Substrate having excellent oil wetting

Abstract

The invention relates to a substrate having a multiply open cavern structure, wherein the substrate has a capillary pressure in the region of the openings of the cavern structure of ≥ 0.5 hPa, preferably ≥ 1.5 hPa, more preferably ≥ 3.0 hPa, and particularly preferably ≥ 4.0 hPa for Miglyol and ≤ 17 hPa, preferably ≤ 15 hPa, more preferably ≤ 14 hPa, and particularly preferably ≤ 10 hPa for water.

Description

[0001] Substrate with excellent oil wetting

[0002] The invention relates to a substrate with a multiply open cavern structure, wherein the substrate has a capillary pressure of > 0.5 hPa for Miglyol and < 17 hPa for water in the region of the opening of the cavern structure. The invention further relates to the use of a multiply open cavern structure with the aforementioned properties for improving the distribution of oil on the surface of a substrate, as well as to a method for producing a substrate according to the invention.

[0003] There is a constant need for surfaces with improved oil wetting properties. The goal is not only to ensure that the oil spreads across the surface where it is applied, but also to ensure that the oil is distributed as quickly and widely as possible. For example, there is a corresponding need for frying pans, where it is important that the applied oil wets the entire surface of the frying pan as quickly as possible, including the vertical edges. It is also desirable that this good wetting behavior can be maintained or at least quickly regained even after (machine) washing cycles.

[0004] Frying pans with various surface finishes are known in the art. The oldest types are cast and wrought iron pans, which develop an oily film on their surfaces after frying. Due to the nature of the material, these pans are not dishwasher-safe, as they lose the oily film during the washing process, thus exhibiting undesirably good water wettability and also becoming susceptible to corrosion.

[0005] To ensure compatibility with dishwasher cleaning, pans are often made of chromium-containing steels. While these are dishwasher-safe and corrosion-resistant, they lose the oil layer that protects food from sticking to the pan's surface during dishwasher cleaning.

[0006] The state of the art therefore uses coatings designed to prevent food from sticking. Fluorine-containing coatings, such as ceramic layers or PTFE coatings, are used for this purpose, as described in EP3200931 B1.

[0007] These layers have a number of disadvantages:

[0008] Perfluoroalkyl compounds are considered perishable chemicals, are harmful to health (especially at excessively high temperatures), and could be withdrawn from the market in the near future due to ECHA regulations.

[0009] PTFE coatings have poor cohesive and adhesive properties, which lead to short lifetimes.

[0010] Due to the oleophobic properties, the oil or fat does not spread, resulting in only a droplet-like wetting. The heterogeneous coating on the pan bottom results in heterogeneous temperature distribution and heat conduction, which leads to uneven frying results and browning levels.

[0011] There is no oil wetting in the edge area of ​​the pan, which results in the food sticking to the edge area.

[0012] Against this background, it was an object of the present invention to provide a substrate surface, in particular for pans as a substrate, which is free of organofluorine compounds, preferably fluorine-free, and has good performance properties and a long service life. In particular, good transport and wetting properties for oil and fat should be provided, preferably not only on the flat substrate surface such as the pan base, but also in vertical areas of the substrate, such as the pan rim. Furthermore, the good performance properties should preferably be retained or quickly regained, particularly after mechanical cleaning. At the same time, it was desirable for the substrate surface to be slightly hydrophilic and preferably even actively water-repellent, in order to prevent water from disrupting oil transport or wetting properties towards oil.

[0013] This object is achieved by a substrate with a multiply opened cavern structure which has a capillary pressure of > 0.5 hPa, preferably > 1.5 hPa, more preferably > 3.0 hPa and particularly preferably > 4.0 hPa for Miglyol and of < 10 hPa, preferably < 7 hPa, more preferably < 0 hPa, more preferably < - 100 hPa, more preferably < - 200 hPa, particularly preferably < - 500 hPa for water.

[0014] A “cavern structure” in the sense of this text is a network of cavities below the surface level of the substrate.

[0015] A "multiple-open" cavern structure means that the system of cavities below the surface has a multitude of openings. For many applications, it is preferable for the openings to be located only on one surface of the substrate, such as in a pan, only leading into the pan's interior.

