Hydrophobic coating process for a glass substrate and hydrophobic glass substrate obtained

Abstract

The invention relates to a hydrophobic coating process for a glass substrate comprising the following successive steps: - formation of a primary layer, preferably comprising silicon oxide, on one of the surfaces of a glass substrate, - formation of a hydrophobic layer by application, on the primary layer, of a composition comprising at least two non-fluorinated alkylsilane compounds A and B, compound A having an alkyl chain Ra comprising 1 to 5 carbon atoms, and compound B having an alkyl chain Rb comprising 6 to 16 carbon atoms.The invention also relates to a hydrophobic glass product, obtainable by the process according to the invention, comprising a glass substrate, a surface of which is at least partially covered with a coating comprising: - a primary layer, preferably comprising silicon oxide, in contact with said surface of the substrate; and - a hydrophobic layer comprising at least two different non-fluorinated alkylsilyl groups Ga and Gb, grafted onto said primary layer, the Ga group having an alkyl chain Ra comprising 1 to 5 carbon atoms, and the Gb group having an alkyl chain Rb comprising 6 to 16 carbon atoms.

Description

Title of the invention: Process for hydrophobicizing a glass substrate and the resulting hydrophobic glass substrate. Technical field

[0001] The invention relates to a method for hydrophobicizing a glass substrate whose surface is rendered hydrophobic by grafting non-fluorinated alkylsilanes, particularly for applications in the transportation sector, such as the automotive or aerospace industries. The present invention also relates to a glass product with a hydrophobic coating, and the use of such a product as glazing. TECHNOLOGICAL BACKGROUND

[0002] Hydrophobic properties are desirable for windows and windshields, particularly in the transportation sector, for example, for motor vehicles or aircraft such as airplanes or helicopters. These hydrophobic properties are essential for improving visibility in the rain, and therefore safety. It is known to treat the outer surface of glazing, generally made of glass and therefore hydrophilic, with a hydrophobic coating that minimizes the spreading and adhesion of water droplets to the surface of the glazing and facilitates their sliding. In particular, water droplets and water films must be able to flow and be efficiently removed, for example, by gravity or by an airflow exerted on the glazing when the vehicle is in motion, possibly in combination with the action of windshield wipers.Thus, hydrophobic treatments optimize the transparency of glazing over a sufficiently large area by preventing the formation of continuous water films that drastically degrade optical qualities.

[0003] The hydrophobic nature of a substrate surface is commonly described by the contact angle (θ) between a water droplet and the substrate (the angle formed between the tangent to the droplet at the point of contact and the line of contact). The larger this angle, the less the droplet spreads on the substrate and the more hydrophobic the substrate surface. Generally, a surface is considered hydrophobic when the contact angle is greater than 90°.

[0004] But the hydrophobic properties of a substrate can also be described using an additional parameter: the hysteresis of the contact angle (A0), which takes into account the dynamic behavior of the droplet / substrate system and the differences in contact angles that can be observed for this same system (the phenomenon of more or less significant adhesion of the droplet to the substrate involving cohesive and / or adhesive forces, which can be linked to chemical or geometric heterogeneities on the surface, are all factors at play. The contact angle hysteresis (A0) is the difference between the extreme values ​​that the contact angle can take, these extreme values ​​being called the leading angle 0a and the recoil angle 0r. These extreme angles can be determined by measuring the contact angles of a droplet on an inclined plane (the limits of angles for which the droplet no longer remains stationary on the sloping substrate) or by increasing or decreasing the volume of a droplet on a horizontal substrate (the limits of angles for which the diameter of the droplet increases or decreases). The contact angle hysteresis reflects the ability of a droplet to move or slide on the substrate surface. The smaller its value, the less the surface resists the movement of the droplets and therefore the more it facilitates their sliding.

[0005] Furthermore, it is essential that hydrophobic coatings preserve the optical quality of the glazing and are also durable. Indeed, hydrophobic treatments can degrade under the effects of abrasion (induced, for example, by friction from dust present in the atmosphere or the repeated action of windshield wipers, if applicable), the natural environment (for example, water causing hydrolysis of the deposits, UV radiation), and / or chemicals (such as cleaning products). Thus, while hydrophobic treatments generally allow for contact angles greater than 90°, the challenge lies in maintaining sufficient hydrophobicity over a long period of time.

