EP1144341A1

EP1144341A1 - Method for producing an ultraphobic surface based on tungsten carbide

Info

Publication number: EP1144341A1
Application number: EP99968356A
Authority: EP
Inventors: Karsten Reihs; Daniel-Gordon Duff; Georg Wiessmeier; Burkhard KÖHLER
Original assignee: Sunyx Surface Nanotechnologies GmbH
Current assignee: Sunyx Surface Nanotechnologies GmbH
Priority date: 1998-12-24
Filing date: 1999-12-20
Publication date: 2001-10-17
Also published as: DE19860135A1; AU2538100A; DE19860135C2; WO2000039051A1

Abstract

The invention relates to a method for producing a surface having ultraphobic properties. According to the inventive method, an essentially smooth surface comprised of tungsten carbide is structured by means of laser ablation, whereby recesses are formed which, in particular, periodically recur along the surface and which have a depth ranging from 10 mu m to 500 mu m. The surface is optionally coated with a bonding agent layer and is subsequently provided with a hydrophobic or oleophobic coating.

Description

Process for producing an ultraphobic surface based on tungsten carbide

The present invention relates to an ultraphobic surface, its manufacture and

Use. The method is characterized in that an essentially smooth surface made of tungsten carbide is structured by means of laser ablation, wherein periodically recurring depressions are formed along the surface with a depth in the range from 10 μm to 500 μm, preferably from 50 μm to 250 μm The surface is then optionally coated with an adhesion promoter layer and then provided with a hydrophobic or in particular oleophobic coating.

Ultraphobic surfaces are characterized by the fact that the contact angle of a drop of a liquid, usually water, lying on the surface is significantly more than 90 ° and that the roll angle does not exceed 10 °. Ultraphobic surfaces with a contact angle> 150 ° and the above Roll-off angles have a very high technical benefit because they e.g. cannot be wetted with water or oil, dirt particles adhere very poorly to these surfaces and these surfaces are self-cleaning. Self-cleaning is understood here to mean the ability of the surface to easily release dirt or dust particles adhering to the surface to liquids that flow over the surface.

There has been no shortage of attempts to provide such ultraphobic surfaces. For example, EP 476 510 AI discloses a method for producing an ultraphobic surface, in which a metal oxide film is applied to a glass surface and then etched using an Ar plasma. However, the surfaces produced using this method have the disadvantage that the contact angle of a drop lying on the surface is less than 150 °. US Pat. No. 5,693,236 also teaches a number of processes for the production of ultraphobic surfaces, in which zinc oxide microneedles are brought onto a surface with a binder and are then partially exposed in different ways (for example by plasma treatment). The surface structured in this way is then coated with a water-repellent agent. To this

Wise structured surfaces, however, also only have contact angles of up to 150 °.

It is therefore the task of providing ultraphobic surfaces and a method for their production which have a contact angle> 150 ° and preferably a roll angle <10 °.

The roll angle here is understood to be the angle of inclination of a basically planar but structured surface with respect to the horizontal, at which a standing water drop of volume 10 μl is moved due to gravity when the

Surface is inclined.

The object is achieved according to the invention by the provision of a method for producing an ultraphobic surface which is the subject of the invention, characterized in that an essentially smooth surface is made of

Tungsten carbide is structured by means of laser ablation, with periodically recurring depressions in particular being formed along the surface with a depth in the range from 10 μm to 500 μm, preferably from 50 μm to 250 μm and an average distance between adjacent depressions from 10 to 500 μm, preferably from 50 up to 250 μm, the surface is then optionally coated with an adhesion promoter layer and then provided with a hydrophobic or in particular oleophobic coating.

A foam body that is to be provided with the surface according to the invention either consists entirely of tungsten carbide or has a surface

Tungsten carbide, the surface being coated with any can be applied by way of driving. Tungsten carbide in the sense of the invention means not only pure tungsten carbide but also alloys or mixtures in which the proportion of tungsten carbide is> 30% by weight, preferably> 45% by weight.

The tungsten carbide can be structured with any laser suitable for laser ablation. The wavelength of the laser light is preferably between 500 and 550 nm. A Nd: YAG laser is particularly preferably used for this.

The laser also preferably has a beam diameter on the sample surface of 30 to 70 μm, particularly preferably 45 to 55 μm.

The power density of the laser on the substrate surface is preferably 10 ⁴ to 10 ⁷ W / cm ² , particularly preferably 10 ⁵ to 10 ⁶ W / cm ² .

The scanning speed (scanning speed) is preferably 30 to 50 mm / s, particularly preferably 35 to 45 mm / s.

The line offset of adjacent scanning lines is preferably 5 to 500 μm, particularly preferably 8 to 250 μm.

After the treatment with the laser, the surfaces thus obtained are provided with a hydrophobic or in particular oleophobic coating.

A hydrophobic material in the sense of the invention is a material which shows a contact angle with respect to water of greater than 90 ° on a flat, non-structured surface.

An oleophobic material in the sense of the invention is a material which, on a flat, non-structured surface, has a contact angle with respect to long-chain n-alkanes, such as n-decane, of greater than 90 °. The ultraphobic surface preferably has a coating with a hydrophobic phobicization aid, in particular an anionic, cationic, amphoteric or nonionic, surface-active compound.