[0016] The capillary pressure is measured as described in Example 1. Miglyol, as used in this text, is MIGLYOL® 812, manufacturer / supplier Caesar & Loretz GmbH, Herderstr. 31, 40721 Hilden, CAS No. 52622-27-2.

[0017] If the measurement method according to Example 1 results in a capillary pressure corresponding to "0," it can be assumed that a barrier to the measuring fluid actually exists. In this case, the negative capillary pressures are determined as described in more detail in Example 1.

[0018] Document WO 2020 / 127594 A1 also discloses a substrate with a multiply open cavern structure. However, the document provides no indication that it is possible to design the corresponding cavern structures in such a way that they simultaneously exhibit very low, preferably even negative, capillarity for water and, at the same time, high capillarity for Miglyol. Although the examples from this document were produced using a similar set of parameters as the examples contained here (see below), they were produced with such deviations that the values ​​exhibited by the present invention are not achieved. In other words, the present invention provides substrates with a cavern structure with a particularly good property window of low hydrophilicity and high oleophilicity. Here, WO 2020 / 127594 A1 provides no indication that such a property window can be achieved at all, let alone how this could be achieved.

[0019] In particular, the inventors of the present invention have determined that the number of pulses applied in direct succession to a surface position before the scanning mirror moves to the next laser position, as well as the time interval, given by the pulse repetition frequency in Hz in conjunction with the applied fluence, are important factors for achieving the property window according to the invention. Other factors that can play a role here are the atmosphere, the substrate material, the thickness of the material, the temperature, and the surface condition. In particular, a high number of pulses focused on one location creates strongly undercut channel structures as disclosed in WO 2020 / 127594 A1. The present invention, in contrast, preferably features more open structures.In addition to the desired surface properties, this also leads to improved infiltration of the caverns by the (desired) liquid, especially oil. The general cleanability is also improved, although the use of surfactants is a preferred cleaning option, especially in the presence of negative capillary pressure compared to water.

[0020] The openings in the cavern structure are preferably formed as pores, which means that there are many small openings that are preferably distributed over the entire (preferably one) substrate surface.

[0021] The cavern structure to be provided according to the invention preferably forms groove-shaped structures, which preferably have gap-like openings to the surface. These openings are arranged such that they run largely parallel to the groove-shaped structures and preferably have a width of 10 μm to 1 mm and / or a length of 100 μm to 50 cm.

[0022] The length-to-width aspect ratio is preferably > 10, preferably > 100, and particularly preferably > 1000. Preferably, more than 50%, preferably more than 60%, further preferably more than 70%, and particularly preferably more than 80% of the openings of the cavern structure have a minimum diameter in plan view of 10 - 500 pm, preferably 20 - 100 pm, further preferably 30 - 80 pm.

[0023] Those skilled in the art will appreciate that the size and shape of the openings play an important role in achieving the capillary pressure provided according to the invention. Thus, length, width, and diameter naturally influence the achievable capillary pressure; accordingly, those skilled in the art will ensure that the respective opening areas are not too large in plan view. This preferably ensures that a corresponding capillary pressure is enabled by the cavern structure provided according to the invention.

[0024] The capillary pressure is determined thermodynamically. In the case of a tube, the capillary pressure depends on:

[0025] PK = 2 x ct x cos(0) / r ct: OF energy of the liquid (mN / m)

[0026] 0: static contact angle r: capillary radius (mm)

[0027] Capillary pressure determines how high the oil can be transported at the edge of the pan. It is clear that to generate the greatest possible capillary pressure, the radius should be as small as possible.

[0028] Furthermore, the contact angle between the material of the undercut structures, the cavern structure, and the cooking oil is crucial for the infiltration of the undercut structures. A contact angle > 90° would prevent the cooking oil from penetrating the capillaries at all. (This would be the case if oleophobic surfaces were present and should be avoided.)

[0029] It has been found that the cavern structure to be provided according to the invention, with the corresponding design with regard to the capillary pressure, is not only able to ensure a good distribution of oils or fats on the substrate surface, but it is also able to ensure that, in the case of three-dimensionally designed substrates such as pans, oil and fat can also be provided at the edges outside the base plane, such as the edge of the pan.

