WO2020169454A1

WO2020169454A1 - Wear-protection layer and method for producing same

Info

Publication number: WO2020169454A1
Application number: PCT/EP2020/053813
Authority: WO
Inventors: Gunter Risse; Helfried Haufe; Klaus Krüger
Original assignee: Gesellschaft Zur Förderung Von Medizin-, Bio- Und Umwelttechnologien E.V:; Rapidobject GmbH
Priority date: 2019-02-20
Filing date: 2020-02-13
Publication date: 2020-08-27
Also published as: DE102019104311A1; DE102019104311B4

Abstract

The invention concerns the field of materials engineering and relates to a wear-protection layer, such as that which can be used to improve the wear resistance of polymer films. The problem addressed by the present invention is that of specifying a wear-protection layer which has a high to very high wear resistance and a simple and inexpensive method for producing same. This problem is solved using a wear-protection layer containing at least one SiO₂ network which is present in the form of at least two domains and the dimensions of the individual domains exceed the nanoscale in all spatial directions, and also containing long-chain polyorganosiloxanes, each having more than 50 repeat units in the Si-O-Si backbone of the polyorganosiloxane, the repeat units having organic side chains bonded, at least comb-like, to the Si-O-Si main chain, and wherein only the SiO₂ network is present in the domains and the long-chain polyorganosiloxanes are at least partly arranged between the domains, and wherein the organic side chains are at least partly chemically covalently coupled to the SiO₂ network.

Description

Wear protection layer and process for its manufacture

The invention relates to the field of materials engineering and relates to a wear protection layer such as that used, for example, to improve the surface quality and wear resistance of surfaces produced by means of 3D printing, to improve the wear resistance of polymer films and other abrasive polymer surfaces and to improve the cleanability of these surfaces can be applied.

Furthermore, the wear protection layer according to the invention can be used, for example, as a corrosion protection layer with increased mechanical wear stability and as a cover layer to improve the mechanical resistance of existing corrosion protection layers. Another application of the wear protection layer according to the invention relates to coated components that were produced by means of additive processes, such as fused layer modeling (FLM). The present invention also relates to a method for producing the wear protection layer.

Wear protection layers are often required for surfaces and are produced in different ways. In order to eliminate the process-related layer optics and other disturbances of surfaces produced by means of 3D printing, material-removing processes, such as grinding and tumbling, or material application processes, such as filling and painting or processes using solvents or solvent vapors, in which surface structures are leveled by dissolving, are currently used, used.

With standard painting, the printed component is first primed. The highly viscous primer, also called filler, specially selected for 3D printing components, seals the open-pored surface structure of the components. Epoxy resins, for example, are used as filler material. After drying and intermediate sanding, a PUR basecoat is applied (https://www.rapidobject.com/de/Leistungen/Finishing/Oberflaechenveredelung-fuer- 3D-Druck-Modelle / Lackierung-von-3D-Druck-Bautteile_1306.html ).

The materials currently in use for leveling surfaces by material-applying processes are materials based on organic polymers which have a comparatively low mechanical wear resistance.

A targeted improvement of the wear resistance of surfaces to be smoothed is not possible with this.

For some applications it is desirable if, at the same time as the leveling of a surface, its mechanical wear resistance can be improved. This is the case, for example, with plain bearings manufactured using 3D printing.

So far, however, no materials and technologies are known that show a correspondingly good to very good surface quality in conjunction with high wear resistance.

Furthermore, flexible luminous films based on organic light-emitting diodes or inorganic electroluminescent layers as well as flexible thin-film solar modules on plastic substrates are known. Foil-based thin-film solar modules open up new areas for use to generate energy by means of photovoltaics, as they can be adapted to unevenly shaped surfaces and only have a fraction of the specific weight of conventional solar modules.

Both product classes have in common that, compared to glass, the films on which the products are based are less robust against mechanical stress (scratches, material removal by dust), the weather (temperature, humidity) and soiling and the associated cleaning steps. There is therefore a need for a coating with which a film, which can be used as "front-side encapsulation" for the applications mentioned, can be equipped with improved wear resistance and, if possible, also with a dirt-repellent, easy-to-clean surface.

DE 202005021689 U1 describes a hydrophilizing coating with increased mechanical and thermal resistance, which can be used to increase the scratch resistance of surfaces, which is designed as a sol-gel coating and is based on nanoscale sol particles with a polymeric inorganic-oxidic basic structure. The coating contains polyether-modified oligo- or polysiloxanes as an additive added to the sol / gel system.

It is disadvantageous that such a coating has no anti-adhesive properties due to its high surface energy. In particular, this can lead to increased adhesion of adhesive organic contaminants.

Flybrid materials are already known which consist of inorganic and organic materials. These are hybrid polymer materials that are manufactured in a 2-stage process. In this process, an inorganic network is first built up through flydrolysis and condensation of organically modified Si-alkoxides (organically modified alkoxysilanes). This is an organically modified Si0 ₂ network. Polymerizable organic groups fixed on the inorganic network are then crosslinked with one another. Organically modified Si alkoxides can also be used, the organic groups of which do not contribute to crosslinking reactions

(https://www.ormocere.de/de/herstellungsverfahren.html).

