WO2009043905A2

WO2009043905A2 - Part including a superficial layer reducing the friction coefficient with a glazed surface

Info

Publication number: WO2009043905A2
Application number: PCT/EP2008/063230
Authority: WO
Inventors: Alexis Braun
Original assignee: Valeo Systemes D'essuyage
Priority date: 2007-10-05
Filing date: 2008-10-02
Publication date: 2009-04-09
Also published as: FR2921930B1; FR2921930A1; WO2009043905A3

Abstract

The invention relates to a part that comprises a profile made of rubber or an elastomer, characterised in that said profile is covered with a superficial layer for reducing the friction coefficient between the profile and the glazed surface, said superficial layer containing nanoparticles having a crystalline structure of the fullerene and/or nanotube type.

Description

Part comprising a surface layer reducing the coefficient of friction with a glazed surface

The present invention relates to a part comprising a rubber profile or elastomer covered with a surface layer, and a method of manufacturing said part. It applies typically, but not exclusively, to the automotive field, including wiper blades for motor vehicle windscreen wiper blades or glass surface louvers for a motor vehicle door. By way of example, US 2006/0112512 discloses a profile of the wiper blade type for wiper blade. This wiper blade, made of rubber, is obtained by mixing with the rubber matrix of said blade of carbon nanoparticles of crystalline structure of the fullerene type and / or nanotube. These nanoparticles (or sliding charges) are incorporated within the rubber matrix itself in an amount of between 0.2 and 2% by weight relative to the total weight of polymer of the rubber blade together with the nanoparticles. However, the wiper blade thus obtained has unsatisfactory slipperiness, or in other words a relatively high coefficient of friction, on a glazed surface. Indeed, the nanoparticles present in the rubber matrix in large quantities disturb the viscoelastic and mechanical properties of the wiper blade. The wiping of the glass surface by this type of wiper blade then becomes difficult. The friction of the wiper blade in alternating movements on the glass surface cause noise and rapid wear of said blade, and the drive motors of the wiper blades then become unsuitable for power. this type of effort

(Rubbing). In addition, the nanoparticles remaining relatively expensive, the blade wiper proposed in this document of the prior art is thus not really economical.

The object of the present invention is to overcome the disadvantages of the solutions of the state of the art by offering in particular a workpiece easy to implement, very economical and having a coefficient of friction significantly reduced on a surface glass.

The solution according to the present invention is to provide a part comprising a section, rubber or elastomer, characterized in that said profile is covered with a surface layer for reducing the coefficient of friction between the profile and a surface glass, said surface layer comprising nanoparticles of crystalline structure of the fullerene type and / or nanotube.

The term "rubber or elastomer profile" means a rubber or elastomer material shaped by an extrusion process or by a compression molding or injection molding process.

[0014] By crystalline structure of the fullerene type is meant any crystalline structure of spherical or ovoid form composed of atoms regularly arranged in pentagons, hexagons and / or heptagons.

By crystalline structure of the nanotube type any tubular crystalline structure composed of atoms arranged regularly in pentagons, hexagons and / or heptagons.

The crystalline structures of the fullerene and / or nanotube type can comprise compounds selected from carbon, fluorine or inorganic compounds.

By way of preferred examples, the inorganic compounds may be chosen from boron nitride and metal elements of formula MX ₂ in which M is molybdenum (Mo) or tungsten (W) and X is sulfur ( S) or selenium (Se).

The nanoparticles of crystalline structure of the fullerene type consisting of carbon typically comprise from 60 to more than 100 carbon atoms, preferably between 60 and 70 carbon atoms.

When these nanoparticles are composed of a mixture of 60- and 70-carbon carbonaceous fullerenes, they are typically called Fullerite.

This mixture is preferred for its low cost compared to so-called "pure" carbon fullerenes at 60 or 70 carbon atoms.

The nanoparticles of crystalline structure of the fullerene type of empirical formula C _m F _2n , in which m and n are integers with m greater than or equal to 60, for example equal to 60 or 70, and n greater than or equal to 15, for example between 15 and 35, can also be used in the context of the present invention. They are typically called polyfluorfullerenes.

Nanoparticles of crystalline structure of the nanotube type can be of two types, namely there exist the single-walled nanotubes or SWNT for angling Single Wall Nanotubes, and the multi-walled nanotubes or MWNT for Anglicism Multi- Wall Nanotubes, MWNT being more economical than SWNT.

In addition, in order to further reduce the cost of the surface layer, the latter may comprise sliding charges well known to those skilled in the art, which are different from said nanoparticles, for example chosen from graphite, polytetrafluoroethylene (PTFE), talc and molybdenum disulfide, or their mixture.

Interestingly, the surface layer comprises an amount of 20 to 60% by weight of nanoparticles relative to the total weight of the nanoparticles and sliding charges of the surface layer.

