FR2976536A1 - PROCESS FOR PROCESSING A WIPING ORGAN - Google Patents

Abstract

The present invention relates to a method of treating a wiper member and in particular a wiper blade, made of elastomer material (s) for a motor vehicle. The method according to the invention comprises a step of treating at least a portion of an external surface of the member by depositing a coating or by chemical treatment while said member is under stress. The invention also relates to an organ obtained using this method and uses thereof.

Description

Method of treating a wiper member

The present invention relates to a method of treating a wiper member and more particularly to a wiper blade wiper, made of elastomer material (s) for a motor vehicle. The invention also relates to a wiper member obtained by this method and uses thereof. In the field of elastomeric-based technical materials, research is often directed towards improving the mechanical properties and / or the surface appearance of the pieces shaped from these materials.

In the case of wiper blades for motor vehicle wiper blade, these blades must have certain characteristics, especially at the surface, allowing effective wiping of the windshield on which they move. Such blades must in particular both be able to conform to the contours of the windshield of the vehicle, and at the same time be sufficiently elastic in order to be able to operate in large temperature ranges of, for example, from -20 ° C to +70 ° C. These blades must also have a sound comfort in use for the occupant of the motor vehicle, that is to say, avoid generating sound waves, so noise.

The generation of sound waves by a wiper blade can have various origins and depends on the operating conditions. Indeed, the behavior of a wiper blade varies greatly if it operates in non-lubricated mode (windshield dry) or lubricated (the lubricant is usually water or windshield wiper fluid) , the latter mode having two sub-modes of operation: wet (continuous presence of lubricant) and drying (corresponding to the transitional phase where the system is no longer supplied with lubricant and where the lubricant evaporates gradually before arriving at an unlubricated mode). The behavior of the coefficient of friction during these different modes and during the transition period from one mode to another, will have an influence on the generation of sound waves. However, this relationship between the coefficient of friction and the generation of sound waves is particularly complex so that it is difficult to predict the exact influence of a modification of this parameter. On the other hand, when a wiper blade is used, a reciprocating motion animates it on the windshield. During scanning, there is a reversal of the direction of pivoting of the wiper blade relative to the wiping heel during which a surface of the wiper blade comes into contact with the window 2976536 -2- to wipe . These come into contact during the reversals of the wiper blade have the effect of creating shocks between different surfaces which are also generating noise harmful to the comfort of use of the vehicle, called rollover noise. However, the most important source of noise pollution is that of so-called "transient" noises. These transient noises are not directly related to the high or low coefficient of friction of the blades of wiper blades but rather depend on the stability of said brushes wet lubricated mode or drying and more particularly in the so-called mixed regime zone. By "mixed regime" is meant a regime in which the operating speed of the blade is between 0 and 400 mm / s. Finally, when using the wiper blade, there is a wear of the blade, particularly at the contact points and / or sometimes a delamination of a possible coating leading to a change in the coefficient of friction . It is therefore desired to have a wiper blade whose characteristics, in particular friction, have a better stability over time. The present invention therefore relates to a method of treating wipers to overcome these problems. It therefore relates to a method of treating a wiper member made of elastomer material (s), comprising the steps of: a) exerting a stress on the wiper member, and, b) concomitantly treating at least a portion of an outer surface of the wiper member by coating deposition and / or chemical treatment. The definitions and preferences detailed below are applicable to the entire application. The material of the wiper member is based on elastomer (s). By "based on" is meant a material comprising at least 10% of elastomer (s), preferably at least 15%, more preferably at least 20%. By "elastomer (s)" is meant a polymer having "hyper-elastic" properties, obtained after crosslinking the polymer. These elastomers comprise natural or synthetic elastomers, alone or as a mixture, in particular the elastomers chosen from the group consisting of natural rubbers (NR), polychloroprenes (CR), ethylene-propylene-diene monomers (EPDM) and polyepoxides. (EP), nitrile rubbers (NBR, HNBR, XNBR), polybutadienes (BR), butyl rubbers, epichlorohydrins (ECO / GECO), ethylene-acrylate copolymers (VAMAC type), 2976536 -3- polyurethanes (PU), fluorinated elastomers and silicone elastomers (VMQ / FMQ). These