|Publication number||WO2004106252 A1|
|Publication date||9 Dec 2004|
|Filing date||23 Dec 2003|
|Priority date||28 May 2003|
|Publication number||PCT/2003/14768, PCT/EP/2003/014768, PCT/EP/2003/14768, PCT/EP/3/014768, PCT/EP/3/14768, PCT/EP2003/014768, PCT/EP2003/14768, PCT/EP2003014768, PCT/EP200314768, PCT/EP3/014768, PCT/EP3/14768, PCT/EP3014768, PCT/EP314768, WO 2004/106252 A1, WO 2004106252 A1, WO 2004106252A1, WO-A1-2004106252, WO2004/106252A1, WO2004106252 A1, WO2004106252A1|
|Inventors||Michael Overs, Gerhard Jonschker|
|Applicant||Nanogate Coating Systems Gmbh|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (8), Referenced by (5), Classifications (10), Legal Events (6)|
|External Links: Patentscope, Espacenet|
Hydrophobic and/or oleophobic coating for glass surfaces with adhesion sites for sealants
This invention is related to a hydrophobic and/or oleophobic easy-to-clean coating on glass surfaces containing particles embedded in the surface of said coating such that the coating exhibits improved adhesion to a sealant.
Easy-to-clean hydrophobic and/or oleophobic coatings for glass surfaces are known for several years now. In recent times, worldwide markets generated an increasing demand for such coatings. With that came an increased demand for quality of these coatings, as well. Typical quality characteristics are abrasion resistance, chemical resistance, but even more importantly, compatibility with typical handling procedures of window manufacturers and facade builders, in particular with current sealants.
Hydrophobic and/or oleophobic coatings, as they are known today, are typically produced by treating a glass pane with some sort of fluorinated alkylsilanes to render the surface hydrophobic and/or oleophobic. Due to the low surface energy of such coatings, usual sealants do not adhere very well to this type of surfaces.
Other coatings known in the art are especially designed to improve the adhesion of a glass pane with common sealants. Most of these known coatings are based on silanes. Current hydrophobic and/or oleophobic coatings for glass do not exhibit good adhesion to common sealants, and on the other hand, adhesion promotion coatings for sealants on glass do not exhibit good hydrophobicity, so far.
A variety of coatings has been taught in the prior art for the purpose to either provide hydrophobic and/or oleophobic coatings on glass surfaces, some of those comprising particles to increase the degree of hydrophobicity and/or to provide better abrasion resistance.
Common adhesion promotion coatings comprise silanes to provide improved adhesion between glass panes and sealants.
As an example for many, US 4,857,366 B teaches a method for treating a glass surface providing improved adhesion of a sealant applied thereafter using a composition comprising a silane.
DE 100 63 739 Al teaches a substrate with a self-cleaning surface obtained by incorporation of particles into an otherwise inorganic coating for obtaining a defined surface roughness and making said surface hydrophobic by using a fluoroalkylsilane.
WO 99/19084 Al teaches a water based coating material comprising an alcohol as a solvent, fluorinated silanes and an acid to provide a hydrophobic coating on glass. EP 0 799 873 Bl teaches a coating material comprising water, an alcohol, fluorinated silanes and an acid to provide a hydrophobic coating in glass.
WO 95/23804 Al teaches a water based coating material comprising fluorinated silanes to provide a hydrophobic coating on a variety of substrates.
US 6,340,502 Bl teaches a coating material comprising a fluorinated alkoxysilane and a fluorinated halosilane for obtaining a hydrophobic coating.
EP 0 545 201 Bl teaches an article comprising a glass substrate, which is treated with a silica primer layer and a perfluoroalkyl alkyl silane.
EP 1 113 064 Al teaches a water based composition comprising a tetraalkoxysilane, an alkylsilane, and an acid for obtaining a hydrophobic coating.
DE 100 51 182 Al teaches nanoparticles that are modified with hydrocarbons, which may be fluorinated, and a process for deposition of hydrophobic coatings comprising said nanoparticles. As may be seen from the examples, it is questionable, whether nanoparticles are formed at all. In this description, no nanoparticles are added to the composition, but nanoparticles are formed in situ. DE 195 44 912 Al teaches microporous polytetrafluoroethylene that is filled with nanoparticles.
