Coating composition for a wiper blade of a windscreen wiper

Abstract

The invention relates to a coating composition for a wiper blade of a windscreen wiper, the composition being an aqueous phase composition comprising at least one resin and from 30 to 60% of at least one solid lubricant in dispersion, the composition further comprising from 0.1 to 2%, preferably from 0.2 to 0.6% of graphene, the percentages being given by weight relative to the total weight of the composition. The invention also relates to a method for preparing the composition, to the use thereof and to a wiper blade for a windscreen wiper, said wiper blade being coated with such a composition.

Description

Coating composition for windshield wiper blade

[0001] The invention relates to a coating composition for a wiper blade for a vehicle windshield wiper blade, the use of such a composition and a method for preparing it. It also relates to a wiper blade for a windshield wiper blade coated at least partially with the composition.

[0002] Motor vehicles are commonly equipped with windshield wiper systems to wash and / or wipe the windshield and prevent the driver's view of their surroundings from being disturbed. The wiper blades of such a system are conventionally driven by arms performing a reciprocating angular movement. These blades rub against the outer surface of the window, for example the windshield, and evacuate the water by bringing it out of the driver's field of vision. In a conventional version, the blades are made in the form of articulated levers that hold the wiper blade at several points. In a more recent version called "flat blade", the blades are made in the form of a semi-rigid assembly that holds the wiper blade along its entire length.

[0003] Generally speaking, a wiper blade is made of elastically deformable material based on an elastomer supplemented with additives, in particular to improve its mechanical properties, elasticity, wear resistance, resistance to external aggressions or to facilitate the implementation of the manufacturing process. This may, for example, be reinforcing fillers, plasticizer, vulcanizing agent, agent for protection against UV radiation, oxidation, ozone and / or wear.

[0004] In the case of wiper blades for motor vehicle windscreen wipers, these blades must have characteristics that allow effective wiping of the windscreen on which they move while providing sound comfort in use for the occupant of the vehicle, i.e. avoiding generating sound waves or noise. However, when using the windscreen wiper, the incessant friction of the blade on the windscreen causes premature wear of the blade, resulting not only in a loss of wiping quality but also in generating noise.

[0005] Blade wear requires the replacement of the entire wiper blade, although the other parts and elements of the wiper blade are still functional. In order to increase the lifespan of a wiper blade, US patent 5,447,645 describes a composition for lubricating and preserving rubber, comprising graphite, butyl titanate and isopropanol. This composition may also include other products such as anti-UV stabilizers, a binder, etc. However, such a composition has a highly flammable character, which requires special storage conditions and is therefore not suitable for direct use by a non-professional.

[0006] FR2977258 describes compositions useful for the renovation of windshield wiper blades which are aqueous compositions comprising 5 to 25% of sliding fillers, preferably graphite powder.

[0007] US2022 / 0220407 describes organic wiper blade coating compositions that contain up to 16% graphene, where the graphene may constitute the entire solid lubricant.

[0008] There is always a need to improve the performance of windshield wiper blades, and in particular their wear resistance, allowing for a longer life. It is also desirable to have coating compositions that can improve these performances, that are easy to implement and that have good adhesion to the wiper blade.

[0009] These and other objects are achieved by the compositions of the present invention.

[0010] This is why the present invention relates to a coating composition for a windshield wiper blade, the composition being an aqueous phase composition comprising at least one resin and from 30 to 60% of at least one solid lubricating agent in dispersion, the composition further comprising from 0.1 to 2%, preferably from 0.2 to 0.6% of graphene, the percentages being given by weight relative to the total weight of the composition.

[0011] For the purposes of the invention, the term "aqueous phase" means a composition which comprises an organic solvent content of less than or equal to 10% by weight of the total weight of the composition. The organic solvent content is preferably less than or equal to 5% by weight, and more preferably equal to 0% by weight of the total weight of the composition.

[0012] The composition generally contains from 5 to 50% of aqueous solvent, that is to say a medium comprising water and optionally one or more hydrophilic co-solvents; such co-solvents may, for example, be of an alcoholic nature, in particular glycolic esters.

[0013] The solid lubricating agent content in the dispersion is adjusted to provide 5 to 25% of solid lubricating agent in the composition. The dispersion is in aqueous phase.