[0030] Among other things, this prevents unwanted adhesion of the food in this area as well. Furthermore, it has been shown that – unlike with oleophobic PTFE coatings, for example – a more even distribution of fat and / or oil can be achieved, thus ensuring more even wetting and thus – in the case of frying pans, for example – a more even heat transfer to the food.

[0031] In addition, for the substrate according to the invention, since oils and / or fats are present in the cavity structure even after the frying process, these are retained to a significant extent even during conventional washing processes, so that the desired properties (e.g., oil wetting) can be quickly regained. Appropriate (re)filling can also be easily ensured.

[0032] The latter effects can be further improved by taking further measures to reduce or prevent the penetration of water into the cavern structure provided according to the invention.

[0033] Accordingly, a substrate according to the invention is preferred, wherein a coating increasing the static water contact angle is present at least in the region of the openings.

[0034] A coating that increases the water edge angle within the meaning of the present invention is a coating that, as a closed coating, has a higher static water edge angle than the material of the substrate (in case of doubt, also closed, i.e. without openings to ensure measurability).

[0035] The substrate to be used according to the invention (with or without the coating increasing the static water contact angle) preferably has a static contact angle for Miglyol 812 N of <80°, more preferably <60°, more preferably <40°, more preferably <20°, and particularly preferably complete wetting. It is very particularly preferred within the meaning of the present invention that the quotient r / cos(0) is between 5 pm and 200 pm. It is preferred within the meaning of the present invention that the coating increasing the static water contact angle is a plasma polymer coating. It is particularly preferred that this coating is fluorine-free, hard, and contour-mimicking.

[0036] Plasma polymer coatings, on the one hand, make it easy to adjust the desired surface properties, particularly with regard to the contact angles with oil and water. On the other hand, the deposition process in a PE-CVD process also allows for easy penetration of the coating into the openings of the cavern structure. This means that not only the uppermost layer of the substrate according to the invention is coated, but also a coating improvement is achieved precisely in the critical area of ​​the cavern structure openings, thus ensuring the desired functionality, particularly in terms of making it more difficult for water to penetrate into the cavern structure. Finally, such coating processes are characterized by the fact that the openings of the cavern structure are not closed.

[0037] According to the invention, a substrate according to the invention is preferred, wherein the cavern structure can be produced or has been produced by laser, preferably by IR laser, particularly preferably by nanosecond pulsed near-IR laser or by CW laser in the IR, near-IR or visible spectral range.

[0038] According to the invention, a substrate according to the invention is preferred, wherein the cavern structure is a partially covered trench structure.

[0039] A trench, as defined in this application, is a three-dimensional structure that is at least ten times larger in one spatial direction than in the other directions. In cases of doubt, branches and intersections with other trench structures / channels are not considered when determining the dimensional lengths.

[0040] A partially covered trench structure is particularly suitable for ensuring the capillary pressures to be provided according to the invention.

[0041] Alternatively, a substrate according to the invention is preferred, wherein the cavern structure consists of (preferably densely packed) cavities, each of which is connected to more than two adjacent cavities. A substrate according to the invention is preferred, wherein the degree of coverage of the cavern structure is 1% to 99%, preferably 5% to 80%, more preferably 10% to 80%, even more preferably 20% to 75%, even more preferably 25% to 70%, and particularly preferably 30% to 65%.

[0042] The degree of coverage within the meaning of the present application is determined in the same way as the degree of coverage in WO 2020 / 127594 A1. In this regard, reference is made in particular to page 8, penultimate paragraph, in combination with Figures 1a and 1b in the cited document, whereby the entire document and in particular the cited text passages are incorporated into this application by reference.

[0043] According to the invention, a substrate according to the invention is preferred, wherein the area proportion of the openings relative to the opening-occupied surface of the substrate is 0.5% to 60%, preferably 2% to 40%, more preferably 5% to 30%, and particularly preferably 10% to 25%.

[0044] This provides a particularly advantageous ratio between openings and solid, load-bearing areas on the substrate according to the invention, which is particularly helpful for use as a pan or cookware.

[0045] A substrate according to the invention is preferred, with a multiply opened cavern structure, wherein the caverns are covered to < 99%, preferably < 95% and more preferably to < 90%, < 80%, < 70%, < 50% and < 30%, based on the plane spanned by the width maximum within the channel parallel to the contact plane.

