DD293340A5 - METHOD FOR PRODUCING HARDENED, MOISTURIZED HYDROPHOBIC LAYERS - Google Patents

Abstract

Process for the production of firmly adhering, moisture-stable hydrophobing layers. The aim of the invention is a durable, water-repellent effect and soil-repellent effect of provided with such layers surfaces. The solution consists in applying an adhesion-promoting SiO 2 -containing layer to the solid surface which is to be provided with the hydrophobization layer. Anschlieszend the application of a preferably silicone-containing hydrophobization layer of thickness 50 nm. The SiO 2 -containing layer can be applied by flame-pyrolytic, by a sol-gel process applied {hydrophobing layer, adhesive, moisture-stable; Intermediate layer; SiO2 sustainably; Hydrophobing layer, containing silicone}

Description

Field of application of the invention

The invention relates to a method for producing a durable, moisture-stable hydrophobization of solid surfaces.

Hydrophobing layers, d. h., Surface layers with a water-repellent effect, which is in large contact angles of water droplets and thus a rapid drainage of water on the surface layer, find a wide technical application, which is often associated with a dirt-repellent effect, since the dissolved dirt in the water at the same time drain quickly with the water drop.

Characteristic of the known state of the art

The hydrophobing of the surface is preferably achieved by applying nonpolar waxes or polymers which are applied or sprayed from solutions or from suspensions (W. Noil: Chemie und Technologie der Silicones, Verlag Chemie, Weinheim 1960), or increased by layers based on silicone. Particularly favorable properties also in terms of chemical and mechanical stability have layers of PTFE (polytetrafluoroethylene), however, which are expensive and expensive to process and thus remain reserved for selected applications. Silicones have high oxidation resistance and good chemical stability (FGAStone, WAGGraham: Inorganic Polymers, Academic Press, New York, London 1962). They are used as silicone oils, usually methyl polysilicones of different molecular weight and thus different viscosity, usually applied from solutions and optionally post-cured by thermal post-treatment at temperatures up to 300 ⁰ C, ie postcrosslinked. Another way to surface hydrophobicize with silicones is the use of reactive silicones, which crosslink with the surface to which they are applied, or even with each other. Such produced layers are usually only thin, ie a few nm thick.

It is also known that adhesion promoters are additionally added to the silicone solutions themselves in order to improve the adhesion to the coated substrate.

The disadvantage of the prior art, which results in insufficient adhesion of the silicone layers to various metallic, oxidic and silicate surfaces, becomes particularly clear from these technical solutions. This disadvantage manifests itself to a particular extent with a load on the interface in the humid environment and even more in the acidic environment. and leads to an increasing with the loading time functional decline of the hydrophobing effect.

Object of the invention

The object of the invention is a method which increases the adhesion of hydrophobing layers, in particular the moisture resistance of the adhesive strength. This is intended to achieve a permanent water-repellent effect and, associated therewith, dirt-repellent effect of surfaces provided with such layers.

Explanation of the nature of the invention

The invention has for its object to achieve a significantly improved in terms of parameters adhesive strength, moisture stability and durability hydrophobing of solid surfaces. The production of adherent, moisture-stable hydrophobing layers on solid surfaces is inventively achieved in that an adhesion-promoting SiO ₂ -containing layer is applied to the solid surface, which is to be provided with the hydrophobization layer. According to the invention, the adhesion improvement by the SiO ₂ -containing intermediate layer indirectly also causes a

Langzoitstabilität the hydrophobing properties of the actual hydrophobing layer, without it to a

mechanical detachment of the hydrophobization layer comes. Such an effect of the adhesive layer is surprising, since the water-repellent effect of the hydrophobing layer is seen more in a wetting effect of the surface or the near-surface region. This is due to the chemical structure of the hydrophobing layers with their non-polar groups, such as methyl groups.

The solution according to the invention could be achieved on SiO ₂ -containing adhesion promoter layers which consist of plastic-metal or ceramic-metal Connected are known to be detected. Various methods are known for the production of such SiO ₂ -containing intermediate layers. So they let themselves through a

produce flame pyrolytic decomposition of Si-alkoxy compounds in variable thickness. Also described are physical processes such as sputtering or reactive vapor deposition and the plasma decomposition of Si-containing compounds in an O ₂ -containing atmosphere. Especially suitable for this are glow discharges, as are known from plasma polymerization.

As a further option, the use of SiO ₂ -containing as a solution according to the invention for the adhesion promotion Layers that are produced via a sol-gel process proven. Exist for the formulation of such solutions

described examples. An improvement, especially on a range of metal oxides and alloys, is achieved by previously depositing a thin (2-5nm) Cr oxide layer. The adhesion-enhancing effect of Cr oxide layers per se is known from other fields of technology. The Cr oxide-forming component may also be included in the SiO ₂ layer-forming

So gel solution can be introduced. The described methods for forming sol-containing hard films lead to layers with high porosity and a Intrinsic elasticity of the layers, which constitute a kind of adhesive bed for the hydrophobing layer, which apparently also the Structure and stability of the hydrophobing layer optimally influenced. Optionally, a further increase in adhesion through the use of an adhesion promoter, on the SiO ₂ -containing Adhesive layer is applied can be achieved. Again, there are known solutions in other fields of technology. In particular, so-called silane coupling agents, which are mostly functionalized trialkoxysilanes, have proven to be useful

acidified alcoholic solutions are used.

embodiment

The essence of the invention will be explained in more detail in three embodiments illustrated below. In order to be able to make clear the technical progress to be achieved using the invention, the contact angle achievable with known methods of hydrophobization and, in contrast thereto, the ratios to be obtained by the method according to the invention are indicated for each exemplary embodiment.