[0014] The composition may further contain polymer microbeads or microparticles, such as those described in FR2925507.

[0015] The composition may also contain additives.

[0016] The invention also relates to the use of the coating composition for coating, at least in part, a wiper blade for a windshield wiper.

[0017] Another object of the invention is a method for preparing the coating composition of a windshield wiper blade.

[0018] The invention also relates to a wiping blade for a vehicle windshield wiper blade coated with said composition.

[0019] Indeed, it has been found in the context of the present invention that the introduction of graphene at specific concentrations into aqueous coating compositions makes it possible to increase the wear resistance of the coating, while maintaining friction properties and wiping quality of the blade. In addition, the compositions containing these levels of graphene have good adhesion to the wiping blade and their performance is not impaired by cold.

[0020] They give the coating good wiping quality, the blade repelling water correctly when wiping, without the formation of streaks or water marks.

[0021] The composition is environmentally friendly and healthy thanks to the use of materials such as graphene, and is not flammable.

[0022] By solid lubricant we mean components other than graphene.

[0023] The solid lubricating agent may be chosen from lubricants known to those skilled in the art. Examples include natural lubricants such as graphite and molybdenum disulfide, as well as synthetic lubricants such as graphite fluoride, tungsten disulfide, boron nitride, tungsten, molybdenum and niobium diselenide, or titanium iodide and disulfide, as well as their various mixtures in all proportions.

[0024] Preferably, graphite and / or molybdenum disulfide are used, and especially powdered graphite in the form of an aqueous dispersion. Preferably, the graphite has a size of less than 10 µm.

[0025] As mentioned above, the concentration of solid lubricating agent in aqueous dispersion is 30 to 60% by weight.

[0026] The distribution of graphene particles and solid lubricant in dispersion in the composition is homogeneous.

[0027] Graphene is a two-dimensional crystalline material which is in the form of a sheet. The graphene used in the compositions according to the invention may comprise from 1 to 10 sheets; it is in the form of fine particles, from 2 to 10 µm, preferably from 5 to 10 µm.

[0028] The concentration of graphene in the coating composition is 0.1 to 2%, especially 0.1 to 1%, preferably 0.2 to 0.6%. For these concentrations, an improvement in the resistance of the coating and an improvement in the wiping quality are surprisingly observed. The performance of the dry abrasion test can, for higher concentrations, be better and then deteriorate. The performance curve takes the form of a Gaussian curve. The improvement in resistance decreases for concentrations greater than 2%, or even for concentrations greater than or equal to 1% by weight.

[0029] Furthermore, the choice of concentrations of 0.1 to 2%, in particular 0.1 to 1% and preferably 0.2 to 0.6% of graphene in the compositions gives the coating good resistance to cold and ice. This property is important for windshield wiper blades intended to be used in cold weather, the coating of which will not be degraded, which increases the service life of the wiper blades. The cold resistance of the coating is degraded for very high concentrations of graphene in the composition or for compositions in an organic medium.

[0030] The concentration of graphene in the composition can thus be approximately 0.1 to 2%, in particular 0.1 to 1%, and in particular 0.2%, 0.3%, 0.4%, 0.5% or 0.6% by weight.

[0031] The resin may in particular be an aqueous phase resin, comprising at least one acrylic, vinyl, styrene or urethane type polymer, in aqueous phase. The polymer may be a homopolymer or a copolymer. These polymers may be used alone or mixed depending on their compatibilities or the desired final properties. Advantageously, the resin contains at least one acrylic polymer in aqueous phase.

[0032] This may include a dispersion or emulsion of polymer in aqueous phase.

[0033] The resin preferably has a glass transition temperature of less than or equal to 0°C, and more preferably less than or equal to -20°C, in order to retain the flexibility properties of the coating film at low temperatures.

[0034] The quantity of resin in the compositions will be adapted by a person skilled in the art according to the desired properties; it is generally 10 to 25% by weight of resin emulsion or dispersion relative to the total weight of the composition, which corresponds to approximately 30 to 50% by weight of resin relative to the weight of the dry components (excluding the solvent).

[0035] The composition according to the invention may further contain at least one additive chosen from thickening agents, spreading agents, dispersing agents, anti-foaming agents and UV protective agents.

[0036] UV protective agents include UV stabilizers and UV inhibitors.

