800 ° C. to 850 ° C. for 4 to 12 minutes.

  It will be noted from the first layer that it is possible to use ferromagnetic flakes. That is, if that is the case, their orientation will be facilitated when the enamel is still liquid, ie when the magnet is applied prior to drying and firing. Drying will make it possible to maintain the orientation of the flakes subjected to the magnetic field of the magnet.

  After firing and cooling the first layer enamel article, a coating enamel slurry B3 is applied.

  The thickness of this second layer is 100 to 200 μm. This layer makes it possible to obtain mechanical reinforcement related to the orientation of the flakes when a magnetic field is applied. This step is optimal and facilitated when the enamel slurry is still liquid (mobility is facilitated). This second firing will be carried out at 750 ° C. to 820 ° C. for 4 to 12 minutes.

  It will be noted that in the case of cast steel metal for cooking applications or small home appliances, the above enamel can be applied either inside or outside the article. Their enhancement of mechanical properties can be done inside the utensils (kitchen utensils, ie multiple contacts with whisks, knives, spatulas ...) or outside the utensils (firing plates, sinks, wire mesh ...). Can be done.

  The above coating has a significant improvement over the same coating without magnetizable flakes oriented in slurry B3. Optimization of the resistance to flaking is beneficial during conventional use, for example in the impact of metal kitchenware.

  The increase in resistance can be observed by non-standardized inspection using a 300 g hammer falling from a height of 15 cm to the surface of an enameled iron article in less than 1 second. Impact occurs without flaking in the case of a flake loaded slurry, while one is observed when there is no flake.

Comparative Example 4 : Production of a protective coating on the outer surface of the iron bottom without magnetizable particles.

As in Example 2, a protective coating comprising an enamel layer 31 is produced, in which a varnish layer 32 and then a silkscreen printed enamel layer 33 is deposited. The protective coating of Comparative Example 4 differs from that of Example 1 by the lack of magnetizable flakes in the enamel layer 31, varnish layer 32, and silk screen printed enamel layer 33.

Example 5 : Evaluation of resistance to exfoliation of aluminum on cooking utensils Example 1 and 2 at the level of regions B and C, and Comparative Example 4 according to the test indicated above (as there is no magnetization, the specific Evaluate suitability to withstand peeling of the protective coating in (no area). The obtained results are shown in Table 9 below.

The peel values displayed in Table 9 correspond to the average value of the metal debris for four measurements per sample.

Comparison of the peel value measured at the level of region B of Example 1 or 2 with that of Comparative Example 4 shows that horizontal flakes can facilitate peeling, so as to obtain peeling with metal It shows that the force applied during inspection is lower when the particles are oriented parallel to the coating than without magnetizable flakes.

  Comparison of the peel value measured at the level of region C of Example 1 or 2 with that measured at the level of region B of the same example shows that the force applied during inspection to obtain a metal peel is Clearly shows that the particles are larger when they are oriented perpendicular to the coating than when they are parallel, which indicates that they are better resistant to flaking when the coating contains oriented particles. means. In this case, they have a strengthening role.

Claims (10)

A heating article (1), characterized in that it comprises a support (2) having two opposing faces (21, 22), at least one (21) covered with a protective coating (3),
Said protective coating (3) comprises at least one enamel layer grains (4, 41) is dispersed in fiber form or flake form comprises (31), said layer comprises at least one region (5), said at least In one region (5), the fibrous or flake shaped particles (4 , 41) essentially comprise particles (41) perpendicular to the enamel layer (31) in the form of a membrane, Heating supplies.   2. Article according to claim 1, characterized in that the particles (4, 41) occupy 0.05 to 10% by weight relative to the total weight of the enamel layer (31).   3. Article according to claim 1 or 2, characterized in that the particles (4, 41) comprise particles (41) which can be oriented by mechanical or physical means.   4. Article according to claim 3, characterized in that the orientable particles (41) are magnetizable particles.   5. Article according to claim 4, characterized in that the magnetizable particles (41) comprise at least one ferromagnetic metal.   6. Article according to claim 4 or 5, characterized in that the enamel layer (31) further comprises non-magnetizable particles. Adjacent to the region (5), at least one region (6) in which the fiber-shaped or flake- shaped particles (4) are arranged randomly or essentially parallel to the enamel layer (31). The article according to any one of claims 1 to 6, further comprising: The enamel layer (31) is
A transparent or colored underlayer (310) without magnetizable particles (41) to be continuous and disposed on a support;
-At least one finishing layer (311) in which the magnetizable particles (41) are dispersed, comprising a finishing layer (311) which is continuous and partially or completely covers the lower layer (310) An article according to any one of claims 4 to 7, characterized in that A method for producing a protective coating (3) comprising at least one enamel layer (31) in which fibers or flake shaped particles (4, 41) are dispersed on a support (2) of a heating article (1). And
A method comprising the step of orienting said fiber or flake shaped particles (41) by physical or mechanical means within at least one region (5) of said enamel layer (31). a) supplying the support (2);
b) applying by spraying one of the faces of the support (2) of at least one enamel composition, in which fiber-shaped or flake-shaped particles containing magnetizable particles (41) are dispersed;
c) an orientation step by magnetization of the magnetizable particles (41) by applying a magnetic field, wherein the magnetization c) is applied during the application b) of the enamel composition to the support or the application An orientation step performed immediately after step b), then d) optionally a drying step, preferably at a temperature between ambient temperature and 150 ° C., followed by
e ) a calcination step performed at a temperature of at least 500 ° C.