Glass product and production method

Abstract

The invention relates to a method for hydrophobizing a glass substrate, the method comprising the following consecutive steps: - forming a primer layer, preferably comprising silicon oxide, on one of the surfaces of a glass substrate, - forming a hydrophobic layer by applying, on the primer layer, a composition comprising at least two non-fluorinated alkylsilane compounds A and B, the compound A having an alkyl chain Ra comprising 1 to 5 carbon atoms, and the compound B having an alkyl chain Rb comprising 6 to 16 carbon atoms. The invention also relates to a hydrophobic glass product that can be obtained by the method according to the invention, comprising a glass substrate, one surface of which is at least partially covered with a coating comprising: - a primer 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 primer layer, the group Ga having an alkyl chain Ra comprising 1 to 5 carbon atoms, and the group Gb having an alkyl chain Rb comprising 6 to 16 carbon atoms.

Description

Description Title of the invention: Glass product and manufacturing process. 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 and 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 a known practice to treat the outer surface of glazing, usually glass and therefore hydrophilic, with a hydrophobic coating that minimizes the spreading and adhesion of water droplets to the surface and facilitates their removal. Specifically, water droplets and film must be able to flow and be efficiently removed, for example, by gravity or by the effect of airflow over the glazing when the vehicle is in motion, possibly in combination with the action of windshield wipers.Thus, hydrophobic treatments make it possible to optimize the transparency of the glazing over a sufficiently large area by preventing the formation of continuous water films which drastically degrade the optical qualities.

[0003] The hydrophobicity of a substrate surface is commonly described by the contact angle (6) between a water droplet and the substrate (the angle 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 surface and the more hydrophobic the substrate surface. Generally, a surface is considered hydrophobic when the contact angle is greater than 90°.

[0004] However, the hydrophobic properties of a substrate can also be described using an additional parameter: the contact angle hysteresis (A6), 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 the droplet adhering more or less strongly to the substrate, involving cohesive and / or adhesive forces, and which can be linked to chemical or geometric heterogeneities on the surface). The contact angle hysteresis (AO) is the difference between the extreme values ​​that the contact angle can take, these extreme values ​​being called the advance angle 0 aand the recoil angle 0r. These extreme angles can be determined by measuring the contact angles of a drop on an inclined plane (the limits of angles at which the drop no longer remains stationary on the sloping substrate) or by increasing or decreasing the volume of a drop on a horizontal substrate (the limits of angles at which the diameter of the drop increases or decreases). The hysteresis of the contact angle reflects the ability of a drop to move or slide on the surface of the substrate. The smaller its value, the less the surface resists the movement of the drops 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 due to abrasion (caused, for example, by friction from atmospheric dust or the repeated action of windshield wipers), the natural environment (such as water causing hydrolysis of the coatings, or 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.

[0006] Furthermore, particularly in the case of aircraft, it is important to be able to restore the hydrophobic function. Hydrophobic coating processes for glazing must therefore be applicable in situ, that is, on glazing mounted on the aircraft, to allow for quick and easy maintenance. Consequently, a good hydrophobic treatment, in addition to being durable, should 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, usually 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. Their persistence in the environment and the human body, coupled with their adverse health effects, has recently increased regulatory pressure on 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] Furthermore, 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 satisfactory hydrophobic properties that last over time, without resorting to perfluorinated compounds.

[0011] It is to the applicant's credit that she 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 G a and Gb, grafted onto said primary layer, the G group afeaturing an alkyl chain Ra comprising 1 to 5 carbon atoms, and the Gb group featuring 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 enables the production of substrates coated with a hydrophobic material that, surprisingly, exhibit hydrophobic properties comparable to those of perfluorinated compound-based coatings, with a contact angle generally exceeding 90°. Furthermore, the combination of grafted groups allows for improved performance in both abrasion and UV resistance compared to substrates obtained with a single type of grafted group. These properties are particularly advantageous in the transportation sector, such as automotive, rail, and aerospace, where glazing has stringent 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 to include the boundaries.

[0019] Unless otherwise stated, the term "free" from a type of compound means that this type of compound is not added to the composition or mixture in question.

