DE10116200A1 - Hydrophilic coating composition for coating of surfaces containing finely divided oxide and surface modifier useful for hot dipping of aluminum, automobile air conditioning systems, for coating textiles and for sanitary coatings - Google Patents

Abstract

A hydrophilic coating composition for coating surfaces containing a finely divided oxide and a surface modifier is new. An Independent claim is also included for coating of surfaces with the composition involving the steps: (a) application of the composition in a solvent to the surface to be coated at room temperature, and (b) removal of solvent at room temperature.

Description

Coating compositions are described that are allow very thin inorganic beings at room temperature to apply layers that are distinctly hydrophilic Show behavior. These coating materials are on Surfaces such as glass or plastic, metal and ceramic can be applied and cause fine water droplets, as they e.g. B. can be reflected by thawing effects run together in a closed film and optically not disturb (anti-fog effect), or generally a better loading effect the wetting behavior of the surface.

The coatings are principally made of 3 com components.

• 1. a very fine oxide (nanoparticles)  
• 2. a surface modifier
• 3. if necessary, auxiliaries such. B. amphiphilic substances (e.g. Tensi de)

In special cases, the surface modifier can also Have a surfactant effect (e.g. for betaine surfactants).

Water serves as the solvent for the coating material. To improve the application behavior (wetting) also water-miscible organic solvents be included (e.g. isopropanol, ethanol).

The principle of action of the coating is based on training a highly porous inorganic network, which through its Si-OH (Me-OH) groups and the large surface a high-energy hydrophilic structure train. The spread of the drop of water will thereby both by interacting with the high-energy porous Surface caused, as well as by capillary effects of extremely fine pores of the network. Possibly. existing hydrophi le, hygroscopic or amphiphilic auxiliaries are used to to reinforce the hydrophilic effect, the applicability improve and the durability especially with ver increase pollution with oleophilic organic substances.

Suitable oxide nanoparticles are e.g. B. silica sols as they un ter be manufactured by Bayer or Dupont. Of others are also nanoparticles based on titanium oxide, Zirconia, alumina and others suitable. In particular the use of strongly anisotropic, platelet-shaped par articles such as B. layered silicates, can be used for different purposes turns be advantageous. As surface modifiers for the oxide nanoparticles used come from various alkali  and alkaline earth ions such as e.g. B. sodium or potassium in question, those for stabilizing the nanoparticles in an aqueous dispersion serve. Inorganic or organic salts also come of compounds such as aluminum, zirconium, zinc or titanium in Question that are suitable for the particulate oxides in a Stabilize coating suitable pH environment.

Furthermore, preferred surface modifiers are preferred used: betaines, quaternary ammonium compounds or sila ne. These connections serve in particular for stabilization the dispersions of the inorganic oxides in aq rig / organic solvent mixtures. Without this stabilisa tors is the resistance of the inorganic dispersions too low compared to gelation or flocculation to be used in to find industrial scale. With the betaines preferably uses the parent substance betaine. Furthermore are also so-called sulfobetaines or other betaine surfactants possible. With the quaternary ammonium compounds is before adds the tetramethylammonium hydroxide used TMAH while in the case of the silanes, preferably cationic aminosilanes or epoxy-modified silanes are used.

In addition to surfactants, special buffer systems are used as auxiliary substances in question to adjust the pH of the coating solutions to one stabilize certain value. Hygroscopic substances like various salts or organic compounds (glycerin) can the hydrophilic effect of the inorganic network strengthen. Hydrophilic polymers such as z. B. Polyethylene oxide PEO, polyvinyl pyrrolidone PVP or polyethylene lenimin PEI, which are also suitable as auxiliary substances. Cationic polymers are particularly preferred since they deal best with the preferred cationic Tolerates nanoparticles and willingly to be coated  Spread surfaces. Preferred for the described applications is the use of a nonionic surfactant as am phiphile excipient.

