Culinary item comprising a rare earth oxide layer

Abstract

Provided is a culinary item, one surface of which is provided with a coating including at least one rare-earth oxide layer. Such a coating has the specific feature of not only having mechanical hardness and abrasion resistance comparable to those of enamels and ceramics, but also excellent intrinsic hydrophobic properties that enable the coating obtained to have a non-stick property that is comparable to that of fluorocarbon coatings and suitable for culinary applications.

Claims

1. A culinary item comprising a support having an inner surface capable of receiving foods and an outer surface intended to face a heat source, and a coating applied to at least one of the two surfaces, wherein the coating comprises at least one rare earth oxide layer comprising a matrix of at least one rare earth oxide, and wherein the rare earth oxide layer further comprises fillers that comprise particles dispersed in said matrix, said fillers being selected from the group consisting of fluorocarbon resins, polyetheretherketonces (PEEK), polyetherketones (PEK), polyimides (PI), polyamide-imides (PAI), polyethersulfones (PES), polyhenylene sulfides (PPS), silicone beads and mixtures thereof.

2. The culinary item according to claim 1, wherein said matrix comprises at least one lanthanide oxide.

3. The culinary item according to claim 1, wherein said matrix comprises cerium oxide, alone or in a mixture with at least one other lanthanide oxide.

4. The culinary item according to claim 1, wherein the fillers include a fluorocarbon resin selected from the group comprising polytetrafluoroethylene (PTFE), tetrafluoroethylene and perfluoropropyl vinyl ether (PFA) copolymers, tetrafluoroethylene and hexafluoropropylene (FEP) copolymers and mixtures thereof.

5. The culinary item according to claim 1, wherein the fillers are present at a concentration of 0.1 to 50% by weight relative to the total dry weight of the rare earth oxide layer.

6. The culinary item according to claim 1, wherein the thickness of the rare earth oxide layer is between 0.1 and 50 m.

7. The culinary item according to claim 1, wherein the rare earth oxide layer is structured such that a surface of the rare earth oxide layer comprises a relief or controlled roughness.

8. The culinary item according to claim 1, wherein the support is made of a metal, glass, ceramic, terracotta or plastic material.

9. The culinary item according to claim 8, wherein the support is metal and is made of aluminum or an aluminum alloy, anodized or not, and or of steel, or of stainless steel, or of cast aluminum, or cast iron, or of copper.

10. The culinary item according to claim 9, wherein the aluminum, aluminum alloy steel, or stainless steel support is polished brushed, sanded, or bead-blasted.

11. The culinary item according to claim 9, wherein the cast steel, cast aluminum, cast iron, or copper support is hammered or polished.

12. The culinary item according to claim 8, wherein the support is made of metal and comprises alternate layers of metal and/or metal alloy, or a cap of cast aluminum, aluminum or aluminum alloy reinforced with a stainless steel exterior base.

13. The culinary item according to claim 1, wherein the coating further comprises, on the rare earth oxide layer, at least one layer comprising at least one fluorocarbon resin, alone or in a mixture with a thermostable binding resin resistant to temperatures greater than 200 C., said resin or resins forming a continuous sintered network.

14. The culinary item according to claim 13, wherein the fluorocarbon resin is selected from the group comprising polytetrafluoroethylene (PTFE), tetrafluoroethylene and perfluoropropyl vinyl ether (PFA) copolymers, tetrafluoroethylene and hexafluoropropylene (FEP) copolymers and mixtures thereof.

15. The culinary item according to claim 13, wherein the binding resin is selected from the polyamide-imides (PAI), polyetherimides (PEI), polyamides (PI), polyetherketones (PEK), polyetheretherketones (PEEK), polyethersulfones (PES), polyphenylene sulfides (PPS) and mixtures thereof.

Description

EXAMPLES

Example 1

Preparation and Application by Spray Pyrolysis of a Cerium Oxide Layer

(1) The precursor composition is prepared as follows: cerium acetate (Ce(OOCCH.sub.3).sub.3H.sub.2O) is diluted in a mixture of water:ethanol with a volumetric concentration of 70:30. then, the solution is agitated for 36 hours at ambient temperature to obtain a clear solution with no precipitates, having a cerium concentration of 0.02 mol/L.

(2) This composition is applied multiple times using spray pyrolysis onto the surface of a stainless steel sample. These applications are implemented by means of a spray gun or nebulizer with the sample approximately 20 cm from the spray gun or nebulizer, the surface of the sample being maintained at a temperature above 350 C. to crystallize the cerium oxide as a solid on the sample's surface.

(3) The application of 10 to 20 spray cycles results in a solid rare earth oxide layer with submicron thickness between 100 and 400 nm.