[0020] 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 (6) 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 0 and increase in A0). For the purposes of the present invention, the "hydrophobic" properties of a surface (including water-repellent 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 the mobility of drops (hysteresis of at most 30°) is considered functional, that is to say, the coating effectively limits the formation of water films and maintains sufficient optical qualities.

[0021] 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.

[0022] 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, curved, or arched (such as 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%.

[0023] The prior formation of a primary, 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 coating's durability. A "primary layer" is an initial layer applied to the substrate to promote the adhesion of the subsequent hydrophobic layer. The primary layer is preferably made of an inorganic material. Preferably, the primary layer contains hydroxyl groups, more preferably silanol (Si-OH) groups. Specifically, during the primary layer formation step, the silicon content at the surface, and in particular the silicon dioxide content, is increased, allowing the generation of active silanol (Si-OH) groups, i.e., groups capable of reacting with alkylsilane compounds.

[0024] Preferably, the primary layer comprises silicon dioxide. Preferably, the primary layer is essentially silica (SiO2). For example, the primary layer comprises at least 80% by mass of silica, preferably at least 90%, and more preferably at least 95%, relative to the total mass of the primary layer.

[0025] The formation of the primary layer can be achieved by any known technique.

[0026] Preferably, the primary layer is formed by applying a solution comprising a tetrachlorosilane and / or a tetraalkoxysilane, preferably a tetraethoxysilane. Preferably, the applied solution is an acidic hydroalcoholic solution.

[0027] More preferably, the formation of the primary layer comprising the silicon oxide is carried out by a sol-gel step in which a tetrachlorosilane and / or a tetraalkoxysilane, preferably tetraethoxysilane, is hydrolyzed in an acidic hydroalcoholic medium.

[0028] 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.

[0029] 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 complete hydrolysis of tetrachlorosilane and / or tetraalkoxysilane.

[0030] The acidic hydroalcoholic solution of tetrachlorosilane / tetraalkoxysilane or tetrachlorosilane can be applied by any technique allowing the formation of a A thin liquid film is applied to the surface of the substrate. Examples of application methods include immersion, liquid curtain, spraying, or wiping. For aircraft regeneration, wiping is the most suitable. Preferably, spraying or nebulization and application with a cloth soaked in a hydroalcoholic solution of tetraalkoxysilane or tetrachlorosilane are used.

[0031] 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.

[0032] Optionally, after the initial primary layer has dried, the application of the tetrachlorosilane and / or tetraalkoxysilane hydroalcoholic solution can be repeated until the desired primary layer thickness is achieved. 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 specifically from 15 nm to 75 nm.

[0033] The primary layer formation step is then followed by a hydrophobic layer formation step, specifically a step involving the grafting of alkylsilyl groups from 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.

[0034] Thus, the hydrophobicization process according to the invention comprises a step of forming a hydrophobic layer by applying, to 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. More particularly, the step of forming the hydrophobic layer comprises grafting, onto the primary layer, at least two different non-fluorinated alkylsilyl groups G a and Gb, the G group a featuring an alkyl chain Ra comprising 1 to 5 carbon atoms, and the Gb group featuring an alkyl chain Rb comprising 6 to 16 carbon atoms.

[0035] Preferably, during the hydrophobic layer formation stage, the applied composition is a hydroalcoholic composition, preferably acidic.

[0036] 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 usable according to the invention have a hydrolyzable group X directly bonded to a silicon atom (X-Si). In other words, the usable alkylsilane compounds are capable of reacting with water, in particular to form a silanol group (Si-OH). The alkylsilane compounds according to the invention are monomeric compounds. They 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.

[0037] It is understood that, during the hydrophobic layer formation step, the composition does not include any syl compounds other than non-fluorinated alkylsilane compounds as defined above. For example, the composition does not include any polymeric syl compounds. In other words, the composition is free of syl compounds other than the monomeric, non-fluorinated alkylsilane compounds defined according to the invention. More specifically, the syl compounds present in the composition are selected from among the monomeric, non-fluorinated alkylsilane compounds of the general formula R-Si-Xs, where R is an alkyl chain as defined above (Ra or Rb), and X is a hydrolyzable group.

[0038] Preferably, during the hydrophobic layer formation step, the applied composition comprises two non-fluorinated alkylsilane compounds A and B as described previously.

