Composition and method for cleaning and regenerating the hydrophobicity of the surface of a transparent polymeric material of high optical quality

Abstract

Disclosed is a composition for cleaning and regenerating the hydrophobicity of the surface of a transparent polymeric material of high optical quality, characterized in that it comprises 20% to 40% by weight of a first liquid mixture of 0.2% to 3% by weight of paraffin and 97% to 99.8% by weight of a petroleum solvent that lies between heptane and decane, and 50% to 85% by weight of a second liquid mixture of 0.2% to 8% by weight of a surfactant having a molecular weight at most equal to 150 g / mol, 2-butoxyethanol, and 4% to 15% by weight of ethanol, the remainder to 100% being water; a method for cleaning and regenerating the hydrophobicity of the surface of a transparent polymeric material of high optical quality by means of this composition.

Description

[0001] Description

[0002] Title of the invention: Composition and method for cleaning and regenerating the hydrophobic coating on the surface of a transparent, optically high-quality polymer material

[0003] [1] Clear visibility must be ensured on aircraft windows under various climatic conditions, particularly in rain. Water on the windows can impair vision and compromise flight safety (including ground phases). The use of windshield wipers is a common solution to improve visibility on aircraft in rainy weather, but this solution is demanding as it requires:

[0004] -the integration of windshield wipers which are complex pieces of equipment to size due to their high aerodynamic load;

[0005] -the swept area is partial due to the sweepable shapes (portions of discs) being different from the shapes of the glazing;

[0006] -the windshield wiper (and motors) induces penalties in terms of mass, electrical consumption and drag;

[0007] -the windshield wiper is an active system whose failure management is complex (brushes, motor, dedicated and general power supply);

[0008] -wipeability is complex on non-developable glazing shapes;

[0009] -risk of scratching the windows;

[0010] -At high speeds, windshield wipers become less effective in heavy rain.

[0011] [2] Thus, hydrophobic solutions, as a substitute for or in addition to windshield wipers, can improve aircraft visibility. Solutions based on perfluorinated products bonded to the surface of glass windows have been developed, but perfluorinated solutions are polluting and, moreover, these solutions are only compatible with (mineral) glass. Solutions based on paraffin solubilized in heptane-type petroleum solvents have been developed. They are applied to the surface of the windows by wiping and polishing. Hydrophobic solutions are not permanent; they require frequent regeneration, which, for paraffin-based solutions, can be every few weeks. This maintenance is burdensome.

[0012] [3] The inventors have designed a hydrophobic cleaning solution that provides hydrophobic performance during normal cleaning operations on glazing with an organic external surface. Thus, providing hydrophobic performance does not require any additional maintenance beyond existing procedures.

[0013] [4] To this end, the invention relates to a hydrophobic cleaning and regeneration composition for the surface of a transparent polymer material of high optical quality, characterized in that it comprises 20 to 40% by mass of a first liquid mixture of 0.2 to 3% by mass of paraffin and 97 to 99.8% by mass of a petroleum solvent between heptane and decane, of linear, branched and cyclic form including mixtures thereof, and 50 to 85% by mass of a second liquid mixture of 0.2 to 8% by mass of a surfactant of molecular mass not exceeding 150 g / mol, which is 2-butoxyethanol, 4 to 15% by mass of ethanol and the remainder 100% water.

[0014] [5] It should be noted that the cleaning and hydrophobicizing solution of this invention also allows, with the same application protocol, the cleaning of mineral glass glazing, but the hydrophobic character is only provided – regenerated – to transparent polymer materials (of high optical quality), but not to mineral glass. The main examples are polycarbonate (PC), poly(methyl methacrylate) (PMMA), poly(ethylene terephthalate) (PET), in particular as a protective film applied to the external surface of plastic or glass glazing, and polyurethane (PU) (for example, but not limited to, as a protective varnish on PC or PET film).

[0015] [6] Achieving cleaning performance is generally contradictory to achieving hydrophobic performance, because cleaning often requires surfactants (or detergents) that tend to remain on the surface of the hydrophobic deposit. This induces wetting defects in the hydrophobic coating. This does not significantly alter the droplet angle but increases droplet adhesion (associated with contact angle hysteresis), which is highly detrimental to water removal.

[0016] [7] Thus, the inventors have implemented detergents with a low molecular weight and have been able to establish that they are sufficiently volatile so as not to remain on the surface of the treated glass and not to disrupt the wetting performance. The detergent therefore has a molecular weight of less than 150 g / mol. The two phases of the composition are immiscible and must be emulsified before application. [8] The composition of the invention provides, at the usual frequency of cleaning operations, a perfectly clean surface and perfect regeneration of the hydrophobic function, without any such additional regeneration being necessary. In particular, it is sufficient to apply the composition by wiping, as will be seen below, to the windshield of a helicopter, once each day of its use.Compared to specifically hydrophobic solutions based on solvent-based paraffin, the hydrophobic cleaning solution allows for frequent regeneration of the hydrophobic function without additional maintenance compared to glazing that would not be functionalized hydrophobic.

[0017] [9] Conveniently, the composition of the invention is obtained by mixing a hydrophobic paraffin-type solution in a petroleum solvent and a cleaning solution, specifically:

[0018] -a hydrophobic solution based on paraffin solubilized in an alkane (the said first liquid mixture), and

[0019] -a hydroalcoholic solvent-based cleaning solution with a low molecular weight surfactant (the said second liquid mixture).

