Production of suspensions of hydrophobic oxide particles

Translation of description of equivalent WO 2004039909 A1

PREPARATION OF SUSPENSION OF HYDROPHOBIC oxide particles

The invention relates to a process for preparing a suspension of hydrophobic oxide particles with a defined, adjustable viscosity, as well as a suspension of hydrophobic oxide particles with a defined, adjustable viscosity and their use for the production of soil and water repellent coatings on articles.

Suspensions of hydrophobic particles nanosfrukturierten be used in the production of soil and water repellent coatings on articles and textile fabrics. In the preparation of these coatings, hydrophobic particles are applied to the surface of an article, thus generating a surface structure with elevations on the surface of the article, which has dirt- and water-repellent properties.

The principle of self-cleaning coatings is well known. To achieve a good self-cleaning a surface, the surface must have in addition to a very hydrophobic surface a certain roughness. A suitable combination of structure and hydrophobicity makes it possible that even small amounts of moving water bring to the surface adhering dirt particles and thus clean the surface (WO 96/04123; US No. 3,354,022).

From EP 0933388 a process for the production of structured surfaces with hydrophobic properties is known in which first preparing a negative mold by photolithography, with this negative mold shapes a plastic foil and then hydrophobicized the plastic film with fluoroalkylsilanes.

The EP-A 0,909,747 describes a method for producing a self-cleaning property to ceramic bodies such as roofing tiles, which comprises applying a dispersion of clay particles in an organic silicone resin solution on the ceramic body and then curing the coating.

From JP 7328532-A, a coating method is known, in which finely divided Particles having a hydrophobic surface to a wet paint applied and these cures. Here, water-repellent surfaces are obtained.

DE 10022 246 AI describes a process, see the hydrophobic nanostructured particles together with an adhesive or a ldeberährilichen component in spray form. Using this method produced slnikturierte surfaces, however, are not permanently resistant.

The methods for producing difficult to wet surfaces described in the prior art are either very expensive or lead to unsatisfactory results. The creation of a structured surface by embossing processes is complex and can be used economically only flat surfaces. Surfaces where a patterning by subsequent application of hydrophobic particles is achieved, are frequently difficult to reproduce or they have only a low mechanical load on. Moreover, this process is very complicated. Furthermore often organofluorine compounds or fluorine-containing polymers are required, which are not only very expensive but also ecologically highly questionable.

In the German patent application DE 101 35 157 a method for applying a self-cleaning coating on fabrics is described. In this method, hydrophobic nanostructured pyrogenic silicas are the chemical cleaning agents, such as perchlorethylene, tetrachlorethylene or naphtha, mixed and generated following the dry cleaning a self-cleaning water-repellent effect on the garments. Also in this process ecologically harmful halogenated solvents are used.

One way to produce self-cleaning textile fabrics with water-repellent surfaces describes the German patent application DE 101 18 346. The suspensions described in this application hydrophobic structured particles have the disadvantage that these suspensions can only be applied by dipping or transfer procedures to the appropriate textiles and dissolving the polymer fiber, the particles are firmly anchored in the polymer fiber surface. It is an object of the present invention to provide a method for producing a suspension of hydrophobic oxidic particles having a defined, adjustable viscosity, the further application process for suspensions of hydrophobic oxidic particles, such as the doctor blade process, in addition to the known methods, such as dipping or spraying to be used.

Surprisingly it has been found that can be produced with defimerter, adjustable viscosity suspensions of hydrophobic oxidic particles by low structured hydrophobic oxidic particles in at least one organic suspension agent and then from 0.05 to 15 wt .-% is added to the suspension medium of high structured hydrophobic oxidic particles , According to the inventive method can suspensions that allow through their adjustable viscosity application processes that pose a lower investment and a lower environmental impact by vaporized suspension medium, are produced. Very particularly advantageous, the fact that now are suspensions with the present inventive method for doctoring processes for textiles or for textile coatings available proves.

The present invention is a process for preparing a suspension of hydrophobic oxide particles with a defined, adjustable viscosity, with low structured hydrophobic oxide particles are suspended, and then 0.05 to 15 wt .-%, based on the suspension medium of high structured hydrophobic oxide particles in at least one organic suspension medium be added.

