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EP-4739444-A1 - PROCESS FOR COATING AN OBJECT

EP4739444A1EP 4739444 A1EP4739444 A1EP 4739444A1EP-4739444-A1

Abstract

The invention relates to a process for coating an object, preferably (slidable) objects which are subject to wear, in particular cooking and baking equipment, with at least two layers, the process comprising the following steps: 1) producing a first layer, comprising the steps of a) applying to the object, in particular the cooking and baking equipment, a powder mixture, dry or in the form of a dispersion in a liquid, comprising powder particles of at least one polyphenylene sulfide (PPS) polymer and optionally a polyaryletherketone (PAEK) polymer, it being possible for the powder mixture to be prepared without adding fluorine or fluorine-containing compounds, the application preferably being performed electrostatically in a fluidised-bed sintering process or as a dispersion in liquid, in particular water; b) in the case of dispersion, completely removing the liquid; c) heating the powder mixture to form a polycondensate; and d) preferably baking the powder mixture above the melting temperature of the polymers; producing a second layer or third layer or further layers on the first layer, the sub-steps a) to c) being repeated and step d) being performed either for each layer individually or for at least two layers together.

Inventors

  • STECHER, CHRISTOPH

Assignees

  • ACS Coating Systems GmbH

Dates

Publication Date
20260513
Application Date
20240627

Claims (17)

  1. 1. A method for coating an object, preferably a wear-prone (sliding) object, in particular cooking and baking accessories or parts with food contact, with at least two layers, comprising the following steps: 1) Production of a first layer comprising a) application of a powder mixture, dry or as a dispersion in a liquid, comprising powder particles of at least one polyphenylene sulfide (PPS) polymer and optionally a polyaryletherketone (PAEK) polymer, wherein the powder mixture can be produced without the addition of fluorine or fluorine-containing compounds, to the article, in particular the cooking and baking accessory, wherein the application is preferably carried out electrostatically, by a fluidized bed sintering process or as a dispersion in 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) preferably baking the powder mixture above the melting temperature of the polymers; 2) producing a second layer or third layer or further layers on the first layer, wherein sub-steps a) to c) are repeated and step d) is carried out either for each layer individually or for at least 2 layers together.
  2. 2. The method according to claim 1, wherein the powder mixture for the first layer contains a higher proportion of PPS polymer than the powder mixture for the second layer, preferably more than 60 wt.%, more preferably more than 70 wt.%, even more preferably more than 90 wt.%, even more preferably more than 95 wt.%, particularly preferably more than 99 wt.% polyphenylene sulfide based on the total mass of the dry powder mixture.
  3. 3. Method according to one of the preceding claims, wherein the powder mixture for the second, third or further layer, preferably at least the cover layer, contains a higher proportion of PAEK polymer than the powder mixture for the first layer, preferably more than 60% by weight, more preferably more than 70% by weight, even more preferably more than 90% by weight, even more preferably more than 95% by weight, particularly preferably more than 99% by weight PAEK polymer based on the total mass of the dry powder mixture.
  4. 4. Process according to one of the preceding claims, wherein the baking temperature (substrate temperature) during the production of the respective layer is 40-60°C above the liquidus temperature of the polymer, in the case of a mixture of the higher melting polymer, or at 350-360°C if a uniform baking temperature is taken over all layers.
  5. 5. Process according to one of the preceding claims, wherein the process, in particular in the step of heating the powder mixture to form a polycondensate, is carried out without using a fluorosurfactant.
  6. 6. Process according to one of the preceding claims, wherein the powder mixture comprises at most 1000 ppb, preferably at most 100 ppb, particularly preferably at most 25 ppb total fluorides, measured by combustion ion chromatography (TOF-CIC).
  7. 7. Process according to one of the preceding claims, wherein the powder mixture further comprises tin (Sn), preferably 0.1 to 5 wt.%, more preferably 0.1 to 2 wt.%, even more preferably 0.5 to 1.5 wt.%, in particular 1 wt.%, based on the total mass of the dry powder mixture.
  8. 8. A method according to any one of the preceding claims, wherein the powder mixture is in the form of a dispersion and the liquid comprises water.
  9. 9. The method according to any one of the preceding claims, wherein the powder mixture comprises at least one PAEK polymer and PPS polymer, wherein the PAEK polymers are preferably selected from the group consisting of polyetheretherketone (PEEK), polyetherketone (PEK), polyetherketoneketone (PEKK) and polyetherketoneetherketone (PEKKEK).
  10. 10. The method of claim 9, wherein the polymers have different melting temperatures.
  11. 11. The process according to claim 9 or 10, wherein the PAEK polymers have different melt viscosities, measured according to ISO 11443 at 400°C.
  12. 12. Process according to one of the preceding claims, wherein the average melt viscosity of at least one polymer 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.
  13. 13. The method according to any one of the preceding claims, wherein the powder mixture further comprises a dry lubricant, excluding fluoropolymers and PFAS, preferably an element from the group consisting of polyamideimide (PAI), polyimide (PI), graphite, M0S2, boron nitride (hexagonal modification; a-boron nitride) and a mixture thereof.
  14. 14. Process according to one of the preceding claims, wherein the powder mixture further contains a reinforcing element, metallic fillers and their oxides, ceramic and mineral fillers, glass particles as flakes or spheres, glass or carbon fibers or soot.
  15. 15. The method of claim 14, wherein the elements are in nanoparticle size.
  16. 16. The method of claim 14, wherein the elements are in the order of magnitude of the layer thickness before the last layer is applied.
  17. 17. Object, preferably subject to wear (sliding ) Object, in particular cooking and baking accessories or parts with food contact, which has a coating produced by the method according to one of claims 1 to 16.