elastomers can be used alone or as a mixture. By way of example, mention is made of the NR / EPDM, NR / CR, EPDM / PP mixtures or other mixtures known to those skilled in the art. Preferably, the elastomers are selected from the group consisting of NRs, EPDMs, CRs and mixtures based on these elastomers. Advantageously, the material comprises at least one basic elastomer, synthetic or natural, and various fillers and / or additives to ensure its mechanical performance and its compatibility with various climatic environments. The fillers used are generally carbon black, graphite, silica, talc or chalk and their derivatives and / or mixtures. The additives include, inter alia, protective agents, for example para-phenylenediamine derivatives which trap UV. The additives also include waxes that migrate at the surface to protect the material. In addition, the additives may comprise plasticizers to improve the cold resistance and the use of the elastomer. The most commonly used plasticisers are naphthenic oil, aromatic oil, paraffinic oil or ester oil. The additives generally comprise a vulcanization system, for example comprising sulfur and / or various reaction efficiency enhancing molecules or peroxide derivatives. The term "wiper member" is intended more particularly for a wiper blade for a wiper blade, for window glass or for a squeegee, as well as a binocular of wipers formed of two wiping blades connected between they. Usually, a wiper blade is composed of three elements: - a lip ensuring contact with the windshield and providing the seal for wiping the water, - a generally rectangular shaped heel making it possible to inserting the blade into the broom; and a hinge (optional) formed by a thin rubber strip located between the lip and the heel and ensuring the correct positioning of the lip on the windshield, in particular during the change of direction. from broom to turning points. By "twin wiper members" is meant two wiping members 35 (wiper blades) joined together, the binocular being generally pre-slit by at least one notch to allow subsequent separation of organs 2976536 -4- one of the other. In the case of wiper blade wipers, the two blades of the binoculars are usually connected by their lip. The wiping members are usually obtained by molding or extrusion and are then vulcanized. The wiper member according to the invention undergoes a chemical treatment or a deposition of a coating when the stress is exerted on the member. The term "chemical treatment" is intended more particularly to methods of hardening and / or surface structuring, known to those skilled in the art, such as, for example and without limitation, halogenation (liquid or gaseous). , the energetic treatments among which may be mentioned electron bombardment, ion bombardment, gamma, ultraviolet or infra-red irradiation or laser beam irradiation. In particular, the halogenation of the wiper member makes it possible to harden the surface of the organ to a certain thickness (creating a "hardened layer") and thus to increase the service life of the latter. . Halogen atoms are covalently attached to the elastomer, in particular by nucleophilic addition to the unsaturations of the carbon chains. Ionic bombardment also makes it possible to harden the surface of the organ to a certain thickness and thus to increase the lifetime of the latter. The bombardment is carried out using a device comprising an ion generator and an ion applicator such as for example those described in FR-A-2 899 242 or US20060042745. For example, irradiation with a laser beam makes it possible to structure the surface of a wiping member. By "deposition of a coating", it is more particularly the deposition on the surface of the member of a layer having slip properties. By way of example, mention may be made of thin film deposition by plasma (plasma polymer) such as DLC ("Diamond Like Carbon") layers or polyethylene layers. The deposit obtained by the graphitization technique, such as, for example, the deposition of a coating of paint type comprising graphite, is also aimed at. This also relates to laser-based layer deposition ("laser cladding"), which consists of coalescing a composition, in the form of a powder, on the surface with a laser (composition that may comprise, for example, graphite particles and powders). polyethylene and / or teflon) and previously disposed on the surface homogeneously. Preferably, the coating deposited by graphitization is therefore a coating based on graphite or polymer particles, such as, for example, polytetrafluoroethylene PTFE, polyethylene or polypropylene type, which makes it possible, in particular, to reduce the friction of the member on the surface to be wiped. More particularly, the coating targeted by the invention is a coating of the paint type, advantageously deposited with the aid of an emulsion comprising water, a binder and fillers making it possible to lower the coefficient of friction of the wiper member. The water present in this emulsion is then evaporated. By way of example, the coating used may be that defined in the example of US Pat. No. 5,883,168. The binder or binders comprise a polymer whose function is to retain fillers, such as graphite or other