[0039] 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, and more preferably greater than or equal to 7. In other words, An = n b -n a > 3, preferably > 5, more preferably > 7 (n b being the number of carbons in the alkyl chain Rb and n a being the number of carbons in the alkyl chain Ra).

[0040] More specifically, 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 R b ), And - X is a hydrolyzable group, that is, an atom or group that can be released in an aqueous or hydroalcoholic medium.

[0041] Preferably, the hydrolyzable group X is a halogen, for example 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.

[0042] The alkylsilane compound A, or its alkylsilyl group G a , may have an alkyl chain -Ra having the molecular formula -C n H 2n+ 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.

[0043] 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.

[0044] The alkylsilane compound B, or its alkylsilyl group Gb, may have an alkyl chain -Rb with the molecular formula -C n H 2n+ 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.

[0045] Advantageously, 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, for example from 8 to 10.

[0046] 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.

[0047] The formation of the hydrophobic layer can be achieved by any known technique.

[0048] Advantageously, the hydrophobic layer is formed 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 alkylsilyl groups G a and Gb of compounds A and B are grafted onto the primary layer. This This step can be implemented in a similar manner to that used for the formation of the primary layer.

[0049] 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.

[0050] 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, and even more preferably from 20 / 80 to 50 / 50. Depending on the alkyl chain pairs used, the resistance performance can be further improved by using appropriate mass ratios.

[0051] 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 hydrophobic coating's resistance to UV radiation.

[0052] 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 abrasion resistance of the hydrophobic coating and an initial contact angle greater than 90°.

[0053] Preferably, the mass content of alkylsilane A compound in the hydroalcoholic composition is 0.2% to 2% relative to the mass of the composition.

[0054] 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.

[0055] 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.

[0056] 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 primary layer. Preferably, the hydroalcoholic composition is applied by spraying, watering or wiping onto the primer layer.

[0057] 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.

[0058] According to another 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 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.

[0059] 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 G a and Gb, grafted onto said primary layer, the G group a featuring an alkyl chain Ra comprising 1 to 5 carbon atoms, and the Gb group featuring an alkyl chain Rb comprising 6 to 16 carbon atoms.

[0060] Preferably, the hydrophobic layer comprises two different non-fluorinated alkylsilyl groups (G a and Gb as defined previously).

[0061] Preferably, in the glass product according to the invention, the difference in the number of carbons An between the alkyl chains Ra and R b (An = n b -n a ) is greater than or equal to 3, preferably greater than or equal to 5, more preferably greater than or equal to 7.

[0062] The alkylsilyl group G a may have an alkyl chain -Ra having the molecular formula -CnHzn+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.

[0063] 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.

[0064] The alkylsilyl group Gb may have an alkyl chain -Rb having the empirical formula -CnHzn+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.

[0065] Advantageously, 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, for example 8 to 10.

[0066] According to a particular embodiment, the hydrophobic layer of the glass product according to the invention comprises two non-fluorinated alkylsilyl groups G a and Gb, grafted onto said primary layer, the G group a featuring an alkyl chain Ra comprising 1 to 4 carbon atoms, and the Gb group featuring an alkyl chain Rb comprising 7 to 16 carbon atoms.

[0067] 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.

[0068] Advantageously, the hydrophobic glass product according to the invention has, after manufacture, a contact angle 6 greater than 70°, preferably greater than 90°, more preferably greater than 95°, even more preferably greater than 100°.

[0069] Advantageously, the hydrophobic glass product according to the invention exhibits, after manufacture, a contact angle hysteresis A6 of no more than 30°.

[0070] Advantageously, the ratio of mass contents of alkylsilyl groups G a / G b 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.

[0071] It is understood that the hydrophobic layer of the product or process according to the invention is free of fluorinated compound.

[0072] The process and hydrophobic glass product according to the invention offer the advantage of producing glazing with excellent 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 by adjusting the alkyl chain ratios used to optimize abrasion resistance and / or UV resistance as needed for specific applications. Examples

[0073] The invention is illustrated by means of the non-limiting examples below, highlighting the hydrophobic properties obtained.

[0074] Initially, different hydroalcoholic compositions are prepared, comprising one to two alkylsilane compounds of different alkyl chain lengths R (listed in Table 1).

[0075] Several samples of transparent glass substrates are functionalized using these different compositions according to the method detailed below.