DE 197 19 948 Al and DE 197 46 885 Al teach a process for obtaining nanostructured surfaces by applying surface modified nanoparticles onto a substrate and polymerizing the composition subsequently.
Sufficient adhesion of a sealant to a hydrophobic and/or oleophobic glass substrate is possible to achieve by covering these parts of the pane that will need to adhere to the sealant before coating, such that these parts remain uncoated and will exhibit normal adhesion of a sealant to glass. Such solution to the underlying problem is not desirable, because it becomes uneconomical with large throughput of glass panes and also adds several additional production steps to the coating process.
Thus, the problem underlying the invention is that current hydrophobic and/or oleophobic coatings for glass do not exhibit good adhesion to common sealants, and on the other hand, adhesion promotion coatings for sealants on glass do not exhibit good hydrophobicity, so far. The problem of the invention is to provide a composition overcoming said contradiction. Surprisingly, it has been found that a coating on glass surfaces is achievable, which exhibits both hydrophobicity and sufficient adhesion to sealants.
In a first embodiment of the invention, the problem of the underlying invention is solved by a composition, comprising a. 0.01% to 10% by weight of particles with a diameter up to 100 nm, b. 0.1% to 10% by weight of at least one alkylsilane conforming to the general formula 1
R1, R2 and R3 each independently is chlorine or an organic residue containing 1 to 17 carbon atoms, 3 to 37 hydrogen atoms, 0 to 6 oxygen atoms, 0 to 33 fluorine atoms, 0 to 33 chlorine atoms, and 0 to 5 nitrogen atoms and
R4 is an organic residue containing 1 to 17 carbon atoms, 3 to
37 hydrogen atoms, 0 to 6 oxygen atoms, 0 to 33 fluorine atoms, 0 to 33 chlorine atoms, and 0 to 5 nitrogen atoms, c. 0.05% to 10% by weight of an acid, and d. a solvent.
According to present invention, the underlying problem is solved, such that the hydrophobic and/or oleophobic coating on glass is selectively rendered adhesive to sealants by incorporation of particles into the coating that function as adhesion sites to the sealant.
"Hydrophobic" according to the invention is characterized by a contact angle against water in air of > 90°. Unless otherwise stated, said contact angle is determined by dynamic advancing contact angle measurements using a Krϋss™ instrument. Fig. 1 shows that typically the embedded particles in a coating composition are covered with the hydrophobic and/or oleophobic material, in the case of the invention this is said alkylsilane. But it was found that the degree of coverage with said alkylsilanes strongly depends on the chemical nature of stabilizers in the particle dispersion and the surface modification of the particles. Very good results have been obtained by using SiO2 particles modified with organic residues containing alcohol functional groups, ethylenic functional groups and/or amino functional groups. Best results have been obtained when the surface modification rages between 1 to 10, in particular 2 to 3 per nm2. As shown in Fig. 2, when using appropriate stabilizers in the particle suspension and an appropriate surface modification, a partial coverage of the particles with alkysilanes can be achieved to allow sealant to attach itself to uncovered parts of the particles.
Fig. 2 demonstrates the basic principle of the present invention. First, the solution contains at least the solvent, particles, non-sticking compounds and sticking compounds or compounds with sticking and non-sticking moieties. When applied to the surface, the solvent evaporates and the particles migrate to the inner sphere of the coating. The components self-assemble to form such a coating that the non- sticking compounds are located on top of the coating, shielding the particles, which are the adhesion sites for the sealant, from dirt. Finally, when sealant is applied, the sealant can reach the adhesion sites (preferably particles) and form stable bonds, in particular chemical bonds. It is of advantage that the particles are present as 0.01% to 10% by weight a colloidal suspension containing 0.01% to 60% by weight particles with a diameter up to 100 nm. In case of suspension the same solvents as used for component (d) may be used.
The solvent may contain mixtures of different solvents including water and aqueous solutions.
