EP3728156A1

EP3728156A1 - Object with a high-temperature-resistant omniphobic non-stick coating, and method for producing such an object

Info

Publication number: EP3728156A1
Application number: EP18807983.4A
Authority: EP
Inventors: Frank JÖRDENS; Carmen MARSCHNER; Andreas Pfuch; Jürgen Salomon; Gerhard Schmidmayer; Tina TÖLKE
Original assignee: BSH Hausgeraete GmbH
Current assignee: BSH Hausgeraete GmbH
Priority date: 2017-12-22
Filing date: 2018-11-23
Publication date: 2020-10-28
Also published as: CN111465585A; DE102017223680A1; US20210071009A1; WO2019120879A1

Abstract

The invention relates to an object having a high-temperature-resistant omniphobic non-stick coating, comprising an inorganic substrate, an adhesion promoter layer containing amorphous silicon dioxide, and an omniphobic non-stick coating, as well as to a method for producing such an object.

Description

A high temperature resistant omniphobic nonstick coating article and method of making the article

The present invention relates to an article having a high-temperature resistant omniphobic non-stick coating which is scratch-resistant and easy to clean, and a method of manufacturing the article.

State of the art

Temperature resistant, scratch resistant nonstick coatings for glass or enamel substrates that are well known for parts of household appliances such as cooking appliances (including glass ceramic cooktops or internal components of, for example, ovens or microwaves) that are heated or come into contact with heated foods. These coatings may e.g. be applied to the surface to be coated by a sol-gel method. Further, these layers may be omniphobic, i. have both hydrophobic and oleophobic properties to improve their cleanability against e.g. To improve food residues.

WO 99/02463 discloses temperature-resistant and scratch-resistant non-stick coatings applied by a one-step sol-gel process. According to WO 99/02463, the layers are temperature resistant up to> 500 ° C. Investigations have shown, however, that these layers are stable only up to a maximum of 300 ° C over a longer period of time, and at temperatures greater than 300 ° C within a short time an increase in the surface energy occurs. This, in turn, causes a deterioration of the cleanability of e.g. burnt food residues and leads to a pronounced staining tendency. Thus, the high temperature resistance of these layers is insufficient.

Furthermore, coatings containing nanoparticles for improving the scratch resistance, such as the "Nanoclean" coatings from the company PEMCO, known. According to "Schlegel, C .:" Glassy Surface Functionalization by Nano-modified Sol-Gel Technology ", XXI International Enamellers Congress, May 18, 2008, pages 41-50, XP002599577," these nanoclean coatings are nanoparticle-modified sol-gel Layers in which, in embodiments, a deposition of an SiO _x intermediate layer takes place via a preceding flame treatment and silanization. These layers are only up to max. 300 ° C heat resistant. EP2281916 A1 and DE102009030876 A1 show two-stage coating processes of substrates, so that a silicon dioxide layer as adhesion promoter layer, which is applied via an atmospheric pressure process, and a further layer, which is applied by means of a wet-chemical process, are obtained. However, these methods require the prior application of a primer to the substrate to ensure the desired adhesion. Furthermore, the temperature resistance of these layers is insufficient.

Especially in view of the fact that cooking appliances are exposed to ever higher temperatures, as e.g. Ovens are heated up faster and faster, so that process-related generally temperatures of 350 ° C or higher can be achieved, the demands on the coatings in terms of their temperature resistance rise.

However, in the prior art no omniphobic non-stick coatings are known for e.g. Glass or enamel substrates are known, which have a high scratch resistance and thus easy cleanability even after a high temperature treatment of e.g. greater than 350 ° C for a longer period, i. There is a need for objects with omniphobic non-stick coatings, which are temperature-resistant, especially at temperatures of 350 ° C. and higher.

Object of the invention

Thus, the object of the present invention is to provide an article which is easy to clean, has a high scratch resistance and which has a high temperature resistance of e.g. greater than 350 ° C, and to provide a method of making this article.