[0006] Furthermore, particularly in the case of aircraft, it is important to be able to regenerate the hydrophobic function. Hydrophobic coating processes for glazing must therefore be able to be implemented in situ, that is, on glazing mounted on the aircraft, so as to allow for simple and rapid maintenance. Consequently, a good hydrophobic treatment, in addition to being durable, must require limited equipment (including safety equipment), a limited number of steps, and a short implementation time.

[0007] It is known to increase the hydrophobicity of vehicle glazing by grafting perfluorinated alkylsilanes onto the surface of the glass substrate, generally after prior creation of a primer layer comprising silica, by a sol-gel process, by physical vapor deposition (PVD) or by chemical vapor deposition (CVD).

[0008] However, perfluorinated compounds are considered harmful to the environment and human health. The persistence of these compounds in the environment and in the human body, combined with their adverse health effects, has recently increased regulatory pressure regarding their use, particularly through the European REACH and POP regulations. This could lead to a widespread ban on these compounds by 2025 or, at the latest, 2030.

[0009] In addition, current hydrophobic treatments do not guarantee sufficient hydrophobicity throughout the lifetime of the glazing, particularly for external applications.

[0010] Thus, alternative hydrophobic substrates are still being researched, particularly for the automotive or aeronautical industries, and there is still a need for glazing with a satisfactory hydrophobic character that lasts over time, without resorting to perfluorinated compounds.

[0011] It is to the applicant's credit that he proposed a hydrophobic glass substrate without perfluorinated compounds and its preparation process which, surprisingly, makes it possible to satisfy both the requirements of efficiency and durability. Summary of the invention

[0012] According to a first aspect, the invention relates to a hydrophobic treatment process for a glass substrate comprising the following successive steps: - formation of a primary layer, preferably comprising silicon oxide, on one of the surfaces of a glass substrate, - formation of a hydrophobic layer by application, on the primary layer, of a composition comprising at least two non-fluorinated alkylsilane compounds A and B, compound A having an alkyl chain Ra comprising 1 to 5 carbon atoms, and compound B having an alkyl chain Rb comprising 6 to 16 carbon atoms.

[0013] The invention also relates, according to a second aspect, to a hydrophobic glass product, obtainable by the process according to the invention, comprising a glass substrate, a surface of which is at least partially covered with a coating comprising: - a primary layer, preferably comprising silicon oxide, in contact with said substrate surface; and - a hydrophobic layer comprising at least two different non-fluorinated alkylsilyl groups Ga and Gb, grafted onto said primary layer, the Ga group having an alkyl chain Ra comprising 1 to 5 carbon atoms, and the Gb group having an alkyl chain Rb comprising 6 to 16 carbon atoms.

[0014] According to another aspect, the invention also relates to the use of a hydrophobic glass product according to the invention as glazing for transport vehicles such as motor vehicles or aircraft cockpits.

[0015] The invention makes it possible to obtain substrates coated with a hydrophobic coating which, surprisingly, exhibit hydrophobic properties comparable to those of coatings based on perfluorinated compounds, with, in particular, a contact angle generally greater than 90°. In addition, the combination of grafted groups makes it possible to achieve improved performance in terms of both abrasion resistance and and UV resistance, compared to substrates obtained with a single type of grafted group. These properties are particularly advantageous in the transport sector, such as automotive, rail, and aerospace, where glazing has high requirements in terms of transparency and resistance to abrasion and external conditions. DETAILED DESCRIPTION

[0016] The general terms used in this text are defined below.

[0017] The expression "including" encompasses the expression "consisting of".

[0018] The expression "from ... to ..." should be understood inclusive of the limits.

[0019] In the context of the present invention, the "hydrophobic" properties of a surface take into account the ability of water to slide over the surface and are evaluated using both the contact angle (θ) and the contact angle hysteresis (A0). After hydrophobic treatment, the hydrophobic glass products according to the invention generally have an "initial" contact angle (i.e., shortly after manufacture) of at least 90°, and preferably an "initial" contact angle hysteresis of at most 30°. It is understood that the hydrophobic properties degrade over time (decrease in θ and increase in A0). For the purposes of the present invention, the "hydrophobic" properties of a surface (including here the water evacuation properties) remain functional as long as the contact angle 0 is at least 50° with a hysteresis of at most 30°.Indeed, it has been observed that, even with a contact angle of 50°, a glazing coating that sufficiently facilitates droplet mobility (hysteresis of at most 30°) is considered functional, meaning that the coating effectively limits the formation of water films and maintains sufficient optical qualities.