Example 2

Preparation and Application by Spray Pyrolysis of a Cerium Oxide Layer

(4) Following the same procedure described in Example 1, a rare earth oxide layer is applied from a precursor composition prepared by adding L-proline as a chelating agent to cerium (III) nitrate hexahydrate (Ce(NO.sub.3).sub.3-6H.sub.2O) in a 1:1 molar ratio.

Example 3

Preparation and Application by Spray Pyrolysis of a Cerium Oxide Layer

(5) A precursor composition is prepared by diluting cerium (III) chloride heptahydrate (CeCl.sub.3-7H.sub.2O) in a water:ethanol mixture with a 3:1 molar ratio to obtain a cerium concentration ranging between 0.05 and 0.025 mol/L.

(6) In this embodiment, the spray deposition is achieved according to the same process described in Example 1 on the surface of a glass sample maintained at 400 C. to obtain a continuous and homogenous rare earth oxide layer.

Example 4

Preparation and Application by Thermal Spray (or Thermal Projection) of a Cerium Oxide Layer

(7) The precursor composition is prepared as follows: 75 g of cerium (III) nitrate hexahydrate (Ce(NO.sub.3).sub.3-6H.sub.2O) are dissolved in 1.5 liters of pure water; then the solution is agitated for 20 minutes.

(8) The precursor composition is then injected into a plasma torch configured with a stream of a carrier gas (such as an Ar-H.sub.2 mixture) capable of causing the pyrolysis of the cerium salts prior to their contacting the surface of the aluminum sample.

(9) The cerium, thus atomized, is found oxidized in the form of cerium oxide on the surface. Gradually, a cerium oxide layer is thus achieved on the sample surface.

Example 5

Preparation and Application by Thermal Spray Application (or Thermal Spraying) of a Cerium Oxide Later Comprising Fluoroploymer Fillers

(10) A powder is prepared by mixing cerium oxide powder with a grain size ranging from 30 to 70 microns, and PTFE powder (or PFA) with a grain size ranging from 10 to 50 microns.

(11) The powder is then injected into a plasma torch configured with a stream of a carrier gas (such as an ArH.sub.2 mixture) capable of causing the pyrolysis of the cerium oxide prior to contacting the surface of the aluminum sample. The projection distance between the torch and the surface of the sample is approximately 125 mm, and the powder is sprayed out of the plasma torch at a linear displacement speed of approximately 75 m/min.

(12) The surface of the sample onto which the powder is applied is maintained at a temperature of 300 C. to improve the kinetic spreading of the molten oxide grains and the homogeneity of the rare earth oxide layer comprising PTFE (or PFA) particles.

(13) The resulting rare earth oxide layer reaches a thickness of a few dozen microns.

Example 6

Preparation and Application via PVD of a Layer of Cerium Oxide, onto a Structured Sample

(14) The superhydrophobic rare earth oxide layer is generated in two successive steps:

(15) 1) texturing the surface of an aluminum-type metal sample; followed by

(16) 2) PVD deposition of the hydrophobic cerium oxide layer on the textured surface of the sample.

(17) There are many possible variations of Step 1), the texturizing step.

(18) For example, the first variant consists of texturizing the sample surface by means of chemically etching the surface (deposition of photocurable resin/exposure via a suitably adapted mask/treatment of unexposed areas with solvent to create the design element to be reproduced), leading to the formation of texturized areas on the sample surface.

(19) Pattern depth can be controlled by the time allotted for etching. The textured areas are 9 m wide, separated from each other by a distance of 11 m and have a depth of 15 m.

(20) The second variation consists of randomly texturizing the surface of the sample with chemical etching.

(21) In this embodiment, the aluminum sample surface is randomly exposed to acid to obtain the following roughness characteristics: Ra of 5 microns, Rq of 5 microns, and Rz of 25 microns.

(22) The third embodiment consists of using a texturized matrix to stamp the surface of the sample.

(23) In this embodiment, the surface of the sample is texturized under pressure using a hard textured matrix made of titanium nitride. The reproduced textured areas are 9 m wide, separated from each other by a distance of 11 pm and have a depth of 15 m.

(24) Step 2 consists of depositing a continuous layer of cerium oxide on the texturized surface using PVD technology. The deposition is performed under vacuum, using a sintered cerium oxide target.

(25) The resulting layer has a thickness of between 50 nm (on the randomly texturized surface of the second variant) and 500 nm (on the surface comprising the areas of the first and third variants) and accurately replicates the texturing contours.

Example 7

Preparation and Application by Sol-Gel Process (Alkoxides) of a Cerium Oxide Layer

(26) Cerium butoxide is mixed with 2-butanol in a molar ratio of 0.1; acetylacetonate, used as a chelating agent, is then added to the mixture.