New and surprising when using this set tion as a coating material is that it is possible to Room temperature is already a sufficiently stable inorganic Network to separate what can be seen without a visible change in the op properties have a sufficiently high hydrophilicity, to produce long-lasting anti-fogging effects and to to achieve permanent good wetting of water. By choice the right inorganic nanoparticles and the right one A pronounced pH value of the coating solution is achieved electrostatic interaction of the nanoparticles with the coating surface. In particular glass surfaces and glazed ceramics show a negative La on the surface dung. If you now select nanoparticles with a positive charge, see above these prefer to beat on the negatively charged upper flat. This can result in very good adhesion Room temperature can be achieved. You choose together accordingly of the nanoparticles, the deposited ones show Layers also have antibacterial effects. Here you can in particular tin, silver and boron oxide-containing nanoparticles be used.

Such coatings are used in particular to annoying fogging of mirrors or plastics in water avoid steam-saturated atmosphere. Furthermore force the drying of wetted surfaces by that no drops form but that a closed one ner water film formed with a high evaporation rate becomes. These hydrophilic coatings can also have an effect have a table dirt effect, because when wetted with water  deposited dirt can be washed away and carried away. Due to the antistatic effect of such layers, the usually electrostatic induced dry soiling z. B. significantly reduced on plastic surfaces.

The coating material described can either be used alone or in combination with conventional cleaning agents (e.g. Sidolin glass cleaner from Henkel) as a combined cleaning agent serving and coating material. The cleaning we The surfactant is optimally prepared for coating with nanotelichen before, during the Drying takes place. That contained in the cleaning solution Nano particles can also remove worn dirt stabilize and thus effectively cleaning performance improve. Bring hydrophilic coatings to the be type on aluminum heat exchangers if you drop formation in the operation of the heat exchanger what can be particularly advantageous in automotive air conditioning systems. Due to the air flow, no drops of the heat rope can fall carried away and carried into the passenger compartment. If you coat textiles, especially after washing them, with this coating material, so the nano store particles also on the fiber and lead to a ver improved hydrophilic behavior. This is particularly the case with Textiles desirable where you have a strong water and want to achieve a sweat-absorbing effect (towels, un terwäsche). Another advantageous application can be in Be waterless urinals as a hygienic coating.

It is also possible to use paper and pulp, as well as other na impregnate hydrophilic door materials. Possible An wounds could be particularly absorbent or Be diapers.  

Preferred nanoteliches are: silica sols (Levasil 200 S, Levasil 300-30, Bayer);
Titanium oxide, zirconium oxide, aluminum oxide, tin oxide, layer silicates (e.g. bentonite, preferably delaminated), mixed oxides, doped oxides, oxycarbides, nitrides, oxynitrides. The shapes can be round, regular or irregular, crystalline and / or amorphous.

The following are considered as surface modifiers:
Alkali and alkaline earth salts, (sodium, potassium, lithium), aluminum, zirconium, zinc or titanium, tungsten and possibly other elements with organic or inorganic counterions or complexing agents;
Betaines (betaine, sulfobetaines, betaine surfactants), quaternary ammonium compounds (tetramethylammonium hydroxide), phosphonium compounds or organofunctional silanes (e.g. aminoethy laminopropyltriethoxysilane, glycidoxypropyltriethoxysilane). Complexing agents such as EDTA (ethylenediaminetetraacetic acid), ethanolamine (ethanolamine, diethanolamine, triethanolamine), acetic acid ester, acetylacetone etc.

In particular, hydrophilic polymers are disclosed as auxiliaries (polyethylene oxide PEO, polyvinylpyrrolidone PVP or polyethylene imine PEI, chitosan)
Surfactants such as anionic, cationic or nonionic ten side; Solubilizers / solvents such as isopropanol, ethanol, butylglycol, glycol, glycerin.

The aforementioned substances can be used in the following levels:
Nanotelichen: 0-100%, preferably 40-80%, particularly preferably 50-70%
Surface modifier: 0-80%, preferably 1-50%, particularly preferably 1-20%
Excipients: 0-80%, preferably 1-50%, particularly preferably 1-20%.