[0020] The hydrophobization process according to the invention includes a step of forming a primary layer, preferably comprising silicon oxide, on one of the surfaces of a glass substrate.

[0021] The substrate comprises, at least in the portion intended to be coated with a hydrophobic layer, a glass plate. The glass may be monolithic or laminated, and optionally tempered. The glass plate may be flat, have curved faces, or bent (such as, for example, a windshield). According to the invention, the glass substrate is transparent. In other words, it has a visible light transmission of at least 80%, preferably at least 90%.

[0022] The prior formation of a primary layer, or intermediate layer, on the surface to be treated strengthens the adhesion of the hydrophobic alkylsilane coating to the substrate (via the intermediate layer) and improves the durability of this coating. In particular, during the primary layer formation step, the silicon content on the surface, and in particular silicon oxide, is increased, allowing the generation of active silanol (Si-OH) groups, i.e. capable of reacting with alkylsilane compounds.

[0023] Preferably the primary layer comprises silicon oxide. Preferably, the primary layer is essentially made of silica (SiO2). For example, the primary layer comprises at least 80% by mass of silica, preferably at least 90%, more preferably at least 95%, relative to the total mass of the primary layer.

[0024] The formation of the primary layer can be achieved by any known technique.

[0025] Preferably, the formation of the primary layer comprising the oxide of silicon, is produced by sol-gel step in which a tetrachlorosilane and / or a tetraalkoxysilane, preferably tetraethoxysilane, is hydrolyzed in acidic hydroalcoholic medium.

[0026] More specifically, during the sol-gel step, an acidic hydroalcoholic solution is prepared by dissolving an appropriate amount of tetrachlorosilane and / or tetraalkoxysilane in a water / alcohol mixture, for example, a water / isopropanol mixture, the pH of the water preferably being adjusted beforehand to a value ranging from 1 to 3. Preferably, the water / alcohol mixture comprises 3% to 50% by mass of water, preferably 5% to 15% by mass of water, relative to the total mass of the water / alcohol mixture. Preferably, the mass content of tetrachlorosilane and / or tetraalkoxysilane in the hydroalcoholic solution is 0.1% to 1%, preferably 0.15% to 0.8%, relative to the mass of the hydroalcoholic solution. Preferably, the molar ratio of water to the silica precursor, i.e. tetrachlorosilane or tetraalkoxysilane, is 400 to 600, preferably 450 to 550 and in particular 480 to 520.

[0027] Preferably, before applying the hydroalcoholic solution to the substrate, the solution is allowed to react at room temperature (20-25°C) for a period of between 2 minutes and 2 hours, preferably between 3 minutes and 1 hour, and in particular between 5 minutes and 30 minutes. This allows for the completion of the hydrolysis of tetrachlorosilane and / or tetraalkoxysilane.

[0028] The acidic hydroalcoholic solution of tetrachlorosilane / tetraalkoxysilane or tetrachlorosilane can be applied by any technique that allows the formation of a thin liquid film on the surface of the substrate. Examples include application by immersion, liquid curtain, spray, or wiping. For aircraft regeneration, wiping is the most suitable. Preferably, spraying or misting and application using a cloth soaked in the hydroalcoholic solution of tetraalkoxysilane or tetrachlorosilane are used.

[0029] Preferably, after application to the surface of the glass substrate, the liquid film formed is left to dry for a period of at least 2 minutes, preferably at least 5 minutes.

[0030] Optionally, after drying of the first primary layer deposit, the application of the hydroalcoholic solution of tetrachlorosilane and / or tetraalkoxysilane can be repeated until the desired primary layer thickness is obtained. The primary layer thickness after drying can be, for example, from 5 nm to 250 nm, preferably from 10 nm to 100 nm, and more particularly from 15 nm to 75 nm.

[0031] The primary layer formation step is then followed by a hydrophobic layer formation step, and more particularly a step of grafting the alkylsilyl groups of at least two different alkylsilane compounds. Preferably, the hydrophobic layer formation step is carried out after the primary layer has dried for at least 2 minutes at room temperature.

[0032] Thus, the hydrophobicization process according to the invention includes a step of forming a hydrophobic layer by applying, on the primary layer, a composition comprising at least two non-fluorinated alkylsilane compounds A and B, compound A having an alkyl chain Ra comprising 1 to 5 carbon atoms, and compound B having an alkyl chain Rb comprising 6 to 16 carbon atoms.