Alkoxysilanes of the form R’xSi (OR) 4-x have been used to modify glasses and ceramics since the 1970s. These precursors lead to ORMOSILEN (Organically Modified Silicates) (H. Schmidt, Mater. Res. Soc. Proc. 1984, 32, 327) or ORMOCEREN (Organically Modified Ceramics) (GL Wilkes, et al: Mater. Res. Soc. Proc . 1990, 15, 171-178).

A layer made of a pure Si0 ₂ network is comparable in its mechanical behavior to a glass layer. It has a comparatively great hardness and at the same time great brittleness. The layer materials produced from organically modified Si alkoxides have a higher flexibility due to the organic content compared to a pure Si0 ₂ network. This enables the production of thicker layers.

Organic groups with R ’= -CH3, -C2H5, -C6H5 are often used for a wide variety of coatings and protective layers (D.R. Uhlmann, et al: J.Non-Cryst. Solids 1997, 218, 113-121).

ORMOCER ^® coatings can have a beneficial effect on the surface properties of many substrates (polymers, ceramics, glass, metal, paper, wood). In addition to increasing the mechanical and chemical resistance of the substrates, various additional functions can be generated on the surface.

The use of organically modified alkoxysilanes to build up inorganic organic copolymers according to the prior art has the result that at least one organic group is bound to each Si atom of the network formed. The resulting network is structurally very different from a pure inorganic Si0 ₂ network, since there are a large number of them of organic groups. The organic groups are present in such a network in a highly dispersed distribution, so that the Si-O-Si chains of the network are frequently interrupted by organic groups. This means that the hardness of such an organic-inorganic composite material is significantly lower than the hardness of a pure SiC network.

It is also known that the production of nanomaterials in general and nanocomposites in particular requires that the finished products retain a nano-scale in at least one dimension.

The hybrid polymers described above, in which nanometer-sized organic and inorganic oligomer units are bonded to one another, belong to the nanomaterials or nanocomposites. In these hybrid polymers, the nano-scale is achieved in particular in that the direct contact between the inorganic nanoparticles is interrupted through the use of organic oligomer units.

Oligomers are polymers with a relatively low molar mass that are built up from just a few (identical) basic building blocks. Most oligomer molecules have between 3 and 20 basic building blocks.

EP 1 672 042 A1 also discloses a non-stick layer made of crosslinked nanoparticles. This non-stick layer made of cross-linked inorganic nanoparticles and additives made of polyorganosiloxanes has a three-dimensional network of polyorganosiloxanes. Such a network is produced according to a sol-gel process, in which an inorganic nanosol is first produced by hydrolysis, an alkoxysilane and partial condensation, followed by the modification of the nanosol by adding polyorganosiloxanes, which have functional groups that enable crosslinking reactions and crosslinking-promoting additives is, and the modified nanosol is applied to a surface and then a three-dimensional network of inorganic nanoparticles and a three-dimensional network of Polyorganosiloxanes formed by a heat treatment, whereby both networks penetrate each other.

Also known is a hydrophilic organically modified siloxane which is used in textile auxiliaries to improve water wetting. This product is water-soluble and the polysiloxane chain is modified with two polyethers of different molar mass, both of which have the same mass content of approx. 40% ethylene oxide and approx. 60% propylene oxide (Tegopren ^® 5863).

After EP2543630 A1 product Tegopren® ^® 5863 is due to its water solubility useful in the melt granulation of sulfur usable.

DE 202005021689 U1 describes a hydrophilizing coating that is designed as a sol-gel coating and is based on nanoscale sol particles with a polymeric, inorganic-oxidic basic structure. The coating can contain various polyether-modified oligo- or polysiloxanes as an additive added to the sol / gel system.

A disadvantage of the solutions of the known prior art is that no coatings can be produced on surfaces with a sufficiently high wear resistance.

The object of the present invention is to specify a wear protection layer which has a high to very high wear resistance and in which the adhesion of substances is reduced, and a simple and inexpensive method for its production.

The object is achieved by the invention specified in the claims. Advantageous refinements are the subject matter of the dependent claims, combinations of the individual dependent claims also being included in the sense of an AND link, provided they are not mutually exclusive.

The wear protection layer according to the invention contains at least one S1O2 network which is present in the form of at least two domains and which Dimensions of the individual domains exceed the nanoscale in all spatial directions, and furthermore contains long-chain polyorganosiloxanes each with more than 50 repeating units in the Si-O-Si basic structure of the polyorganosiloxane, which have organic side chains attached at least in a comb-like manner to the Si-O-Si main chain, and wherein only the SiC network is present in the domains and the long-chain polyorganosiloxanes are at least partially arranged between the domains, and at least some of the organic side chains of the long-chain polyorganosiloxanes are chemically covalently coupled to the SiC network.

The smallest dimension of the SiC network is advantageously more than 100 nm.

The SiC network produced from a silica sol by crosslinking linearly shaped SiC particles of a silica sol by means of condensation using a sol-gel process is also advantageously built up from SiC particles.

