Wiping member made from a material based on over-crosslinked elastomer(s)

Abstract

The invention relates to a wiping member (10) comprising an elastomer-based material, a coating being provided on at least part of an external surface of the material. At least part of the surface of the assembly formed by the elastomer-based material and the coating has an increased degree of cross-linking over at least one surface thickness of the assembly. The invention also relates to a windshield wiper blade and to a method for treating a wiping member.

Claims

1. A wiping member comprising a material based on elastomer(s), the wiping member being obtained by a process comprising: depositing a coating on at least one portion of an outer surface of the material based on elastomer(s), wherein the coating comprises a first layer and a second layer, the first layer is a layer comprising a binder and a filler, for which the ratio of the dry weight of the filler to the dry weight of the binder is between 1 and 2 and the second layer is a layer comprising a binder and a filler, for which the ratio of the dry weight of filler to the dry weight of binder is between 3 and 10; and treating, by ion bombardment carried out using a device comprising an ion generator and an ion applicator, at least one portion of an assembly constituted by the material based on elastomer(s) and the coating, wherein the first layer is disposed between the material based on elastomer(s) and the second layer.

2. The wiping member as claimed in claim 1, wherein the first layer aiming to enable adhesion of the second layer and the second layer aiming to reduce friction.

3. The wiping member as claimed in claim 1, wherein the coating is co-crosslinked with the material based on elastomer(s).

4. The wiping member as claimed in claim 1, wherein the second binder of the second layer is the same as the first binder of the first layer.

5. A method for manufacturing a wiping member as claimed in claim 1, the method comprising: depositing a coating on at least one portion of an outer surface of a material based on elastomer(s); and treating, by ion bombardment, at least one portion of an assembly constituted by the material based on elastomer(s) and the coating, wherein the coating comprises a first layer and a second layer, wherein covalent bonds being created through said ions bombardment between macromolecular chains of the second layer of the coating and acromolecular chains of a first layer of the coating and between macromolecular chains of the material based on elastomer and macromolecular chains of the first layer of the coating.

6. A wiping member comprising a material based on elastomer(s), the wiping member being obtained by a process comprising: depositing a coating on at least one portion of an outer surface of the material based on elastomer(s); and treating, by ion bombardment, at least one portion of an assembly constituted by the material based on elastomer(s) and the coating, wherein the coating comprises a first layer and a second layer, the first layer aiming to enable adhesion of the second layer to the material based on elastomer(s) and the second layer aiming to reduce friction, wherein the first layer comprises a first binder and a first filler, wherein a first ratio of a dry weight of the first filler to a dry weight of the first binder is between 1 and 2, and wherein the second layer comprises a second binder and a second filler, wherein a second ratio of a dry weight of the second filler to a dry weight of the second binder is between 3 and 10.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other features and advantages of the invention are described in the following examples, given solely by way of nonlimiting example and with reference to the drawings in which:

(2) FIGS. 1a and 1b are schematic perspective views respectively of a conventional windshield wiper and of a flat windshield wiper,

(3) FIG. 2 is a schematic perspective view of a wiping blade according to one embodiment of the invention,

(4) FIG. 3 is an enlargement of the detail III from FIG. 1,

(5) FIG. 4 is a schematic view of a pair of wiping blades,

(6) FIG. 5 is a diagram illustrating a process for treating the wiping member according to one embodiment of the invention.

(7) FIGS. 1a and 1b represent a schematic perspective view of a conventional windshield wiper 11 or flat windshield wiper 11 comprising a wiping blade 10 according to the invention.

(8) FIG. 2 is a representation of the wiping blade 10 which comprises a heel 12 which makes it possible to insert the blade into a windshield wiper 11. This blade 10 also comprises a lip 16 which provides the contact with the surface to be wiped and a hinge 14 formed by a thin strip of rubber located between the lip 16 and the heel 12. This hinge 14 provides the correct positioning of the lip 16 on the surface to be wiped, in particular during the change of direction of the wiper 11 at the reversal points. The surface to be wiped is, in the present case, a motor vehicle windshield.

