Item with non-stick coating

Abstract

The invention relates to an article, in particular cooking and baking accessories, with a coating comprising a first and a second layer, wherein the second layer is a surface layer and comprises a polycondensate of a polymer selected from the group consisting of polyaryletherketone (PAEK) polymer, polyphenylene sulfide (PPS) polymer and a combination thereof, wherein the second layer has a silicon content, measured by energy dispersive X-ray spectroscopy (EDS), of at least 0.05 wt.%, preferably at least 0.1 wt.%, more preferably at least 0.5 wt.%, even more preferably at least 1 wt.%, even more preferably 1-10 wt.%, even more preferably 1-5 wt.%, even more preferably 1-3 wt.% and particularly preferably 1-2 wt.%. Furthermore, the invention relates to a method for coating an article, in particular cooking and baking accessories.

Description

[0001] The present invention relates to an article, in particular cooking and baking accessories, with a coating comprising a polycondensate of a polymer selected from the group consisting of polyaryletherketone (PAEK) polymer, polyphenylene sulfide (PPS) polymer and a combination thereof, wherein the coating has a silicon content, measured by energy dispersive X-ray spectroscopy (EDS), of at least 0.05 wt.% and a method for coating an article, in particular cooking and baking accessories.

[0002] PTFE coatings, which are usually applied as a triple coating for higher-quality cookware, i.e. in three layers, usually with at least two baking processes, are state of the art. First, a base layer, usually consisting of a binding resin dissolved in a solvent, for example, PAI dissolved in NMP, is wet-sprayed, dried, and pre-crosslinked. Subsequently, a transition layer and a top layer are sprayed on wet-on-wet, with the top layer essentially containing fluoropolymer, usually PTFE. The entire coating is then baked for approximately 10 minutes at 420°C. These coatings can be modified with pigments and various fillers. The disadvantage is the use of fluoropolymers and the fact that the baking temperature is significantly higher than the decomposition temperature of PTFE, which can produce substances that are hazardous to health (PFAS).In addition, they have the disadvantage of releasing toxic substances (PFAS) when used at high temperatures.

[0003] In addition, so-called ceramic sol-gel coatings, which contain silicones to achieve the non-stick effect and are usually very brittle and not durable, are known.

[0004] According to the EU regulation, the limit value for PFAS in the EU is to be reduced from 2024 onwards to such an extent that, from today's perspective, PTFE coatings ("Teflon") will have to be replaced as non-stick coatings.

[0005] The object of the present invention is to provide a coated article, in particular coated cookware and bakeware, with an improved non-stick coating and a manufacturing process therefor.

[0006] The above object is achieved by providing an article, in particular a cooking and baking accessory, according to claim 1 and a method according to claim 6. Preferred embodiments are presented in the subclaims. According to the invention, the term "cooking and baking accessory" encompasses any article whose shape is suitable for holding food and subsequent cooking and baking. Therefore, in addition to pans, the above term also encompasses baking trays, baking pans, etc., as well as grill trays, grill containers, grill racks, etc.

[0007] In a first aspect of the invention, an article is provided, in particular cooking and baking accessories, with a coating comprising a first and a second layer, wherein the coating has a surface layer and wherein the first and optionally the second layer comprise a polycondensate of a polymer selected from the group consisting of polyaryletherketone (PAEK) polymer, polyphenylene sulfide (PPS) polymer and a combination thereof, wherein the surface layer of the coating has a silicon content, measured by energy dispersive X-ray spectroscopy (EDS), of at least 0.05 wt.%, preferably at least 0.1 wt.%, more preferably at least 0.5 wt.%, even more preferably at least 1 wt.%, even more preferably 1-10 wt.%, even more preferably 1-5 wt.%, even more preferably 1-3 wt.% and particularly preferably 1-2 wt.%.

[0008] To measure the silicon content, sample plates with the coatings measuring approximately 2 x 2 cm are prepared. Since the coatings are not electrically conductive, they are sputtered with gold. The samples are then analyzed using energy-dispersive X-ray spectroscopy (EDS). At least nine spectra are recorded on each sample surface, and the results are averaged. The analysis software of an EDS system typically outputs the measurement results in wt.%. These values ​​can be converted to atomic percent by dividing them by the value for the respective atomic weight.

[0009] Energy-dispersive X-ray spectroscopy (also known as EDS, EDX, or EDXA) is a powerful technique that allows users to analyze the elemental composition of a desired sample. The main operating principle of EDS is the ability of high-energy electromagnetic radiation (X-rays) to eject "core" electrons (electrons not in the outermost shell) from an atom. This principle is known as Moseley's law, which states that there is a direct relationship between the frequency of the emitted light and the atomic number of the atom.