lubricating particles, on the wiper member. It is incorporated as a suspension, dispersion or powder depending on the application of the coating. The binder polymer is selected from acrylic derivatives, styrene acrylic derivatives, acrylonitriles and their derivatives, ester or ether polyurethanes and their derivatives and polyvinyl chloride (PVC). The binder may also comprise a fluoroelastomer, silicones or siloxanes, elastomeric latices, polyamide, polyethylene or polypropylene powders. The binder may also include a melamine, isocyanate or epoxy crosslinking agent to impart enhanced mechanical and chemical strength properties to the coating as well as wax to improve the impermeability of the film formed by the binders. The load or charges for lowering the coefficient of friction of the wiper member are selected from the group consisting of graphite, molybdenum disulfide (MoS2), talc, polytetrafluoroethylene (PTFE), particles UHMWPE ("Ultra High Molecular Weight PolyEthylene"), polyethylene, polypropylene, silicones, nanostructured fillers such as fullerenes, carbon nanotubes (CNT) or mixtures thereof. Preferably, the filler is graphite powder. The incorporation of these sliding charges into a liquid binder will be facilitated by dispersing agents such as polyacrylates. Thickening agents to avoid sedimentation are also often required. It will be appreciated that the outer surface of the elastomeric material (s) may be partially or fully chemically treated and / or coated. Advantageously, the lip and at least the zone (slice) of the lip, intended to be in contact with the surface to be wiped, undergoes the stress exerted and is chemically treated and / or coated. In addition, when the stress is exerted, several treatments can be performed (chemical treatment and / or coating deposition) concomitantly or successively. The process according to the invention makes it possible to obtain microstructures or micro-and nano-structures on the surface of the material, creating a specific texture. Indeed, the surface of the material, put under stress, is treated. This treatment then leads to different mechanical properties between the surface and the core of the elastomer. The removal of the constraint thus leads to the creation of residual stresses which are released by the appearance of a network of structures preferentially oriented in the direction of the initial constraint (s). The structures have characteristic dimensions related to the stress conditions and the physical characteristics (conditions) of the treatment. Thanks to this process of surface structuring, various and varied geometries can be produced in a controlled way (ex: rectangle, line ...). In addition, such a method has the advantage of not requiring the use of form for the production of structures, which forms can be used during the manufacture of the wipers. The quality of the organ is thus continuous throughout the production. On the other hand, this method is very simple to implement, whatever the method of obtaining the member (for example by molding or extrusion). The method according to the invention also considerably reduces the problems of delamination of said coating following the tensioning of the product 20 during its operation on the windshield. The coefficient of friction obtained after structuring the surface is improved compared to the same treatment but applied without stress and there is also a disappearance of transient noises. In addition, an improvement in rollover noise is also measured on surface-structured brooms because of the process. On the other hand, the hydrophobicity of the surfaces thus structured is enhanced compared to the same unstructured surface with water contact angle values greater than 90 °, these values on an untreated surface being of the order of 80. °, and on a surface treated by unstressed halogenation exerted, of the order of 60-70 °. In addition, when the process is carried out with a chemical radiation laser structuring treatment, it makes it possible to reduce, for a laser beam of a given size, the mark left on the surface, leading to a faster and more precise structuring. . For example, if one elongates, for example, along an axis at 100% elongation, and then irradiated with a laser to create on the surface linear patterns 10 μm in diameter, with an inter-distance between two After successive patterns of 10 .mu.m, after relaxation, linear patterns having a diameter of 5 .mu.m are obtained with an inter-distance also reduced by half (5 .mu.m). By "inter-distance" is meant the distance between the end of the first pattern n and the beginning of the pattern n + 1, which, in the case described above, corresponds to creating a line with the laser, of 10 pm of width every 20 pm. Finally, another advantage of the process according to the invention lies in the fact that even when the organ is in action, for example during rubbing on the glass, there is no break in the treatment having been applied during the process according to the invention (under stress). Indeed, during friction, the elastomer material of the wiper member is subjected to deformations which can be between 0 and 40%. If the surface is treated without stress, when the