Preferably, said solvent (d) comprises 20% to 99.9% by weight of a solvent having a dielectric constant 5 < ε < 40, especially preferably a protic solvent, and 0% to 70% by weight of water. The solvent preferably is a linear or branched alcohol containing 1 to 10 carbon atoms, in particular isopropanol.
In a preferred embodiment said alkylsilane corresponding to formula (1) comprises residues R4 conforming to the general formula (2)
Z is selected from the group H, Cl, and F,
1 < n < 15, 1 < m < 4, and
R1, R2, and R3 each are independently selected from Cl or cyclic, linear or branched alkoxy groups each containing 1 to 10 carbon atoms.
Especially preferably, Z is F. Said particle material is preferably a metal oxide and even more preferably SiO2. The advantage of metal oxides is, that they show good compatibility with the composition system and particularly SiO2 particles are readily available in various diameters and in water and/or in various inorganic and/or in various organic solvents. It was found that completely hydroxylated particles in a water suspension, such as in Levasil™ 200 E 20, do not solve the problem of the underlying invention exceptionally well. And when no particles are used at all, the underlying problem cannot be solved. On the other hand, when using surface modified, in particular organic surface modified particles in organic solvents, such as Highlink™ OG 502-31, the problem of the underlying invention can be solved well. Very good results have been obtained by using Si02 particles modified with organic residues containing alcohol functional groups, ethylenic functional groups and/or amino functional groups. Best results have been obtained when the surface modification ranges between 1 to 10, in particular 2 to 3 per nm2. For this reason, the particles are preferably not fully hydroxylated. And to avoid optical scattering, the preferred size of the particles is not larger than 50 nm, in particular not larger than 30 nm.
It is preferred for the protic solvent having a dielectric constant 5 < ε < 40 to be an alcohol, and especially preferred to be isopropanol. In the experiments, isopropanol turned out to be the best suited solvent with optimal solvent properties and visual appearance of the coating after drying. Key criteria for judgment of visual appearance include veil formation, transparency, and clarity. The acid is preferably a mineral acid, and especially preferred sulfuric acid. Sulfuric acid has the particular advantage of being non-volatile, non- oxidizing, and having a high acid strength.
It is preferred for said afkysilane to conform to the general formula 1, wherein m = 2 and R1, R2, and R3 each are independently selected from alkoxy groups each containing from 1 to 2 carbon atoms, and especially preferred to be 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyltriethoxysilane. It is evident from the experiments, that the longer the perfluorinated chain is, the better is the abrasion resistance and the stability of the hydrophobic and/or oleophobic property.
To improve adhesion properties, the composition contains preferably from 0.02% to 2% by weight of at least one silane conforming to the general formula 3
R4, R6, R7, and R8 each are independently selected from the group of Cl, oxime, and of linear and branched alkyl groups each containing 1 to 10 carbon atoms, and linear or branched alkoxy groups each containing 1 to 10 carbon atoms.
For reasons of commercial availability and already established coating technology, the silane conforming to general formula 2 is preferably selected from the group tetramethoxysilane, tetraethoxysilane, and dimethyldiethoxysilane. In a second embodiment of the invention, the problem of the underlying invention is solved by a coated substrate with a hydrophobic and/or oleophobic coating containing a composition conforming to above description on at least one surface of the substrate, where the material of the substrate is selected from the group containing glass, ceramic, metal, stone, concrete and/or glazed articles.
Preferably, the coated substrate is a glass substrate, since glass is the largest market for sealants.
In a third embodiment of the invention, the problem of the underlying invention is solved by a process for the preparation of said glass substrate with a hydrophobic and/or oleophobic coating comprising the steps in the following sequence:
a. cleaning said substrate, b. applying a composition conforming to the first embodiment of the invention to said substrate, and c. drying said composition.
The coating may be applied to the fire side and/or to the tin side of the glass substrate. Preferably, the composition is applied to the fire side of the glass substrate. Typically, the fire side of glass substrates exhibits better adhesion to sealants. The method of application in step b. is preferably selected from the group of spray coating, polishing, curtain coating, dip coating and roller coating.
It may be of advantage with respect to manufacturing costs, when the drying is performed at room temperature and normal pressure.