Brief description of the invention

This object is achieved by the subject matter of claim 1. Preferred embodiments of the subject matter are defined in subclaims 2 to 10, which are also included in combination with one another. Further, the object is achieved by the method according to claim 1 1. Preferred embodiments of the method are defined in claims 12 to 15, which are also included in combination with each other.

Detailed description of the invention

The present invention relates to an article having a high temperature resistant omniphobic release coating comprising: an inorganic substrate, an amorphous silica-containing adhesive layer, and an omniphobic release layer. The amorphous silica-containing primer layer is located between the substrate and the omniphobic non-stick coating. It is also preferred if the non-stick coating is applied directly to the primer layer.

In accordance with the invention, it is particularly preferred that the primer layer be applied directly to the substrate, i. that e.g. no primer is used. In embodiments, the article is comprised of an inorganic substrate, an amorphous silica-containing primer layer, and an omniphobic release layer.

Surprisingly, it has been found that the specific combination of inorganic substrate, amorphous silicon dioxide-containing adhesion promoter layer, and omniphobic non-stick layer is easy to clean, has high scratch resistance, and has high temperature resistance.

High temperature resistant in the sense of the present invention means a resistance to temperatures higher than 350 ° C, preferably higher than 380 ° C, and in embodiments up to 400 ° C, over a period of at least 24 hours, preferably 48 hours. High-temperature resistance in the sense of the present invention also means that, after at least ten contamination cycles, there is a cleanability of the surface of a suitably temperature-treated sample of baked food residues, i. that the treated layer does not differ from the original layer.

Omniphobe means both hydrophobic and oleophobic, i. repellent to polar substances, e.g. Water, as well as non-polar substances, e.g. organic compounds.

The primer layer according to the invention comprises amorphous silicon dioxide. In particular, the proportion of amorphous silica in the layer is 70-100% by weight, preferably 90-99% by weight, particularly preferably 95-98% by weight. In embodiments, the primer layer itself is amorphous. The adhesion promoter layer preferably consists of amorphous silicon dioxide. However, crystalline components, e.g. crystalline nanoparticles, including nanoparticles of crystalline silica.

The presence of amorphous silicon dioxide (SiO ₂ ) in the primer layer is, surprisingly, associated with positive effects compared to SiO _x -containing primer layers in which the silicon oxide contains organic residual groups. This can be explained by the fact that Si0 ₂ layers form a higher adhesion to the inorganic substrate, which associated with improved temperature resistance. The reason for this is that the chemical compatibility of the Si0 ₂ layer to the inorganic substrate is larger in comparison to SiO _x layers. Thus, the omniphobic release layer can be more strongly bonded to the substrate, which in turn increases the scratch resistance and high temperature resistance.

The nature of the substrate is not limited according to the invention, as long as the substrate is inorganic. The substrate may be planar (such as baking trays or slices) or three-dimensional in shape (such as oven tubes). In embodiments, the organic substrate comprises a material selected from the group comprising glass, enamel, metal, or ceramic. All types of glass are suitable as substrate, e.g. Borofloate, soda-lime, or quartz glass. Preferably, the inorganic substrate is enamel, e.g. an enamelled metal surface. In embodiments, the substrate comprises hydroxyl groups on the surface. These can form covalent bonds with the amorphous silicon dioxide-containing adhesion promoter layer with elimination of water, which in turn results in excellent adhesion of the adhesion promoter layer to the substrate.

The primer layer can be applied by any conventional coating method, e.g. with liquid coating methods (such as spray or dipping method), if appropriate using solvents or dispersants, or with deposition methods from the gas phase. In particular, the primer layer is a primer layer obtainable by a process in which the substrate is coated at atmospheric pressure and is selected from the group of CVD plasma processes or flame treatment processes. With suitable setting of the process parameters, an amorphous silicon dioxide-containing adhesion promoter layer can be produced, which forms a good adhesion to the substrate as well as to the omniphobic non-stick layer. Next, the equipment required by atmospheric pressure processes is much lower than in processes that take place in a vacuum.