[0037] The thickeners are preferably chosen from modified celluloses and modified urethane polymers. The content is preferably less than or equal to 0.5% by weight relative to the total weight of the composition.

[0038] The spreading agent makes it possible to reduce the surface energy of the composition. It can in particular be chosen from silicone surfactants, such as dimethylsiloxane modified polyethers.

[0039] Dispersing agents are intended to ensure better dispersion of particles, such as glass particles and solid lubricating agent. The dispersing agent is in particular a water-soluble polymeric agent; preferably, the polymeric dispersing agent comprises an ionic form of the polymer or copolymer used as resin. For example, a polyacrylate will preferably be used when the resin is a polyacrylic resin.

[0040] The polymer microbeads, when present in the compositions, may be made of a polymer which may be a homopolymer or a copolymer. The polymer of the microparticles may in particular be chosen from polymers based on acrylates, diallyl phthalates, epoxy units, vinyl acetate-ethylene, urea-formaldehyde, phenols, amide (such as for example nylon), carbonate, fluoropolymers (such as for example polytetrafluoroethylene), organosiloxanes, unsaturated esters, polyethylene, ethylene terephthalate, amide-imide imide, propylene, styrene, sulfone, ether sulfone, urethane, vinyl chloride. These polymers may be used alone or mixed depending on their compatibilities or the desired final properties. The polymer of the microparticles is preferably a hydrophobic polymer, and resistant to oxygenated solvents.It may in particular be chosen from polymers based on acrylates, amide (such as nylon), carbonate, fluoropolymers, organosiloxanes, styrene. The polymer is preferably chosen from silicones, such as polyorganosiloxanes. Polymethylsilsesquioxane is preferably used. The polymer microparticles are introduced into the dispersion in an amount capable of producing a dispersion of microspheres.

[0041] The composition must be homogeneous, to facilitate its subsequent application to the wiping blade. Homogeneity can be assessed by the uniformity of the distribution of the graphene particles in the resin, so that at any point in the mixture there is no over-representation or under-representation of the particles, at least macroscopically. A person skilled in the art will be able to recognize whether the distribution is homogeneous either with the naked eye or microscopically.

[0042] The invention therefore also relates to a process for preparing a coating composition as defined in the present description, the process comprising the following steps:

[0043] (a) preparation of a dispersion of a solid lubricating agent in aqueous phase,

[0044] b) introducing the graphene particles into the dispersion obtained in step a, to obtain a dispersion of the particles and the solid lubricating agent, and

[0045] c) adding at least one resin in aqueous phase to the dispersion obtained in step b.

[0046] In particular, a dispersion of a solid lubricant such as a graphite dispersion is prepared in a first step, which is then mixed with powdered graphene.

[0047] According to a variant of the invention, a ready-to-use, available dispersion of a lubricating agent is used. It is understood that step a also encompasses the case where such a ready-to-use dispersion is used.

[0048] According to one embodiment of the invention, the graphene is introduced in the form of dry powder.

[0049] According to another embodiment of the invention, the graphene is introduced in the form of a suspension in an aqueous medium. The concentration of graphene in the suspension will be adapted so as to obtain the final concentration of graphene defined above. For example, suspensions comprising 4% by weight of graphene are used; in this case, the quantity of suspension is in particular 2.5 to 25%.

[0050] A resin dispersion, for example acrylic resin, in aqueous phase is then added to the previous mixture.

[0051] Any additives are added, if applicable, after step c.

[0052] The solvent(s) are also added after this step c. These are in particular water and possibly one or more co-solvents such as glycol ethers, such as 2-butoxyethanol.

[0053] If necessary, polymer microparticles are introduced in step c, mixed with the resin in aqueous phase. The process is known to those skilled in the art from patent FR2925507.

[0054] The contents of the various constituents are as indicated above.

[0055] The invention also relates to the use of a coating composition as defined in the present text or capable of being obtained by the process described above, for at least partially coating a wiper blade for a windscreen wiper.

[0056] The composition can, for example, be applied directly to the wiper blade or to a profiled rubber strip, which is then re-cut into two or three parts to obtain the wiper blade. The coating composition is applied by dipping the wiper blade or profiled rubber strip into the composition, by spraying the composition onto the wiper blade or profiled rubber strip, or by coating the wiper blade or profiled rubber strip with the composition. The wiper blade or profiled rubber strip is then dried. In the case of the rubber strip, this is finally re-cut into two or three parts to obtain the wiper blades.