[0046] The exact determination of these conditions is described in WO 2020 / 127594 A1, here in particular on page 8, lines 22 to 25 in combination with Figure 1 and the associated descriptions on page 5, line 5 to page 6, line 13. These passages are incorporated into the present description by way of reference, whereby the references to channels in the said passages are to be applied analogously to the cavern structure to be provided according to the invention.

[0047] A substrate according to the invention is preferred, wherein the volume accessible to an oil filling relative to the opening-covered surface of the substrate is between 0.1 pL / cm 2 and 15pL / cm 2 , preferably between 0.15 pL / cm 2 and 10pL / cm 2 , more preferably between 0.5pL / cm 2 and 8pL / cm 2 and particularly preferably between 1 pL / cm 2 5pL / cm 2large. The stated volume is determined by means of the measurement as described in Measurement Example 2. It is obvious to the person skilled in the art that the stated values ​​for the volume per unit area apply only to the region of the substrate in which the open cavern structure to be provided according to the invention is present.

[0048] According to the invention, it is preferred that the cavern structure to be provided according to the invention is located in metal, preferably a metal selected from the group consisting of iron, chromium, aluminum, copper, titanium, gold and their alloys.

[0049] This is particularly useful for a variety of applications, in particular in the application preferred according to the invention, wherein the substrate is selected from the group consisting of cookware, in particular frying pans, bearings, in particular plain bearings, in particular for underwater applications, pistons, cylinders and rolling bearings.

[0050] While open trenches without undercuts (overlaps) lead to only a low capillary pressure build-up, capillaries formed from trenches with undercuts lead to a high capillary pressure (see measurement example 1).

[0051] Trench openings that are too large or too long result in a capillary barrier, thus limiting the potential capillary pressure. This can be used, for example, to limit the cooking surface of a pan.

[0052] If the cavern structures to be provided according to the invention are made of metal, the initial wetting with an edible oil is always good because the metal surface has a high surface energy in the clean state.

[0053] After initial use, the capillaries are filled with oil. Further addition of oil results in the oil being evenly distributed over the substrate—especially the pan base. Adding food, for example, causes the food to rest loosely on the raised areas of the surface structure, where it caramelizes, similar to a deep-frying process. Sticking is largely prevented by the even oil layer and the small contact surface.

[0054] The oil-filled undercut surface structures (cavern structures) act as an insulating layer, equalizing temperature differences caused by uneven heating of the pan (hot spots) or uneven placement of the food. This prevents excessive caramelization of the food edges.

[0055] Preferred frying pans according to the invention can be cleaned in a standard dishwasher. The oil is removed from the undercut structures. After drying, the undercut structures can be easily re-infiltrated with oil during the subsequent frying process.

[0056] If the food is partially stuck to the raised areas of the undercut structures (cavern structures), it can be removed with a scraper. In addition to wooden and plastic scrapers, metal scrapers can also be used for this purpose. Due to the hardness of the undercut structures, especially when made of metal as the base material, these are not altered or only slightly altered by scraping, making the frying pan with the cavern structure particularly durable.

[0057] In the edge area of ​​the preferred pan according to the invention, the surface structures are filled with oil due to capillarity, even at pan edge heights of a few centimeters. This prevents the food from sticking and the formation of hot spots, even in the edge area.

[0058] According to the invention, cavern structures to be provided according to the invention are preferred, such as partially covered trench structures which extend from the center of the substrate, in particular a pan, to the edge, so that the oil is transported from the center to the edge.

[0059] To ensure that the entire cooking surface is covered with these structures, it is advisable to branch these cavities. This ensures that the oil is distributed particularly evenly and quickly across the cooking surface. An example of an arrangement of the cavities (trenches) is shown in Figure 1.

[0060] Figure 1 shows a cavern structure to be provided in accordance with the invention as trench structures with branches for a uniform oil distribution.

[0061] An excessively high degree of coverage makes the substrates according to the invention more difficult to clean and reduces the accessibility of the cavities and the capillary pressure. Therefore, degrees of coverage of < 80% are preferred (see also above). The invention also includes the use of a multiply open cavern structure provided according to the invention to improve the distribution of oil on the surface of a substrate.