(9) Represented in FIG. 3 is an enlargement of the lip 16 of a wiping blade 10. This lip 16 comprises a material based on elastomer(s) 18 and a coating 19 on its outer surface 22, that is to say the surface of the lip located on the opposite side from the heel 12. The coating has a surface 23 intended to be in contact with the surface to be wiped.

(10) It can be seen that the material based on elastomer(s) 18 comprises macromolecular chains represented by horizontal lines 24. Similarly, the coating 19 comprises, in this example, two layers 20 and 21 each comprising a filler represented by particles 26 and 27 trapped in binder formed of a polymer matrix, the macromolecular chains of which are represented by horizontal lines 28 and 29. The particles 26 and 27 may be of a different nature. Thus, in this example, the particles 26 are graphite particles whereas the particles 27 are a mixture of carbon nanotubes with graphite.

(11) A schematic representation of the increased crosslinking that exists between the macromolecular chains 24, 28 and 29 can also be seen.

(12) The increased crosslinking is, in the present case, carried out by ion bombardment. The ions bombarded may either be implanted by participating in the covalent bonding between the two polymer chains or else merely communicate its energy, which will enable the creation of the covalent bond between the two polymer chains.

(13) This increased crosslinking is therefore due to covalent bonds between macromolecular chains 29 created owing to the ions bombarded. These covalent bonds between the macromolecular chains are represented in FIG. 3 by vertical lines 30. As a function of the parameters of the ion bombardment, covalent bonds 30 may also be formed between the macromolecular chains 28 and between the macromolecular chains 24.

(14) The reader will understand that the macromolecular chains 24, 28 and 29 are not necessarily horizontal chains, that they can be oriented in all directions, criss-cross. Nevertheless, the chains 24, 28 and 29 are not mixed with one another in the sense that they each belong to an independent layer or material before ion bombardment.

(15) This increased crosslinking has the effect of stiffening the member at least over its superficial thickness. It also makes it possible to create a barrier across which the various chemical species cannot migrate, whether from the outside to the inside or from the inside to the outside.

(16) In the layers 20, 21 of the coating, this increased crosslinking makes it possible to create a polymer matrix that is also more dense, which more effectively traps the particles 26 and 27. This makes it possible to reduce the shedding of these particles 26, 27 and therefore the wear of the blade.

(17) When the covalent bonds 30 are created, owing to the ions bombarded, between the macromolecular chains of different layer(s) and material it is then referred to more specifically as co-crosslinking. Covalent bonds are created between macromolecular chains 29 of the second layer 21 of the coating 19 and macromolecular chains 28 of the first layer 20 of the coating 19 and also between macromolecular chains 24 of the material based on elastomer(s) 18 and macromolecular chains 28 of the first layer 20 of the coating 19 through the ions bombarded. These bonds enable a better anchoring of the coating 19 to the material based on elastomer(s) 18 and of the layers 20 and 21 to one another.

(18) A process for treating a pair 32 of wiping blades according to one embodiment of the invention will now be described with reference to FIGS. 4 and 5.

(19) In order to move from one step to the next of this process, the wiping member is, in this example, borne by a conveyor belt that may comprise rollers.

(20) Represented in FIG. 4 is a cross-sectional view of a pair 32 of wiping blades. A transverse axis of central symmetry of the pair, parallel to the axis X is defined. On either side of this axis, two faces of the pair 32 are defined.

(21) This pair 32 may, for example, be obtained by a step of extrusion 40 of material based on elastomer(s). The two blades are extruded together and are attached to one another via the outer surface 22 of the lip 16 through a sacrificial bonding element 36. After vulcanization, a pair 32 of wiping blades 10 made of a material based on elastomer(s) is obtained, but in which the material based on elastomer(s) is raw, that is to say that it has not undergone any post-vulcanization treatment.

