Method for making glass substrate hydrophobic

Abstract

The present invention relates to a method for hydrophobizing a glass substrate. The method includes the following series of steps: forming a primer layer, preferably silica, on one of the main surfaces of a glass substrate; 16 Alkyltrialkoxysilane and / or C8-C 16 The present invention also relates to a hydrophobic glass substrate obtained by the present invention, which comprises a transparent glass substrate coated on one of its main surfaces with a silica primer layer, the silica primer layer being a C8 to C 16 It is grafted with alkylsilyl groups.

Description

[Technical Field]

[0001] The present invention relates to glass substrates whose surfaces have been rendered hydrophobic by grafting with non-fluorinated alkylsilanes, and to a method for producing such substrates. [Background technology]

[0002] Hydrophobicity is required for side windows and windscreens in the transport sector, and in particular for automobiles, where, for obvious safety reasons, optimizing the transparency of the glazing unit even when it rains is essential: Raindrops should not stick to the outer surface of the glazing unit as much as possible, but should flow away easily under the influence of gravity or aerodynamic flow.

[0003] Two parameters used to characterize the hydrophobicity of the surface of a glazing unit are the water droplet contact angle (θ) and the contact angle hysteresis (Δθ).

[0004] The hydrophobicity of the window must of course withstand abrasion by the environment (water, UV radiation) and chemical attack for as long as possible.

[0005] It is generally known to increase the hydrophobicity of vehicle glazing units by grafting one of the perfluorinated alkylsilanes (perfluoroalkylsilanes) onto the surface of the glass sheet after previously preparing a silica primer layer by the sol-gel method, magnetron sputtering or chemical vapor deposition (CVD).

[0006] However, perfluorinated compounds are considered harmful to the environment and human health. The persistence of these compounds in the environment and the human body, combined with their adverse health effects, has led to increased regulatory pressure on their use in recent years, particularly through the European REACH and POPs regulations. This could lead to a large-scale ban on these compounds by 2025, or at the latest by 2030.

[0007] The object of the present invention is to propose a method for hydrophobizing glass substrates, in particular glass substrates intended for the automotive industry, which method makes it possible to obtain glazing units with satisfactory and lasting hydrophobicity without using perfluorinated compounds (perfluoro compounds).

[0008] As part of a study aimed at finding non-toxic molecules that could replace the perfluorinated alkylsilanes previously used to hydrophobize glass substrates, the applicant tested a number of hydrophobic functional silanes bearing fatty hydrocarbon chains.

[0009] Almost all of the alkylsilanes tested made it possible to achieve satisfactory water droplet contact angles (θ) greater than 90°, or greater than 95°, and in some cases greater than 100°, with hysteresis (Δθ) lower than those obtained after grafting with 1H,1H,2H,2H-perfluoroalkyltriethoxysilane (SiF5E), and also made it possible to achieve satisfactory resistance to ultraviolet light and satisfactory corrosion resistance. Summary of the Invention [Problem to be solved by the invention]

[0010] A technical problem encountered was the short lifespan of the hydrophobic coatings thus prepared: some of them had insufficient resistance to mechanical abrasion. [Means for solving the problem]

[0011] The present invention is 16 It is based on the discovery that alkylsilanes with aliphatic chains, in contrast to alkylsilanes with relatively short or relatively long hydrocarbon chains, make it possible to produce durable hydrophobic coatings on glass substrates, i.e. coatings with satisfactory resistance to mechanical abrasion, UV resistance and corrosion resistance.

[0012] The present application therefore relates to a method for hydrophobizing a glass substrate, the method comprising the following sequence of steps: - forming a primer layer, preferably silica, on one of the main surfaces of the glass substrate; - C8~C 16 Alkyltrialkoxysilane and / or C8-C 16 Grafting a layer of alkyltrichlorosilane onto the primer layer. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present application also relates to a glass substrate obtained by the above method. The hydrophobic glass substrate comprises a transparent glass substrate, which is covered on one of its main surfaces with a primer layer, preferably silica, and the primer layer is C 8~16 Alkylsilyl group, preferably linear C 8~16 It is grafted with alkylsilyl groups.

[0014] The glass substrate obtained by the method of the present invention is preferably a side window of an automobile.