Likewise advantageously, there are more than 100 repeating units in the siloxane chain, particularly advantageously more than 300 repeating units in the siloxane chain.

And also advantageously present as long-chain polyorganosiloxanes with organic side chains are polyorganosiloxane / polyether copolymers (= polyether-modified polyorganosiloxanes) or hydroxyalkyl polyorganosiloxanes or polyol-modified polyorganosiloxanes.

It is also advantageous if the proportion of organic side chains in the polyorganosiloxane is from 40 to 60% by mass.

It is also advantageous if the alcoholic or phenolic hydroxyl groups present on the organic side chains of the long-chain polyorganosiloxanes by condensation reactions with silanolic hydroxyl groups of the domains of the SiCte network are at least partially converted into ether groups.

It is also advantageous if 1 to 30% by mass, advantageously 2 to 15% by mass, very advantageously 2 to 8% by mass of long-chain polyorganosiloxane is present.

And it is also advantageous if additives and auxiliaries known per se are present.

In the method according to the invention for producing wear protection layers from an SiC network and long-chain polyorganosiloxanes with organic side chains which are chemically covalently coupled to the Si0 ₂ network, at least one silica sol, which was produced by hydrolysis and partial condensation, and at least 1 - 30 mass% of a long-chain polyorganosiloxane and at least one solvent, which forms stable real solutions or stable colloidal solutions with the components of the wear protection layer during the layer deposition process, a mixture is produced and this is applied to the surface to be protected against wear, during and / or after the application and when the applied mixture is plastically deformable, compressive and / or shear forces are applied at least in regions to the layer formed and during the application of compressive and / or shear forces and / or subsequently the applied and / or compacted layer is dried.

Advantageously, a silica sol is used for the preparation of which a water to tetraethoxysilane ratio in the range from 1: 1 to 1: 2 was used.

It is also advantageous to use linearly shaped Si0 ₂ nanoparticles in a silica sol with a solids content in the range from 2 to 25%.

It is also advantageous to use 2 to 15 mass%, more advantageously 2 to 8 mass%. %, of a long-chain polyorganosiloxane added to the mixture. And also advantageously as polyether-modified polyorganosiloxane BYK 333 (BYK Additives & Instruments), Tego Glide 410, TEGO Glide 450 (Evonik Industries), dimethylsiloxane (60% propylene oxide- 40% ethylene oxide) block copolymer AB 114269 (ABCR)) and / or as Hydroxyalkyl polyorganosiloxane Hydroxymethyl polyorganosiloxane with lateral methyl groups and / or a glycerol-modified polyorganosiloxane used as the polyol-modified polyorganosiloxane.

It is also advantageous if tetrahydrofuran, methoxyethanol, dioxane, glycol ethers, such as ethylene glycol monomethyl ether, ethylene glycol dimethyl ether and ethylene glycol monoethyl ether or mixtures of different solvents are used as solvents.

It is also advantageous if the starting materials are mixed at room temperature or at temperatures below the decomposition or reaction temperatures of the starting materials and using a mixer or stirrer or by means of ultrasound.

It is also advantageous if, after the layer has been applied, compressive and / or shear forces are applied to the layer at least in regions.

It is also advantageous if the layer is dried at temperatures of up to 120 ° C. and within 2 hours up to several days.

With the present invention it is possible for the first time to specify a wear protection layer that has high to very high wear resistance, in which the adhesion of substances is furthermore reduced, and also to specify a simple and inexpensive method for its production.

This is achieved by the wear protection layer according to the invention, which contains at least one SiC network.

An SiC network is advantageously present, which consists of a silica sol according to a sol-gel process through the crosslinking of SiC particles of a silica sol by means of condensation. A SiCte network produced in this way is made up of S1O2 particles which, as starting materials for the production process of the wear protection layer according to the invention, had a linear shape.

In the case of the presence of a SiC network with SiC particles which, as starting materials for the production process of the wear protection layer according to the invention, have had a linear shape, particularly good properties of the wear protection layer according to the invention have resulted.

At least two domains of the SiC network have been produced from the advantageously linearly shaped SiC nanoparticles by crosslinking by means of condensation. In this way, the originally nanoscale S1O2 particles are connected to form larger (above nanoscale) domains of an SiC network made of interconnected Si0 ₂ particles. Thus, there are no longer any nanoparticles of the silica sol used in the coating material in the wear protection layer according to the invention.

At the molecular level, the sol-gel process for silicon alkoxides can be described by the reaction steps hydrolysis and condensation, some of which take place simultaneously and in competition. The hydrolysis sensitivity of the alkoxysilanes leads to the hydrolytic cleavage of the Si-OR bond of this alkoxy compound when tetraethoxysilane (TEOS) is converted in an acidic or basic medium. The hydrolytically formed silanoies are unstable, and in the subsequent condensation reactions

Si OH + ROH _« Z Si OR + H20

Si OR + ROH Si OR '+ ROH form siloxane bonds with the release of alcohol or water.