(22) Each face of the pair 32 undergoes a step 42 of depositing a coating during which at least one layer of coating 19 that makes it possible to reduce the friction of the wiping blade 10 with the windshield is deposited on a portion of the lips 16 of the wiping blades 10. This coating 19 is deposited in particular at the location where the lip 10 will be pre-split.

(23) The pair 32 then passes to the pre-splitting step 44, that is to say that using a cutting tool, a notch 34, 35 of the pair will be made on each face of the pair, perpendicular to the connection between the lip 16 of each wiping blade 10 and the sacrificial linking element 36 while leaving a portion of this connection uncut. Thus, each blade 10 is connected to the sacrificial linking element 36 by a bridge of material 38 which may be easily cut but that is strong enough to enable handling of the pair 32 without the two wiping blades 10 separating.

(24) These notches make it possible to have access to a large portion of the frontal wiping surface 37 of the material based on elastomer(s) 18. Their accuracy may be finely adjusted to within 0.10 mm or even less than 0.05 mm.

(25) More particularly, the pair 32 is continuously notched by putting the pair under tension in order to facilitate the pre-splitting operation. The cutting tool is guided by elements which provide a stable tension and also a reliable guiding of the tool.

(26) A pair 32 is thus obtained in accordance with FIG. 4, in which the notches 34, 35 are in a closed position after cutting and are represented by straight lines and in which it is possible to see the bridge of material 38 connecting each blade 10 to the sacrificial element 36 enabling the pair 32 to be handled as a single element.

(27) In order to treat the edges of the notch 34 and therefore a portion of the frontal wiping surface 37, the pair 32 is positioned so as to place the notches 34 made on one side of the pair 32 in an open position. The ion bombardment is carried out in step 46. In the open position of the notch 34, the walls of the notch 37 form an angle between 20 and 60, preferably this angle is 45.

(28) This opening of the notches 34 is achieved owing to the particular shape of the support over which the pair 32 advances.

(29) The angle formed by the walls of the notches and the angle of the beam of ions make it possible to treat, by ion bombardment, a portion of the frontal wiping face 37 and also a portion of the surface of the assembly formed by the material based on elastomer(s) 18 and coating 19 as can be seen in FIG. 3. An increased crosslinking is therefore generated over a superficial thickness between the macromolecular chains of the various layers of the coating and of the material based on elastomer(s) but also over a superficial thickness of the frontal wiping surface 37. This increased crosslinking makes it possible to guarantee good cohesion of the layers 20, 21 of the coating with one another and with the material based on elastomer(s) 18.

(30) When the first face has been treated by ion bombardment, the pair is turned over and the second face is positioned so that the notches 35 of the second face of the pair 32 are in the open position, in which position they may be treated by ion bombardment. The pair 32 is therefore treated over the two faces so that the four notches 34, 35 are treated.

(31) Preferably, the ion bombardment is carried out by placing the sources of ions vertical to the notches 34 with an angle between 0 and 45, preferably with an angle of 20.

(32) Moreover, the ion bombardment may be carried out by microsources which may be based, for example, on filament technology or on ECR (electron cyclon resonance) technology with multi-energetic nitrogen ions. Due to their very small size, these microsources make it possible to design a device for which the space requirement is not very big.

(33) The ion bombardment is generally carried out by a succession of sources of ions placed in series in order to obtain the desired treatment intensity as a function of the speed of movement of the pair 32. As a function, in particular, of the conditions for adjusting the sources, the number of sources and the speed of movement of the pair 32, it is possible to implant between 10.sup.14 and 10.sup.16 ions/cm.sup.2 in the material. The extraction voltage is between 35 kV and 100 kV.

(34) Finally, in a splitting step 48, each blade 10 is separated from the sacrificial linking element 36 by cutting the bridge of material 38. Two blades 10 are thus obtained comprising a material based on elastomer(s) 18, an outer surface of which is coated at least partly by a coating 20, the material bearing the coating having an increased crosslinking over a superficial thickness.