A pre-treatment of the surface can be omitted due to the cleaning effect of the mixture or it becomes a forerunner cleaning with suitable agents (glass cleaner). Pre-cleaning with residue-free polishing paste is preferred ste.

In the case of plastics, pretreatment with plasma, Co rona, flame pretreatment (also with reactive gas, e.g. Si containing), primer (aminosilane hydrolyzate, for example).

For further treatment of the coated surface sufficient drying at room temperature; Can warm the However, increase the durability of the hydrophilic coating. The maximum temperature is determined by the decomposition / melting temperature of the key to the performance of hydrophilicity limited ingredient (up to <1000 ° C with pure nano particle systems!)

example 1

Betaine (anhydride) is in aqueous silica sol (e.g. Levasil 100/40, Bayer) and then with Diluted water and isopropanol. After that, different ones Amounts of a nonionic surfactant (e.g. Marlipal 24/100,  Condea; Brij-30 or Brij-700, from ICI). This Mixing can be done afterwards without further processing Coating can be used at room temperature. larger Amounts of surfactant generally make application easier and polishing out the layers and lead to very good anti fog effects. But at the same time, the liability of layers deposited at room temperature are reduced. to If the surfactant content is too high, it can also be difficult due to foam formation. The exact composition depends on the specific application.

application

with a pure soaked with the above product room towel (or with another suitable absorbent material the surface to be treated (usually glass or glazes) and rubbed in after a short drying time clear polished. The surfaces then have a good anti Fog effect when moisture is applied from the Atmosphere and contact angle against water of <20 °. Ge compared to commercial anti-fogging agents (e.g. rain-x Anti fog for car windows; Quaker State) they show a white considerably higher long-term effects, especially under leaching Conditions such as B. during permanent condensation of air humidity with formation of drops and runoff ended.

Example 2

Betaine (anhydride) is dissolved in aqueous silica sol (e.g. Levasil 300/30, Bayer) and then diluted with water. Polyvinyl alcohol (Mowiol 10-98, Clariant) is homogeneously dissolved in this mixture. This mixture can be used for subsequent coating at room temperature without further processing. Compared to Example 1, PVA1 does not have a foam-stabilizing effect and generally does not reduce the adhesion of the layers deposited at room temperature to inorganic surfaces. But it is also achieved if anti-fog effect.
Application see example 1

Example 3

Betaine (anhydride) is in aqueous silica sol (e.g. Levasil 300/30, Bayer) and then with Diluted water and isopropanol. In this mixture Triethanolamine dissolved. This mixture can be used without further ver work for subsequent coating at room temperature be used.

Example 4

Betaine (anhydride) is dissolved in aqueous zirconia sol (NZS 30A, Nissan) and then diluted with water and isopropanol. Various amounts of a nonionic surfactant (for example Marlipal 24/100, Con dea; Brij-30 or Brij-700, ICI) are then stirred in. This mixture can be used for subsequent coating at room temperature without further processing. The use of ZrO2 instead of SiO2 enables the setting of higher refractive indices, which are desired for some applications for optical reasons. The coatings show the same good anti-fogging effects as the coatings from Example 1.
Application see example 1

Example 5

Betaine (anhydride) is dissolved in cationically stabilized silica sol (Levasil 200S, Bayer) and then diluted with water. Various amounts of a nonionic surfactant (for example Marlipal 24/100, from Condea; Brij-30 or Brij-700, from ICI) are then stirred in. This mixture can be used for subsequent coating at room temperature without further processing.
Application see example 1

Example 6 Anhydrous formulation

Betaine is dissolved in ethanol (anhydrous, denatured with methyl ethyl ketone) and stabilized silica sol in alcohol (Highlink, Clariant) is added with stirring. By slowly metering in with vigorous stirring, clear mixtures can be obtained without annoying flocculation. This mixture can be used for subsequent coating of plastic surfaces at room temperature without further processing. Due to the high alcohol content and the lack of water, it wets well on plastics.
Application see example 1