[0010] When these electrons are removed from the system, a gap remains that can be filled by a higher-energy electron, which releases energy as it relaxes. The energy released during this relaxation process is unique for each element in the periodic table, and so bombarding a sample with X-rays can be used to determine which elements are present and in what proportions.

[0011] EDS works with three main components: an emitter, a collector, and an analyzer. These components are typically also equipped with an electron microscope such as a SEM or TEM. The combination of these three components allows for analysis of both the number of emitted X-rays and their energy (compared to the energy of the originally emitted X-rays).

[0012] The EDS data are displayed as a graph with KeV on the x-axis and peak intensity on the y-axis. A computer program converts the peak positions on the x-axis into the atoms for which the energy changes represent.

[0013] Preferably, the first layer contains no silicon. This can be achieved by not using any ingredients containing silicon in the production of the first layer. This improves the adhesion between the first and second layers. Furthermore, the adhesion between the first layer and the object, particularly cooking and baking utensils, is also improved.

[0014] The advantage of the invention is that the positive properties regarding mechanical properties, wear resistance, and chemical resistance can be combined with excellent non-stick properties that are equal to and even superior to those of PTFE. In contrast, coatings made of silicone resins, elastomers, or sol-gel coatings are mechanically and chemically less resilient and quickly lose their non-stick properties.

[0015] The object can also be a sheet, plate, etc. made of aluminum, steel, stainless steel, copper, and other metals with a melting point above 300°C. The object can be coated on one or both sides. A particular advantage is that these can be subsequently formed, folded, drawn, or embossed without the coating detaching from the substrate and without the second layer peeling or peeling off the first.

[0016] The polycondensate is preferably made of at least one polymer with an average melt viscosity of more than 150 Pa.s, preferably 200-500 Pa.s, more preferably 300 to 500 Pa.s, and preferably also of a polymer with an average melt viscosity of at most 150 Pa.s, preferably at most 120, more preferably at most 100 Pa.s or particularly preferably at most 90 Pa.s, measured according to ISO 11443 at 400°C. By using a polycondensate made of at least one polymer with an average melt viscosity of more than 150 Pa.s, the adhesion to the object and between the layers is improved. By using another polymer with an average melt viscosity of at most 150 Pa.s, the leveling of the layer during production is improved. In addition, the production of a sufficiently fine-particle (based on the solids) dispersion is facilitated.

[0017] The article, in particular cooking and baking accessories, preferably has a contact angle of the coating against water of at least 90°, preferably at least 95°, particularly preferably 100° to 120°. In comparison, a coating with pure PAEK polymer has a contact angle of approximately 90°, and a coating with polytetrafluoroethylene (PTFE) has a contact angle of approximately 100°. For measurement, water droplets are placed on the coating, and the contact angle is optically evaluated using a camera. The measurements are carried out according to DIN EN ISO 19403-2:2020-04. With the help of the coating according to the invention, very good non-stick properties can therefore be achieved, which can even exceed those of PTFE.

[0018] Preferably, the article, in particular the cooking and baking accessory, comprises several sublayers. It is possible to vary the silicon content of the sublayers. Since a higher silicon content leads to improved coating hardness, the surface layer or the near-surface layers preferably have a higher silicon content. The sublayers may also be indistinguishable, so that the coating appears as a single layer. In this case in particular, the silicon content of the coating can increase toward the surface of the coating, regardless of the presence of sublayers.

[0019] Preferably, the coating can be produced without fluorine compounds. According to the invention, this is particularly the case if the coating contains a maximum of 1000 ppb, preferably a maximum of 100 ppb, and particularly preferably a maximum of 25 ppb of total fluorides, measured by combustion ion chromatography (TOF-CIC).

[0020] Specifically, to perform the combustion ion chromatography (TOF-CIC) measurement method, coating samples are placed in ceramic boats and introduced into a furnace, where pyrohydrolysis takes place at 900–1000 °C in a humid, O2-rich environment. Under these conditions, the samples are oxidized, the strong carbon-fluorine bond is broken, and the vapors are passed through an absorption solution containing Ar. The HF produced during the combustion of organic fluorine dissociates in the absorption solution to form H+ and F- ions. The absorption solution samples, which also contain an internal standard for calibrating the analytical results, are then transferred to an ion chromatograph for analysis, where fluoride is measured.

[0021] The non-stick effect (tested using standard pancakes according to DIN EN 60350-2) of the coating according to the invention met the expectations for a non-stick effect in cookware without the addition of oil and without any fluorine components. In particular, no fluorosurfactant was required to promote leveling in the production of the coating.