Said composition can be applied on the whole glass pane, on the center of the glass pane and on the edges and borders of the glass pane as well. Said composition allows to seal also the coated parts with common available sealants without the necessity of protecting the parts of the glass pane that should be sealed later in production. It is also not necessary to remove said coating from said parts of the glass pane before sealing, which is also common for existing coating materials.
For best adhesion, adhesion sites may also be introduced by partial removal of the coating.
Another explanation for the positively influenced adhesion may be that loose packings of not fully crosslinked silanes are hampered by adding said nanoparticles.
For economic reasons, the coating process is preferably a continuous process. The process may also coat the substrates from both sides simultaneously. It should be understood that this description does not preclude chemical interactions among the components listed, but instead describes the components of a composition according to the invention in the form in which they are generally used as ingredients to prepare such a composition.
The glass substrates are cleaned using a commercially available generic scouring milk and isopropanol before coating. Coating was performed on the fire side of the substrates. After addition of each component to the reaction mixture, the reaction mixture was stirred. The components are added in the order they are mentioned. Following product names and abbreviations are used: Highlink™ OG 502-31 an organically surface modified colloidal suspension of 30% by weight of SiO2 particles with an average particle size of 13 nm in isopropanol by Clariant™. The surface of these particles is modified with organic residues containing alcohol functional groups, ethylenic functional groups and/or amino functional groups. The degree of surface modification ranges between 2-3 per nm2. The colloidal suspension generally contains less than 1% water by weight. Dynasylan™ F 8261 3,3,4,4,5,5,6,6,7,7,8,8,8-
Tridecafluorooctyltriethoxysilane by Degussa™ TMOS Tetramethoxysilane DMDEOS Dimethyldiethoxysilane
Dow Corning™ 897 Sealant for natural stone and facades
Kδdisif Hac Sealant for sanitary and various other applications
Kδdisil™ Hac-A trans Sealant for sanitary and various other applications, which is transparent.
Otto Fugendicht™ Sealant for sanitary applications Dow Corning 781 Acetoxy silicone sealant for non-porous surfaces such as glass, aluminum, painted surfaces and composite boards.
Novasil S70 Neutral silicone sealant on oxime basis for stone
Dow Corning 794s Neutral silicone sealant for windows Dow Corning 796 Neutral silicone sealant for PVC-U, glass, glazed surfaces and brickwork.
Kδdisil™ A Fungicidal neutral silicone sealant for windows.
Abrasion resistance was tested in analogy to ASTM D2486 using a washability tester, which was equipped with a usual mason's sponge (Triuso™) and a liquid containing abrasive material (Tana™ Scheuermilch, Werner & Mertz™, DE). The mass of the mount for the sponge is 345.45 g. After covering the mounted substrate with the liquid containing abrasive material, the sponge is moved about the substrate with a speed of 37 cycles/minute. The result is quantified by measuring the contact angle (CA) with demineralized water before the determination of abrasion resistance and after 200, 500, 1000, 1500, 2000, ... cycles. Visual appearance was determined by the human eye. Key criteria for judgment of visual appearance include veil formation, transparency, and clarity.
Adhesion to sealants was tested by the following procedure:
- application of a sealant to the glass substrate (7 cm long, 0,5 cm diameter) using a caulk gun
- drying sealant for 7 days
- characterizing the adhesion (bad adhesion, good adhesion, adhesion errors on edge of substrate, adhesion only to edge of substrate, adhesion only in middle of substrate)
Eight different common sealants for natural stone, facades, plastic, glass, acetoxy, PVC-U, aluminum and wood as mentioned above were used.
Hydrophobicity was evaluated by contact angle measurement against demineralized water in air. Unless otherwise stated, said contact angle is determined by dynamic advancing contact angle measurements using a Kruss instrument.
Results of the following examples are presented at the end of this section in table 1. In this table, key criteria are rated "good", "average" and "bad". The following definitions for the key criteria are used: Hydrophobicity: "good" = initial contact angle >100°; "average" = initial contact angle between 90° and 100°; "bad" = initial contact angle < 90°.