[0057] The application step may be preceded by a preheating step and baking of the coating, particularly in an infrared oven or a convection oven.

[0058] The thickness of the coating layer is between 1 and 10 µm, preferably between 2 and 6 µm, and more preferably between 3 and 5 µm.

[0059] The invention also relates to a windshield wiper blade to which the coating composition has been applied. The blade is coated with a composition comprising at least solid lubricants, graphene and resin, as defined above, but in which the solvent has been evaporated. Brief description of the figures

[0060] The invention will be better understood on reading the following description, given solely by way of example and with reference to the appended drawings in which:

[0061] represents a wiping blade of a windshield wiper blade according to the invention.

[0062] represents the percentage improvement in coating composition strength as a function of the percentage of graphene in the formulation.

[0063] represents the results of a low-percentage graphene aqueous coating before and after a window washer fluid adhesion test, as well as the result of an ice adhesion test.

[0064] represents the dry abrasion results obtained from 3 compositions: reference (without graphene), according to the invention (0.6% graphene) or containing 13.5% graphene.

[0065] According to the invention, the wiping blade 1 of a windscreen wiper blade according to the invention has an elongated shape and is intended to be carried by a body of the blade (not shown). The blade 1 comprises a lip 3 and a heel 5 which are connected by a hinge 7. The lip 3, heel 5, hinge 7 assembly forms a basic body of the blade 1.

[0066] The heel 5 allows the blade 1 to be hooked into the body of the wiper. The lip 3 is intended to be in contact with the outer surface of a window such as a windshield for wiping.

[0067] The hinge 7 is formed by a thin strip of material which gives the blade a certain flexibility and allows it to tilt when the direction of movement of the broom changes, in other words a forward and backward tilting movement of the lip.

[0068] Blade 1 is obtained by a conventional manufacturing process known to those skilled in the art.

[0069] Advantageously, at least a portion of the blade 1 is coated with the coating composition as described above, in particular the base body of the blade is coated with this composition. It is thus possible to envisage embodiments in which, for example:

[0070] - only lip 3 is coated with the composition,

[0071] - the entire blade 1 is coated with the composition.

[0072] Example 1: Composition preparation

[0073] The following compositions are prepared:

[0074] Reference 1A1B1Reference 2A2B2C2D2Resin(s)17,817,817,724,524,524,424,123,3Lubricating charge(s)57,457,357,134,13433,933,432,4Particles polymer---3,33,33,33,33,2Additive(s)1,11,11,11,31,31,31,31,2Solvent(s)23,723,623,536,836,736,535,934,9Graphene00,20,600,20,625Lubricating filler(s)57,457,357,134,13433,933,432,4

[0075] The compositions are prepared as follows:

[0076] - the lubricating agent dispersion is ready to use or manufactured, preferably ready to use;

[0077] - to this dispersion of lubricating agent is added the resin with additives, for example, spreading agent and anti-foam agent (based on mineral oils, polymers or silicone agents) at a rate of 1 to 1.5% by weight. Example 2

[0078] Strength enhancing properties, coating adhesion to blade and dry abrasion test performance are evaluated for the compositions of Example 1.

[0079] The results are presented in table 2 below:

[0080] Reference 1A1B1Reference 2A2B2C2D2Adhesion testConformConformConformConformConformConformConformConformConformDry abrasion <0.5 mm30.060.060.05-----Improvement in coating resistance-+6%+22%-+24%+26%+13%+12%

[0081] Dry abrasion test: Wear resistance performance is measured by dry abrasion test with different coating compositions.

[0082] Coated blades are positioned to slide over a smooth glass surface under compressive load (here 15 N / m) for a given number of cycles (here 43200 cycles). After a given number of cycles, rubber deposition on the glass and blade wear are assessed.

[0083] Adhesion test: the adhesion of different coating formulations to rubber is evaluated.

[0084] The adhesion test consists of moving back and forth over the coated wiper blade using paper soaked in alcohol-based windshield cleaning fluid and then observing and rating the surface of the coating using an internal grid.