[0022] There are no particular restrictions on the thickness of the coating. It can be up to 1 mm, for example. However, for cookware and frying utensils, a maximum of 50 µm is sufficient, preferably a maximum of 40 µm, more preferably a maximum of 30 µm, and particularly preferably a maximum of 25 µm, and / or the second layer preferably has a thickness of a maximum of 100 µm, preferably for cookware and frying utensils a maximum of 20 µm, more preferably 1 to 15 µm, and even more preferably 1 to 5 µm. In another embodiment, this can also have a thickness of 5 to 15 µm. The measuring method is carried out in accordance with the standard DIN EN ISO 2808:2019-12. The stated layer thicknesses are average values ​​resulting from at least 3 measurements at one point and at least 3 different points on a surface. The layer thickness is measured using a layer thickness measuring device, e.g. the “QNIX 4500” device from the manufacturer Automation Dr. Nix GmbH & Co KG.For magnetic substrates, the measurement is performed using a change in the magnetic field or the Hall effect (DIN EN ISO 2178, ASTM B499, ASTM D7091). For non-magnetic substrates, the measurement is performed using eddy current (DIN EN ISO 2360, ASTM D7091). The principles of measurement technology (DIN 1319, Parts 1 and 3) are observed.

[0023] Therefore, only a thin layer is needed to meet all the requirements of a non-stick coating for food contact. Currently, wear-resistant polytetrafluoroethylene (PTFE) coatings are commonly used in three layers with a layer thickness of approximately 50-60 µm. This coating significantly reduces material usage, volatile organic compounds (VOCs), and energy consumption, in addition to completely avoiding per- or polyfluoroalkyl compounds (PFAS).

[0024] Preferably, the coating also comprises a dry lubricant selected from the group consisting of polyamideimide (PAI), polyimide (PI), graphite, MoS2, boron nitride (hexagonal modification; α-boron nitride), and a mixture thereof, or a decomposition product thereof that may be formed during heating and baking of the coating. This can further improve the cohesion of sublayers and wear resistance.

[0025] In a second aspect of the invention, a method is provided for coating an article, in particular cooking and baking accessories, with a coating comprising a first and a second layer, wherein the coating has a surface layer, comprising the following steps: 1) Production of a first layer comprising a) applying a powder mixture, dry or as a dispersion in a liquid, comprising powder particles comprising a polymer selected from the group consisting of polyaryletherketone (PAEK) polymer, polyphenylene sulfide (PPS) polymer and a combination thereof, to the article, in particular the cooking and baking accessory, wherein the application is preferably carried out electrostatically, by fluidized bed sintering or as a dispersion in a liquid, in particular water; b) in the case of dispersion, complete removal of the liquid; c) heating the powder mixture to form a polycondensate; and d) baking the polycondensate above the liquidus temperature of the polycondensate; 2) optionally producing a second or further layer on the first or lower layer, wherein sub-steps a) to d) are repeated, wherein the powder mixture optionally comprises particles selected from the group consisting of silicon particles, silicon dioxide particles and a combination thereof, wherein, optionally after step 1d) or 2), a second or further layer comprising an organic silicon compound, preferably an element from the group consisting of silicone oil, polysiloxane resin, silicone elastomer and a mixture thereof is applied and cured between the glass transition temperature and the liquidus temperature of the first and optionally further layer(s), and wherein the silicon content of the surface layer of the second or further layer is controlled by one of the group consisting of silicon content in the powder mixture, silicon content in the layer comprising an organic silicon compound and a combination thereof such that the surface layer of the article has a silicon content, measured by energy dispersive X-ray spectroscopy (EDS), of at least 0.05 wt.%, preferably at least 0.1 wt.%, more preferably at least 0.5 wt.%, even more preferably at least 1 wt.%, even more preferably 1-10 wt.%, even more preferably 1-5 wt.%, even more preferably 1-3 wt.% and particularly preferably 1-2 wt.%.

[0026] The layer comprising the organic silicon compound preferably has a maximum thickness of 100 µm, preferably a maximum of 20 µm for cookware and frying utensils, more preferably 1 to 15 µm, even more preferably 1 to 5 µm. In another embodiment, it can also have a thickness of 5 to 15 µm. The measurement method was carried out as described above for measuring the thickness of the coating in the first aspect of the invention.

[0027] Preferably, 0.1 to 5 wt.%, preferably 0.5 to 2.5 wt.%, particularly preferably 1 to 2 wt.% of particles consisting of the group selected from silicon particles, silicon dioxide particles and a combination thereof are added.

[0028] Preferably, the particles consisting of silicon particles, silicon dioxide particles, and a combination thereof have a mass-related particle size distribution D50 of at most 1 µm, as measured by static image analysis according to ISO 13322-1:2014. The addition of macroscopic glass particles, for example, glass spheres or glass flakes with dimensions greater than 1 µm, can improve the mechanical resistance and hardness of the coating at elevated temperatures, but has a negative effect on the non-stick effect after wear / aging. The same applies to carbon fibers.

[0029] The layer comprising the organic silicon compound preferably has a thickness of at most 30 µm, preferably at most 20 µm, more preferably at most 15 µm, even more preferably at most 10 µm, and most preferably at most 5 µm. The measurement method was carried out as described above for measuring the thickness of the coating in the first aspect of the invention.