[0025] These lower and upper limits make it possible to guarantee optimum slip efficiency when the nanoparticles are mixed with other sliding loads.

According to a particular characteristic of the invention, the surface layer has a thickness of at most 20 microns, preferably at most 10 microns.

Indeed, beyond 20 microns thick, it may appear more easily cracks on the surface layer as well as surface defects.

For example, the formation of cracks or surface defects on the surface layer typically causes streaks on the surface. glazed during the sliding of the piece on said surface. According to another particular characteristic of the invention, the amount of said nanoparticles is at most 0.1% by weight relative to the total weight of polymer of the profile. This upper limit provides a room with optimal slip for a relatively low cost. Another object of the present invention is a method of manufacturing a part as defined above, said method comprising the following steps: i. preparing the composition comprising nanoparticles of crystalline structure of the fullerene and / or nanotube type, and ii. covering the profile, rubber or elastomer, with the composition, to form the surface layer, so as to obtain said piece. In step ii, the composition may be applied to said profile by any suitable method. According to a first embodiment according to the invention, step ii. is carried out by a method of recovery in so-called "dry" way. In other words, the dry route means that it is not necessary to disperse the composition in a liquid medium to deposit it on the rubber or elastomer profile. The holding or adhesion of the nanoparticles on the profile is made in a manner well known by Van der Waals bonds. By way of example, said profile is covered with the composition using a process chosen from dusting processes, in particular electrostatic powdering, cold deposition plasma and atmospheric plasma. At the end of step ii, the surface layer is thus directly formed so as to obtain said part. According to a second embodiment according to the present invention, step ii. is carried out by a method of recovery on track

"Wet". In other words, the wet route means that it is necessary to disperse the composition in a liquid medium to apply it to the rubber or elastomer profile.

By way of example, said profile is covered with the composition by using a process chosen from the methods for spraying the composition on the profile, dipping (or dipping) the profile in a bath of the composition or coating the profile by means of the composition.

In this second embodiment, the method further comprises the following steps:

dispersing the composition in a liquid medium, before step ii, and

heat treating the composition to evaporate the liquid medium, after step ii, to form the surface layer.

The liquid medium may be water or an organic solvent such as for example toluene or benzene. [0044] Interestingly, the composition may comprise a dispersing agent to promote the dispersion of the nanoparticles in the liquid phase composition. Of course, the viscosity of the liquid phase composition is adapted to different types of wet process used, in particular by a greater or lesser dilution of the composition in the liquid medium. Furthermore, in step i of the method according to the present invention, whether with the first or the second embodiment described above, the composition may further comprise a polymeric binder which is intended to improve the holding or adhesion of the nanoparticles on the surface of the profile. The polymeric binder may comprise any type of crosslinkable polymer or not, well known to those skilled in the art. By way of example, the polymeric binder is chosen from polyurethanes, silicones, polyacrylates and polyacrylonitriles, or their mixture. The peculiarity of these polymers is that their elasticity is in line with the elasticity of the rubber profile or elastomer. When the composition comprises a polymeric binder, the amounts of nanoparticles and polymeric binder are respectively between 40 and 80% by weight of the composition and between 20 and 60% by weight of the composition. The lower limit of 40% (nanoparticles) provides excellent slip while maintaining a sufficient strength of the nanoparticles on the profile, while the upper limit of 80% (nanoparticles) allows to maintain excellent adhesion while obtaining an acceptable slip of the nanoparticles on the profile.

When the polymeric binder requires a heat treatment to allow its crosslinking, and when the recovery step ii is carried out wet, the evaporation of the liquid medium can be carried out simultaneously or separately with the step of crosslinking by heating.

Of course, the crosslinking process is adapted to the nature of the polymeric binder and may be for example any other crosslinking process well known to those skilled in the art such as ultra violet treatment (UV crosslinking).

Other features and advantages of the present invention will become apparent in light of the examples which follow, said examples being given for illustrative and not limiting.

In order to show the advantages of the parts according to the present invention, Table 1 below details various compositions in accordance with the invention.

More particularly,

the composition 1 is composed mainly of nanoparticles of the fullerene type and of a polymeric binder;

the composition 2 is composed mainly of nanoparticles of the fullerene type and of the nanotube type, as well as of a polymeric binder;

the composition 3 is composed mainly of nanoparticles of the fullerene type and of another slip filler, as well as of a polymeric binder; and

the composition 4 is composed mainly of nanoparticles of the fullerene type and of another slip load.

In this respect, it should be noted that the amounts mentioned in Table 1 are conventionally expressed as a percentage by weight of the composition.

[0058] Table 1

Table 1

The origin of the various constituents of Table 1 is as follows.