[0020]

[0010] Preferably, the composition of the invention comprises at most 35% by mass of the first liquid mixture.

[0021]

[0011] Preferably, the first liquid mixture comprises 0.5 to 2.5, preferably at most 2% by mass of paraffin.

[0022]

[0012] The petroleum solvent is between heptane and decane, in linear, branched and cyclic form including mixtures thereof.

[0023]

[0013] Preferably, the second liquid mixture comprises 0.5 to 6, preferably at most 4% by mass of a surfactant with a molecular mass of at most 150 g / mol.

[0024]

[0014] The surfactant with a molecular mass of at most 150 g / mol is 2-butoxyethanol.

[0025]

[0015] Preferably, the second liquid mixture comprises 5 to 12% by mass of ethanol.

[16] The invention also relates to a method for cleaning and restoring the hydrophobic coating of the surface of a transparent, optically high-quality polymer material, characterized in that a cloth is soaked with a composition described above, the surface is rubbed with this cloth, the liquid deposit from the soaked cloth is allowed to dry on the surface, and then the surface is rubbed with a dry cloth to restore vision through the optically high-quality polymer material. Before soaking the cloth, it is preferable to shake the hydrophobic cleaning mixture. A whitish deposit develops as the hydrophobic cleaning solution dries. Rubbing the surface with a dry cloth restores the optical quality of the glazing by polishing. The resulting surface is clean and hydrophobic.

[0026]

[0017] The invention will be better understood in light of the following example.

[0027]

[0018] Example

[0028] A first liquid mixture of 2% by mass of paraffin and 98% by mass of heptane is mixed with a second liquid mixture of 2% by mass of 2-butoxyethanol, 8% by mass of ethanol, and 90% by mass of water. The two mixtures—immiscible liquid solutions—are thus emulsified.

[0029]

[0019] A cloth is soaked in such mixtures in different proportions, and then the surface of PMMA sheets is rubbed to deposit each mixture onto a sheet. The deposited treatment mixture is left to air dry. A whitish deposit thus appears on the coated surface. A dry cloth is then rubbed over the surface to restore high optical quality transparency through each treated PMMA sheet. The effective cleaning of each surface is visible to the naked eye, evidenced by the absence or disappearance of dust, streaks, marks, etc., affecting the transparency of the sheet. The hydrophobic nature of each surface is then tested according to the composition of the coating applied to it.

[0030]

[0020] [Fig. 1] represents on the one hand the detachment volume of water drops in pl on a surface inclined at 45° (curve drawn between small disks), scale of values ​​on the vertical axis on the right, and on the other hand the angle of contact with water in ° of water drops of 4 pl (curve drawn between small squares), scale of values ​​on the vertical axis on the left, as a function of the mass percentage of the first liquid mixture (scale of values ​​on the horizontal axis).

[0031]

[0021] It can be seen that the volume of water droplet detachment increases between 0 and 10% by mass of the initial liquid (hydrophobic) mixture, then decreases sharply between 10 and 20%, and then more slowly from 20 to 100%. In other words, good hydrophobicity is observed from a mass proportion of 20% of the initial hydrophobic mixture, and by adding more of this hydrophobic mixture between 20 and 100%, the gain in hydrophobicity is moderate, and the cleaning capacity is lost.

[0032]

[0022] This is confirmed by the water contact angle curve for 4 µm droplets. This angle increases sharply between 0 and 20% by mass of the first liquid mixture (hydrophobic), then only slightly from 20 to 100%. A proportion of 20 to 40%, preferably not exceeding 35% by mass, of the first liquid mixture (hydrophobic), and therefore 60 to 80%, and preferably not exceeding 65%, of the second liquid mixture (cleaning agent) provides both perfect cleaning and perfect regeneration of hydrophobicity.

Claims

Demands

1. A cleaning and hydrophobic surface regeneration composition for a transparent polymer material of optical quality required for aeronautical glazing, characterized in that it comprises 20 to 40% by mass of a first liquid mixture of 0.2 to 3% by mass of paraffin and 97 to 99.8% by mass of a petroleum solvent between heptane and decane, of linear, branched and cyclic form including mixtures thereof, and 50 to 85% by mass of a second liquid mixture of 0.2 to 8% by mass of a surfactant of molecular mass not exceeding 150 g / mol, which is 2-butoxyethanol, 4 to 15% by mass of ethanol and the remainder 100% water.

2. Composition according to claim 1, characterized in that it comprises at most 35% by mass of the first liquid mixture.

3. Composition according to claim 1, characterized in that the first liquid mixture comprises 0.5 to 2.5, preferably at most 2% by mass of paraffin.

4. Composition according to claim 1, characterized in that the second liquid mixture comprises 0.5 to 6, preferably at most 4% by mass of a surfactant with a molecular mass not exceeding 150 g / mol.

5. Composition according to claim 1, characterized in that the second liquid mixture comprises 5 to 12% by mass of ethanol.

6. A method for cleaning and regenerating the hydrophobicity of the surface of a transparent polymer material of optical quality required for aeronautical glazing, characterized in that a cloth is soaked with a composition according to claim 1, the surface is rubbed with this cloth, the liquid deposit taken from the soaked cloth on the surface is allowed to dry, and then the surface is rubbed with a dry cloth to restore vision through the high optical quality polymer material.

Images