DK171058B1 - Method of coating household and household items - Google Patents

Abstract

Cooking utensils are coated with a non-stick layer by plasma spraying with several hard coatings made of different hard material powder whose grain size increases away from the surface of the utensil. The hard layers are then coated with non-stick layers.

Description

DK 171058 B1

The invention relates to a method for coating household articles with an antitaking adhesive layer and of the kind specified in the preamble of claim 1.

The invention also relates to a household object of the kind specified in the preamble of claim 5, which is manufactured by the method according to the invention.

A method and a household object of the above kind are known from British Patent Specification No. 944,836.

By "household object" is meant any household object which is subjected to mechanical stresses in use, in particular scraping or cutting effects. An example is a roasting pan whose roasting surface is subjected to mechanical influences by a metallic roasting lever, roaster or knife when turning or cutting a frying material. A similar 15 conditions apply to pots, saucepans, baking trays, baking trays and the like. Further examples include irons whose sole at the hoop is subjected to mechanical stresses when ironed over buttons, zippers, rivets or the like. Other household items include 20 cookware, hot or hot plates on which pots, pans or jugs are placed, which are therefore subjected to considerable scratching effects, as well as cladding of baking or barbecue stoves to which fat can be deposited that can only be removed with difficulty. by significant mechanical stresses or by using aggressive chemicals (baking oven spray).

Within the scope of the present invention, "household object" is also understood to mean any kind of objects used in the household or industry which may be subjected to mechanical influences in the manner mentioned, for example.

In the above-mentioned British Patent Specification No. 944,836, a method for coating frying pans is disclosed, in which, on DK 171058 B1 2, the sandblasted metallic surface of the frying pan is applied two layers in succession by flame spraying. The first layer consists of nickel and chromium oxide and is applied in three steps with a thickness of 25.4 μιη each, so that the first layers have a total thickness of approx. 76 μπι. The second layer consists of alumina and is applied in four steps at a thickness of 25.4 μιη each, giving a total thickness of the second layer of approx. 100 μπι. The first and second layers together have a thickness of approx. 176 μιη. A layer of polyfluorocarbon having a thickness of approx. 25 μπι and this layer is cured at approx. 285 ° C.

German Patent Publication No. 3,604,762 discloses a bra deflate of a frying pan or an iron sole, ie. a metallic surface with an adhesive backing, for example a nickel-aluminum layer or a chromium-nickel layer. A ceramic layer of hard material is applied to this adhesive substrate by plasma spraying, e.g. consists of alumina or alumina plus titanium oxide or any other material known from plasma spraying technology.

In the known method or prior art, respectively, the thickness of the anti-adhesive layer is chosen such that this layer, viewed in a microscope, fills the valleys between the tips of the sprayed ceramic grains and the tips of these grains are also covered by a thin anti-adhesive layer. The macroscopic hardness of the layer thus formed is of the same order of magnitude as the hardness of corundum, i.e. ca. 9 Mohs. It is likely that the tips of the hard grains upon loading the surface with a metallic object will determine the hardness of the layer, while the anti-adhesive substance introduced into the valleys between the tips - in terms of the anti-adhesive properties - determines the sliding properties.

Experiments with household items of the above type have shown that even at the order of 100,000 influences with a metallic knife and a cutting load of 5 N, the anti-adhesion properties are completely maintained.

DK 171058 B1 3

US Patent No. 4,311,755 discloses a steel household article provided with an anti-adhesive layer. For this purpose, the steel body of the household article is first coated with a first layer of a non-porous ceramic frit, upon which a second layer of a porous ceramic frit is applied. As a frying material, e.g. quartz, feldspar, hydrated borax or the like. On the second layer of the porous ceramic frit, a third layer of a fluorocarbon primer is applied. This occurs because the primer of the second layer 10 predominantly penetrates into the porous ceramic frit and forms a closed layer of the primer material. Finally, a fourth layer of fluorocarbon is applied to this upper closed layer of the primer. Thereby, the adhesion of the fourth layer to the second layer is improved, as the primer of the third layer penetrates better into the second layer of the porous ceramic frit, thereby providing an adhesion thereto, and the adhesion between the third and fourth layers. each consisting of fluorocarbon is better.