Also provided by the present invention suspensions of hydrophobic oxidic particles having a defined, adjustable viscosity and the use thereof for producing soil and water repellent coatings on articles.

The inventive method suspensions of hydrophobic oxidic particles having a defined, adjustable viscosity are accessible. Thus suspensions of hydrophobic oxide particles having a higher viscosity than in the prior art and also pastes can now be made of hydrophobic oxide particles. The suspensions produced with the aid of the method according erfmdungsge- therefore permit other application methods, such as the doctor blade process to use. According to the prior art, the suspensions are sprayed from hydrophobic oxide particles or of the article to be coated is immersed in the suspension of the hydrophobic oxide particles. This caused are higher investment costs and also increase environmental pressure due to the higher proportion of organic suspending agents for the application of the hydrophobic oxide particles. The inventive suspensions are particularly suitable for the self-cleaning and water-repellent coating of textiles, as is already being used here for the coatings according to the prior art, for example, with polyurethane coating compositions, a doctor blade process.

The process for preparing a suspension with a defined, adjustable viscosity of hydrophobic oxide particles is characterized in that medrigstrukturierte hydrophobic oxide particles are suspended in at least one organic suspension medium, and then preferably added by 0.05 to 15 wt .-%, preferably 1-12 .-%, particularly preferably from 2 to 10 wt .-% based are added to the suspension medium of high structured hydrophobic oxidic particles.

In the inventive process as the hydrophobic oxide particles, both low and high structured, preferably hydrophobic fumed oxide particles, consisting of a material selected from silica, alumina, zirconia, titania or a mixture of these materials, or hydrophobic precipitated oxide particles selected from silicon oxide, alumina, zirconia, titania or a mixture of these materials, preferably hydrophobic precipitated silicas, are used. hydrophobic fumed silicas are particularly preferred in the process of the invention. In a particular embodiment of the method according to the invention a mixture of low structured hydrophobic oxidic particles is used. But it can also be a mixture of high structured hydrophobic oxide particles are used.

The hydrophobicity of the oxide particles can be inherent or the oxide particles may have been rendered hydrophobic in a manner known to those skilled in his (Pigments,

Number 18, Degussa AG). This is preferably done by treatment with at least one compound selected from the group of the alkylsilanes, alkyldisilazanes, for example, hexamethyldisilazane, or perfluoroalkyl silanes.

In a first process step of the inventive method are preferably from 0.05 to 2.5 wt .-%, preferably from 0.1 to 2.0 wt .-%, particularly preferably from 0.5 to 1.2 wt .-% based on the suspension medium of low structured hydrophobic oxidic particles in at least one organic suspension agent.

As a suspending agent alcohols, ketones, ethers, esters, aliphatic or aromatic hydrocarbons, amides or sulfoxides can be used in the inventive method. In a particular embodiment of the inventive mixtures of the above-mentioned suspension means can be used, preferably a suspending medium is used which contains the organic suspension agent or the organic suspension mixture water.

Under low structured hydrophobic oxidic particles are understood in the context of this invention hydrophobic oxide particles over the corresponding high structured hydrophobic oxide particles decreased by at least 30% dibutyl phthalate absorption (DBP absorption) - measured in accordance with DIN 53 601 - have. Furthermore, the employed in the process according to the invention low structured hydrophobic oxidic particles an increased by at least 50% tamped density - measured according to DIN 53 194 - compared to the corresponding high structured hydrophobic oxide particles on. For example, Aerosil R 812 S, a high structured hydrophobic fumed silica has a tamped density of 50 g / 1 in, whereas Aerosil VP LE 8241 as niedrigstxulcturierte hydrophobic fumed silica has a tamped density of 140 g / 1 on.

The medrigstrukturierten hydrophobic oxide particles can be produced from 5,959,005 high structured hydrophobic oxide particles produced by a dry, according to EP 0637616 Bl or US, this is an intensive milling procedure that requires continuous addition of a Destaikturierung oxide particles above the normal particle size reduction. This is an irreversible process.

In one particular embodiment of the inventive process both as low- and as high structured hydrophobic pyrogenic oxide particles Aerosils®^® used. As low structured hydrophobic Aerosil^® is preferably Aerosil^® VP LE 8241 used. The Aerosil^® R 812 S is in this particular embodiment of the inventive hydrophobic than highly structured Aerosil^® used.