At pH values of 2 to 5, the condensation is the rate-determining step. Monomers and smaller oligomers with reactive silanol groups lie side by side. Since the acid-catalyzed condensation takes place preferably between monomers and the ends of weakly branched oligomers, the addition of stoichiometric amounts of water results in widely extended linear polymers (M.Buckley, M.Grennblatt, J. Chem. Education 1994, 71, 599-602).

Since water is released again during the condensation, two moles of water per mole of TEOS are theoretically sufficient for complete hydrolysis. Silica sols with linearly shaped SiO ₂ nanoparticles are obtained with a molar ratio of Si (OR) 4 to H2O of 1: 1 to about 1: 2 (S.Sakka, K.Kamiya, J.Non-Cryst. Solids 1982, 48, 31-46). The further condensation leads to a relatively weakly branched network (J.Sefcik, AVMcCormick, Catalysis Today 1997, 35, 205-223).

In contrast, hydrolysis is the rate-determining factor in a basic medium. The clusters grow mainly through the condensation with monomers. This results in highly branched networks with large spherical particles and large pores. (K.D. Keefer, D.W.Schaefer, Phys. Rev. Lett. 1986, 56, 2376-2387). Complex formation, as observed in titanium alkoxides with acetic acid, determines the preferred formation of linear polymers ([H. Schmidt, J. Sol-Gel-Sci. Technol. 1994, 1, 217-231). The at least partial use of complex-forming acids can be advantageous for the creation of the desired linear shape of the SiC particles as starting materials for the production of the layer according to the invention.

According to the invention, the SiC network is present in the wear protection layer in the form of at least two domains.

In the context of the present invention, domains of the SiC network in the wear protection layer are to be understood to mean areas with a uniform structure, that is to say exclusively as a three-dimensional SiC network with a similar material composition.

According to the invention, the dimensions of the individual domains should exceed the nanoscale in all spatial directions. In the context of the present invention, dimensions up to 100 nm should be defined under nanoscale, so that the wear protection layer according to the invention in any case only has domains with dimensions in all spatial directions above 100 nm.

In addition to the domains of the Si0 ₂ network, the wear protection layer according to the invention also contains at least long-chain polyorganosiloxanes each with more than 50 repeating units in the Si-O-Si basic structure of the polyorganosiloxane.

More than 100 repeating units in the siloxane chain are advantageous. More than 300 repeating units in the siloxane chain are particularly advantageous.

Such long-chain polyorganosiloxanes can be polyether-modified polyorganosiloxanes, such as the products BYK 333 (BYK Additives & Instruments), Tego Glide 410, TEGO Glide 450 (Evonik Industries), dimethylsiloxane (60% propylene oxide- 40% ethylene oxide) block copolymer AB 114269 (ABCR)) .

According to the invention, the long-chain polyorganosiloxanes are located between the domains of the SiC network on the surface of the domains. The long-chain polyorganosiloxanes are arranged between the domains of the Si0 ₂ network of the wear protection layer according to the invention, which have a uniform structure and similar material composition.

The long-chain polyorganosiloxanes present according to the invention have organic side chains bonded to the Si-O-Si main chain in a comb-like manner.

With these organic side chains of the long-chain polyorganosiloxanes bound to the Si-O-Si main chain in a comb-like manner, these are at least partially chemically covalently coupled to the Si0 ₂ network.

The polyorganosiloxanes are also found in bound form on the surface of the wear protection layer according to the invention. The structure of the wear protection layer according to the invention results in mutual mechanical support of the domains of the SiC network. This in turn results in a special hardness of the wear protection layer. Covalent bonds between the polyorganosiloxanes and the domains of the Si0 ₂ network create a firm cohesion of the overall structure. On the other hand, the flexibility of the polyorganosiloxanes brings about the reduction of tensions and thus a reduced material brittleness compared to a pure SiC layer.

The properties of the layer according to the invention can be varied and adjusted via the ratio of the mass fraction of the S1O2 to the mass fraction of the long-chain polyorganosiloxanes. This relates both to the mechanical properties and to the surface energy of the layer according to the invention. A small proportion of the polyorganosiloxane reduces the wear resistance due to internal stresses and brittleness, and on the other hand a high proportion of the polyorganosiloxane reduces the hardness of the wear protection layer.

The person skilled in the art can determine the optimal mass ratio of the Si0 ₂ network to polyorganosiloxane for his application with simple experiments in small numbers.

Surprisingly, it has been shown that even with a relatively low proportion of 1-10% by weight, advantageously 2-8% by weight, of long-chain polyorganosiloxane in the wear protection layer according to the invention, a significantly reduced brittleness and increased wear resistance compared to layers of the Prior art is obtained.

The surface energy of the wear protection layer according to the invention is also dependent on the ratio of the mass fraction of the Si0 ₂ network to the mass fraction of the long-chain polyorganosiloxanes. It was found that the wear protection layer according to the invention with increased wear resistance also has a surface energy that is reduced compared to a pure SiO ₂ layer. In the area of the ratio of the mass fraction of the S1O2 network to the mass fraction of the long-chain polyorganosiloxanes, in which a particularly high wear resistance is obtained, there is also a special one low surface energy. There is obviously a material-specific relationship between these two layer properties. This enables the wear protection layer according to the invention to be used simultaneously for dirt-repellent surfaces. When the polyorganosiloxane content is increased beyond an optimal range, there is a significant increase in the surface energy and thus a loss of the anti-adhesive layer properties. With a proportion between 2 and 15% by mass of long-chain polyorganosiloxane in the wear protection layer according to the invention, a total surface energy of approx. 20 mN / m and a water contact angle of over 100 ° can be obtained. With the further increase in the polyorganosiloxane content, an increasing increase in the surface energy and a decrease in the water contact angle of the wear protection layer according to the invention were found.