Surfactant compounds with any desired are used as phobicization aids

Molecular mass to look at. These compounds are preferably cationic, anionic, amophotere or non-ionic surface-active compounds, such as those e.g. in the directory “Surfactants Europa, A Dictionary of Surface Active Agents available in Europe, Edited by Gordon L. Hollis, Royal Socity of Chemistry, Cambridge, 1995.

The following may be mentioned as anionic phobicization aids: alkyl sulfates, ether sulfates, ether carboxylates, phosphate esters, sulfosucinates, sulfosuccinatamides, paraffin sulfonates, olefin sulfonates, sarcosinates, isothionates, taurates and Linginian compounds.

Quaternary alkylammonium compounds and imidazoles may be mentioned as cationic phobicization aids

Amphoteric phobicization aids are, for example, betaines, glycinates, propionates and imidazoles.

Examples of nonionic phobing aids are: alkoxylates, alkyloamides, esters, amine oxides and alkypolyglycosides. Also suitable are: reaction products of alkylene oxides with alkylatable compounds, such as. B. fatty alcohols, fatty amines, fatty acids, phenols, alkylphenols, arylalkylphenols, such as styrene-phenol condensates, carboxamides and resin acids.

Phobicization aids are particularly preferred in which 1 to 100%, particularly preferably 60 to 95%, of the hydrogen atoms are substituted by fluorine atoms. Examples include perfluorinated alkyl sulfate, perfluorinated alkyl sulfonates, and perfluorinated Called alkyl phosphonates, perfluorinated alkyl phosphinates and perfluorinated carboxylic acids.

Compounds with a molecular weight M _w > 500 to 1,000,000, preferably 1,000 to 500,000 and particularly preferably 1,500 to 20,000 are preferably used as polymeric phobicization aids for hydrophobic coating or as polymeric hydrophobic material for the surface. These polymeric phobicization aids can be nonionic, anionic, cationic or amphoteric compounds. Furthermore, these polymeric phobicization aids can be homopolymers and copolymers, graft and graft copolymers and random block polymers.

Particularly preferred polymerizing auxiliaries are those of the type AB, BAB and ABC block polymers. In the AB or BAB block polymers, the A segment is a hydrophilic homopolymer or copolymer and the B block is a hydrophobic homopolymer or copolymer or a salt thereof.

Anionic, polymeric phobing aids are also particularly preferred, in particular condensation products of aromatic sulfonic acids with formaldehyde and alkylnaphthalenesulfonic acids or from formaldehyde, naphthalenesulfonic acids and / or benzenesulfonic acids, condensation products from optionally substituted phenol with formaldehyde and sodium bisulfite.

Also preferred are condensation products which can be obtained by reacting naphthols with alkanols, additions of alkylene oxide and at least partial conversion of the terminal hydroxyl groups into sulfo groups or half esters of maleic acid and phthalic acid or succinic acid.

In another preferred embodiment, the phobicization aid is from the group of the sulfosuccinic acid esters and alkylbenzenesulfonates. Sulfated, alkoxylated fatty acids or their salts are also preferred. As alkoxylated fat Acid alcohols are understood in particular to be those with 5 to 120, with 6 to 60, very particularly preferably with 7 to 30 ethylene oxide units, C ₆ -C ₂₂ fatty acid alcohols which are saturated or unsaturated, in particular stearyl alcohol. The sulfated alkoxylated fatty acid alcohols are preferably in the form of a salt, in particular in the form of alkali or amine salts, preferably in the form of the diethylamine salt.

In order to improve the adhesion of the hydrophobic or oleophobic coating on the lasered surface, it can be advantageous to coat the lasered surface first with an adhesion promoter layer. An adhesion promoter layer is therefore optionally applied between the surface and the hydrophobic or oleophobic coating. In principle, any substance which is familiar to the person skilled in the art and which increases the bond between the surface and the respective hydrophobic or oleophobic coating is suitable as an adhesion promoter. Preferred adhesion promoters, e.g. for thiols as a hydrophobic coating, noble metal layers are e.g. made of Au, Pt or Ag or those made of GaAs, especially gold. The layer thickness of the

Adhesion promoter layer is preferably from 10 to 100 nm.

With the method according to the invention, ultraphobic surfaces can be produced in which the contact angle of a drop lying on the surface is> 155 °. The invention therefore also relates to the ultraphobic surfaces obtained by the process according to the invention.

These ultraphobic surfaces have the advantage, among other things, that they are self-cleaning, and the self-cleaning can be carried out by exposing the surface to rain or moving water from time to time. Through the ultraphobic

The water droplets roll off the surface and dirt particles, which adhere very poorly to the surface, deposit on the surface of the rolling pots and are thus removed from the ultraphobic surface. This self-cleaning works not only in contact with water but also with oil. There are a large number of possible technical uses for the surface produced using the method according to the invention. The following applications of the ultraphobic surfaces produced by the process according to the invention are therefore also claimed:

With the ultraphobic surface produced by the method according to the invention, ship hulls can be coated in order to reduce their frictional resistance.