[0033] Preferably, during the hydrophobic layer formation step, the applied composition is a hydroalcoholic composition, preferably acidic.

[0034] For the purposes of this invention, "alkylsilane compound" means a compound having an alkylsilyl group, that is, an alkyl chain R directly bonded to a silicon atom (R-Si). The alkylsilane compounds according to the invention are monomeric compounds and are therefore distinct from polymeric organosilane compounds and silicone polymers. It is understood that, within the scope of this invention, the alkylsilane compounds and their alkylsilyl group are non-fluorinated, that is, they do not contain a fluorine atom.

[0035] Preferably, during the hydrophobic layer formation step, the applied composition comprises two non-fluorinated alkylsilane compounds A and B as described above.

[0036] Preferably, in the hydrophobization process according to the invention, the difference in the number of carbons An between the alkyl chains Ra and Rb is greater than or equal to 3, preferably greater than or equal to 5, more preferably greater than or equal to 7. In other words, An = nb-na > 3, preferably > 5, more preferably > 7 (nb being the number of carbons in the alkyl chain Rb and na being the number of carbons in the alkyl chain Ra).

[0037] More particularly, the alkylsilane compounds usable according to the invention can be represented by the general formula R-Si-X3 where: - R is an alkyl chain as previously described (Ra or Rb), and - X is a hydrolyzable group, that is, an atom or group that can be released in an aqueous or hydroalcoholic medium.

[0038] Preferably, the hydrolyzable group X is a halogen, for example a chlorine, or an alkoxy group comprising 1 to 3 carbon atoms, for example a methoxy or ethoxy group. More preferably, the hydrolyzable group X is an alkoxy group comprising 1 to 3 carbon atoms, preferably an ethoxy group.

[0039] The alkylsilane compound A, or its alkylsilyl group Ga, may have an alkyl chain -Ra having the molecular formula -CnH2n+i, where n is an integer from 1 to 5, for example from 1 to 4. Preferably n is from 1 to 3, more preferably from 2 to 3, even more preferably n = 3.

[0040] Advantageously, the alkyl chain Ra is linear and has the formula - (CH2)n i-CH3, where n is an integer from 1 to 5, for example from 1 to 4, preferably from 1 to 3, more preferably from 2 to 3, even more preferably n = 3.

[0041] The alkylsilane compound B, or its alkylsilyl group Gb, may have an alkyl chain -Rb having the molecular formula -CnH2n+i, where n is an integer from 6 to 16, preferably from 7 to 16, more preferably from 8 to 16, even more preferably from 8 to 12, for example from 8 to 10.

[0042] Advantageously, the alkyl chain Rb is linear and has the formula - (CH2)„ i-CH3, where n is an integer from 6 to 16, preferably from 7 to 16, more preferably from 8 to 16, even more preferably from 8 to 12, for example from 8 to 10.

[0043] According to a particular embodiment, during the hydrophobic layer formation step, the applied composition comprises two non-fluorinated alkylsilane compounds A and B, compound A having an alkyl chain Ra comprising 1 to 4 carbon atoms, compound B having an alkyl chain Rb comprising 7 to 16 carbon atoms.

[0044] The formation of the hydrophobic layer can be achieved by any known technique.

[0045] Advantageously, the formation of the hydrophobic layer is achieved by a sol-gel step in which the alkylsilane compounds A and B are hydrolyzed in an acidic hydroalcoholic medium. More specifically, during this step, the Ga and Gb alkylsilyl groups of compounds A and B are grafted onto the primary layer. This step can be implemented in a similar manner to that used for the formation of the primary layer.

[0046] Preferably, the grafting composition is prepared by dissolving an appropriate amount of alkylsilane compounds A and B in a water / alcohol mixture, preferably a water / isopropanol mixture. Preferably, the water / alcohol mixture contains 5% to 70% by mass, preferably 10% to 50% by mass, of water. Advantageously, the water is pre-acidified, preferably to a pH of 1 to 3.

[0047] The mass ratio A / B in the composition can be from 20 / 80 to 80 / 20, preferably from 20 / 80 to 60 / 40, more preferably from 20 / 80 to 55 / 45, even more preferably from 20 / 80 to 50 / 50. Depending on the pairs of alkyl chains used, the resistance performance can be further improved by using appropriate mass ratios.

[0048] Advantageously, the alkylsilane compound A represents at least 20% by mass, relative to the total mass of non-fluorinated alkylsilane compounds in the composition, more preferably from 20% to 50%. This optimizes the resistance of the hydrophobic coating to UV radiation.