[0030] The powder mixture preferably comprises at least two polymers, and powder particles comprising the first polymer preferably have a mass-related grain size distribution D50, measured by static image analysis according to ISO 13322-1:2014, of at most 70 µm, preferably at most 60 µm, more preferably at most 50 µm, even more preferably at most 40 µm, in particular at most 30 µm, and powder particles comprising the second polymer preferably have a mass-related grain size distribution D50, measured by static image analysis according to ISO 13322-1:2014, of at most 30 µm, preferably 25 µm, more preferably at most 20 µm, even more preferably at most 15 µm, in particular preferably 10 µm. This can increase the mechanical resistance. This could be achieved, for example, by adding PEK and / or PEKK. Even smaller mass-related concentrations of the second polymer of at least 2 wt.-%, preferably at least 5 wt.%, particularly preferably at least 10 wt.% showed a wear-reducing effect.

[0031] Conversely, by adding PPS in amounts of up to 80 wt.%, 90 wt.%, or 95 wt.%, a further reduction in the baking temperature during coating production and a further improvement in the non-stick effect of the produced coating could be measured.

[0032] Preferably, the powder mixture is in the form of a dispersion and comprises the liquid water.

[0033] Preferably, the PAEK polymers are selected from the group consisting of polyetheretherketone (PEEK), polyetherketone (PEK), polyetherketoneketone (PEKK) and polyetherketoneetherketone (PEKKEK), and wherein the powder mixture preferably comprises at least two PAEK polymers, or at least one PAEK polymer and PPS polymer.

[0034] Preferably, the at least two PAEK polymers, or at least one PAEK polymer and PPS polymer, have different melting temperatures.

[0035] Preferably, the two PAEK polymers, or at least one PAEK polymer and PPS polymer, have different melt viscosities, measured according to ISO 11443 at 400°C.

[0036] The average melt viscosity of at least one polymer is preferably more than 150 Pa.s, preferably 200-500 Pa.s, more preferably 300 to 500 Pa.s, measured according to ISO 11443 at 400°C. This primarily improves the adhesion of the second layer to the first layer. The average melt viscosity of at least one further polymer is preferably at most 150 Pa.s, preferably at most 120, more preferably at most 100 Pa.s or particularly preferably at most 90 Pa.s, measured according to ISO 11443 at 400°C. This makes the flow on heating for polycondensation on a surface to be coated significantly smoother. The non-stick effect of the coated surface is thereby improved. This applies even when the particles are large relative to the layer thickness (e.g. 25 µm grain size D50 for 25 µm layer thickness).

[0037] Preferably, the powder mixture comprises a dry lubricant selected from the group consisting of polyamideimide (PAI), polyimide (PI), graphite, MoS2, boron nitride (hexagonal modification; α-boron nitride) and a mixture thereof.

[0038] Preferably, the powder mixture comprises the dry lubricant in an amount of 0.1 to 20 wt.%.

[0039] The baking temperature (substrate temperature) is preferably at most 60°C, preferably at most 50°C, more preferably at most 40°C, even more preferably at most 30°C, and most preferably at most 20°C above the liquidus temperature of the polycondensate. Tests have shown that the non-stick effect improved with decreasing baking temperature, while it became too poor at too high a baking temperature.

[0040] Preferably, the process, in particular in the step of heating the powder mixture to form a polycondensate, is carried out without using a fluorosurfactant.

[0041] Preferably, the layer comprising the organic silicon compound has a thickness of at most 30 µm after curing, preferably at most 20 µm, more preferably at most 15 µm, even more preferably at most 10 µm, and most preferably at most 5 µm. The measurement method was carried out as described above for measuring the thickness of the coating in the first aspect of the invention.

[0042] Preferably, the powder mixture is in the form of a dispersion and the liquid comprises water.

[0043] In the following, the invention is explained in more detail using exemplary embodiments and the associated figures.

[0044] The figures serve solely to facilitate a better understanding of the invention and are only schematic and not drawn to scale. The invention is also not intended to be limited to the exemplary embodiments. Identical or equivalent parts are provided with the same reference numerals. Fig. 1 shows cooking and baking accessories with an applied dispersion layer in schematic cross-section according to a reference example, Fig. 2 shows cooking and baking accessories with coating according to a reference example, Fig. 3 shows a process sequence for coating using various process stages according to an embodiment of the process according to the invention, Fig. 4 shows a flow diagram for a coating using a dispersion process. Fig. 5 shows a section of a sample plate for EDS measurement

[0045] An object to be coated or an area of ​​the cooking and baking equipment to be coated represents the substrate SU to be coated. The surface to be coated can first be subjected to a chemical and / or mechanical activation treatment. This can be done by mechanical roughening, for example, using a sandblaster, or by etching with acids, alkalis, or by plasma or laser treatment. A suitably pretreated surface has additional chemical / physical bonding points, is clean and grease-free, and, in the case of roughening, has a larger surface area, which leads to better adhesion of the coating to be applied.