[0076] Each 10 cm x 10 cm sample is cleaned by polishing with a felt pad impregnated with an aqueous suspension containing 20% ​​cerium oxide particles. The polished sample is rinsed with distilled water and dried with a dry cloth.

[0077] 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% acid water (0.3N HCl) and 90% isopropanol. The solution is stirred for 30 minutes 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.

[0078] 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 alkylsilane compound(s) (in the proportions given in Table 1 for a mixture of two compounds) in a water / alcohol mixture comprising 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 composition of alkylsi lanes is applied to the primary layer by wiping. The substrate thus coated with the hydrophobic layer is left to dry for approximately 15 minutes at room temperature.

[0079] 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.

[0080] In a second step, the hydrophobic properties of the glass products obtained are evaluated using procedures well known in the field and described below. Measurement of the contact angle:

[0081] The contact angle of a water droplet (6) at equilibrium is measured using a Krüss DSA100 Drop Shape Analyzer goniometer on a 3 lm droplet. The droplet is observed using a high-speed camera which takes pictures from which the contact angle is then recorded.

[0082] The results obtained in Table 1 are generally good, with "initial" contact angles generally greater than 90°. Measurement of contact angle hysteresis:

[0083] Contact angle hysteresis is also measured using a Krüss DSA100 Drop Shape Analyzer goniometer. The instrument 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 continues until the contact angle remains constant. The value of this contact angle (averaged over at least three repetitions) is called the advance angle (θ). The instrument then gradually aspirates the water from the droplet to return it to a smaller volume. Aspirating the water is continued until the contact angle remains constant. The recoil angle (θ) is called the The value (average over at least three repetitions) of this contact angle. The hysteresis (A0) is the difference between the advance angle and the recoil angle: A0 = 0a -0r. Opel test: EN 1096-2 or DIN61200 standard:

[0084] The Opel® friction test involves rubbing the hydrophobic surface of the sample with a sheep's wool felt of H1 hardness subjected to a pressure load of 0.397 kg / cm². 2 , on a surface of 1.5 cm 2 at a speed of 50 back-and-forth cycles per minute and a rotation speed of 6 revolutions per minute. A sample is considered satisfactory when, after 5000 back-and-forth cycles, the contact angle 0 is always greater than or equal to 50°, the hysteresis is at most 30°, and the sample is free of optical defects. UV resistance:

[0085] UV resistance is evaluated using a Weather-O-meter® device equipped with a 4000 W xenon arc lamp (under SAEJ 2412 standard conditions with watering).

[0086] 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. 2 / nm. 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.

[0087] For the purposes 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°. 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). [Table 1]

[0088] 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. For shorter chain alkylsilyl groups (C1-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. [Table 2]

[0089] Table 2 shows that the grafted glass samples combining the two types of alkyl groups according to the invention exhibit very good hydrophobic properties (excellent initial values ​​of 0 and AO). The glass products according to the invention also exhibit good long-term resistance to abrasion and UV radiation, and this long-term resistance can be further improved when the ratio of short to long chains is carefully selected.

[0090] In particular, by adding up to 50% of short C3 chains, it is possible to increase UV resistance by more than 50% compared to coatings containing only C8 or C1 alkyl chains, without altering abrasion resistance.

Claims

Demands 1. A process 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 application, on the primary layer, of 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-Xs where: - R is an alkyl chain Ra or Rb as defined according to the preceding claim, and - X is a hydrolyzable group, preferably chosen 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)ni-CH3, where n is an integer from 1 to 5, preferably from 1 to 4, more preferably from 1 to 3, more preferably from 2 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)ni-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 an acidic hydroalcoholic medium.

6. A process according to any one of the preceding claims, wherein the hydrophobic layer is formed by a sol-gel step 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, obtainable by the process according to any one of claims 1 to 10, 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 - a hydrophobic layer comprising at least two, preferably two, different non-fluorinated alkylsilyl groups G a and G b grafted onto said primary layer, the G group a featuring an alkyl chain Ra comprising 1 to 5 carbon atoms, and the G group b featuring an Rb alkyl chain 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)ni-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. Hydrophobic glass product according to claims 11 or 12, wherein the alkyl chain Rb is linear and has the formula - (CH2)ni-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.

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