[0049] Advantageously, the alkylsilane compound B represents at least 50% by mass, preferably from 50% to 80% by mass, relative to the total mass of non-fluorinated alkylsilane compounds in the composition. This allows for better resistance of the hydrophobic coating to abrasion and an initial contact angle greater than 90°.

[0050] Preferably, the mass content of alkylsilane compound A in the hydroalcoholic composition is 0.2% to 2% relative to the mass of the composition.

[0051] Preferably, the mass content of alkylsilane B compound in the hydroalcoholic composition is 0.5% to 3.5% relative to the mass of the composition.

[0052] Preferably, the molar ratio of water to the sum of alkylsilane compounds, in particular H2O / (A + B), is 70 to 200, preferably 80 to 150, more preferably 90 to 140.

[0053] Preferably, the hydroalcoholic composition of alkylsilane compounds is left at room temperature for approximately 10 minutes to approximately 3 hours to allow hydrolysis before being applied to the primer. Preferably, the hydroalcoholic composition is applied by spraying, watering, or wiping onto the primer.

[0054] According to a particular embodiment, during the hydrophobic layer formation step, the applied composition comprises two non-fluorinated alkylsilane compounds A and B, compound A having an alkyl chain Ra comprising 3 carbon atoms, compound B having an alkyl chain Rb comprising 8 to 10 carbon atoms, and the mass ratio A / B is 40 / 60 to 55 / 45, preferably 40 / 60 to 50 / 50.

[0055] According to another embodiment, during the hydrophobic layer formation step, the applied composition comprises two non-alkylsilane compounds fluorinated A and B, compound A having an alkyl chain Ra comprising 1 carbon atom, compound B having an alkyl chain Rb comprising 8 to 10 carbon atoms, and the mass ratio A / B is 20 / 80 to 60 / 40, more preferably 20 / 80 to 50 / 50.

[0056] The present invention also relates to a hydrophobic glass product, obtainable by the process according to the invention, comprising a glass substrate, a surface of which is at least partially covered with a coating comprising: - a primary layer, preferably comprising silicon oxide, in contact with said substrate surface; and - a hydrophobic layer comprising at least two non-fluorinated alkylsilyl groups Ga and Gb, grafted onto said primary layer, the Ga group having an alkyl chain Ra comprising 1 to 5 carbon atoms, and the Gb group having an alkyl chain Rb comprising 6 to 16 carbon atoms.

[0057] Preferably, the hydrophobic layer comprises two different non-fluorinated alkylsilyl groups (Ga and Gb as defined above).

[0058] Preferably, in the glass product according to the invention, the difference in the number of carbons An between the alkyl chains Ra and Rb (An = nb-na) is greater than or equal to 3, preferably greater than or equal to 5, more preferably greater than or equal to 7.

[0059] The alkylsilyl group Ga may have an alkyl chain -Ra having the molecular formula -CnH2n+i, where n is an integer from 1 to 5, for example from 1 to 4. Preferably n is from 1 to 3, more preferably from 2 to 3, even more preferably n = 3.

[0060] Advantageously, the alkyl chain Ra is linear and has the formula - (CH2)ri |-CHb where n is an integer from 1 to 5, for example from 1 to 4, preferably from 1 to 3, more preferably from 2 to 3, even more preferably n = 3.

[0061] The alkylsilyl group Gb may have an alkyl chain -Rb having the molecular formula -CnH2n+i, where n is an integer from 6 to 16, preferably from 7 to 16, more preferably from 8 to 16, even more preferably from 8 to 12, for example 8 to 10.

[0062] Advantageously, the alkyl chain Rb is linear and has the formula - (CH2)„ i-CH3, where n is an integer from 6 to 16, preferably from 7 to 16, more preferably from 8 to 16, even more preferably from 8 to 12, for example 8 to 10.

[0063] According to a particular embodiment, the hydrophobic layer of the glass product according to the invention comprises two non-fluorinated alkylsilyl groups Ga and Gb, grafted onto said primary layer, the Ga group having an alkyl chain Ra comprising 1 to 4, carbon atoms, and the Gb group having an Rb alkyl chain comprising 7 to 16 carbon atoms.

[0064] Advantageously, the primary layer of the hydrophobic glass product according to the invention has a thickness of 5 nm to 250 nm, preferably from 10 nm to 100 nm, more particularly from 15 nm to 75 nm.