[0046] A layer of DS of a dispersion is then applied to this surface. This dispersion contains all the components of the coating in a finely divided and, as far as possible, homogeneous particle size distribution, dispersed in a solvent or solvent mixture. An application method is selected that is suitable for producing the desired layer thickness. The average particle size (D50) of the solids contained in the dispersion corresponds at most to the desired layer thickness for the coating, but is preferably selected to be lower. Fig. 1 shows a substrate SU coated in this way with an applied dispersion layer DS.

[0047] After carrying out a temperature program during which the substrate provided with the dispersion layer DS or the cooking and baking accessories is heated to a temperature above the melting point of the thermoplastic(s) contained in the dispersion, a homogeneous coating BS is obtained which is pore-free and thus dense and has good mechanical cohesion and good adhesion to the substrate SU. Fig. 2 shows the finished cooking and baking accessories based on a reference example.

[0048] It is possible to apply the coating to only a portion of the surface. The remaining area not to be coated can be masked, or an application method for the dispersion can be selected that can differentiate between different surface areas, for example, brushing or printing. The masking can also be achieved using a shadow mask while the dispersion is sprayed on. This shadow mask can also be in the form of a film that is applied to the surface of the substrate SU and leaves out the areas of the surface to be coated. After the dispersion layer DS has been applied, the film can be removed and, for example, peeled off, whereby the areas of the dispersion layer DS applied over it are also peeled off.

[0049] Fig. Figure 3 shows an embodiment of the method according to the invention, in which the silicon content of the surface layer of the coating is controlled by the silicon content of the powder mixture for the second layer. For example, the powder mixtures of embodiments 1 or 2, which are specified below, can be used for this purpose. In embodiments 3 and 4, the organic silicon compound for the second layer can be solid or liquid. If the organic silicon compound is solid in embodiments 3 and 4, it can be applied as a dispersion, as in embodiments 1 and 2. If it is liquid, the liquid can be applied, optionally diluted in solvent.

[0050] In the embodiments 1 to 4, despite a smaller particle diameter of the solids contained in the dispersion, a higher layer thickness can still be achieved. For this purpose, after applying the first dispersion layer DS1, as in Fig. 3a, at least the solvent is removed, or alternatively, the first dispersion layer is additionally pre-compacted by a heat treatment. In a second step, the dispersion coating is repeated and a second dispersion layer DS2 is applied. If necessary, this layer can also be pre-compacted and the coating step repeated again. Finally, as shown in Fig. As shown in Figure 3c, the structure of dispersion layers consisting of several partial layers is brought to a temperature above the melting point of the thermoplastic in a final step, whereby a completely compacted, pore-free, closed coating BS is obtained on the substrate SU.

[0051] A composition suitable for application by dispersion processes and also friction-reduced according to the invention contains, for example, solids in the following weight proportions: Example 1: Layer 1 (DS1): 100 weight percent PEEK; Layer 2 (DS2): 99 weight percent PEEK and 1 weight percent SiO2 particles Example 2: Layer 1 (DS1): 100 weight percent PEEK; Layer 2 (DS2): 50 weight percent PEEK, 49 weight percent PPS and 1 weight percent SiO2 particles Example 3: Layer 1 (DS1): 100 weight percent PEEK; Layer 2 (DS2): 100 weight percent organic silicon compound Example 4: Layer 1 (DS1): 50 weight percent PEEK and 49 weight percent PPS; Layer 2: 100 weight percent organic silicon compound

[0052] The PEEK particles in embodiments 1 to 4 have a high molecular weight fraction (or first polymer) with an average melt viscosity of 300 to 500 Pa.s and a low molecular weight fraction (or second polymer) with an average melt viscosity of at most 90 Pa.s, measured according to ISO 11443 at 400°C. Powder particles comprising the first polymer have a mass-related grain size distribution D50, measured by static image analysis according to ISO 13322-1:2014, of at most 30 µm, and powder particles comprising the second polymer have a mass-related grain size distribution D50, measured by static image analysis according to ISO 13322-1:2014, of at most 10 µm.

[0053] The silicon dioxide particles in embodiments 1 and 2 have a mass-related grain size distribution D50 of 1 µm, measured by static image analysis according to ISO 13322-1:2014.

[0054] Color additives can be added if necessary. It is possible to apply one or more coats.

[0055] The solids are dispersed, optionally with auxiliary agents, in a solvent, which may be water or, advantageously, is miscible or mixed with water, e.g., alcohol and, in particular, isopropanol. The dispersion mixture then contains approximately 30 percent by weight of the above-mentioned solids.