material will be subjected to friction, it will deform, this deformation resulting in the appearance of cracks in the treatment and / or the appearance of areas with less treatment, which lead either to friction instabilities and / or preferential wear primers. With the method according to the invention, these problems are solved. The stress exerted can be constant or variable. Several constraints can also be exercised at the same time so as to achieve different modes of solicitation. These stresses are chosen more particularly from traction, compression, torsion, bending or shear, alone or in combination. These different modes of solicitation can be performed alone or coupled, the combination of constraints leading to several concomitant modes of solicitation in order to create a specific geometry of structures (line, square, ...), specific dimensions of structures (nanometric and / or micrometric). Indeed, the structures and their dimensioning are functions of the loading and the conditions of the treatment (such as for example, the nature of the treatment, the temperature, the duration of the treatment, the thickness of the coating and / or the hardened layer ). Advantageously, during the bias, the deformation of the wiper member is between 0.1 and 600%, preferably between 0.5 and 300% and more preferably between 1 and 100%. The modes of stress can be reiterated and / or alternated, so as to obtain the same or different deformation, the member then being treated with a chemical treatment and / or an identical or different coating deposition. A variable and controlled geometry of the surface of the wiper member is thus obtained. The method according to the invention may further comprise a step of: c) treating at least a portion of an outer surface of the blade by depositing a coating or by chemical treatment without any constraint be exercised on the blade. This step is particularly advantageous in the case where the steps a) and b) on the one hand and c) on the other hand are repeated and / or alternated. The invention thus proposes a wiping member, in particular a wiper blade, made of elastomer-based material (s), comprising on an external surface micro- and / or nanostructures resulting from a difference in mechanical properties. (eg, internal stresses, hardness, etc.) between the elastomeric material and the layer resulting from the treatment. By "layer resulting from the treatment" is meant the "cured layer" or the coating. Indeed, chemical treatment such as the deposition of a coating creates an identifiable surface thickness as a cured layer for chemical treatment and as a coating layer in the case of deposition. Preferably, the cured layer has a thickness of between 0.1 μm and 50 μm and the coating has a thickness of between 1 and 50 μm, preferably between 1 and 20 μm and more preferably between 2 and 15 μm. The invention also relates to a wiper member, in particular a wiper blade, obtained by the method according to the invention. The invention also relates to a wiper blade comprising a blade 20 as obtained by the method according to the invention. Note that the wiper blade can be either a conventional broom or a flat broom. By "conventional broom" means a broom whose pressure distribution printed by the arm supporting the blade is provided by spreaders distributed along the broom. While for a "flat blade", the pressure distribution printed by the arm supporting the blade is provided by a metal vertebra having a curvature and a calculated pressure. Thus, one can remove the pedals of the brush which in particular allows a reduction of the height of the brush. Finally, it aims to use a wiper member and more particularly a wiper blade according to the invention, to reduce the noise generated during the scanning of a windshield. Indeed, an improvement of the reversal noises and transient noises was measured on the brushes structured on the surface by this method. Other features and advantages of the invention are described in the examples which follow, given solely by way of non-limiting example and with reference to the drawings, in which: FIG. 1 is a diagrammatic view in perspective of a conventional wiper blade (la) or flat (lb), - Figure 2 is a schematic perspective view of a wiper blade according to one embodiment of the invention, and FIGS. 3 and 4 are photographs taken by scanning electron microscopy of the wiper blade surface exhibiting the micro- and / or nanostructures obtained using the method according to the invention. Figure 1 shows a schematic perspective view of a wiper blade 11 conventional (la) or flat (1 b) comprising a wiper blade 10 according to the invention. FIG. 2 is a representation of the wiper blade 10 which comprises a heel 12 which makes it possible to insert the blade into a wiper blade 11. This blade 10 also comprises a lip 16 which ensures contact with the surface to be wiped. and a hinge 14 formed by a thin rubber strip located between the lip 16 and the heel 12. This hinge 14 ensures the correct positioning of the lip 16 on the surface to be wiped, in particular during the change of direction of the blade 11 to the points reversal. The surface to be wiped is in this case a windshield of a motor vehicle.