Low structured hydrophobic oxide particles used in the process according to the invention preferably have a surface having an irregular fine structure in the nanometer range, that is in the range of 1 micron to 1000 nm, preferably from 2 nm to 750 nm and most preferably from 10 nm to 100 nm, , Under Feinsh iktur Staikturen be understood, whose heights, peaks, crevices, ridges, cracks, undercuts, notches and / or holes in the distances and areas mentioned above. The fine structure of low structured hydrophobic oxidic particles can preferably have elevations having an aspect ratio of greater than 1, more preferably greater than 1.5. The aspect ratio is in turn defined as the quotient of maximum height to maximum width of the elevation, with ridges or other elongate elevations, the width taken perpendicular to the longitudinal direction.

Preferably niedrigstnikturierte hydrophobic oxide particles are used in the process according to the invention having an average particle diameter of 0.005 microns to 100 microns, preferably of 0.01 microns to 50 microns and more preferably from 0.01 microns to 30 microns are used. Thus, even low structured hydrophobic oxidic particles, which assemble in the suspension medium from primary agglomerates or aggregates having a size of 0.02 microns to 100 microns, are used.

To destroy any agglomerates present it is advantageous suspending the hydrophobic oxide particles with high shear energy input, for example by means of dissolver. perform. The use of turbulence-increasing internals, such as baffles or other obstacles which serve to prevent the formation of standing waves can also be advantageous. The Reynolds number is preferably above 2320. The Richardson number is the strength of the thermal stratification in a relationship with the magnitude of shear a flow. It is thus a measure of the ratio of the sizes that are responsible for the propagation or the decay of the turbulence. The Richardson refers to a local gradient at one point of the flow, the Richardson number is for the novel process at a maximum of 0.25. A definition of the Richardson number is found, inter alia, in H. Kobus (lecture script "Water Hydraulics" Department of Hydraulic and Groundwater, Institute of Hydraulic Engineering, University of Stuttgart).

Depending on the attached amount of high structured hydrophobic oxidic particles can suspensions with dynamic viscosities at a shear rate of greater than 20 s^"1 preferably from 1.0 to 1000 mPa s, preferably from 1 to 500 mPa s, particularly preferably from 1 to 400 mPa · s are prepared. With an amount of high structured hydrophobic oxidic particles, such as the Aerosil^® R 812 S, of> 5 wt .-%, based on the suspension medium can even suspension can be prepared with a sttukturviskosem flow behavior by means of the inventive method.

The inventive suspension of hydrophobic oxide particles with a defined, adjustable viscosity, characterized by the fact that medrigstrukturierte hydrophobic oxide particles, and preferably from 0.05 to 15 wt .-%, preferably from 1 to 12 wt .-% and particularly preferably 2 to 10 suspended wt .-% based on the suspension medium of high structured hydrophobic oxidic particles in at least one organic suspension agents are present.

The suspension of the invention comprises preferably 0.05 to 2.5 wt .-%, preferably from 0.1 to 2.0 wt .-%, particularly preferably from 0.5 to 1.2 wt .-%, based on the suspension medium at low structured hydrophobic oxidic particles on.

Preferably, the suspension of the invention is prepared by the inventive method described above.

The suspension of the invention comprises as a hydrophobic oxide particles, both low and high structured, preferably hydrophobic fumed oxide particles, consisting of a material selected from silica, alumina, zirconia, titania or a mixture of these materials, or hydrophobic precipitated oxide particles selected from silicon oxide, aluminum , zirconium oxide, titanium oxide or a mixture of these Materials, preferably hydrophobic precipitated silicas on. Particularly preferably, the suspension of the invention comprises hydrophobic fumed silicas. In a particular embodiment, the suspension of the invention, it comprises a mixture of hydrophobic oxide particles medrigstrukturierten. The suspension of the invention may also have a mixture of high structured hydrophobic oxide particles.

The hydrophobicity of the oxide particles can be inherent or the oxide particles may have been rendered hydrophobic in a manner known to those skilled in his (Pigments, number 18, Degussa AG). This is preferably done by treatment with at least one compound selected from the group of the alkylsilanes, alkyldisilazanes, for example with hexamethyldisilazane. or perfluoroalkyl silanes.