[0056] In Fig. Figure 4 illustrates the process sequence just described more clearly using a flowchart. The process comprises, as step 1, the production and preparation of the powder mixture. For this purpose, the ingredients, which are selected from thermoplastic polymer, silicon or silicon dioxide particles, organic silicon compound (if present as a solid), filler, and dry lubricant, are either reduced to a suitable particle size, preferably by grinding and / or by subsequent sorting according to the desired grain size distribution, as narrow as possible.

[0057] In parallel, in step 2, the solvent is prepared. This solvent is preferably environmentally and health-safe, preferably water-based, and in particular consists of a mixture of alcohol and water, e.g., isopropanol and water. A preferred solvent composition contains, for example, 25 to 75 percent by weight of isopropanol in water. A solvent containing approximately 25-50 percent by weight of isopropanol in water is particularly preferred.

[0058] In step 3, the dispersion is prepared by adding the solvent to the prepared powder mixture, preferably maintaining a solids content of 20 to 50 percent by weight. To improve dispersion stability, known dispersion aids can be added in small amounts.

[0059] In step 4, the surface of the object is coated, for example, by spraying, dipping, brushing, printing, or spin-coating. The goal is to achieve the most homogeneous layer thickness possible for the dispersion layer, and any areas of the surface not to be coated are left out of the coating.

[0060] In step 5, the solvent is removed, preferably by evaporation, which may optionally be assisted by reduced pressure or elevated temperature, for example 80°C.

[0061] In the next step 6, the cooking and baking accessories with the applied dried dispersion layer are converted into a homogeneous coating by heating and melting the thermoplastics and then the cooking and baking accessories are cooled down again.

[0062] Following this step 6, for embodiments 1 to 4, a finished coating can be obtained at point 7 after passing through one of the process variants V1 to V3 (optionally several times). In embodiments 1 and 2, the silicon content of the coating is controlled solely by the content of silicon dioxide particles in the powder mixture such that the coating of the article, in particular the cooking and baking accessory, has a silicon content, measured by energy-dispersive X-ray spectroscopy (EDS), of at least 0.05 wt.%, preferably at least 0.1 wt.%, more preferably at least 0.5 wt.%, even more preferably at least 1 wt.%, even more preferably 1-10 wt.%, even more preferably 1-5 wt.%, even more preferably 1-3 wt.% and particularly preferably 1-2 wt.%.

[0063] According to a variant V1 of the method, it is possible to carry out steps 4 to 7 again directly after step 5.

[0064] A second variant V2 follows step 6, whereby after melting the first dispersion layer, a new dispersion layer is applied (step 4) and compacted accordingly (steps 5 to 7).

[0065] According to a third variant V3 of the process, after producing a first coating according to step 6, a second partial coating layer, different from the first coating, is applied. For this purpose, a further dispersion is produced according to process steps 1 to 3 and used to coat the cooking and baking accessories according to steps 4 to 6. Here, too, the process according to variants V1 and V2 can be modified by repeating individual process steps or individual process step sequences to achieve a desired layer thickness.

[0066] In embodiments 3 and 4 (powder mixture without silicon or silicon dioxide particles), the silicon content of the surface layer of the coating is controlled such that the surface layer has a silicon content, measured by energy-dispersive X-ray spectroscopy (EDS), of at least 0.05 wt. %, preferably at least 0.1 wt. %, more preferably at least 0.5 wt. %, even more preferably at least 1 wt. %, even more preferably 1-10 wt. %, even more preferably 1-5 wt. %, even more preferably 1-3 wt. %, and particularly preferably 1-2 wt. In contrast, in embodiments 1 and 2, the same silicon content of the surface layer of the coating is achieved by controlling the silicon content of the powder mixture for the second layer (DS2).

[0067] It is also possible to combine the principles from embodiments 1 / 2 with those from 3 / 4, ie to use a silicon-containing powder mixture for the second layer and to apply a further layer comprising an organic silicon compound. In this case, the silicon content of the coating is controlled by both the silicon content in the powder mixture and the silicon content in the surface layer such that the coating of the article, in particular the cooking and baking accessory, has a silicon content, measured by energy-dispersive X-ray spectroscopy (EDS), of at least 0.05 wt.%, preferably at least 0.1 wt.%, more preferably at least 0.5 wt.%, even more preferably at least 1 wt.%, even more preferably 1-10 wt.%, even more preferably 1-5 wt.%, even more preferably 1-3 wt.% and particularly preferably 1-2 wt.%.

[0068] Fig. Figure 5 shows a section of a sample plate with the coating according to the invention. The entire sample plate has a size of approximately 2 x 2 cm. Since the coatings are not electrically conductive, they are sputtered with gold before measurement. As shown in Fig. As shown in Figure 5, at least nine spectra are recorded from each sample surface using an EDS measuring device. This yields values ​​for the silicon content in wt.%, which are then averaged.