Example 7 Anhydrous formulation with silane

N- (2-Aminoethyl) -3-aminopropyltrimethoxysilane is dissolved in anhydrous ethanol and reacted with equimolar amounts of glycide ther 100. After a reaction time of at least 6 h at room temperature, the solution is neutralized with 10% ethanolic sulfuric acid and further diluted with anhydrous ethanol. Then the turbid mixture is mixed with stabilized silica sol in alcohol. This mixture can be used without further processing for subsequent coating of glass, glazes, ceramics or plastics at room temperature. Condensation of the silane components, which can be initiated by application of atmospheric moisture, gives layers which have a higher long-term effect than commercial anti-fogging agents.
Application see Example 1.

Claims (24)

1. Hydrophilic coating composition for coating surfaces, characterized in that it has a finely divided oxide and a surface modifier. 2. Composition according to claim 1, characterized in that it also contains auxiliary substances. 3. Composition according to claim 2, characterized in that the auxiliary substances are amphiphilic substances is. 4. Composition according to claim 3, characterized in that the amphiphilic excipients are hydrophilic polymers are. 5. Composition according to claim 3, characterized in that the excipients are preferably non-ionic tensides act. 6. Composition according to one of claims 1 to 5, characterized characterized that the finely divided oxide silica sol is.   7. Composition according to one of claims 1 to 5, characterized characterized that the finely divided oxide nanoparticles based on titanium oxide, zirconium oxide, aluminum oxide and the like. 8. Composition according to one of claims 1 to 5, characterized characterized that the finely divided oxide layered silica contains kate. 9. Composition according to one of the preceding claims, characterized in that the surface modifiers are selected from the group consisting of alkali and Alkaline earth metals, and inorganic or organic salts of compounds of Al, Zr, Zn or Ti. 10. Composition according to one of claims 1 to 8, characterized characterized that the surface modifiers are out chooses are from the group consisting of betaines, quartä ren ammonium compounds and silanes. 11. The composition according to claim 10, characterized in that that prefers betaine, tetramethylammonium hydroxide and epoxy-modified silanes can be used. 12. Composition according to one of the preceding claims, characterized in that it is to be coated surfaces around glass, plastic, metal or Kera mic acts. 13. The composition according to any one of claims 1 to 11, because characterized by the fact that they are to be coated surfaces are textiles.   14. Composition according to one of the preceding claims, characterized in that the substances contained have the following contents:

• a) finely divided oxide 0-100%, preferably 40-80%, particularly preferably 50-70%;
• b) surface modifier 0-80%, preferably 1-50%, particularly preferably 1-20%; and
• c) auxiliaries 0-80%, preferably 1-50%, particularly preferably 1-20%.

15. A method for coating surfaces with a hydrophilic composition according to one of claims 1 to 13, characterized by the following steps:

• a) applying the composition dissolved in a solvent at room temperature to the surface to be coated; and
• b) removing the solvent at room temperature.

16. The method according to claim 15, characterized in that the removal of the solvent at a higher temperature happens. 17. The method according to claim 15 or 16, characterized in net that the surfaces to be coated is glass, plastic, metal or ceramic. 18. The method according to claim 17, characterized in that pretreatment is carried out if it is surface to be coated is plastic. 19. The method according to claim 18, characterized in that pretreatment with plasma, corona or primer  will or that it is a flame pretreatment is. 20. The method according to any one of claims 15 to 19, characterized ge indicates that water is used as the solvent becomes. 21. The method according to any one of claims 15 to 20, characterized ge indicates that the composition in combination with a conventional cleaning agent is used. 22. Use of the composition according to one of the claims 1 to 14 in aluminum heat exchangers, in particular in car air conditioners. 23. Use of the composition according to one of the claims 1 to 14 for coating textiles. 24. Use of the composition according to one of the claims 1 to 14 as a hygienic coating for waterless urina len.