[0015] According to the first embodiment, C8 to C 16 Alkyltrialkoxysilanes have the formula CH3(CH2) n SiR3 linear chain, where n=7-15, preferably n=7-11, and each R is C 1~3 It represents an alkoxy group, preferably a methoxy group or an ethoxy group.

[0016] According to another embodiment, C8 to C 16 Alkyltrichlorosilanes have the formula CH3(CH2) n It is an alkyltrichlorosilane of the formula SiR3, where n=7 to 15, preferably n=7 to 11, and each R represents a chlorine atom.

[0017] By n=7-15, it is meant that n can be any integer value between 7 and 15, including the upper and lower limits.

[0018] The best results, especially the best UV resistance and the best salt corrosion resistance, are achieved with linear C 10 Alkyl chains (n=9) were obtained.

[0019] To achieve good durability of the hydrophobic coating on glass substrates, it is necessary to first form a primer layer, preferably a silica primer layer, on the surface to be treated. For this primer layer to be effective in anchoring the alkylsilane hydrophobic coating on the substrate, it is important that it contains as many active silanol groups (Si-OH) as possible, i.e., groups that can react with the alkoxy functional groups of alkyltrialkoxysilanes or the silanol groups released by hydrolysis of the chlorine atoms of alkyltrichlorosilanes. It is also important to fully condense the silica primer layer before depositing the acidic aqueous-alcoholic solution containing alkyltrialkoxysilanes and / or alkyltrichlorosilanes. This is because if the silica layer is not sufficiently condensed, there is a risk that it will be removed or damaged during the formation of the hydrophobic functional layer.

[0020] Therefore, C8~C 16 Alkyltrialkoxysilane or C8-C 16 It is recommended that the grafting of alkyltrichlorosilane be carried out after the primer layer has dried at room temperature for at least 5 minutes, preferably 15 minutes. 16 Alkyltrialkoxysilane and / or C8-C 16 The step of grafting alkyltrichlorosilane onto the silica primer layer is advantageously carried out less than 2 hours, preferably less than 1 hour, after this step of drying the primer layer.

[0021] Furthermore, prior to the step of forming the primer layer, it is desirable to carry out a step of abrading the substrate using, for example, felt impregnated with an aqueous suspension of abrasive particles, followed by rinsing with water and drying.

[0022] The silica primer layer is formed by a sol-gel process in which tetrachlorosilane and / or tetraalkoxysilane, preferably tetraethoxysilane, is hydrolyzed in an acidic aqueous-alcoholic medium.

[0023] To carry out this step, a suitable amount of tetrachlorosilane or tetraalkoxysilane is dissolved in a water / alcohol mixture, typically a water / isopropanol mixture, the pH of which is pre-adjusted to a value between 1 and 3. The content of tetrachlorosilane and / or tetraalkoxysilane in this aqueous-alcoholic solution is advantageously between 0.1 and 1% by weight, preferably between 0.15 and 0.8% by weight. The molar ratio of water to silica precursor, i.e., the molar ratio of water to tetrachlorosilane or tetraalkoxysilane, is generally between 400 and 600, preferably between 450 and 550, in particular between 480 and 520.

[0024] It is preferable not to apply the aqueous-alcoholic solution immediately after dissolving the tetrachlorosilane and / or tetraalkoxysilane, but to allow the hydrolysis to occur at room temperature (20-25°C) over a period of 30 minutes to 4 hours, preferably 40 minutes to 3.5 hours, and especially 45 minutes to 3 hours. During this period, it is advisable to stir the solution to ensure good homogeneity of the reaction medium. Generally, it is not necessary to supply heat energy to the solution during this hydrolysis step.

[0025] In principle, the acidic aqueous-alcoholic solution of 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 immersion, curtain coating, spraying, or wiping. Preferably, spraying or spraying with a sprayer, as well as application with a fabric immersed in the aqueous-alcoholic solution of tetraalkoxysilane and / or tetrachlorosilane, are used.

[0026] After application to the surface of the glass substrate, the formed liquid film is allowed to dry for a period of at least 5 minutes, preferably at least 15 minutes.

[0027] After the first deposit has dried, the aqueous-alcoholic solution can be reapplied until the desired silica primer layer thickness is achieved.

[0028] The silica primer layer advantageously has a thickness of 5 nm to 250 nm, preferably 10 nm to 100 nm, in particular 15 nm to 75 nm.