The amorphous Si0 ₂ in embodiments may be formed reactively during the deposition process, eg, from precursor substances (ie, precursors). Suitable precursors are not limited according to the invention, as long as they are able to form Si0 ₂ in the deposition process. In particular, the primer layer is formed using a siloxane and / or silane precursor, preferably HMDSO (hexamethyldisiloxane), TEOS (tetraethylorthosilicate), DMS (dimethylsilane) or combinations thereof. Thus, an efficient and inexpensive formation of an amorphous silica-containing adhesion promoter layer according to the present invention is possible. Suitable process conditions for a CVD plasma process at atmospheric pressure are as follows: The ignition of the plasma in a plasma nozzle takes place by means of an electrical discharge. The discharge can be both an arc discharge and a disabled discharge. The treatment of the substrate surface can take place in a relative movement of the nozzle to the substrate surface. As adjustment parameters are possible in embodiments: 50-200 W, preferably 80-120 W, electrical power; Treatment width: 1-20 mm, preferably 5-10 mm; Traversing speed: 1-10 cm / s, preferably about 4-6 cm / s; Nozzle distance to substrate surface: 1-20 mm, preferably approx. 5-10 mm. Compressed air (flow rate: 1-20 l / min, preferably 5-10 l / min) can be used as the carrier gas. The process gas can be added at a flow rate of 1-50 ml / min, preferably 20-40 ml / min.

Suitable process conditions for an atmospheric pressure flame treatment method are e.g. as follows: As the fuel gas, e.g. Propane and / or butane used. A mixture of air, fuel gas and precursor gas may e.g. ignited in a Schlitzbrennerdüse and the substrate surface are traversed with the colorless area of the flame. The "fuel gas: air" ratio may be e.g. 10 l / min: 5,000 l / min, preferably 50 l / min: 1,000 l / min. The travel speed in embodiments is 1-10 cm / s, preferably about 4-6 cm / s. The precursor gas flow in embodiments is 1-20 ml / min, preferably 5-15 ml / min. The distance to the substrate surface is e.g. 10-100 mm, preferably 20-50 mm.

The layer thickness of the adhesion promoter layer is not critical. In embodiments, the adhesion promoter layer has a layer thickness in the range of less than 500 nm, preferably 1-300 nm, more preferably 5-100 nm, more preferably 10-50 nm. Such layer thicknesses allow a particularly good adhesion, so that the high temperature resistance is particularly good is guaranteed. This can be clarified by the fact that this low layer thickness enables a good mechanical connection of the non-stick layer to the substrate. Furthermore, transparent coatings can be obtained which are preferred according to the invention.

The release layer is not limited as long as it has omniphobic properties. Omniphobic release coatings are known in the art. In particular, the commercially available "Nanoclean" coatings of the company. PEMCO can be used. The non-stick layer is preferably applied wet-chemically and then dried, wherein the application preferably takes place via a spraying, dipping, flooding, abrading or spinning process.

The non-stick layer preferably comprises a silicon compound. Thus, a particularly good adhesion to the adhesion promoter layer and to the substrate is the formation of covalent bonds possible, which in turn results in improved scratch resistance and high temperature resistance.

In preferred embodiments, the release layer is an organic-modified network deposited via a sol-gel process. Thus, an omniphobic non-stick coating can be produced which has a particularly good cleanability, scratch resistance and adhesion to the substrate. In particular, the non-stick layer contains nanoparticles, which further increases the scratch resistance.

In particular, an alcoholic solution of a mixture of tetraethylorthosilicate and methyltriethoxysilane (or their homologues), which are acidic or basic activatable, can be used for the sol-gel process.

The non-stick layer preferably comprises fluorine-containing compounds, in particular preferably fluorine-containing silanes and / or siloxanes, such as e.g. 1 H, 1 H, 2H, 2H-perfluorooctyltriethoxysilane or its homologs. By incorporating such fluorine-containing compounds, particularly good omniphobic effects can be achieved.