1. Hydrophobization of roof tiles

The water-cleaned and dried roof tiles had a H ₂ O contact angle of 55 °. When using a known silicone oil-containing solution for producing a hydrophobing layer shows the Roof tile surface a contact angle for water of 74 °. The layer was a temperature of 25 ⁰ C for 15min

subjected. After boiling the sample in an acidic aqueous solution (pH 4-5) for five hours, the

Contact angle at 68 °.

Silicone solution: 2,25mllsopropanol 0,37mlDioxane 0,03 ml NM1-200 (silicone oil) 0,06 ml WON 100 (wetting agent)

An inventive treatment of Dachziegeloberlfäche (Slllcoater-Verfahran 5min + silicone solution [25O ⁰ C, 15mini) results in a contact angle of 98 °.

After a boiling test of 5 hours in an acid solution (pH 4-5), the contact angle for water is slightly reduced to 89 °, but is significantly higher than the results for untreated samples and indicates good stability of the hydrophobing layer.

2. Water-repellent treatment of an Al ₂ O 3 ceramic pretreatment: · Cleaning with acetone

• Drying at 12O ⁰ C

After this pretreatment of the surface, a HjO contact angle of 39 ° is measured. If the ceramic surface is treated with a silicone oil-based treatment and tempered for 10 minutes at 300 ° C., the contact angle of water increases to 90 ° C. After a five-hour boiling in an acidified solution (pH 4-5), the contact angle is reduced to 58 °. A conditioning according to the invention of the Al ₂ O ₃ ceramic surface with the method steps

- Silicoater method 5min + silicone solution (250 ⁰ C, 15min) - provides a H ₂ O contact angle of 105 °. Even after boiling in an aqueous solution with a pH of 5 for 5 hours, the contact angle is still at 70 ° and thus far above that of the untreated samples.

3. Hydrophobing of window glass Pretreatment: · Cleaning with acetone

• Drying at 120 ^° C

After this pretreatment procedure, the window glass surface had a contact angle for H ₂ O of 36 °. When applying a hydrophobizing layer based on silicone oil, the contact angle increases to 103.6 °. However, it decreases by more than half (53.7 °) after a cooking time of 5 hours, indicating a reduced stability of the hydrophobing layer. The treatment by the process according to the invention (silicoater process 5 min + silicone solution 250 ⁰ C, 15 min) leads to a contact angle of 95 °. This high value is not only retained after cooking, but also increases to 106.7 °, which can only be explained by a considerable stability of the hydrophobing layer.

Claims (11)

1. A process for the production of adherent, moisture-stable hydrophobing layers Solid surfaces, characterized in that the solid surface with a 2-100nm, preferably 10-30nm, coated thick SiO2-containing layer and then a preferably silicone-containing hydrophobization layer of thickness> 50 nm is applied. 2. The method according to claim 1, characterized in that the SiO ₂ -containing layer is produced by a flame-pyrolytic decomposition of an Si-containing compound, preferably an alkoxysilane. 3. The method according to claim 1, characterized in that the SiO ₂ -containing layer is applied via a sol-gel process. 4. The method according to claim 2 or 3, characterized in that the SiO ₂ -containing layer has a carbon content of 5-40 parts by mass in%, preferably in the form of hydrocarbon-containing end groups, on the SiO ₂ scaffold. 5. The method according to claim 1, characterized in that the silicone-containing hydrophobing layer produced by brushing, dipping or spraying a silicone oil-solvent mixture and then at 150 ⁰ C to 250 ⁰ C-preferably 200 ⁰ C-2 to 20 min - preferred 5min - is cured. 6. The method according to claim 5, characterized in that the silicone-containing hydrophobing layer is produced by photochemical curing. 7. The method according to claim 5, characterized in that the silicone-containing hydrophobing layer by repeated application - preferably twice applying and curing of the layer - is generated. 8. The method according to claim 5, characterized in that the SiO ₂ -containing layer before the application of the hydrophobization layer with a coupling agent - preferably a Silanhaftvermittler the type of a functionalized trialkoxysilane - coated. 9. The method according to claim 8, characterized in that the Silanhaftvermittler in an acidic Solution - preferably a mixed with HCI or acetic acid alcoholic solution - is used. 10. The method according to claim 8 ", characterized in that between the solid surface and SiO ₂ -containing layer, a layer of an adhesive oxide preferably a Cr oxide of an average density of 1-1 Onm, preferably 3 nm, is applied. 11. The method according to claim 8, characterized in that the Cr-oxide is applied via a Cr-containing SoI gel silicate solution.