[0029] Similar to the formation of the silica primer layer, the step of grafting the alkyltrialkoxysilane and / or alkyltrichlorosilane is carried out by a sol-gel process, in which the alkyltrialkoxysilane and / or alkyltrichlorosilane is hydrolyzed in an acidic aqueous-alcoholic medium, which can be carried out in a manner similar to that used to form the primer layer, except that the grafting of the alkyltrialkoxysilane or alkyltrichlorosilane is preferably carried out in a single application step.

[0030] The graft composition is C8 to C 16 Alkyltrialkoxysilane and / or C8-C 16 Acidic aqueous-alcoholic (water / isopropanol) solutions of alkyltrichlorosilanes. C8-C in acidic aqueous-alcoholic solutions. 16 Alkyltrialkoxysilane and / or C8-C 16 The content of alkyltrichlorosilanes is preferably 1 to 4% by weight, in particular 2.5 to 3.5% by weight, and is preferably of the formula CH3(CH2) n SiR3 linear C8~C 16 Alkyltrialkoxysilane (wherein n=7 to 11 and R is C 1~3 represents an alkoxy group).

[0031] H2O / C8-C of the acidic aqueous-alcoholic solution used for grafting 16Alkyltrialkoxysilane or H2O / C8~C 16 The molar ratio of alkyltrichlorosilane is 70-200, preferably 80-150, and particularly 90-140.

[0032] C8~C 16 Alkyltrialkoxysilane or C8-C 16 The aqueous-alcoholic solution of alkyltrialkoxysilanes is advantageously C8-C 16 Alkyltrialkoxysilane or C8-C 16 It is left at room temperature, preferably with stirring, for a period of about 30 minutes to about 3 hours to allow hydrolysis of the alkyltrialkoxysilane, and then applied by spraying, sprinkling, or wiping onto a glass substrate coated on one of its major surfaces with a silica primer layer.

[0033] In some cases, the inventors encountered the technical problem of a milky appearance of the resulting alkylsilane deposit. This visual problem was observed more particularly in the case of application by wiping. The treated surface of the glazing unit became slightly diffused, which unacceptably reduced the transparency and gloss of the glazing unit. C8-C 16 Alkyltrialkoxysilane and / or C8-C 16 This problem could be overcome by a polishing step carried out after the step of grafting the alkyltrichlorosilane layer. Advantageously, this polishing step is carried out by rubbing the surface with a cloth soaked in a solvent, advantageously a mixture of water and alcohol, until specular reflection is re-established over the entire treated surface. The water / alcohol mixture is preferably a water / isopropanol mixture, containing 30% to 90% by weight of water, preferably 50% to 80% by weight of water.

[0034] Evaluate the hydrophobicity of the deposit using standard procedures known in the art of hydrophobic coatings:

[0035] Contact angle measurement:

[0036] The contact angle (θ) of a water droplet at equilibrium is measured with a 3 μl droplet using a Kruess DSA-100 goniometer (Drop Shape Analyzer). The droplet is observed using a high-speed camera, which takes a photograph from which the contact angle is recorded. The higher the contact angle value, the more hydrophobic the surface of the tested sample.

[0037] Contact angle hysteresis measurement:

[0038] Contact angle hysteresis is also measured using a Kruess DSA goniometer. The instrument deposits a 5 μl droplet of water onto the hydrophobic surface of the sample being tested. Water is then injected (at a rate of 0.5 μl / min) into the droplet to increase its volume. The increase in volume is accompanied by an increase in the contact angle. The volume is increased until a contact angle plateau is reached. The contact angle value at the plateau (averaged over at least three repeats) is used to calculate the advancing angle (θ a The device then slowly aspirates the water from the drop, returning it to a smaller volume. Suction continues until the contact angle reaches a plateau. The value of the contact angle at the plateau (averaged over at least three repeats) is the receding angle (θ r ) is called.

[0039] Hysteresis (Δθ) is the difference between the advancing and receding angles: Δθ=θ a -θ r

[0040] The objective is generally to obtain as low a water droplet contact angle hysteresis as possible.

[0041] Opel test: standard EN1096-2 or DIN61200

[0042] Opel™ friction test is 0.397 kg / cm 2 Sheep wool felt of hardness H1 subjected to a pressure load of 1.5 cm 2The test consists of rubbing the hydrophobic surface of the sample over an area of ​​1000 mm at a speed of 50 double strokes per minute and a rotation speed of 6 rpm. After 5000 double strokes, the sample is considered satisfactory if the contact angle θ is still greater than 90° and the sample is free of optical defects.