As a suspending agent the suspension according to the invention alcohols, ketones, ethers, esters, aliphatic or aromatic hydrocarbons, amides or sulfoxides may have. Preferably, the suspension of the invention contains a mixture of the above suspending agents, however, preferably a suspension medium, which in addition to the organic suspending agent or suspending agent mixture to the organic water.

Under low structured hydrophobic oxidic particles are understood in the context of this invention hydrophobic oxide particles over the corresponding high structured hydrophobic oxide particles decreased by at least 30% dibutyl phthalate absorption (DBP absorption) - measured in accordance with DIN 53 601 - have. Furthermore, the particles in the suspension according to the invention low structured hydrophobic oxidic particles an increased by at least 50% tamped density - measured according to DIN 53 194 - compared to the corresponding high structured hydrophobic oxide particles on. For example, Aerosil R 812 S, a high structured hydrophobic fumed silica has a tamped density of 50 g / 1 in, whereas Aerosil VP LE 8241, a low structured hydrophobic fumed silica has a tamped density of 140 g / 1 on.

Low structured hydrophobic oxidic particles can by a dry grinding in accordance with EP 0637616 Bl or US 5,959,005 are made of high structured hydrophobic oxide particles, this is an intensive milling procedure that conditional on the normal particle size reduction also going destructuring metal oxides. This is an irreversible process.

The suspension of the invention comprises not only as low but also as high structured hydrophobic oxidic particles preferably Aerosils®^® on. This suspension has a low structured hydrophobic Aerosil^® preferably Aerosil^® VP LE 8241 on. In this particular embodiment of the suspension of the invention comprises these hydrophobic than highly structured Aerosil^® Aerosil^® R 812 S on.

The contained in the suspension according to the invention never gstrukturierten hydrophobic oxide particles preferably have a surface having an irregular fine structure in the nanometer range, that is in the range of 1 nm to 1000 nm, preferably from 2 nm to 750 nm and very particularly preferably from 10 nm to 100 nm, on. Among fine structure refers to structures, elevations, peaks, columns, burrs, cracks, undercuts, notches and / or holes in the distances and areas mentioned above have. The fine structure of meckigslxvtkturierten hydrophobic oxide particles may preferably have elevations having an aspect ratio of greater than 1, more preferably greater than 1.5. The aspect ratio is in turn defined as the quotient of maximum height to maximum width of the elevation, with ridges or other elongate elevations, the width taken perpendicular to the longitudinal direction.

Preferably, the suspension of the invention has low structured hydrophobic oxide particles having an average particle diameter of 0.005 microns to 100 microns, preferably from 0.01 microns to 50 microns and more preferably from 0.01 microns to 30 microns. Thus, even low structured hydrophobic oxidic particles, which assemble in the suspension medium from primary agglomerates or aggregates having a size of 0.02 microns to 100 microns, be included in the suspension of the invention.

Depending on the contained amount of high structured hydrophobic oxide particles, the suspension of the invention may have a dynamic viscosity at shear rates of greater than 20 s^"1 have preferably from 1.0 to 1000 mPa s, preferably from 1 to 500 mPa s, particularly preferably from 1 to 400 mPa s. With an amount of high structured hydrophobic Oxide particles, such as the Aerosil^® R 812 S, of> 5 wt .-%, based on the suspension medium may comprise the suspension of the invention a pseudoplastic flow behavior.

The suspensions according to the invention and the suspensions prepared by the process of the invention can be used for the production of soil and water repellent coatings on articles, wherein in the coating process, hydrophobic particles are applied to the surface of the articles, thus generating a surface structure with elevations on the surface of the articles is having dirt and water repellent properties. The coating of the objects is characterized in that a suspension of the invention or a suspension prepared by means of the inventive method applied to at least one surface of an article and the suspension medium is subsequently removed.

In a particular embodiment of the use of the suspension according to the invention or a suspension produced by the novel process for producing soil and water repellent coating, the suspension of the invention or a suspension produced using the inventive method with a squeegee on the surface to be coated is preferably of textiles, applied. The suspension of the invention or a suspension produced using the inventive method is preferably suitable for the production of coated fabrics, which have water and dirt repellent properties, or for the preparation of soil and water repellent coatings on textiles.