Description

Description Method for coating an object The present invention relates to a method for coating an object, preferably a wear-prone (sliding) object, in particular cooking and baking accessories, with at least two layers, and an object coated by the method, preferably a wear-prone (sliding) object, in particular cooking and baking accessories or parts with food contact. PTFE coatings are state of the art and are usually applied as a triple coating for higher quality cookware, i.e. in 3 layers with usually at least 2 layers of baking. First, a base layer, usually consisting of binding resin dissolved in a solvent, for example PAI dissolved in NMP, is wet-sprayed, dried and pre-crosslinked. Then 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 approx. 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 (PEAS). These also have the disadvantage of releasing toxic substances (PEAS) when used at high temperatures. 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. According to EU regulations, the limit value for PEAS 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. The object of the present invention is to provide a method for a universally applicable coating for an object, preferably a wear-prone (sliding) object, in particular for cooking and baking utensils or parts with food contact, without fluoropolymers and without the addition of fluorine. The above object is achieved by providing a method according to claim 1, and an object, preferably a wear-prone (sliding) object, in particular cooking and baking accessories or parts with food contact, according to claim 17. Preferred embodiments are presented in the subclaims. According to the invention, the term cooking and baking accessories or parts with food contact includes any object whose shape is suitable for holding food and subsequent cooking and baking. Therefore, in addition to pans, baking trays, baking molds, etc., as well as grill trays, grill containers, grill racks, etc. are also included in the above term, as well as machine parts for processing food. In a first aspect of the invention, a method for coating an object, preferably a wear-prone (sliding) object, in particular Cooking and baking utensils or parts intended for contact with food, with at least two layers comprising the following steps: 1) Production of a first layer comprising a) application of a powder mixture, dry or as a dispersion in a liquid, comprising powder particles of at least one polyphenylene sulfide (PPS) polymer and optionally a polyaryletherketone (PAEK) polymer, wherein the powder mixture can be produced without the addition of fluorine or fluorine-containing compounds, to the article, in particular the cooking and baking accessory, wherein the application is preferably carried out electrostatically, by a fluidized bed sintering process or as a dispersion in 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) preferably baking the powder mixture above the melting temperature of the polymers; 2) producing a second layer or third layer or further layers on the first layer, wherein sub-steps a) to dc) are repeated and step d) is carried out either for each layer individually or for at least 2 layers together. According to the invention, the powder mixture can be produced without the addition of fluorine or fluorine-containing compounds. This is particularly the case according to the invention if the powder mixture does not exceed certain limit values for total fluoride after combustion at 900 ° C - 1000 ° C in a moist, oxygen-free atmosphere. The powder mixture therefore preferably contains at most 1000 ppb, preferably at most 100 ppb, particularly preferably at most 25 ppb. Total fluorides, measured by Combustion ion chromatography (TOF-CIC) . In detail, to carry out the combustion ion chromatography (TOF-CIC) measurement method according to the invention, samples of the powder mixture are filled into ceramic boats and introduced into a furnace where pyrohydrolysis takes place at 900-1000 °C in a humid, O2-rich environment. The samples are oxidized under these conditions, 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