[0069] In particular, when using fine particles for the dispersion, a particularly homogeneous coating can be obtained, which makes multiple coatings advantageous or even necessary due to the small particle diameters.

[0070] A protein test was conducted, which tests the non-stick properties against egg white, specifically the whites of chicken eggs. The pan was manufactured according to Example 1. The pan was rinsed before the test and then baked at 300°C for 30 minutes. The pan was then heated on the stovetop to 190°C + / - 10°C. An egg white was added and fried for approximately 2-3 minutes (until solid) without prior addition of oil or fat.

[0071] This test was repeated until the protein could no longer be removed without leaving residue.

[0072] A pan with a PEEK / PPS coating without Si failed this test, or only passed it a few times. In contrast, the pan according to the invention passed the test 20 to >100 times, depending on the design, and the higher the Si content, the higher the test rate.

[0073] However, a version with a single-layer pan with silicon or SiO2 had a reduced scratch resistance (cross-cut) and wore faster (Stiwatest).

[0074] Although the invention has been explained using only a few exemplary embodiments, it is not limited to these. Possible variations arise in particular through the appropriate selection of fillers and, if appropriate, through mixtures of different fillers. The proportions of the components of the coating are selected depending on the desired load of the coating. The same applies to the layer thicknesses, which are not limited to the examples given. The coating is advantageously applied to metallic surfaces, although it can also be applied to other surfaces such as ceramic, glass, or suitable plastic. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited non-patent literature

[0000] ISO 11443 [0016, 0036, 0052] DIN EN ISO 19403-2:2020-04

[0017] EN ISO 2808:2019-12

[0022] DIN EN ISO 2178

[0022] ASTM B499

[0022] ASTM D7091

[0022] DIN EN ISO 2360, ASTM D7091

[0022] DIN 1319, Part 1 and Part 3

[0022] ISO 13322-1:2014 [0030, 0052]