[0062] Furthermore, part of the invention is a method for producing a substrate according to the invention, comprising the steps a) providing a substrate, preferably as defined in more detail above, b) producing a cavern structure, preferably as defined in more detail above and c) optionally coating at least in the region of the openings of the cavern structure with a coating, preferably as defined in more detail above.

[0063] The carver structure to be provided according to the invention can preferably be produced by laser structuring according to WO 2020127594 A1.

[0064] Alternatively, the convex structure to be provided according to the invention can preferably be produced using additive processes such as selective laser melting (SLM), electron beam melting (EBM), or binder jetting. In selective laser melting, a layer of metal powder with grain sizes of 10 pm to 300 pm is preferably poured onto a substrate—in particular, a ladle base—and this layer is melted or sintered by laser melting. This creates a layer with a protruding convex structure according to the invention, the channels of which are particularly highly branched, thus creating a coherent network of undercut structures.

[0065] Furthermore, a cavern structure to be provided according to the invention is accessible by forming processes such as pressing and rolling, by compressing tips of raised areas and thus creating undercuts.

[0066] Structures formed via laser-induced periodic surface structures (ripples or LIPSS) or laser-induced non-periodic surface structures (LINPSS) are explicitly excluded as processes because they do not allow for sufficiently undercut structures and thus do not provide sufficient capillarity. According to the invention, a process according to the invention is preferred, wherein the surface of the substrate is smoothed after step b) and optionally before step c).

[0067] By means of this smoothing, the substrates produced according to the invention can be further improved with regard to a number of their properties.

[0068] On the one hand, this applies to an enlarged contact surface for frying food in pans, for example. However, it has surprisingly been found that smoothing, especially when performed by grinding and / or laser cleaning and / or laser smoothing, also has a positive influence on the desired properties of low hydrophilicity and high oleophilicity.

[0069] With regard to smoothing, grinding processes are preferred, selected from the group consisting of grinding, polishing, blasting, chemical pickling, electrolytic polishing, rolling, milling, laser polishing, ultrasonic cleaning, vibrofinishing, magnetic polishing, thermal polishing, nanocoating, barrel finishing / vibratory grinding, honing, lapping and straightening.

[0070] As already described above, in a preferred embodiment, an additional coating is to be applied in step c). Gas-phase deposition is preferably used, preferably—as already mentioned above—PE-CVD processes. Even if coating processes from the liquid phase are not excluded within the meaning of the present invention, they are disadvantageous in many cases, since there is a risk that the cavern structures to be provided according to the invention would be infiltrated and at least partially filled, resulting in no or only reduced oil absorption.

[0071] Preferably, silicon-organic coatings are used to increase the static water contact angle, more preferably plasma-polymer silicon-organic coatings, and especially preferably coatings such as those described in the German application with the official file number 10 2023 125 172.4 are suitable. This application is incorporated by reference into the present application, with particular reference being made to the embodiments as set forth in the patent claims. Measurement examples:

[0072] 1. Measurement of capillary pressure by rising experiment (analogous to measurement example 1 from DE102020120343A1 :

[0073] A 1 cm wide and 20 cm long metal strip is fitted with a multi-opening cavities. The sample is immersed in the center of a glass vessel filled with a 1 cm volume of a measuring liquid. The glass vessel is sealed with a lid, and the sample is drawn out through an opening in the center of the lid. Because the measuring liquid can spread through the capillaries of the metal strip and evaporate, the measurement is not performed under equilibrium conditions. Using the formula

[0074] Height of rise x density of the liquid (p) x location factor (g) results in the capillary pressure (20 cm ~ 18 mbar).

[0075] The assessment of the rise height is carried out after 1 h of liquid contact with a filter paper strip, which is pressed from the upper, non-immersed end of the sample along the created capillary and indicates an absorption of the measuring liquid at the respective maximum rise height.

[0076] 2. Measurement of the accessible cavern volume using a Wilhelmy balance

[0077] Use of the Wilhelmy balance DCAT25 from Dataphysics

[0078] Use of a sample with surface porosity, sample geometry 1 cm x 1 cm, as well as 1 cm x 2 cm, treated on both sides with the laser

[0079] Immerse the sample so that it comes into contact with the oil (Miglyol 812N).