The layer thickness of the non-stick layer is not restricted according to the invention. In embodiments, the non-stick layer has a layer thickness in the range of less than 100 nm, preferably 2-50 nm, more preferably 5-20 nm, more preferably 10-15 nm. This allows a particularly good high-temperature resistance. Furthermore, transparent coatings can thereby be obtained, which are preferred according to the invention.

In embodiments, the total layer thickness, i. the sum of the adhesion promoter layer and anti-adhesion layer, 1-600 nm, preferably 10-500 nm, more preferably 20-400 nm.

The non-stick layer is omniphobic, and in particular exhibits a contact angle to a polar substance such as water of 90 ° or more and / or a contact angle to non-polar substances such as methylene iodide, ethylene glycol, thiodiglycol or diiodomethane of 70 ° or more. These contact angle requirements are preferably maintained at a temperature of 350 ° C for 24 hours, preferably at a temperature of 350 ° C for 48 hours.

The article in embodiments has a surface energy of 25 mN / m or less, preferably 20 mN / m or less, these surface energy requirements preferably after a temperature treatment at 350 ° C for 24 hours, more preferably at 48 ° C for 350 ° C Hours, get preserved. The article is preferably selected from household or kitchen appliances, such as, for example, glass window covers, door panes, sight glasses, extractor hoods, or (kitchen) cupboard windows. Further, the article may be a kitchen accessory, such as baking trays, pans, pots, baking pans, cooking utensils, kettles, side or top parts of, for example, hobs or countertops, lamp covers, or a portion of cooking appliances, such as ovens or microwave ovens. In particular, heating plates, glass ceramic hobs, oven tubes, door inner panes, chrome-plated accessory parts or parts made of stainless steel in or on the cooking chamber, such as, for example, grilling grills, grilled spit rods, receiving grids for baking trays, telescopic trays, steam strips, and / or air outlet shutters are suitable as parts of cooking appliances. In particular, the article is an article that is heated and / or comes into contact with heated food. The article is particularly preferably a baking tray or a pan.

The article may be completely or partially coated. When the article is partially coated, the coating is preferably on the part of the article that is heated and / or comes into contact with heated food.

Further, the present invention relates to a method for producing an article having a high-temperature resistant non-stick coating. The method comprises the steps of providing an inorganic substrate, applying an amorphous silicon dioxide-containing adhesion promoter layer to the substrate, applying an omniphobic non-stick layer to the adhesion promoter layer. With this method, an article can be prepared that is easy to clean, has high scratch resistance, and that exhibits high-temperature resistance at temperatures of, for example, 60.degree. greater than 350 ° C.

Preference is given to prior purification of the substrate by washing with aqueous (e.g., acidic or basic) detergents or organic detergents. In this case, possibly existing coarse dirt such. Dust, oils, grease, fingerprints, etc. removed. So the liability can be increased.

In embodiments, the method is a method in which covalent bonds are formed by condensation reaction of hydroxyl groups of the substrate surface and reactive groups of the adhesion promoter when the adhesion promoter layer is applied to the substrate. So the liability can be further increased.

In particular, in the method, the adhesion promoter layer can be applied to the substrate at atmospheric pressure, the method being selected from the group of plasma CVD processes or flame treatment methods. In a preferred embodiment takes place the application of the adhesion promoter layer using a siloxane and / or silane precursor, in particular HMDSO, TEOS, DMS or combinations thereof. Preferably, the application of the non-stick layer by wet chemical deposition via a sol-gel process and subsequent drying, wherein the application is preferably carried out via a spraying, dipping, flooding, Abreibungs- or spinning process.

These and other embodiments of the method and their advantages are described in detail with respect to the subject matter of the invention and will not be further explained here.

Examples:

The following measuring methods were used to determine the parameters layer thickness, contact angle and surface energy:

Spectral ellipsometry is a measurement method with which the dielectric material properties (complex permittivity or real or imaginary part of the complex refractive index) as well as the layer thickness of thin layers or layer systems can be determined. Ellipsometry determines the change in polarization state of light upon reflection (or transmission) on the sample. As a result of the measurements and by adaptation of a layer model, statements are made on the thickness and the refractive index of the applied layer.