From US-Book "Deposition Technologies for Films and Coatings" 20 by Bunshah, et al., Noyes Publications, 1982, it is known that the thickness of plasma sprayed layers can be adjusted by using coating powders of various grain sizes.

In practice, it has been found that, from an optical point of view, household objects made by this known method are not always completely satisfactory, since especially in the case of overheating, cracks in the surface may be formed, which may be due to the presence of grease or the like. in the ceramic layer.

The object of the invention is to further develop a method 30 and a household object of the kind mentioned above, so that the optical quality of the surface is maintained while increasing the load capacity.

DK 171058 B1 4

A method of the kind mentioned initially according to the invention is characterized in that when the hard material layer is applied, the pores in the substrates of the hard material layer are first filled with a very fluid resin-based baking enamel to a first level such that at least the bottom layers are filled with the baking enamel, and then the pores in the other layers of the hard material layer are filled with a non-adhesive enamel.

Thereby, the thin-flowing burn-in lacquer penetrates into the capillaries of the powder of hard material in the transition to the metallic surface of the household object or adhesive substrate. In this way, the ceramic hard material is completely sealed to the ground, so that even after prolonged use and overheating of the household object, foreign bodies such as fat or the like will not penetrate into the area of the hard material layer. In this way, staining of the coating of the household object is safely avoided, so that from the aesthetic point of view, even with long use of such a coated household object, no disadvantages arise.

The non-adherent enamel according to the invention can be constituted by a polytetrafluoroethylene based enamel. Furthermore, prior to the application of the layer of hard materials, an adhesive base layer can be applied as an adhesive, preferably at a thickness of between 1 and 20 µm, especially with a thickness of less than 25 µm. Thereby, the adhesion of the overall layer structure to the surface of the household object increases substantially.

According to the invention, a household object of the kind mentioned initially is characterized in that the pores in the substrates of the hard material layer are filled to a first level with a hardened resin-based baking enamel, so that at least the substrate is filled with the baking enamel while the pores in the upper layers of the hard material layer are filled with a hardened anti-adhesive enamel.

DK 171058 B1 5

The invention will be explained in more detail below with reference to the drawing, in which 1 shows a large scale and partially cut out frying pan as an example of a household object according to the invention; FIG. 2 shows a system for carrying out the method according to the invention for coating the household object; and FIG. 3 is a section through a coating on the household article of the invention applied in four different steps by the method of the invention.

In FIG. 1 represents 10 a frying pan which, as an example of a household object according to the invention, will be explained below. However, this is just one example. Household items also include pots, saucepans, baking trays, irons, stoves, plates, hotplates, oven covers, grill covers and the like.

The frying pan 10 has a pan body 11 and a shaft 12. The pan body 11 may consist of metal, for example steel, cast iron or cast aluminum. Attitudes with pottery bodies 20 and glass can also be used.

The pan body 11 has a flat bottom 13 with an upper surface 14, which in the pan pan example 10 is the pan surface itself.

The bottom 13 is as shown in FIG. 1, of a metallic base body 15 first provided with an adhesive base 16. The adhesive base 16 may be a nickel-aluminum layer or a chromium-nickel layer or the like, as is known from plasma coating technique for mediating adhesion. The adhesive substrate 16 preferably has a thickness of 2-20 μηι and is preferably thinner than 30 μµη.

On the adhesive substrate 16, there is a layer of hard material, in particular a ceramic layer, which preferably consists of alumina or a mixture of alumina and titanium oxide and is made up of four layers 20, 21, 22, 23 on top of each other.

The hard material layer is provided with two superposed layers 24, 25 of an anti-adhesive layer, of which the upper 25 is preferably made on a polytetrafluoroethylene (PTFE) basis.