For certain applications, particularly thick wear protection layers with a layer thickness of up to several μm are required. This is the case, for example, if very rough surfaces are to be leveled at the same time as the coating. For such applications, the tendency to crack formation in the layers can be reduced by increasing the polyorganosiloxane content beyond the range which is optimal for very high wear resistance, so that significantly thicker, crack-free layers can be obtained. For the production of such thick layers according to the invention, it can be advantageous if the maximum proportion of polyorganosiloxane increases to about 30% by mass.

Such layers with an increased polyorganosiloxane content do not have the maximum wear resistance that can in principle be achieved with the wear protection layer according to the invention, but tend to a lesser extent to crack formation during curing when the layer is thick. The use of layers of this type is advantageous for certain applications, since they have greater wear resistance compared to layers of comparable thickness which can be realized according to the prior art

According to the invention, it occurs through the formation of chemical compounds (condensation) between Flydroxylgruppen of the Si0 ₂ network and Hydroxyl groups of the organic side chains of the long-chain polyorganosiloxanes to reduce the number of hydrophilic centers, so that the influence of the hydrophobic polyorganosiloxane component is greater. This results in the hydrophobicity and the low surface energy of the wear protection layer according to the invention. With a proportion of organic side chains in the polyorganosiloxane of 40 to 60 mass%, particularly favorable mass ratios are present for the most complete possible reduction of the hydrophilic centers.

The polyorganosiloxanes contained in the wear protection layer can be, for example, polyorganosiloxane / polyether copolymers (= polyether-modified polyorganosiloxanes) or hydroxyalkyl polyorganosiloxanes or polyol-modified polyorganosiloxanes.

Alcoholic or phenolic hydroxyl groups are present on the organic side chains of the long-chain organosiloxanes.

The hydrophobic layers according to the invention can also advantageously have additives and auxiliaries known per se.

A hydroxymethyl polyorganosiloxane is advantageously used as the hydroxyalkyl polyorganosiloxane. A hydroxymethyl polyorganosiloxane with lateral methyl groups, the production of which is described, for example, in US Pat. No. 8907039B2, is particularly advantageous.

A glycerol-modified polyorganosiloxane, the production of which is disclosed, for example, in US 2005/0261133, can advantageously be used as the polyol-modified polyorganosiloxane.

Furthermore, linearly shaped SiC nanoparticles are advantageously used as a constituent of a silica sol whose solvent phase is particularly well compatible with the polyorganosiloxane used. Such a solvent can be, for example, tetrahydrofuran, methoxyethanol, methoxypropanol or dioxane. The solids content (mass fraction of the nanoparticles) in the silica sol used is advantageously in the range from 5 to 25%.

The solvent should not only be usable in the coating material for depositing the wear protection layer according to the invention, but should also be compatible with all components of the coating material. In addition to tetrahydrofuran, methoxyethanol and dioxane, glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol dimethyl ether and ethylene glycol monoethyl ether or mixtures of different solvents meet this requirement.

The mixing of the starting materials is advantageously carried out at room temperature or at temperatures below the decomposition or reaction temperatures of the starting materials and can be carried out using a mixer or stirrer or by means of ultrasound. After the starting materials have been mixed, they are applied according to the invention to the surface to be protected from wear and the solvent is removed, for example evaporated.

When the wear protection layer is deposited, a so-called “green layer” is created which still contains a proportion of solvent. When the solvent is subsequently removed from the green sheet, pores remain, which can result in a reduced density of the resulting wear protection layer. A reduced density is associated with a reduction in the mechanical strength of the wear protection layer that is created. A common method for densifying the layer-forming material in the deposition of layers based on Si0 ₂ networks according to the prior art is to carry out a thermally activated sintering process. Such layer compaction by thermally activated sintering cannot be carried out in the production of the wear protection layer according to the invention, since at least the polyorganosiloxane as one of the layer-forming components is not thermally sinterable. A method for non-thermal compression of the wear protection layer according to the invention must therefore be implemented. For example, a mechanical compression of the layer material can be carried out, the layer-forming components being compressed by exerting pressure and shear forces. Due to the specific properties of the starting materials for producing the wear protection layer according to the invention, combined with the start of the formation of solid structures immediately after the removal of the solvent, these structures would at least partially be destroyed in the event of the subsequent action of mechanical forces. This would lead to a decrease in the mechanical strength of the wear protection layer that is created.

In an advantageous variant of the method for depositing the wear protection layer according to the invention, the layer material is therefore compacted by the action of pressure and shear forces simultaneously with the process of removing the solvent present in the green layer. The compaction process that takes place here is approximately comparable to a commonly used polishing process.