[0080] The Wilhelmy balance automatically brings the samples into contact with the oil surface and measures the time-resolved mass increase.

[0081] If the sample is completely wetted, a mass saturation value Ms (in mg) is established. This depends on the area of ​​the sample AP (in cm 2 ), of the pore volume per area MVA (in pl / cm 2 ) and systematic measurement errors Merr (in mg) that are independent of the surface area, such as the sample buoyancy due to partial oil immersion.

[0082] Ms (Ap) = Merr + MVA ■ Ap

[0083] The measurement of the saturation masses Ms of two samples of different lengths, with the same width and thickness, which have the same contact areas with the oil, without being bound to any theory, also shows the same systematic error Merr. The difference in the saturation masses divided by the difference in area Ap1-Ap2 of the samples yields the weight of oil stored in the pore volume per unit area (MVA). The quotient of the MVA and the density of the oil yields the accessible pore volume per unit area. The cavern structures on the substrates are oriented as perpendicular to the oil surface as possible to enable wetting of the available structures.

[0084] Measurement of weight gain after complete filling / wetting of the pores

[0085] Reference of weight gain to the wetted / filled area.

[0086] The accessible pore volume can be determined by taking into account the density of the oil and the increase in mass.

[0087] Implementation examples:

[0088] Example 1: Production of multiply opened cavern structures

[0089] Description of production / storage

[0090] Material: Steel: 1 .4404, flat substrates bright rolled

[0091] Laser: 100W Nd:YAG laser (type CL100 from CleanLaser, Herzogenrath, Germany with stamp optics and f(330) f-theta lens

[0092] Emitted wavelength: 1064 nm

[0093] Pulse length at 100 kHz: 129 ns Energy distribution in the laser spot: Gauss

[0094] Spot diameter in focus: approx. 107 pm

[0095] Target power: 100% (100 W)

[0096] The scanning speed between the focal points on the surface was 4000 mm / s. Laser processing was performed using a "jump-and-shot" process. In this process, several pulses are applied in direct succession to a position on the surface before the scanning mirror moves to the next laser position.

[0097] The remaining structuring parameters are listed in the following table:

[0098] Table 1 : Parameters for structuring the surfaces Sanding and cleaning

[0099] Some of the samples were smoothed by mechanically removing approximately 20 pm of the protruding peaks on the surfaces.

[0100] The surface grinding of the laser-structured surface was carried out as follows:

[0101] The surface is sanded manually in a cross-grinding pattern using a sanding block and dry with waterproof sandpaper in the following order:

[0102] 1 . Grain P400, abrasive grains corundum

[0103] 2. Grain P600, abrasive grains corundum

[0104] 3. Grain P800, abrasive grains corundum

[0105] 4. Grit P1000, abrasive grains corundum

[0106] 5. Grit P1200, silicon carbide abrasive grains

[0107] As a result, roughness peaks of approximately 20 pm were removed.

[0108] Subsequently, grinding dust was removed using a compressed air nozzle at 10 bar. Subsequent laser cleaning was performed using a 100 W Nd:YAG laser (type CL100 from CleanLaser, Herzogenrath, Germany) with stamp optics and f(330) f-theta lens, at nominal power: 100 W, pulse repetition frequency: 200 kHz; spot diameter: 107 pm; pulse overlap in feed and lines of 50%; in two orthogonal scans on the workpiece surface.

[0109] Coating

[0110] Some of the ground and cleaned samples were coated with an anti-adhesion coating (a coating that increases the static water contact angle), with layer type 13 from German patent application with the official file number 10 2023 125 172.4 with a layer thickness of approximately 250 nm. Table 2: Measurement data of the coating deposited on a silicon wafer (German patent application with the official file number 102023 125 172.4).

[0111] In this context, particular attention is drawn to the examples of the German patent application mentioned above and in particular to the tables

[0112] 9, 14, 19 and 23 and the corresponding explanations and these passages are included as part of this description.