FIG. 2 shows a coating system consisting of a feeding belt 30, 10 on which the frying pans 10 are guided in the direction of the arrow 31. On the feed belt 30, the frying pans 10 achieve a state in which the metallic base body 15 is preferably already roughened by sand blasting and degreased by a suitable solvent or by heat treatment. In this state, the roasting pans 10 first pass the working area of a first plasma coating station 32 and then the working area of a second, third, fourth and fifth plasma coating station 33, 34, 35, 36. Thereafter, the roasting pans 10 pass a first coating station 37 and a second coating station 38 before reaching the area of a heating station 39. After passing through the heating station 39, the frying pans 10 are taken off by the conveyor belt 30.

In the first plasma coating station 32, the adhesive substrate 16 is applied (if one exists). To this end, a metallic powder 50, for example a nickel-aluminum mixture or alloy or a chromium-nickel mixture or alloy, is applied by means of the first plasma coating station 32 on the sandblasted and degreased surface of the metallic base body 15.

If the hard material layer is to be multilayer, a second powder of relatively small grain size 51 is applied to the second plasma coating station 33. The grain size is preferably between 5 µm and 20 µπι. By this, DK 171058 B1 7 is understood in practice a powder whose grain size varies according to a Gaussian distribution between 5 μτη and 20 μτη, whereby approx. 70% of the powder mass has a grain size of about 12 μτη. This target in the raw state is similarly changed when the hard material powder reaches the arc of the second plasma coating station 33, since the ceramic powder then assumes a doughy consistency and in this consistency is sprayed onto the adhesive support 16. Upon impact of the adhesive substrate 16, the individual "grain" is expanded, flowing to the side so that the thickness of the later stiffening grain in the flow direction is substantially smaller than in the direction perpendicular thereto.

In the third, fourth and fifth plasma coating stations 34, 35, 36, a further layer of hard material is sprayed in a similar manner by means of additional ceramic powders 52, 53, 54, with the grain size increasing continuously, for example from the said range between 5 μτη and 20 μτη, most nearly in a range between 5.6 μτη and 22.5 μτη with a 70% maximum at 14 μιη finally to a grain size between 5.6 μτη and 40 μτη with a 70% maximum at a grain size of about 20 μπι.

20 It is understood that these grain sizes are illustrative only and that variations in up and down direction are possible.

While the adhesive backing is only applied relatively thinly with a thickness of preferably less than 10 μτη, the layer of 25 hard material by the coating stations 33-36 can be applied almost at the same thickness and preferably with a thickness of 15 μτη, so that the total layer of hard material has a thickness of 60 μτη. Here too there is the possibility of variations.

The layers of 30 hard material thus applied and, for example, 60 mm thick are a porous formation, at the surface of which the thickest grains with the aforementioned lateral propagation are found.

In the first coating station 37, a first lacquer 55 is applied to the porous ceramic layer. The first lacquer 55 is an extremely thin resin-based burn-in lacquer, for example the one obtained under the designation CENO-THERM® lacquer under type no. 071230-5 702.533 from Weilburger Lakfabrik, J. Grebe GmbH, D-6290

Weilburg. Optionally, the first lacquer 55 may be diluted by a suitable solvent.

Before the first lacquer 55 is dried, a second lacquer 56 is applied by the "nose-in-nass" method to the first lacquer 55 by means of the second lacquer station 38. The second lacquer 56 is a polytetrafluoroethylene lacquer, e.g. anti-adhesive coating 12/31 of type No. 071230-702,534 from Weilburger Lakfabrik, which can be diluted by a suitable solvent.

FIG. 3 shows layer structure in larger target conditions, as can be seen in various stages of the embodiment shown in FIG. 2 illustrated coating process.

In the embodiment shown in FIG. 3, the four layers 20-23 of hard material with powders 51-54 of increasing grain size are already applied to the adhesive support 16. The frying pans 10 are accordingly in FIG. 2 behind the fifth plasma coating station 3 6.