The layer thickness was measured by means of spectral ellipsometry using a spectral ellipsometer SE850 from Sentech. It is measured in the wavelength range of 350-820 nm and based on a Cauchy model approach.

The contact angle was measured with an OCA 15 plus angle angle measuring device from Dataphysics according to the well-known contact angle measuring method according to Owens, Wendt, Rabel and Kaelble.

The contact angle is referred to as the contact angle, and is the angle that a liquid droplet forms on the surface of a solid to form a surface. The balance of forces of an on-surface liquid drop is given by the surface tensions of the liquid and the solid and the interfacial tension between the two media. This balance determines whether a drop of liquid spreads on a surface (ie, the surface wets well) or whether the liquid remains as a drop (the surface wets poorly). In terms of surface tension, a distinction is made between polar and disperse interactions according to the underlying interaction mechanisms between the molecules. The polar forces have their cause in different ways Electronegativities of the atoms of a molecule, resulting in permanent dipoles. The dispersion forces arise from temporarily asymmetrical charge distributions and are thus present between all molecules. The surface tension results from the sum of the polar and the disperse fraction. The determination of the surface tension of a solid is carried out by measuring the different contact angles which leave different test liquids on the solid. The Owens, Wendt, Rabel and Kaelble method is a standard method for calculating the surface free energy of a solid from the contact angle with multiple liquids. The surface free energy is split into a polar part and a disperse part. In the tests, measurements were made on ten drops per sample, the result being the arithmetic mean of the measurements. The test liquids used to determine the surface tensions are water, methylene iodide, ethylene glycol, thiodiglycol and diiodomethane.

Surface energy was determined using the Dataphysics SCA20 software based on contact angle data.

Example 1 :

The substrate used was an enamelled baking tray, which was pre-cleaned by washing and then dried.

Onto the substrate, an amorphous silica-containing primer layer was applied via a CVD plasma process at atmospheric pressure. In this case, a plasma was ignited in a plasma nozzle by an electric arc discharge and treated in a relative movement of the nozzle to the substrate surface, the surface. Setting parameters were: approx. 100 watts electrical power, approx. 10 mm treatment width, approx. 5 cm / s travel speed, approx. 10 mm nozzle distance to the substrate surface, approx. 5 bar compressed air (10 l / min). HMDSO was used as process gas (flow rate: approx. 30 ml / min.). The layer thickness of the transparent adhesion promoter layer was below 200 nm.

Subsequently, the surface coated with the adhesion promoter was provided with an omniphobic non-stick layer. In this case, a commercially available "Nanoclean" coating from PEMCO was sprayed with a spray gun in accordance with the manufacturer's instructions. The process conditions were as follows: pressure: 2.5 bar, distance 15 cm, 2 passes, drying at room temperature. The total layer thickness of the resulting transparent coating (adhesion promoter + omniphobic non-stick layer) was less than 500 nm. The properties of the coated baking tray after production were as follows: contact angle: greater than 90 ° (water); Contact angle greater than 70 ° (methylene iodide); Surface energy: less than 20 mN / m. After 24 hours of storage at 350 ° C of the coated baking sheet, the results were as follows: contact angle: greater than 90 ° (water); Contact angle greater than 70 ° (methylene iodide); Surface energy: less than 20 mN / m.

Example 2:

The production of a coated baking sheet was carried out analogously to Example 1, with the difference that the amorphous silicon dioxide-containing adhesive layer was applied by means of flame treatment. In this case, a gas mixture (air, fuel gas and HMDSO precursor) was ignited in a Schlitzbrennerdüse and traversed the substrate surface with the colorless region of the flame. The fuel gas to air ratio was 50 / 1,000 l / min, the travel speed 5 cm / s, the gas flow rate 10 ml / min (15% HMDSO), the distance to the substrate surface was 30 mm.