[0113] Measuring

[0114] E-modulus density OFE pol O / Si C / Si M+D T+Q (M+D) / (T+Q) BE(SI2p) FWHM (SI2p) position

[0115] [GPa] [g / cm 3 ] [mN / m] [mN7m] [eV] [eV]

[0116] 1 35.5 1 ,60 27.2 1 ,55 1 ,21 1 ,3 37 63 0.58 102.50 2.11

[0117] 2 1 ,23 1 ,3 36 64 0,55 102,45 2,20

[0118] MW 1.22 1.3 36 64 0.57 102.48 2.16

[0119] [Table: Various measurement data of a selected coating with an HMDSO / O2 ratio of 2.8 and a self-bias of 300V (XPS measurement data and their evaluation at 2 measurement positions with averaging - explanations under official file number 10 2023 125 172.4)

[0120] The measurements described below, according to Example 1, were carried out within 30 days of sample preparation. They were stored and tested at room temperature (20-25 °C) and a relative humidity of 20-25% rh.

[0121] Measurement of the capillary pressure according to measurement example 1: Measurement of the rise height / capillary pressure

[0122] Density: Cyclohexane: 0.780 g / cm 3 ; Water: 1 g / cm 3 ; Miglyol (812): 0.956 g / cm 3

[0123] Table 3: Measured values ​​after 60 minutes

[0124] Control + correction of capillary pressures

[0125] Test fluids

[0126] Measurement of the cavern volume according to measurement example 2:

[0127] Sample geometry: 1 cm x 1 cm, as well as 1 cm x 2 cm, treated with the laser on both sides with Ap1 = 2 cm 2 and Ap2 = 4 cm 2 .

[0128] The Wilhelmy measurement results in a pore volume per area of ​​4, depending on the surface structures, for the difference in saturated mass divided by the difference in areas and the density of the oil. The measurement error results from half the sum of the standard deviations of three measurements on the 2 cm x 1 cm and 1 cm x 1 cm samples. Table 4: Determination of pore volume

[0129] Table 5: Measurement of the coverage of the channels as described above (according to

[0130] W02020 / 127594 A1)

[0131] Measurement of negative pressures. If the capillary pressure measurement result according to Example 1 was "0" (see Table 3), it can be assumed that there is indeed a negative capillary pressure with respect to the liquid in question, in this case water. This means that in case of doubt, an (additional) external pressure must be present for water to penetrate the capillary. To confirm and measure this, the following procedure was used: Material: The test specimens from Table 3 in the ground and coated state. A length-marked silicone tube with an inner diameter of 9 mm and an outer diameter of 12 mm was pressed onto the surface to be tested.

[0132] Deionized water was filled into the tube, and the height of rise until the resulting structures were impregnated was measured. The height of rise was continuously increased and amounted to h = 5.5 m for all samples tested in Table 3 (A10, C04, D05, E02). However, the channel structures were not impregnated outside the attached tube. This resulted in a capillary pressure of p < -0.539 bar for all samples with water, meaning that even when an external pressure of 0.539 bar was applied, the structures could not be filled with water.

[0133] Example 2: Laser structure (steel)

[0134] Description of production / storage Material: Stainless steel pan, 24cm "Profi" from WMF, EAN 4000530516817

[0135] Laser: 100 W Nd:YAG laser (type CL100 from CleanLaser, Herzogenrath, Germany with stamp optics and f(330) f-theta lens

[0136] Emitted wavelength: 1064 nm

[0137] Pulse length at 100 kHz: 129 ns Energy distribution in the laser spot: Gauss

[0138] Spot diameter in focus: approx. 107 pm

[0139] Target power: 100% (100 W)

[0140] Scanning speed between the focus points on the surface was 4000 mm / s

[0141] The laser processing was carried out using a "jump-and-shot" process. In this process, several pulses are applied in direct succession to a position on the surface before the scanning mirror moves to the next laser position.

[0142] The remaining parameters for structuring are listed in the following Table 6: Table 6: Parameters for structuring the surfaces

[0143] Sanding and cleaning

[0144] Some of the samples were smoothed by mechanically removing approximately 20 μm of the protruding surface peaks using an orbital sander. The grinding dust was then removed with a compressed air nozzle at 10 bar. Subsequent laser cleaning was performed using a 100 W Nd:YAG laser (type CL100 from CleanLaser, Herzogenrath, Germany) with stamp optics and f(330) f-theta lens, at nominal power: 100 W, pulse repetition frequency: 200 kHz; spot diameter: 107 μm; pulse overlap in feed and lines of 50%; in two orthogonal scans on the workpiece surface.