The suspensions of the invention or suspensions produced using the method of the invention can be used for the manufacture of clothing, in particular for the manufacture of protective clothing, rainwear and protective clothing with signal effect, technical textiles, in particular for the production of tarpaulins, tents, protective coverings truck tarpaulins, and fabrics textile construction, are used in particular for the production of sunscreen roofs, such as awnings, awnings, umbrellas. The following examples will illustrate the invention as well as suspensions of the invention in detail, without the invention being restricted to this embodiment.

Example 1:

In an Ultraturrax were 1 part by weight of Aerosil^® VP LE 8241 (Degussa AG) are suspended denatured absolute ethanol in 100 parts by weight. This suspension of Aerosil^® VP LE 8241 in ethanol was measured using an Ultraturax 5 parts by weight of Aerosil^® R 812 S (Degussa AG) were added and vigorously mixed.

Example 2:

There the suspension of Example 1 was prepared in Aerosil^® VP LE 8241 applied in denatured ethanol with a squeegee with a layer thickness of 50 microns on a motor-liner of the Fa. SCA Flex Pack Papers GmbH. After evaporation of the suspension medium at room temperature, a polyurethane dispersion from Novotex Italy according to the table 1 by means of a film-drawing doctor blade in a layer thickness of 50 microns was applied to the pretreated lining paper. In the wet surface of the polyurethane coating, a tricot fabric was laminated in a polyamide fabric (Decotex from IBENA Textilwerke Beckmann GmbH). The polyurethane coating was 2 minutes thermally cured at a temperature of 150 ° C and then removed the liner.

TABLE 1 Experimental parameters Example 2

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The characterization of the coated textile sheet materials were initially visually. +++ Means formation of water droplets is almost complete. The roll-off angle is below 10 °. ++ Means that the formation of water droplets is not ideal, the roll-off angle is below 20 °.

Example 3:

In an Ultraturrax were 1 part by weight of Aerosil^® VP LE 8241 was suspended in 100 parts by weight of an organic suspending agent. To this suspension of Aerosil VP LE 8241 was measured using an Ultraturax Aerosil^® R added 812 S and vigorously mixed. The suspension was applied to a polyester blend fabric (Decotex from IBENA Textilwerke Beckmann GmbH) with a squeegee with a layer thickness of 50 microns. Subsequently, the suspension medium is evaporated at room temperature or in a drying oven.

Table 2. Experimental parameters Example 3

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The characterization of the coated textile sheet materials were initially visually. +++ Means formation of water droplets is almost complete. The roll-off angle is below 10 °. ++ Means that the formation of water droplets is not ideal, the roll-off angle is below 20 °. Example 4: a.) In an Ultraturrax were 5 part by weight of Aerosil^® R 812 S suspended in 100 parts by weight in toluene and vigorously mixed. The suspension obtained was applied to a polyester blend fabric (Decotex from IBENA textile Beckmann GmbH) by means of a doctor blade in a layer thickness of 50 .mu.m then the suspension medium is evaporated at room temperature or in a drying oven. After drying, the coated fabric defects were added. The lotus effect could not be determined due to poor adhesion of the oxide particles on the fabric.

b.) In an Ultraturrax were 1 part by weight of Aerosil^® VP LE 8241 was suspended in 100 parts by weight in toluene. This suspension of Aerosil^® VP LE 8241 was using Ultraturrax Aerosil^® R added 812 S and vigorously mixed. The suspension obtained was applied to a polyester blend fabric (Decotex from IBENA textile Beckmann GmbH) by means of a doctor blade in a layer thickness of 50 .mu.m then the suspension medium is evaporated at room temperature or in a drying oven. The characterization of the thus-coated fabric was made anfanglich visually and gave an assessment of the lotus effect of +++. This means that water droplets form almost completely and the roll-off is less than 10 °.

Example 5:

Analogously to Example 1 were suspensions of Aerosil^® VP LE 8241 and Aerosil®^® R 812 S manufactured with various solvents, and then the dynamic viscosity at a temperature of 23 ° C and a shear ramp of γ = 0.3 to 50 s^"1 measured by a rheometer Haake type RS75 by the cone and plate measurement system HC 60/2 °. A compilation of the results and the particular composition of the suspension shown in the table 3. Table 3:

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