[0085] Resistance test: comparative test between different coatings that can be made on the same rubber. The resistance of the coating is measured as follows:

[0086] The coated blades are positioned so that they slide over a smooth glass surface on which a dust-simulating coating is applied. They are subjected to a compressive load (here 15N / m) for a determined number of cycles (here 10 cycles). The observation of the coating wear is observed and measured via a video microscope.

[0087] The presence of graphene in the composition increases the resistance of the coating.

[0088] It does not have a negative impact on other important criteria such as dry abrasion, friction or adhesion.

[0089] Example 3: Abrasion resistance test

[0090] The abrasion resistance and stiffness properties of a blade coated with coating compositions in which the amount of graphene is varied are evaluated.

[0091] The results are shown in Figure 2.

[0092] Example 4: Wiping quality

[0093] The coated blades are evaluated under real-life conditions, i.e. on a vehicle windshield. The evaluation of defects such as streaks, haze, noise, etc. are evaluated on a scale of 1 to 10. 10 being the best.

[0094] The results are shown in the following table.

[0095] Reference 1A1B1Upward direction6.67.07.0Downward direction8.58.58.8Average7.57.87.9

[0096] An improvement in wiping quality is observed with the addition of graphene.

[0097] Example 5: cold resistance of coatings

[0098] A stream of water is applied along the lip of the rubber blade coated with the graphene-containing composition, in the parking position, placed at -20°C. A dry detachment of the blade from the ice is then carried out. Observation is carried out on the residual ice and on the rubber blade itself.

[0099] For a blade coated with a composition containing an initial graphene concentration of 0.6% according to the invention, no peeling of the coating is observed; the surface of the blade is intact. There is no coating deposit on the glass. The results are shown in Figure 3.

[0100] Example 6: Comparative dry abrasion test

[0101] The dry abrasion test is carried out on a blade treated with a reference formulation not containing graphene, a formulation containing graphene according to the invention, and on a blade treated with a formulation containing graphene at a concentration higher than that of the invention.

[0102] The compositions are prepared as described in Example 1.

[0103] The results are shown in Figure 4.

[0104] A degradation in performance is observed for the coating composition containing a high concentration of graphene. The composition according to the invention does not modify the result and therefore does not alter the wear resistance of the composition.

Claims

Coating composition for a windshield wiper blade, the composition being an aqueous phase composition comprising at least one resin and from 30 to 60% of at least one solid lubricating agent in dispersion, the composition further comprising from 0.1 to 2%, preferably from 0.1 to 1% of graphene, the solid lubricating agent being other than graphene, the percentages being given by weight relative to the total weight of the composition. Coating composition according to claim 1, characterized in that it contains 5 to 25% of solid lubricating agent. Coating composition according to at least one of claims 1 or 2, characterized in that the solid lubricating agent is chosen from graphite particles and molybdenum disulfide particles. Composition according to at least one of claims 1 to 3, characterized in that the resin is an acrylic, vinyl, styrenic and / or urethane polymer, in aqueous phase. Coating composition according to at least one of claims 1 to 4, characterized in that it comprises from 10 to 25% by weight of resin emulsion or dispersion relative to the total weight of the composition. Coating composition according to at least one of claims 1 to 5, characterized in that it further contains at least one additive chosen from thickening agents, spreading agents, dispersing agents, anti-foaming agents and UV protective agents. Coating composition according to at least one of claims 1 to 6, characterized in that it contains polymer microbeads. Coating composition according to at least one of claims 1 to 7, characterized in that it contains from 0.2 to 0.6% by weight of graphene. Process for preparing a coating composition according to any one of the preceding claims, characterized in that it comprises the following steps: a) preparation of a dispersion of a solid lubricating agent in aqueous phase, b) introduction of the graphene particles into the dispersion obtained in step a, to obtain a dispersion of the particles and the solid lubricating agent, etc.) addition of at least one resin in aqueous phase to the dispersion obtained in step b. Preparation process according to claim 9, characterized in that in step b) the graphene is introduced in the form of a suspension in an aqueous medium. Preparation process according to claim 9 or 10 characterized in that after step c, it comprises a step of adding at least one additive and / or one solvent. Use of a composition according to at least one of claims 1 to 8, or capable of being obtained by the process according to at least one of claims 9 to 11, for at least partially coating a wiper blade for a windscreen wiper. Wiper blade for a windscreen wiper blade coated at least in part with a composition according to one of claims 1 to 8.

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