[0065] Advantageously, the hydrophobic glass product according to the invention has, after manufacture, a contact angle 0 greater than 70°, preferably greater than 90°, more preferably greater than 95°, even more preferably greater than 100°.

[0066] Advantageously, the hydrophobic glass product according to the invention exhibits, after manufacture, a contact angle hysteresis A0 of at most 30°.

[0067] Advantageously, the ratio of the mass contents of alkylsilyl groups Ga / Gb is 20 / 80 to 80 / 20, preferably 20 / 80 to 60 / 40, more preferably 20 / 80 to 55 / 45, even more preferably 20 / 80 to 50 / 50.

[0068] It is understood that the hydrophobic layer of the product or process according to the invention is free of fluorinated compound.

[0069] The process and hydrophobic glass product according to the invention have the advantage of enabling the production of glazing with very good hydrophobic properties (including the mobility of water droplets on the substrate surface). Furthermore, these properties are long-lasting (very good abrasion resistance as well as very good UV resistance of the coatings) and can be optimized according to the application. In addition, the durability can be further improved depending on the alkyl chain ratios used, to further optimize, according to the needs and applications, abrasion resistance and / or UV resistance. Examples

[0070] The invention is illustrated by means of the non-limiting examples below, highlighting the hydrophobic properties obtained.

[0071] Initially, different hydroalcoholic compositions are prepared, comprising one to two alkylsilane compounds of different alkyl chain lengths R (listed in Table 1).

[0072] Several samples of transparent glass substrates are functionalized using these different compositions according to the method detailed below.

[0073] Each 10 cm x 10 cm sample is cleaned by polishing with a felt impregnated with an aqueous suspension containing 20% ​​cerium oxide particles. The polished sample is rinsed with distilled water and dried with a dry cloth.

[0074] For the formation of the primary silica layer: - A hydroalcoholic solution is prepared by mixing 0.3% by mass of tetraethoxysilane (TEOS) in a mixture of 10% acidic water (0.3N HCl) and 90% of isopropanol. The solution is stirred for 30 minutes of reaction at room temperature. - The resulting solution is applied using a soaked cloth to the surface of the previously cleaned glass substrate sample. The substrate coated with the primer is left to dry for approximately 5 minutes.

[0075] For the formation of the hydrophobic layer: - A hydroalcoholic composition comprising the tested alkylsilane compound(s) is prepared beforehand by dissolving 1.5% by mass of the alkylsilane compound(s) (in the proportions given in Table 1 for a mixture of two compounds) in a water / alcohol mixture containing 10% acid water (0.3N HCl) and 90% isopropanol. The mixture is kept under mechanical stirring for 1 hour. - Immediately after the brief drying step of the primary layer obtained above, the hydroalcoholic alkylsilane composition is applied to the primary layer by wiping. The substrate thus coated with the hydrophobic layer is allowed to dry for approximately 15 minutes at room temperature.

[0076] The excess reagents (whitish traces) are then removed by polishing with a cloth soaked in a water / alcohol mixture containing 70% by mass of water and 30% by mass of isopropanol until the diffusing residues on the surface of the glazing disappear.

[0077] In a second step, the hydrophobic properties of the glass products obtained are evaluated using procedures well known in the field and described below.

[0078] Measurement of the contact angle:

[0079] The contact angle of a water droplet (0) at equilibrium is measured using a Krüss DSA100 goniometer (Drop Shape Analyzef) on a 3 µm droplet. The droplet is observed using a high-speed camera which takes pictures from which the contact angle is then recorded.

[0080] The results obtained in Table 1 are generally good, with "initial" contact angles generally greater than 90°.

[0081] Measurement of contact angle hysteresis:

[0082] Contact angle hysteresis is also measured using a Krüss DSA100 goniometer (Drop Shape Analyzer). The device deposits a 30 lp water droplet onto the hydrophobic surface of the sample to be tested. Water is then injected (at a rate of 0.5 lp / min) into the droplet to increase its volume. This increase in volume is accompanied by an increase in the contact angle. The volume increase is continued until the contact angle no longer changes. The value (averaged over at least 3 repetitions) of this contact angle is called the advance angle (θ). The device then gradually aspirates the water from the droplet to return it to a smaller volume. The aspirating action is continued until the contact angle no longer changes. The recoil angle (θr) is called the value (average over at least three repetitions) of this contact angle. The hysteresis (A0) is the difference between the advance angle and the retreat angle: A0 = 0a-0r.