The compression of the layer material can be carried out as long as there is the possibility of plastic deformation of the layer material due to the presence of a solvent phase.

A device for compressing the layer material can be a tool that can implement pressure and shear forces and thus start the processes that lead to the compression of the wear protection layer. As tools for the realization of pressure and shear forces, e.g. Polishing rollers are used. It is also possible to use several polishing devices, analogous to polishing heads, which e.g. are used in vehicle polishing machines, the corresponding movements, e.g. eccentric rotary movements, and thus cover the entire surface to be coated. However, tools with a smooth or structured surface to which the coating material to be compacted exhibits the least possible adhesion can also be used.

In order to achieve compaction of the layer material, it is necessary that the forces exerted and the deformability of the wear protection layer to be compacted are coordinated in such a relationship that a shear force is exerted on a green layer without it becoming a local one complete displacement of the layer material comes from the surface to be coated. According to the invention, the wear protection layer is dried during the application of force or subsequently.

During and immediately after the wear protection layer dries, the process of curing or crosslinking of the layer materials by means of condensation begins. The condensation reaction already takes place during drying and during storage at room temperature and can be accelerated by increasing the temperature. In this way, the chemical bond is formed in the layer material with a minimal mass fraction of hydrocarbon compounds.

The wear protection layer can be completely dried and cured at temperatures of up to 120 ° C and within 2 hours to several days. For example, brief tempering at up to 120 ° C. for 30 minutes and subsequent aging at room temperature for 3 days is advantageous.

Surprisingly, it has been shown that the condensation reaction between hydroxyl groups of the SiC network (silanolic hydroxyl groups on products from hydrolysis and partial condensation of, for example, tetraethoxysilane) and alcoholic or phenolic hydroxyl groups, which are present on organic side chains of the polyorganosiloxane, causes rapid covalent chemical Coupling takes place with the formation of Si-OC bonds, which leads to the formation of the wear protection layer according to the invention with high wear resistance.

On the one hand, the wear protection layer according to the invention improves the resistance of the wear protection layer, which leads to an improved protection of surfaces against abrasion. The wear protection layer according to the invention also reduces the adhesion of dirt to the wear protection layer. The wear protection layer according to the invention has a hardness a little below the hardness of a pure SiC network and well above the hardness of the long-chain polyorganosiloxanes. The structure of the wear protection layer according to the invention partially approximates the structure of the pure SiC network, whereby the hardness of the SiC network largely corresponds to the mechanical properties of the wear protection layer according to the invention.

Surprisingly, it was found that a combination of a SiC network, which is quasi a hard material, with long-chain polyorganosiloxanes (= silicone), which are quasi an extremely soft material, has a significantly greater wear resistance than a similarly treated layer that only consists of a pure SiC network.

So that the SiC network can bring its hardness as largely as possible into the wear protection layer according to the invention, the SiC network must not have any organic side chains which would reduce the overall hardness of the inorganic structure. Therefore, to produce the Si0 ₂ network of the wear protection layer according to the invention, Si compounds must be used, from which an exclusively pure SiC network can arise by means of hydrolysis and condensation.

The silica sol used was formed from alkoxysilanes (Si alkoxides) which are not organically modified, such as tetraethoxysilane (TEOS), through hydrolysis and condensation reactions. During the production according to the invention of the wear protection layer according to the invention, a pure SiC network is formed therefrom in a sol-gel transition. It is of particular importance according to the invention that the silica sol used has linearly shaped S1O ₂ nanoparticles. Surprisingly, the special structure produced from these linearly shaped particles of the S1O ₂ network present according to the invention has a particularly advantageous effect on the wear resistance of the layer. The special properties of the wear protection layer according to the invention, in particular high wear resistance and reduced adhesion of adhesive materials, are achieved according to the invention by combining the hardness of the pure SiC network with the flexibility and low surface energy of the long-chain polyorganosiloxane.

When mixing the starting materials, it is also advantageous if the silica sol and polyorganosiloxane molecules are thoroughly mixed in a solvent and, in particular, during the removal of the solvent in the course of the layer formation, there is no phase separation in the coating material. The solvent to be used according to the invention must therefore form stable real solutions or stable colloidal solutions with all components of the wear protection layer during the layer deposition process.

It is also necessary according to the invention to achieve good to very good chemically covalent coupling between the pure Si0 ₂ network areas and the organic side chains of the polyorganosiloxane.

Furthermore, organic side chains, for example, which are bound to the polyorganosiloxane and make no contribution to the formation of the compound, have a negative effect on the wear resistance, so that the aim is to largely avoid the presence of such side chains. The length of the organic side chains present on the polyorganosiloxanes, which, together with the hydroxyl groups they carry, contribute to the formation of compounds, should also be limited to a minimum.

According to the invention, the polyorganosiloxane for the wear protection layer should advantageously have an optimal number of side chains bearing hydroxyl groups distributed over the length of the Si-O chain, with which an intensive connection with the SiC network can be realized without a significant number of unreacted hydroxyl groups the condensation reaction is retained. That affects both the Wear resistance as well as the dirt repellency of the layers have a positive effect, since with the minimization of the number of hydroxyl groups remaining after the crosslinking of the layer material, the polarity of the layer surface also decreases.