(27) Then, an aqueous solution of hydrochloric acid concentrated to 1 mol/L is introduced, while stirring, drop by drop (note that the molar ratio of cerium butoxide/acetyl acetonate is 2, and that of cerium butoxide/water is 0.5), and the resulting sol is agitated for 48 hours to reach the appropriate balance of hydrolysis and condensation reactions.

(28) An inorganic black pigment, composed of a copper-chrome oxide and iron, is then added at 5% by weight relative to the total weight of the solution, and finally, an alpha alumina filler is introduced, while stirring, at up to 4% by weight relative to the total weight of the solution.

(29) In this embodiment, a layer of cerium oxide is formed by sol-gel process, making use of the hydrolysis/condensation of the cerium butoxide.

(30) To do this, the obtained solution, as previously described, is sprayed onto the surface of an aluminum sample, which has been previously sanded and degreased, the surface of the sample having been heated to a temperature of 60 to 80 C. to prevent dripping and to vent a portion of the solvents during the coating process.

(31) To achieve adequate layer thickness while minimizing the risk of cracking, the initial layer undergoes a drying process at 80 C. for 5 minutes, prior to spraying a second layer of the same sol-gel solution onto the sample.

(32) The rare-earth oxide layer undergoes a prebaking step at 120 C. for 10 minutes to evaporate the majority of solvents.

(33) Finally, the entire sample and rare earth oxide layer is subject to thermal treatment at 350 C. to densify the cerium oxide network.

(34) The obtained rare earth oxide layer has a thickness of 15 m, with no visible cracking observed using a binocular microscope.

Example 8

Preparation and Application, using a Sol-Gel (Alkoxides) Pprocess, of a Rare Earth Oxide Layer Comprising Fluoropolymer Fillers

(35) A PTFE powder is added to the sol-gel solution from Example 7, constituting up to 2% by weight of the total weight of the solution. Then a cerium layer is applied using a sol-gel process, making use of the hydrolysis/condensation reaction of the cerium butoxide as described in Example 7.

(36) It should be noted that these PTFE particles are used to improve the hydrophobicity and non-stick properties of the rare earth oxide layer.

Example 9

Preparation and Application, using a Sol-Gel (Salts) Process, of a Cerium Oxide Layer Comprising Fluoropolymer Fillers

(37) Cerium nitrate is dissolved in deionized water to obtain a concentration of 1 mol/L, then 99.5% purity grade citric acid is added, while stirring, with a cerium nitrate/citric acid molar ratio of 0.5

(38) The solution is agitated for 1 hour at ambient temperature, and a mixture of isopropanol and PTFE powder (mass ratio of 48/2) is then added to the solution in a volumetric ratio of 1:1, to improve the service life of the sol and to introduce fluorinated fillers to improve the hydrophobic properties of the coating.

(39) Finally, the solution is agitated for 24 hours to obtain a stable and translucent sol.

(40) The obtained solution is then sprayed to obtain a layer of rare earth oxide on the surface of a smooth and previously degreased aluminum sample, the surface of the which has been heated to a temperature of 40 to 60 C. to prevent dripping and to vent a portion of the solvents during the coating process.

(41) After an initial drying at 100 C. for 10 minutes, the aluminum sample undergoes a thermal treatment at 380 C. for 30 minutes to condense the cerium oxide network.

(42) A 500 nm thick cerium oxide layer is obtained.

Example 10

Preparation and Application, by an Electrochemical Sintering Process of a Layer of Cerium Oxide

(43) A smooth and previously degreased aluminum sample is positioned on the negative electrode of an electroplating system.

(44) The precursors Ce(NO.sub.3).sub.3-6H.sub.2O are in an aqueous solution (0.1 mol/L) in the presence of ammonia NH.sub.3 at a 5% volumetric concentration.

(45) The cerium hydroxide-based rare earth oxide layer is formed in 1 hour by applying a 3V deposition potential to the electroplating system.

(46) The amorphous cerium hydroxide-based rare earth oxide layer is finally oxidized by air at 550 C. for 5 hours to produce a film of cerium oxide 0.5 microns in thickness.

RESULTS OF TESTS CONDUCTED

(47) Hydrophobicity testing of the obtained coatings

(48) The hydrophobic nature of the coatings obtained according to the preceding examples were tested by measuring the contact angle of a drop of water on the coating using a GBX Digidrop goniometer. The results of these measurements are shown in the table below.

(49) TABLE-US-00001 Contact angle Examples (in ) 1 105 2 105 3 105 4 110 5 115 6 170 7 105 8 115 9 115 10 115