[0145] The coating was carried out analogously to Example 1.

[0146] The execution of a laser structuring of the pan bottom and pan rim up to a height of 1 cm was carried out in the pattern shown in Figure 1 .

[0147] The capillary pressure was measured within 48 hours of sample preparation. The samples were stored and tested at room temperature (20-25 °C) and a relative humidity of 20-25% rh.

[0148] Frying experiments:

[0149] The execution of a laser structuring of a pan bottom and pan rim up to a height of 1 cm was carried out in the pattern shown in Figure 1 .

[0150] After heating the pan and adding cooking fat (a product called Palmin), the fat immediately liquefied and infiltrated the gaps in the undercut surface structure, both in the pan base and the pan rim. Excess fat, after liquefaction, formed a uniform oily film on the pan bottom.

[0151] After heating the pan to 120°C, frying a fried egg was effortless, and the food didn't stick. Removing the food was easy.

[0152] After heating the pan to 200°C, frying a steak was effortless, and the food was successfully prevented from sticking. There was no sticking on the pan surface.

[0153] The pan could be cleaned in a standard household dishwasher.

[0154] The above-mentioned frying tests could be repeated 10 times without any change in the frying behavior.

Claims

Patent claims:

1. Substrate with a multiply opened cavern structure, wherein the substrate in the region of the openings of the cavern structure has a capillary pressure of > 0.5 hPa, preferably > 1.5 hPa, more preferably > 3.0 hPa and particularly preferably > 4.0 hPa for Miglyol and of < 10 hPa, preferably < 7 hPa, more preferably < 0 hPa, more preferably < - 100 hPa, more preferably < - 200 hPa, particularly preferably < - 500 hPa for water.

2. Substrate according to claim 1, wherein a coating increasing the static water contact angle is present at least in the region of the openings.

3. The substrate of claim 2, wherein the static water contact angle increasing coating is a plasma polymer coating.

4. Substrate according to one of the preceding claims, wherein the cavern structure can be produced by laser, preferably by IR laser, particularly preferably by nanosecond pulsed near-IR laser or by roll forming.

5. Substrate according to one of the preceding claims, wherein the cavern structure is a partially covered trench structure.

6. Substrate according to one of the preceding claims, wherein the degree of coverage of the cavern structure is 1% to 99%, preferably 5% to 80%, more preferably 10% to 80%, even more preferably 20% to 75%, even more preferably 25% to 70% and particularly preferably 30% to 65%.

7. Substrate according to one of the preceding claims, wherein the area proportion of the openings relative to the opening-occupied surface of the substrate is 0.5% to 60%, preferably 2% to 40%, more preferably 5% to 30% and particularly preferably 10% to 25%.

8. Substrate according to one of the preceding claims, wherein the volume accessible to oil filling relative to the opening-covered surface of the substrate is between 0.1 pL / cm 2 and 15pL / cm 2 , preferably between 0.15 pL / cm 2 and 10pL / cm 2, more preferably between 0.5pL / cm 2 and 8pL / cm 2 and particularly preferably between 1 pL / cm 2 5pL / cm 2 is large.

9. Substrate according to one of the preceding claims, wherein the cavern structure is located in metal, preferably a metal selected from the group consisting of steel, stainless steel, aluminum, copper, titanium, magnesium, and their alloys.

10. Substrate according to one of the preceding claims, wherein the substrate is selected from the group consisting of cookware, in particular frying pan, Plain bearings, pistons, cylinders and rolling bearings.

11. Use of a multiply opened cavern structure, as defined in any one of the preceding claims, for improving the distribution of oil or lubricants on the surface of a substrate.

12. A method for producing a substrate as defined in any one of claims 1 to 10, comprising the steps: a) providing a substrate, preferably as further defined in any one of claims 9 or 10, b) producing a cavern structure, preferably as further defined in any one of claims 4 to 9, and c) optionally coating at least in the region of the openings of the cavern structure with a coating, preferably as further defined in any one of claims 2 or 3.

13. The method according to claim 12, wherein after step b) and optionally before step c) a smoothing of the surface of the substrate is carried out.

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