[0043] Salt corrosion resistance, as described in the NF ISO 9227 standard, is measured by a test known as the NSS test. This test involves spraying fine droplets of neutral (pH 7) salt water (50 g / l NaCl solution) onto a substrate inclined at 20° to the vertical for 14 days at a temperature of 35°C and a relative humidity of 100%. After 7 days, or better still, at the completion of the 14-day test, the contact angle should always be greater than 90° and the hysteresis should be less than 30°.

[0044] UV resistance: Measurements were carried out using a Weather-O-meter™ equipped with a 4000 W xenon arc lamp (under standard SAEJ 1885 or SAE-J 2527 (2004) conditions).

[0045] The specimens are continuously exposed to radiation whose spectrum is similar to the terrestrial solar spectrum. The irradiance at 340 nm is 0.55 W / m 2 / nm.

[0046] In the context of this application, a sample is considered satisfactory if, after 1000 hours of exposure to UV radiation, the contact angle is still greater than 70° and the hysteresis is less than 30°. example

[0047] Glass substrate samples are functionalized with different alkyltrialkoxysilanes in the following manner:

[0048] A 10 cm x 10 cm sample is cleaned by polishing with felt impregnated with an aqueous suspension containing 20% ​​cerium oxide particles. The polished sample is rinsed with distilled water and dried with compressed air.

[0049] To form the silica primer layer, a 0.3% solution of tetraethoxysilane (TEOS) is prepared in a mixture of isopropanol and water at pH = 1 (0.1 N HCl in demineralized water). The HO / TEOS ratio is 500. Stirring is carried out at room temperature for 1 hour. The solution thus prepared can be used for approximately 4 hours.

[0050] After stirring at room temperature for 1 hour, the solution is sprayed onto a cleaned glass sample and allowed to dry for approximately 15 minutes.

[0051] Immediately afterwards, a 3% solution of alkyltriethoxysilane in an acidic isopropanol / water mixture (0.1 N HCl, pH = 1) is applied by spraying onto the silica primer layer thus obtained, the 3% solution of alkyltriethoxysilane being prepared one hour beforehand in a molar ratio of 94.5 HO / alkyltriethoxysilane and maintained under mechanical stirring.

[0052] This is allowed to dry at room temperature for 15 minutes and then the excess (whitish marks) is removed by wiping with a cloth saturated with isopropanol.

[0053] Table 1 shows the water droplet contact angle (θ), hysteresis (Δθ), salt corrosion resistance, ultraviolet (UV) resistance and abrasion resistance (Opel test) for all samples prepared in this way, compared to prior art samples prepared using perfluoroalkyltrialkoxysilanes.

[0054] [Table 1]

[0055] C8 to C on silica primer layer 16 It is observed that only glass sheets grafted with layers of alkylsilanes exhibit sufficiently durable hydrophobicity. For shorter chain alkylsilanes (branched C5 and C6), the abrasion resistance is insufficient.

[0056] It should be noted that C 10 Alkylsilanes make it possible to obtain hydrophobic glass substrates with particularly durable hydrophobic properties, ie salt corrosion resistance of more than 14 days and UV resistance of more than 1000 hours.

Claims

1. 1. A method for hydrophobizing a glass substrate, comprising the following steps: - forming a primer layer, preferably silica, on one of the main surfaces of said glass substrate; - C on the primer layer ８ ~C １６ Alkyltrialkoxysilane and / or C ８ ~C １６ grafting a layer of alkyltrichlorosilane; - optionally a polishing step using a cloth soaked in a water-alcohol mixture containing from 30% to 90% by weight of water; Including, Said C ８ ~C １６ Alkyltrialkoxysilanes are compounds of the formula CH ３ (CH ２ ) ｎ SiR ３ where n=7-15 and each R is C １～３ represents an alkoxy group, preferably a methoxy group or an ethoxy group, ８ ~C １６ Alkyltrichlorosilanes have the formula CH ３ (CH ２ ) ｎ SiR ３ wherein n=7 to 15 and each R represents a chlorine atom; method.