[0083] Opel test: EN 1096-2 or DIN61200 standard:

[0084] The Opel® friction test consists of rubbing the hydrophobic surface of the sample with a sheep's wool felt of hardness H1 subjected to a pressure load of 0.397 kg / cm², over an area of ​​1.5 cm², at a rate of 50 back-and-forth cycles per minute and a rotational speed of 6 revolutions per minute. A sample is considered satisfactory when, after 5000 back-and-forth cycles, the contact angle θ is still greater than or equal to 50°, the hysteresis is at most 30°, and the sample is free of optical defects.

[0085] UV resistance:

[0086] Resistance to UV radiation is evaluated using a Weather-O-meter® device equipped with a xenon arc lamp with a power of 4000 W (under the conditions of SAEJ 2412 standard with watering).

[0087] The sample is alternately exposed to a day phase with radiation whose spectrum is similar to the solar spectrum at ground level and a night phase. During the day phase, the irradiance at a wavelength of 340 nm is 0.55 W / m² / nm. The atmospheric conditions are 62°C and 50% RH. During the night phase, the temperature is lowered to 38°C and the humidity is increased to 95% RH with watering.

[0088] In the context of this application, a sample is deemed satisfactory when, after 1000 hours of exposure to UV radiation, the contact angle is still greater than or equal to 50° and the hysteresis is at most 30°.

[0089] The results are listed in Table 1 (performance with a single type of alkylsilyl group) and in Table 2 (performance in the case of a mixture of two alkylsilyl groups according to the invention). [Tables 1] Alkyie chain (Q 8 (initial) A8 (initial) UV (max duration: supported + 8 obtained) Opel test (max cycles supported + 8 / A8 obtained) -Cl 79» 15® >1500 h(78®) < 5000 (40® / 5Û®) 95° 17® >1500 h (56®) < 5000 (45c / 50®) 103° 18® 1000 h (55®) <5000 (65® / 50®) -Cs^rassW 103® 29® 1000 h(58®) 5000 -a 103° 20® 1000b(59®) 7500 (77® / 50®) -Cs 105° 25® 1000 h (58») >10000 (99® / 14°) -Cio 107e 15° 800 h(71®) >10000 (103® / 10®) <12 106® 15® SOS h(70®) >10000 (107® / 8®) -Key 108e 24$ 808 h(50®) >10000 (105® / !^®) triethoxystisne (fluoride reference) 110° 36° >2000 h(104®) < 5000 (60® / 55®)

[0090] The results in Table 1 show that glass samples grafted with a single type of alkylsilyl group, and whose alkyl chain comprises 6 to 16 carbon atoms (n=6 to 16), exhibit hydrophobic properties with good abrasion resistance. However, their resistance to UV radiation is not optimal.

[0091] For shorter chain alkylsilyl groups (Ci-C3 alkylsilyl group, i.e. comprising 1 to 3 carbon atoms), resistance to UV radiation is higher than that of samples grafted with a "long" chain alkylsilyl group, but abrasion resistance is less satisfactory. [Tables 2] Alpha chains Ra / Rà (G) Mass ratio (A / B) 8 (initial!) A6 (initial) UV (maximum duration supported + S obtained) Opel test (maximum cycles supported 4 8 / AS obtained) -Ci / -Cs 20 / 80 102 29 1200 (50®) >5000 (83® / 26®) -Ci / -Csa 30 / 70 95 23 nd >5000 (89® / 19®) -Ca / -C8 60 / 40 100 18 nd <5000 (48® / 50°) 58 / 50 94 15 1200 (52e) 5000 (5SV25®) 40 / 60 97 19 1400 (52e) 5000 (55® / 28°) -C3 / -C1S 80 / 20 101 24 1200 (53®)' <5000 {50® / 50®) 60 / 40 106 29 1500 (53®) <5009 (5G® / 40®) 50 / 50 103 19 1500 (57®) >10000 (Sl® / 29®) 40 / 60 106 22 1000 (59®) >10008 (S9® / 20®)

[0092] Table 2 shows that the grafted glass samples combining the two types of alkyl groups according to the invention exhibit very good hydrophobic properties. (initial values ​​of 0 and A0 excellent). The glass products according to the invention also exhibit good resistance over time to abrasion and UV, and this resistance over time can be further improved when the ratio of short to long chains is well chosen.