The layer thicknesses achieved were analogous to Example 1. The coated baking sheet had a contact angle of greater than 90 ° (water) and a contact angle of greater than 70 ° (methylene iodide) both directly after preparation and after storage for 24 hours at 350 ° C ), as well as a surface energy of less than 20 mN / m.

Comparative Example

As a comparative example, a coated baking sheet is produced analogously to Examples 1 and 2, with the difference that an SiO _x layer was applied instead of the amorphous silicon dioxide-containing adhesion promoter layers. The substrate was silanized before application of the "Nanoclean" coating according to the manufacturer's instructions from PEMCO by flame treatment.

The so coated baking sheet had a surface energy of 20 mN / m directly after production. However, surface energy increased to 48 mN / m after 24 hours storage at 350 ° C, i. the temperature resistance was lower. As a result, the cleanability of the baking sheet was deteriorated in comparison with Examples 1 and 2.

Claims

Claims:

An article having a high temperature omniphobic non-stick coating comprising: an inorganic substrate, an adhesion promoter layer containing amorphous silica, and an omniphobic release coating.

2. The article of claim 1, wherein the inorganic substrate comprises a material selected from the group consisting of glass, enamel, metal or ceramic, preferably enamel.

3. An article according to claim 1 or 2, wherein the primer layer is obtainable by a method in which the substrate is coated at atmospheric pressure, and which is selected from CVD plasma method or flame method.

4. The article according to at least one of claims 1 to 3, wherein the adhesion promoter layer is formed using a siloxane and / or silane precursor, in particular HMDSO, TEOS, DMS or combinations thereof.

5. An article according to any one of claims 1 to 4, wherein the non-stick layer comprises a silicon compound and is preferably an organic modified network deposited via a sol-gel process.

6. The article according to at least one of claims 1 to 5, wherein the non-stick layer comprises fluorine-containing compounds, preferably fluorine-containing silanes and / or siloxanes.

7. The article according to at least one of claims 1 to 6, wherein the adhesion promoter layer has a layer thickness in the range of less than 500 nm, preferably 1-300 nm, more preferably 5-100 nm, more preferably 10-50 nm, wherein the layer thickness is measured by spectral ellipsometry.

8. The article according to claim 1, wherein the non-stick layer has a layer thickness in the range of below 100 nm, preferably 2-50 nm, more preferably 5-20 nm, more preferably 10-15 nm , wherein the layer thickness is measured by spectral ellipsometry.

9. The article according to at least one of claims 1 to 8, wherein the contact angle of the non-stick coating against water is 90 ° or more and / or the contact angle to methylene iodide 70 ° or more, preferably after a temperature treatment at 350 ° C for 24 h , wherein the contact angle is measured with a contact angle measuring device according to the contact angle measuring method according to Owens, Wendt, Rabel and Kaelble.

10. An article according to any one of claims 1 to 9, wherein the surface energy of the non-stick coating 25 mN / m or less, preferably 20 mN / m or less, preferably after a temperature treatment at 350 ° C for 24 h, wherein the Oberflä - Energy is determined on the basis of contact angle data according to Owens, Wendt, Rabel and Kaelble.

1 1. A method of making an article having a high temperature non-stick coating comprising the steps of:

Providing an inorganic substrate,

Applying an amorphous silica-containing primer layer to the substrate,

Apply an omniphobic non-stick layer to the primer layer.

12. The method of claim 1 1, wherein covalent bonds are formed by condensation reaction of hydroxyl groups of the substrate surface and reactive groups of the adhesion promoter during application of the primer layer to the substrate.

13. The method of claim 11 or 12, wherein applying the primer layer to the substrate at atmospheric pressure is by a method selected from the group of CVD plasma or flame method.

14. The method according to at least one of claims 11 to 13, wherein the application of the adhesion promoter layer using a siloxane and / or silane precursor, in particular HMDSO, TEOS, DMS order combinations thereof, takes place.

15. The method according to at least one of claims 11 to 14, wherein the application of the non-stick layer by wet-chemical deposition via a sol-gel process and subsequent drying takes place, wherein the application preferably via a spray, dipping, flooding, abrasion , or spin process takes place.