Claims

[1] Article, in particular cooking and baking accessories, with a coating comprising a first and a second layer, wherein the coating has a surface layer and wherein the first and optionally the second layer comprise a polycondensate of a polymer selected from the group consisting of polyaryletherketone (PAEK) polymer, polyphenylene sulfide (PPS) polymer and a combination thereof, and wherein the surface layer of the coating has a silicon content, measured by energy dispersive X-ray spectroscopy (EDS), of at least 0.05 wt%, preferably at least 0.1 wt%, more preferably at least 0.5 wt%, even more preferably at least 1 wt%, even more preferably 1-10 wt%, even more preferably 1-5 wt%, even more preferably 1-3 wt% and particularly preferably 1-2 wt%. [2] Article, in particular cooking and baking accessories, according to claim 1, wherein the polycondensate is at least made of a polymer having an average melt viscosity of more than 150 Pa.s, preferably 200-500 Pa.s, more preferably 300 to 500 Pa.s, and preferably further made of a polymer having an average melt viscosity of at most 150 Pa.s, preferably at most 120, more preferably at most 100 Pa.s or particularly preferably at most 90 Pa.s, measured according to ISO 11443 at 400°C. [3] Article, in particular cooking and baking accessories, according to one of claims 1 or 2, wherein the coating has a contact angle against water of at least 90°, preferably at least 95°, particularly preferably 100° to 120°, measured according to DIN EN ISO 19403-2:2020-04. [4] Article, in particular cooking and baking accessories, according to one of claims 1 to 3, wherein the coating comprises further partial layers in addition to the first and second layers and / or wherein the silicon content of the coating increases towards the surface of the coating. [5] Article, in particular cooking and baking accessories, according to one of claims 1 to 4, wherein the coating can be produced without fluorine compounds, preferably at most 1000 ppb, preferably at most 100 ppb, particularly preferably at most 25 ppb total fluorides, measured by combustion ion chromatography (TOF-CIC). [6] Article, in particular cooking and baking accessories, according to one of claims 1 to 5, wherein the thickness of the coating is at most 50 µm, preferably at most 40 µm, more preferably at most 30 µm, particularly preferably at most 25 µm and / or wherein the second layer has a thickness of 5 to 20 µm, preferably 10 to 15 µm. [7] Method for coating an article, in particular cooking and baking accessories, with a coating comprising a first and a second layer, wherein the coating has a surface layer, comprising the following steps: 1) Production of a first layer comprising a) applying a powder mixture, dry or as a dispersion in a liquid, comprising powder particles comprising a polymer selected from the group consisting of polyaryletherketone (PAEK) polymer, polyphenylene sulfide (PPS) polymer and a combination thereof, to the article, in particular the cooking and baking accessory, wherein the application is preferably carried out electrostatically, by fluidized bed sintering or as a dispersion in a liquid, in particular water; b) in the case of dispersion, complete removal of the liquid; c) heating the powder mixture to form a polycondensate; and d) baking the polycondensate above the liquidus temperature of the polycondensate; 2) optionally producing a second or further layer on the first or lower layer, wherein sub-steps a) to d) are repeated, wherein the powder mixture for the second or further layer optionally comprises particles selected from the group consisting of silicon particles, silicon dioxide particles and a combination thereof, wherein optionally after step 1d) or 2) a second or further layer comprising an organic silicon compound, preferably an element from the group consisting of silicone oil, polysiloxane resin, silicone elastomer and a mixture thereof is applied and cured between the glass transition temperature and the liquidus temperature of the first and optionally further layers, and wherein the silicon content of the surface layer of the coating is selected from the group consisting of silicon content in the powder mixture, silicon content in the layer comprising the organic silicon compound and a combination thereof,is controlled so that the surface layer of the coating of the article, in particular the cooking and baking accessory, has a silicon content, measured by energy dispersive X-ray spectroscopy (EDS), of at least 0.05 wt.%, preferably at least 0.1 wt.%, more preferably at least 0.5 wt.%, even more preferably at least 1 wt.%, even more preferably 1-10 wt.%, even more preferably 1-5 wt.%, even more preferably 1-3 wt.% and particularly preferably 1-2 wt.%. [8] Method according to claim 7, wherein the layer comprising the organic silicon compound has a thickness of at most 30 µm, preferably at most 20 µm, more preferably at most 15 µm, even more preferably at most 10 µm, particularly preferably at most 5 µm. [9] The method according to claim 7 or 8, wherein 0.1 to 5 wt.%, preferably 0.5 to 2.5 wt.%, particularly preferably 1 to 2 wt.% of particles consisting of the group selected from silicon particles, silicon dioxide particles and a combination thereof are added to the powder mixture. [10] A method according to any one of claims 8 to 9, wherein the particles consisting of the group selected from silicon particles, silicon dioxide particles and a combination thereof have a mass-related particle size distribution D50 of at most 1 µm, measured by static image analysis according to ISO 13322-1:2014. [11] Method according to one of claims 7 to 10, wherein the layer comprising organic silicon compound has a thickness of at most 30 µm, preferably at most 20 µm, more preferably at most 15 µm, even more preferably at most 10 µm, particularly preferably at most 5 µm, after curing. [12] Method according to one of claims 7 to 11, wherein the powder mixture comprises at least two polymers, and wherein powder particles comprising the first polymer have a mass-related grain size distribution D50, measured by static image analysis according to ISO 13322-1:2014, which is at most 70 µm, preferably at most 60 µm, more preferably at most 50 µm, even more preferably at most 40 µm, in particular at most 30 µm, and powder particles comprising the second polymer have a mass-related grain size distribution D50, measured by static image analysis according to ISO 13322-1:2014, which is at most 30 µm, preferably 25 µm, more preferably at most 20 µm, even more preferably at most 15 µm, in particular preferably 10 µm. [13] A method according to any one of claims 7 to 12, wherein the powder mixture is in the form of a dispersion and the liquid comprises water. [14] Method according to one of claims 7 to 13, wherein the PAEK polymers are preferably selected from the group consisting of polyetheretherketone (PEEK), polyetherketone (PEK), polyetherketoneketone (PEKK) and polyetherketoneetherketone (PEKKEK), and wherein the powder mixture preferably comprises at least two PAEK polymers, or at least one PAEK polymer and PPS polymer. [15] The method according to claim 14, wherein the at least two PAEK polymers, or at least one PAEK polymer and PPS polymer, have different melting temperatures. [16] A process according to claim 14 or 15, wherein the two PAEK polymers, or at least one PAEK polymer and PPS polymer, have different melt viscosities, measured according to ISO 11443 at 400°C. [17] Process according to one of claims 7 to 16, wherein the average melt viscosity of at least one polymer is more than 150 Pa.s, preferably 200-500 Pa.s, more preferably 300 to 500 Pa.s, and preferably the average melt viscosity of at least one further polymer is at most 150 Pa.s, preferably at most 120, more preferably at most 100 Pa.s or particularly preferably at most 90 Pa.s, measured according to ISO 11443 at 400°C. [18] Method according to one of claims 7 to 17, wherein the powder mixture comprises a dry lubricant selected from the group consisting of polyamideimide (PAI), polyimide (PI), graphite, MoS2, boron nitride (hexagonal modification; α-boron nitride) and a mixture thereof. [19] The method of claim 18, wherein the powder mixture comprises the dry lubricant in an amount of 0.1 to 20 wt%. [20] Article according to one of claims 1 to 6, wherein the article is a sheet, a plate, etc. made of aluminum, steel or stainless steel, copper and other metals whose melting temperature is above 300°C, coated on one or both sides.

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