Furthermore, sanitary facilities, in particular toilet bowls, can be provided with the ultraphobic surface produced by the process according to the invention in order to reduce their susceptibility to contamination.

The fact that water does not adhere to the ultraphobic surface produced by the process according to the invention makes it suitable as a rust preventive for base metals of any kind.

Another application of the ultraphobic surface is the coating of surfaces on which no water should adhere in order to avoid icing. The surfaces of heat exchangers are an example here. in refrigerators or the surfaces of aircraft called.

The surfaces produced with the method according to the invention are also suitable for attachment to house facades, roofs, monuments in order to make them self-cleaning.

The ultraphobic surfaces produced by the method according to the invention are also particularly suitable for coating shaped articles whose surface is subjected to high mechanical stress. The ultraphobic surfaces produced using the method according to the invention are also particularly suitable for coating shaped articles which are translucent. In particular, it is translucent glazing of buildings, vehicles, solar panels. For this purpose, a thin layer of the ultraphobic surface according to the invention is evaporated onto the molded body.

The invention also relates to a material or building material having an ultraphobic surface according to the invention.

Another object of the invention is the use of the ultraphobic surface according to the invention for the friction-reducing lining of vehicle bodies, aircraft or ship hulls.

The invention also relates to the use of the ultraphobic surface according to the invention as a self-cleaning coating or planking of

Buildings, roofs, windows, ceramic building material, e.g. for sanitary facilities, household appliances.

The invention further relates to the use of the ultraphobic surface according to the invention as a rust-protecting coating of metal objects.

The method according to the invention is explained below using an example, which, however, does not restrict the general idea of the invention.

example

A tungsten carbide substrate (WC 64%, Co 6%, grade: THM SPUN 633 (US); K10-K25 190412; WIDIA, 19x19 mm ² , 5mm thick) is covered on an area of 10x10 mm ² with the following registration conditions by a Nd : YAG laser structured:

Wavelength: 532nm

Scan speed: 40 mm / s, line offset 10 μm

Laser power: 3 W (pulse length 100 ns, frequency 4 kHz) Beam diameter: 50 μm

The inscribed pattern has approximately square columns in the format 67 x 67 μm ² , the height of which is 200 μm. The distance between the columns is approximately 200 μm. The tungsten carbide surface is roughened due to melting or condensation processes in the area of the inscribed areas.

The substrate treated in this way was coated with an approximately 50 nm thick gold layer by sputtering. This coating corresponds to the method which is also common for preparation in electron microscopy and according to Klaus Wetzig, Dietrich Schulze, "In situ Scanning Electron Microscopy in Material Research",

Pages 36 - 40, Akademie Verlag, Berlin 1995. This reference is hereby introduced as a reference and is therefore part of the disclosure.

Finally, the gold layer of the sample was coated with a few drops of a solution of n-decanethiol in ethanol (1 g / 1) at room temperature in a closed vessel for 24 hours, then rinsed with ethanol and dried.

The surface has a static contact angle of 155 ° for water. If the straight surface is inclined by <10 °, a drop of water with a volume of 10 μl will roll off spontaneously.

Claims

claims

1. A method for producing a surface with ultraphobic properties, characterized in that an essentially smooth surface made of tungsten carbide is structured by means of laser ablation, wherein along the

Surface, in particular periodically recurring depressions, are formed with a depth in the range from 10 μm to 500 μm, preferably from 50 μm to 250 μm and an average spacing of the depressions from 10 to 500 μm, preferably from 50 to 250 μm optionally coated with an adhesion promoter layer and then provided with a hydrophobic or in particular oleophobic coating.

2. The method according to claim 1, characterized in that the wavelength of the laser is 500 to 550 nm.

3. The method according to any one of claims 1 or 2, characterized in that a frequency-doubled Nd / YAG laser is used as the laser.

4. The method according to any one of claims 1 to 3, characterized in that the beam diameter of the laser on the surface is 30 to 70 microns, preferably 45 to 55 microns.

5. The method according to any one of claims 1 to 4, characterized in that the laser power density on the surface is 10 ⁴ to 10 ⁷ W / cm ² , preferably 10 ⁵ to 10 ⁶ W / cm ² .

6. The method according to any one of claims 1 to 5, characterized in that the surface is scanned in a punctiform manner with the laser beam and the scanning speed is 30 to 50 mm / s, preferably 35 to 45 mm / s.

7. The method according to claim 6, characterized in that the line offset of adjacent scanning lines is 5 to 500 microns, preferably 8 to 250 microns.

8. Ultraphobic surface obtained by a method according to any one of claims 1 to 7.

9. Material or building material having an ultraphobic surface according to claim 8.

10. Use of the ultraphobic surface according to claim 8 for the friction-reducing lining of vehicle bodies, aircraft or ship hulls.

11. Use of the ultraphobic surface according to claim 8 as a self-cleaning coating or planking of buildings, roofs, windows, ceramic building material, e.g. for sanitary facilities, household appliances.

12. Use of the ultraphobic surface according to claim 8 as a rust-protecting coating of metal objects.