It has also surprisingly been found that the surface of the wear protection layer according to the invention is water-repellent.

At the same time, this wear protection layer is characterized by good mechanical strength and low roughness. A typical water contact angle of a wear protection layer according to the invention is in the range of 100 ° and more. The water wetting behavior of the wear protection layer according to the invention, which was produced using polyether-modified polydimethylsiloxane, is therefore particularly surprising since materials of this type are used as hydrophilicizing agents according to the prior art.

The wear protection layer according to the invention has a significantly increased wear resistance compared to previous nanocomposite materials or nanoscale (inorganic / organic) hybrid polymers. An essential difference between the solutions of this prior art for nanocomposite materials is that it is essential for the known solutions that the nanoparticles are present in the final state of the layers. According to the invention, this is precisely not the case, since all the nanoparticles of the silica sol have passed into an Si0 ₂ network.

The formation of additional chemical bonds in the wear protection layer can have an advantageous effect on its strength. Such a connection formation can take place via the crosslinking of polyether chains of the long-chain polyorganosiloxanes. Known crosslinking agents can be used for this, such as, for example, 1,6-hexamethylene diisocyanate and isophorone diisocyanate, polyisocyanates or polyisocyanates with a uretdione structure, prepared by catalytic dimerization and, if appropriate, simultaneous trimerization of monomeric aliphatic or cycloaliphatic diisocyanates. In order to increase the hardness and wear resistance of layers made of polymeric materials, hard particles are known to be added to the layer materials. This can take place particularly effectively according to the invention, since the wear protection layers according to the invention incorporate particles such as S1O2 particles particularly well into their structure and these particles lead to particularly good wear protection due to their already existing strength.

The invention is explained in more detail below using several exemplary embodiments.

example 1

Deposition of thin wear protection layers on polymer films Production of the silica sol:

90.9 g of 0.053N HCl in 142 g of THF are added dropwise with stirring to a mixture of 526 g of tetraethoxysilane and 142 g of tetrahydrofuran (THF). The resulting mixture is stirred for 14 days at room temperature. Then 638 g of THF are added.

1.5 g Aeroxid LE1 (BASF) are mixed into 25 g of ethylene glycol monomethyl ether under the action of ultrasound. 2.2 g of polysiloxane (dimethylsiloxane (60% propylene oxide- 40% ethylene oxide) block copolymer (AB 114269, supplier: ABCR) are stirred into the mixture in 10 g of silica sol, and the mixture is made up with 390 g of silica sol.

A polymer film (TEONEX Q65FA, unfilled polyethylene naphthalate (PEN), 125 μm) is provided with a silica sol adhesive layer using known methods. The mixture of the coating material is then applied by spraying and a homogeneously closed, smooth layer with a layer thickness in the range from 0.8 to 1.1 μm is thus produced. The coated film is tempered for 30 minutes at 110 ° C. and stored for 2 days at room temperature. For a comparative assessment of the wear resistance of the layers, tests were carried out using a tribometer according to the ball-on-disk principle. A firmly clamped ball, which is pressed with a force F, rubs on the material to be tested. Typical test parameters are: ball material Si3N4, diameter 8 mm, frequency 3 Hz, number of oscillations (periods) up to 10,000, load 2.2N. Through the microscopic evaluation of the wear track using a 3D laser scanning microscope, the progress of wear was compared for different samples with the same number of oscillations.

The measurement by means of a tribometer with a contact force of 2.2 Newtons up to 10,000 periods shows no buried wear track in the layer according to the invention and thus a significantly increased abrasion resistance compared to the uncoated film, in which a wear track with a depth of up to 3 μm was obtained.

The hydrophobic character of the layer according to the invention is demonstrated by a measured water contact angle of 102 °.

Example 2

Coating mixture with a low tendency to crack for leveling rough polymer surfaces

Coating mixture:

0.15 g of dibutyltin dilaurate and 2.5 g of bis (4-hydroxyphenyl) sulfone are dissolved in 350 g of the silica sol according to Example 1. Then 1.2 g of 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate and 7.7 g of polysiloxane (dimethylsiloxane (60% propylene oxide- 40% ethylene oxide) block copolymer (AB 114269, supplier: ABCR) are mixed in with stirring. The coating mixture produced in this way is sprayed onto a polymer surface produced by means of 3D printing. The spraying process is repeated twice after each intermediate drying at room temperature and the material treated in this way is then stored for 3 days at room temperature.

As a result, a layer is obtained which has clear anti-adhesive properties in relation to a solidified polymer melt.

Using a trimbometer, an increased abrasion resistance of the applied layer according to the invention can be detected, for which a wear track depth of up to 1.5 μm was measurable, compared to the polymer surface produced by means of 3D printing, in which a wear track with a depth of up to 5.5 μm was determined has been.