Phase II shows the state after passage of the first coating station 37. It is seen that the gap between the grains of 25 hard material powders 51, 52 and 53 is filled (the latter in part) with the very thin-flowing burn-in lacquer 55 to a first level 60. 55 is penetrated into the very narrow capillaries between the fine first powder of hard material 50 and into the adhesive support 16.

Due to the highly volatile solvent of the burn-in lacquer 55 and due to the ambient temperature in the region of the feed belt 60 which can reach 80 ° C or more, the burn-in lacquer 55 is obtained by the second coating station 38. already lowered to a second level 61 or below in the second layer of hard material 21. The lowering from the first level 60 to the second level 61 occurs by the incineration lacquer 55 penetrating the smallest capillaries, while the frying pan 10 from the first coating station 37 is passed to the second coating station 38 on conveyor belt 30, and the burn-in paint 55 is heated, thereby becoming even more thin-flowing.

Phase III shows the condition immediately after the passage of the second paint station 38, and it is seen that the antifoam lacquer is applied to the three layers 21, 22 and 23 of the hard material layer and is above the burn-in lacquer 55. As a result of the antifoam lacquer 56 is diluted with a volatile solvent, and due to the relatively high ambient temperature, the antifoam lacquer 56 is preferably applied in such an amount that the mirror is on a third level 62 above the top layer of hard material 23.

Phase IV shows the final state after the passage of the heat stations 39. Due to the prevailing process temperature which is set between 320 ° C and 450 ° C, preferably between 400 ° C and 420 ° C, both the burn-in paint 55 is fourth level 63 below the second level 61 penetrated deep into the capillaries of the lower layers 16, 20 and 21, just as the anti-adhesive lacquer 56 at 25 contraction has penetrated further into the capillary structure. By appropriately sizing the applied amounts of lacquer 55 and 56 at a corresponding setting of the burn-in temperature in the heating station 39 in relation to the flow rate of the frying pans 10, a surface 14 of the kind mentioned initially 30 is formed, at which the top grains at the surface of the fourth layer of hard material 23 is coated only by a relatively thin anti-adhesive layer of a thickness of a few μτη, for example 5 μπι, while the adjacent valleys are filled with the material of the non-adhesive layer.

DK 171058 B1 On the other hand, all capillary areas of the porous structure are completely filled by burn-in lacquer 55 and anti-adhesive lacquer 56, respectively, so that foreign bodies, for example, liquid fat, will not be able to penetrate into the capillary structure 5 of layers 16, 20-23.

Claims (5)

A method of coating household articles with an anti-adhesive layer, wherein a method of coating the household article by a plasma spraying method is provided with a porous hard material layer (20, 21, 22, 23) and the hard material layer (20, 21, 22, 23). ) is then provided with an anti-adhesive layer (24, 25), characterized in that when the hard material layer (20, 21, 22, 23) is applied, the pores in the substrates (20, 21, 22, 23) are filled by the hard material layer first with a very fluid resin-based baking enamel (55) to a first level (60) so that at least the lower layer (20) is filled with the baking enamel (55), and then the pores are filled in the other layers (21, 22, 23) of the hard material layer 15 with a non-adherent enamel (56). Process according to claim 1, characterized in that the non-adherent enamel is a polytetrafluoroethylene based enamel. Method according to claim 1 or 2, characterized in that an adhesive base layer (16) is applied before the hard material layer (20, 21, 22, 23) is applied. Method according to claim 3, characterized in that the adhesive base layer (16) is applied with a thickness of between 1 μτη and 20 μτη, preferably less than 10 μτη. 25 A household article with a non-adhesive layer, wherein a porous hard material layer (20-23) consisting of hard material powder (50-54) is provided over the surface of the article and an anti-adhesive layer (24, 25) is applied to the the hard material layer (20-23), characterized in that the pores in the 30 substrates (20, 21, 22) of the hard material layer are filled to a first level (60) with a hardened resin-based baking enamel (55), so that in each if the substrate (20) is filled with the baking enamel (55), the pores in the upper layers (21, 22, 23) of the hard material layer are filled with a hardened anti-adhesive enamel (56). 5