EXAMPLE 1 Surface-structuring method according to the invention

1. Obtaining simple microstructures The parts are implemented by extrusion or by any other processing means (for example, molding) and are vulcanized. The wiper member is then subjected to simultaneous traction along the X axis of 20% of its length and along the Y axis of 40% of its length. During this traction, a bromine halogenation treatment is applied for 5 min. The constraint is then released. The micro-structures obtained using this method are illustrated by the photographs taken by scanning electron microscopy at different scales and presented in FIG. 3. In FIGS. 3A and 3B, it is clearly possible to observe the presence of a microstructure. surface composed of micro-metric rectangular blocks evenly distributed on the surface of the elastomer-based member. The photograph taken at the highest magnification (Figure 3C) does not indicate the presence of nanostructure.

2. Obtaining Micro- and Nanostructures The parts are processed by extrusion or other processing means (eg, molding) and are vulcanized. The wiper member is then subjected to: a first traction along the X axis of 5%; during this pulling, a bromine halogenation treatment is applied for 1 min. The constraint is then released. a second simultaneous traction along the X axis of 40% of its length and along the Y axis of 5% of its length; during this traction, a bromine halogenation treatment is applied for 4 min. The stress is then released. The micro- and nano-structures obtained using this method are illustrated by the photographs taken by scanning electron microscopy at different scales presented in FIG. 4. In FIGS. 4A and 4B, it is clearly possible to observe the presence of a 15 surface microstructure composed of a succession of micro-metric lines (succession of hollows and bumps) distributed regularly on the surface of the elastomer-based member. The photograph taken at the highest magnification (4C) indicates, contrary to Example 1, the presence on the surface of these microstructures of nanometric structures.

EXAMPLE 2 Effect on the Coefficient of Friction The parts are used by extrusion or by any other means of transformation (for example, molding). Friction measurements were made on a friction bench in which a glass plate moves laterally at a constant speed, and alternatively. The latter is in contact with a wiper blade connected to a fixed frame by which one can adjust the support force and measure the tangential force to deduce the coefficient of friction. The measurements were made in non-lubricated mode with a bearing force of 30 N / m and a travel speed of 300 mm / s. Material Friction Treatment surface NR / 3.53 ± 0.15 NR Halogenation * 2.05 ± 0.07 NR process such as 1.19 ± 0.05 described in example 1.2 -11- NR = Natural rubber * Time halogenation with the bromine element = 5 mn Conclusion: The coefficient of friction obtained after structuring the surface in non-lubricated mode is improved compared to the same treatment but applied without stress (up to 40% measured improvement).

Claims (10)

REVENDICATIONS1. A method of treating a wiper member made of elastomer material (s), comprising the steps of: a) exerting a stress on the wiper member, and, b) concomitantly, treating at least one part of an outer surface of the wiper member by depositing a coating and / or by chemical treatment. 2. The method of claim 1, wherein the stress exerted is constant or variable. 3. The method of claim 1 or 2, wherein the stress (s) exerted (s) result in different stresses selected from traction, compression, torsion, flexion or shear, alone or in combination. 4. The method of claim 3, wherein during the stress, the deformation of the wiper member is between 0.1 and 600%. The method of any preceding claim, further comprising the step of: c) treating at least a portion of an outer surface of the slide by coating or chemical treatment without any constraint be exercised on the blade. 6. The method of claim 5, wherein the steps a) and b) on the one hand and c) secondly are repeated and / or alternated. 7. A wiper, in particular a wiper blade, made of elastomer material (s), comprising on an external surface micro- and / or nanostructures resulting from a difference in mechanical properties between the material based on of elastomer and the layer resulting from the treatment. 8. Wiper member, in particular wiping blade, obtained by the method according to any one of claims 1 to 6. A wiper blade having a blade according to claim 7 or 8. 10. Use of a windscreen wiper blade according to claim 7 or 8, to reduce the noise generated during the scanning of a windshield.