[0093] More specifically, by adding up to 50% of short C3 chains, it is possible to increase UV resistance by up to 50% compared to coatings comprising only C8 or C1 alkyl chains, without altering abrasion resistance.

Claims

Demands

1. A method for hydrophobicizing a glass substrate comprising the following successive steps: - formation of a primary layer, preferably comprising silicon oxide, on one of the surfaces of a glass substrate, - formation of a hydrophobic layer by applying, on the primary layer, a composition comprising at least two, preferably two, non-fluorinated alkylsilane compounds A and B, compound A having an alkyl chain Ra comprising 1 to 5 carbon atoms, and compound B having an alkyl chain Rb comprising 6 to 16 carbon atoms.

2. A process according to claim 1, wherein the non-fluorinated alkylsilane compounds A and B are compounds of formula R-Si-X 3 where: - R is an alkyl chain Ra or Rb as defined according to the preceding claim, and - X is a hydrolyzable group, preferably selected from a halogen, more particularly chlorine, and an alkoxy group comprising 1 to 3 carbon atoms, more particularly a methoxy or ethoxy group, more preferably an ethoxy group.

3. A method according to claim 1 or 2, wherein the alkyl chain Ra is linear and has the formula - (CH2)n i-CH3, where n is an integer from 1 to 5, preferably from 1 to 4, more preferably from 1 to 3, even more preferably n = 3.

4. A method according to any one of the preceding claims, wherein the alkyl chain Rb is linear and has the formula -(CH2)n i-CH3, where n is an integer from 6 to 16, preferably from 7 to 16, more preferably from 8 to 16, even more preferably from 8 to 12.

5. A process according to any one of the preceding claims, wherein the primary layer is made of silicon oxide and is formed by a sol-gel step in which a tetrachlorosilane and / or a tetraalkoxysilane, preferably a tetraethoxysilane, is hydrolyzed in acidic hydroalcoholic medium.

6. A method according to any one of the preceding claims, wherein the hydrophobic layer is formed by a sol-gel step in in which the non-fluorinated alkylsilane compounds A and B are hydrolyzed in acidic hydroalcoholic medium.

7. A method according to any one of the preceding claims, further comprising, after the hydrophobic layer formation step, a polishing step, preferably using a cloth soaked in a water / alcohol mixture, more preferably a water / isopropanol mixture.

8. A method according to any one of the preceding claims, wherein the mass ratio between compounds A and B in the composition is 20 / 80 to 80 / 20, preferably 20 / 80 to 60 / 40, more preferably 20 / 80 to 55 / 45, even more preferably 20 / 80 to 50 / 50.

9. A process according to any one of the preceding claims, wherein the alkylsilane compound A represents at least 20% of the non-fluorinated alkylsilane compounds in the composition, more preferably from 20% to 50%.

10. A process according to any one of the preceding claims, wherein the alkylsilane compound B represents at least 50%, preferably from 50% to 80% of the non-fluorinated alkylsilane compounds in the composition.

11. Hydrophobic glass product, capable of being obtained by the process according to any one of claims 1 to 10, comprising a glass substrate having a surface at least partially covered with a coating comprising: - a primary layer, preferably comprising silicon oxide, in contact with said surface of the substrate - a hydrophobic layer comprising at least two, preferably two, different non-fluorinated alkylsilyl groups Ga and Gb, grafted onto said primary layer, the Ga group having an alkyl chain Ra comprising 1 to 5 carbon atoms, and the Gb group having an alkyl chain Rb comprising 6 to 16 carbon atoms.

12. Hydrophobic glass product according to claim 11, wherein the alkyl chain Ra is linear and has the formula - (CH2)n i-CH3, where n is an integer from 1 to 5, preferably from 1 to 4, more preferably from 1 to 3, even more preferably n = 3.

13. A hydrophobic glass product according to claims 11 or 12, wherein the alkyl chain Rb is linear and has the formula - (CH2)n i-CH3, where n is an integer from 6 to 16, preferably from 7 to 16, more preferably from 8 to 16, even more preferably from 8 to 12.

14. Hydrophobic glass product according to any one of claims 11 to 13, wherein the primary layer of the hydrophobic glass product according to the invention has a thickness of 5 nm to 250 nm, preferably 10 nm to 100 nm, more particularly 15 nm to 75 nm.

15. Use of a hydrophobic glass product according to any one of claims 11 to 14 as glazing for motor vehicles or aircraft cockpits.