Example 3

Method for layer deposition with compaction of the layer material

Analogously to Example 1, a layer of the coating material is applied to a film. Immediately thereafter (before evaporation of the solvent) the coating material is brought into contact with a rotating polymer surface and scanned through it, the polymer surface having a concentric ring structure with a structure depth of 2 μm. In this way, the coating material is plastically deformed. This creates a layer which has structures in which the solidified coating material is present in curved, parallel lines. The layer formed in this way is tempered for 30 minutes at 110 ° C. and stored for 2 days at room temperature. Measurements by means of a tribometer confirm the high abrasion resistance of the layer surface, which is shown by the fact that after 10,000 periods with 2.2 Newtons of contact force, only slight abrasion marks are visible at the heights of the surface structure.

No wear track depth can be measured on the film coated according to the invention. The wear track of the uncoated film has a depth of up to 3 μm.

Claims

1. Wear protection layer, containing at least one SiCte network, which is present in the form of at least two domains and the dimensions of the individual domains exceed the nanoscale in all spatial directions, and furthermore containing long-chain polyorganosiloxanes each with more than 50 repeating units in the Si-O-Si Basic structure of the polyorganosiloxane, which have at least a comb-like organic side chains bonded to the Si-O-Si main chain, and wherein only the SiC network is present in the domains and the long-chain polyorganosiloxanes are at least partially arranged between the domains, and at least partially the organic side chains of the long-chain polyorganosiloxanes are chemically covalently coupled to the SiC network.

2. Wear protection layer according to claim 1, in which the smallest dimension of the Si0 ₂ network is more than 100 nm.

3. Wear protection layer according to claim 1, in which the SiC network produced from a silica sol by crosslinking linearly shaped SiC particles of a silica sol by means of condensation using a sol-gel process is composed of SiC particles.

4. Wear protection layer according to claim 1, in which there are more than 100 repeating units in the siloxane chain, particularly advantageously more than 300 repeating units in the siloxane chain.

5. Wear protection layer according to claim 1, in which the long-chain polyorganosiloxanes with organic side chains are polyorganosiloxane / polyether copolymers (= polyether-modified polyorganosiloxanes) or hydroxyalkyl polyorganosiloxanes or polyol-modified polyorganosiloxanes.

6. Wear protection layer according to claim 1, in which the proportion of organic side chains in the polyorganosiloxane is 40 to 60% by mass.

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7. Wear protection layer according to claim 1, in which the alcoholic or phenolic hydroxyl groups present on the organic side chains of the long-chain polyorganosiloxanes are at least partially converted into ether groups by condensation reactions with silanolic hydroxyl groups of the domains of the SiC network.

8. Wear protection layer according to claim 1, in which 1 to 30% by mass, advantageously 2 to 15% by mass, very advantageously 2 to 8% by mass of long-chain polyorganosiloxane is present.

9. Wear protection layer according to claim 1, in which additives and auxiliaries known per se are present.

10. Process for the production of wear protection layers from an S1O2 network and long-chain polyorganosiloxanes with organic side chains which are chemically covalently coupled to the SiC network, in which at least one silica sol, which was produced by means of hydrolysis and partial condensation, and at least 1 - 30 mass% of a long-chain polyorganosiloxane and at least one solvent, which forms stable real solutions or stable colloidal solutions with the components of the wear protection layer during the layer deposition process, a mixture is produced and this is applied to the surface to be protected against wear, with during and / or after the application and if the applied mixture is plastically deformable, compressive and / or shear forces are applied at least regionally to the layer formed and during the application of compressive and / or shear forces and / or subsequently the applied and / or compacted layer is dried.

11. The method according to claim 10, in which a silica sol is used, for the preparation of which a water to tetraethoxysilane ratio in the range from 1: 1 to 1: 2 was used.

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12. The method according to claim 10, in which linearly shaped SiC nanoparticles are used in a silica sol with a solids content in the range from 2 to 25%.

13. The method according to claim 10, in which 2- 15 mass%, advantageously 2 to 8 mass. %, of a long-chain polyorganosiloxane are added to the mixture.

14. The method according to claim 10, in which the polyether-modified polyorganosiloxane BYK 333 (BYK Additives & Instruments), Tego Glide 410, TEGO Glide 450 (Evonik Industries), dimethylsiloxane (60% propylene oxide- 40% ethylene oxide) block copolymer AB 114269 (ABCR) ) and / or as the hydroxyalkyl polyorganosiloxane hydroxymethyl polyorganosiloxane with lateral methyl groups and / or as the polyol-modified polyorganosiloxane a glycerol-modified polyorganosiloxane can be used.

15. The method according to claim 10, wherein the solvent used is tetrahydrofuran, methoxyethanol, dioxane, glycol ethers, such as ethylene glycol monomethyl ether, ethylene glycol dimethyl ether and ethylene glycol monoethyl ether, or mixtures of different solvents.

16. The method according to claim 10, in which the mixing of the starting materials is realized at room temperature or at temperatures below the decomposition or reaction temperatures of the starting materials and using a mixer or stirrer or by means of ultrasound.

17. The method according to claim 10, in which, after the application of the layer, pressure and / or shear forces are applied to the layer at least in regions.

18. The method according to claim 10, wherein the drying of the layer is carried out at temperatures of up to 120 ° C and within 2 hours up to several days.

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