2. Said C ８ ~C １６ The alkyltrialkoxysilane has the formula CH ３ (CH ２ ) ｎ SiR ３ where n=7-11 and each R is C １～３ 2. The method according to claim 1, characterized in that it represents an alkoxy group, preferably a methoxy or ethoxy group.

3. Said C ８ ~C １６ Alkyltrichlorosilanes have the formula CH ３ (CH ２ ) ｎ SiR ３ 2. The method of claim 1, wherein n=7 to 11 and each R represents a chlorine atom.

4. 4. The method according to claim 1, wherein the primer layer is made of silica and the silica primer layer is formed by a sol-gel process in which tetrachlorosilane and / or tetraalkoxysilane, preferably tetraethoxysilane, is hydrolyzed in an acidic aqueous-alcoholic medium.

5. 5. The method according to claim 4, characterized in that the sol-gel process for forming the silica primer layer is carried out using an acidic aqueous-alcoholic solution containing 0.1% to 1% by weight of tetraalkoxysilane and / or tetrachlorosilane.

6. H of the acidic aqueous-alcoholic solution ２ O / tetraalkoxysilane or H ２ 6. The process according to claim 5, wherein the molar ratio of O / tetrachlorosilane is 400 to 600, preferably 450 to 550, in particular 480 to 520.

7. 7. The method according to claim 5, wherein the aqueous-alcoholic solution of tetraalkoxysilane and / or tetrachlorosilane is left at room temperature for about 30 minutes to about 4 hours before being applied to the glass substrate by immersion, curtain coating, spraying or wiping.

8. C ８ ~C １６ Alkyltrialkoxysilane and / or C ８ ~C １６ The step of grafting alkyltrichlorosilane is carried out by a sol-gel process, and in the sol-gel process, ８ ~C １６ Alkyltrialkoxysilane and / or the C ８ ~C １６ 8. The method according to claim 1, wherein the alkyltrichlorosilane is hydrolyzed in an acidic aqueous-alcoholic medium.

9. C ８ ~C １６ Alkyltrialkoxysilane and / or C ８ ~C １６ The step of grafting alkyltrichlorosilane comprises 1 wt. % to 4 wt. % of C ８ ~C １６ Alkyltrialkoxysilane and / or C ８ ~C １６ Alkyltrichlorosilanes, preferably of the formula CH ３ (CH ２ ) ｎ SiR ３ Linear C ８ ~C １６ It is carried out using an acidic aqueous-alcoholic solution containing alkyltrialkoxysilanes, where n=7-11 and R is C １～３ The method of claim 8 wherein the alkyl group represents an alkoxy group.

10. H of the acidic aqueous-alcoholic solution ２ O / Alkyltrialkoxysilane or H ２ 10. The process according to claim 9, wherein the molar ratio of O / alkyltrichlorosilane is between 70 and 200, preferably between 80 and 150, in particular between 90 and 140.

11. C ８ ~C １６ Alkyltrialkoxysilane and / or C ８ ~C １６ 11. The method of claim 9 or 10, wherein the aqueous-alcoholic solution of alkyltrichlorosilane is left at room temperature for about 30 minutes to about 3 hours before being applied by spraying or wiping to the glass substrate coated on one of its major surfaces with the silica primer layer.

12. C ８ ~C １６ Alkyltrialkoxysilane and / or C ８ ~C １６ 12. The method according to any one of claims 1 to 11, characterized in that the grafting of alkyltrichlorosilane is carried out after the silica primer layer has been dried at room temperature for at least 5 minutes.

13. A hydrophobic glass substrate obtainable by the method according to any one of claims 1 to 12, comprising a transparent glass substrate, the transparent glass substrate being coated on one of its main surfaces with a silica primer layer, the silica primer layer comprising a linear C ８ ~C １６ The linear C ８ ~C １６ Alkyl is a group of the formula CH ３ (CH ２ ) ｎ wherein n=7 to 15.

14. 14. The hydrophobic glass substrate of claim 13, wherein n is between 7 and 11, inclusive, preferably n=9.

15. 15. Hydrophobic glass substrate according to claim 13 or 14, characterized in that the silica primer layer has a thickness of 5 nm to 250 nm, preferably 10 nm to 100 nm, in particular 15 nm to 75 nm.

16. The hydrophobic glass substrate according to any one of claims 13 to 15, which is an automobile side window.

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