Abrasion Resistance: "good" = after 1000 cycles the contact angle is above 90°; "average" = after 100 cycles the contact angle is between 80° and 90°; "bad" = after 1000 cycles the contact angle is below 80°. ' Abrasion resistance and hydrophobicity were measured independent of the adhesion testing. The substrates used for testing of abrasion resistance and hydrophobicity were not exposed to sealant before measurement.
Adhesion to sealants: "good" = has good adhesion to at least 75% of the eight different sealants; "average" = has good adhesion to between 50% and 75% of the eight different sealants; "bad" = has good adhesion to less than 50% of the eight different sealants.
Synthesis of the solution, which is used to treat glass substrates to yield improved adhesion of glass sealant to hydrophobic and/or oleophobic glass coatings
24,7 g Isopropanol, 2,49 g Clariant Highlink™ OG 502-31 and 0,67 g 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyltriethoxysilane were added to a reaction vessel and stirred briefly. After addition of 96,89 g isopropanol, the mixture was stirred for 60 minutes. 0,54 g H2SO4, which was dissolved in 53,39 g demineralized water, was then slowly added and the reaction mixture was stirred for 10 minutes. lOx 10 cm glass substrates were coated using an air-brush and then stored in an oven at 40°C for 30 minutes. The following sealants were applied and tested as described above: Dow Coming™ 897, Kόdisil™ Hac, Kόdisil™ Hac-A trans, Otto Fugendicht™, Dow Corning™ 781, Novasil™ S70, Dow Corning™ 794s, Dow Corning™ 796, Kόdisil™ A, Henkel Sista™ F107, and Soudal Formflex™ Bau.
The results obtained by the sum of all sealants are presented in table 1.
Comparative Example 1:
29,83 g Isopropanol, 0,32 g Clariant Highlink™ OG 502-31 and 0,27 g 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyltriethoxysilane were added to the reaction vessel and stirred briefly. After addition of 39,25 g isopropanol, 0,43 g H2SO4 was directly added and the reaction mixture was stirred for 60 minutes. lOx 10 cm glass substrates were coated using an air-brush and then stored at room temperature overnight. The results are presented in table 1. Adhesion to sealants was not tested.
Omission of water in the last step of the synthesis leads to insufficiently hydrophobic and/or oleophobic and abrasion resistant coatings.
Table 1 :
Table 1. ("+" stands for "good", "0" stands for "average", "-" stands for "bad")
In this table, uncoated glass corresponds to measurements on the fireside of uncoated float-glass. Typical hydrophobic coatings correspond to coatings as obtained by products such as Rain-X™ of Unelko as described in US 3579540 B.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|DE10051182A1 *||16 Oct 2000||2 May 2002||Nano X Gmbh||Nanoparticle useful for coating substrate surfaces to impart hydrophobicity and oleophobicity, has specific substituents consisting of perfluorinated carbon chains and/or hydrocarbon chains|
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|US4857366 *||11 Mar 1988||15 Aug 1989||Minnesota Mining And Manufacturing Company||Method for obtaining adhesion of urethane sealant to a painted or glass surface|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|WO2012167017A2 *||1 Jun 2012||6 Dec 2012||The University Of North Carolina At Chapel Hill||Superhydrophobic coatings and methods for their preparation|
|WO2012167017A3 *||1 Jun 2012||21 Mar 2013||The University Of North Carolina At Chapel Hill||Superhydrophobic coatings and methods for their preparation|
|DE102007010955A1||5 Mar 2007||11 Sep 2008||Leibniz-Institut Für Neue Materialien Gemeinnützige Gmbh||Beschichtungszusammensetzung|
|US8153834||4 Dec 2008||10 Apr 2012||E.I. Dupont De Nemours And Company||Surface modified inorganic particles|
|US9675994||1 Jun 2012||13 Jun 2017||The University Of North Carolina At Chapel Hill||Superhydrophobic coatings and methods for their preparation|
|International Classification||C03C17/00, B05D5/08, C09D4/00|
|Cooperative Classification||C03C17/007, B05D2203/35, B05D5/08, C09D4/00|
|European Classification||C09D4/00, C03C17/00D2, B05D5/08|
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