Fullerite is a mixture consisting of carbon-containing fullerenes with 60 and 70 carbon atoms, marketed by Aldrich.

MWNT nanotubes are carbon nanotubes with multiple walls, marketed by Fullerene International.

Graphite is reference graphite KS6, marketed by Timcal.

Polyurethane resin is a polyurethane resin without reference catalyst Hybridur 570, sold by the company Safic Alcan.

Dispersion Agent is a Disperbyk 190 reference dispersion agent marketed by Byk.

Viscosity agent is a viscosity agent of the reference polyacrylate type Solthix A100, marketed by LUBRIZOL.

In a first step (step i), the various constituents of the compositions 1 to 4, referenced in Table 1, are mixed and dispersed in water to obtain aqueous phase compositions in order to apply said compositions to a wet process.

The compositions 1 to 4 further comprise a dispersing agent which improves the dispersion of the nanoparticles in a liquid medium.

The composition 4 does not comprise polymeric binder (polyurethane resin), it is preferable that it further comprises a viscosity agent to adjust the viscosity of said composition depending on the wet process used.

Of course, the compositions 1 to 4 can also be applied by a dry process. In this case, the dispersing agent of the compositions 1 to 4 is not necessary.

In general, the compositions 1 to 4 may be used preferentially to cover profiles of the wiper blade type for wiper blade of a motor vehicle or the type of glass liner surface for a motor vehicle door.

Thus, in a second step (step ii), four wiper blade wiper blades are covered respectively by the compositions 1 to 4 in the aqueous phase.

In order to improve the adhesion of said nanoparticles on the blades, the latter may be previously coated with a halogen coating, this type of coating being well known to those skilled in the art.

Said second step is carried out for example by spraying (or spraying) the aqueous composition on said wiper blade by means of nozzles, the viscosity of the composition in the aqueous phase being previously adjusted, thanks to the polymeric binder. or the viscosity agent, depending on the diameter of said nozzles in order to have a homogeneous surface layer on said blade.

In a third step, the compositions 1 to 4 in the liquid phase are then heat treated to firstly crosslink the polymeric binder and secondly evaporate the liquid medium (drying of the composition).

Thus, each of the four wiping blades covered respectively with compositions 1 to 4 in the aqueous phase is placed in an oven or an infrared (IR) oven at a temperature and for a time sufficient to evaporate the water and for allow the polyurethane resin to crosslink thermally.

Of course, the heat treatment step concerning the polymeric binder is only necessary in the case where the polymeric binder requires a temperature setting to give it its hold, or in other words in the case where the polymeric binder is thermally crosslinkable.

The crosslinking step of the polymeric binder is thus optional in the of the present invention, and is dependent on the nature of said binder. After this third step, the surface layer is formed and is obtained respectively four parts according to the present invention, these parts can be used directly as wiper blade for windshield wiper motor vehicle. The thickness of the surface layer on each wiper blade is about 6 microns and each piece comprises at most 0.1% by weight of nanoparticles relative to the total weight of polymer of the wiper blade. The four parts according to the present invention all have excellent slip on a glass surface for a relatively low cost. The present invention is not limited to the examples of parts that have just been described and relates in general to all the possible parts from the general indications provided in the description of the invention. In particular, and by way of example, it is conceivable to coat the profile of a first surface layer obtained from a composition comprising predominantly nanoparticles and 40% by weight of polymeric binder in the composition to ensure a very good adhesion of the nanoparticles on the profile. Then, this first surface layer may be covered with a second surface layer comprising only nanoparticles to ensure excellent slipperiness.

Claims

claims

1. Part comprising a profile, rubber or elastomer, characterized in that said profile is covered with a surface layer for reducing the coefficient of friction between the profile and a glass surface, said surface layer comprising nanoparticles of crystalline structure fullerene and / or nanotube type.

2. Part according to claim 1, characterized in that the crystalline structures of the fullerene and / or nanotube type comprise carbon, fluorine, boron nitride, tungsten disulfide and / or molybdenum disulphide.

3. Part according to claim 1 or 2, characterized in that the crystalline structures of the fullerene type comprise 60 to 70 carbon atoms.

4. Part according to claim 1 or 2, characterized in that the crystalline structures of the nanotube type comprise multi-walled carbon nanotubes (MWNT).

5. Part according to any one of claims 1 to 4, characterized in that the surface layer further comprises slip fillers selected from graphite, polytetrafluoroethylene (PTFE), talc and molybdenum disulphide, or their mixture .

6. Part according to claim 5, characterized in that the surface layer comprises an amount of 20 to 60% by weight of nanoparticles relative to the total weight of the nanoparticles and sliding charges of the surface layer.

7. Part according to any one of claims 1 to 6, characterized in that the surface layer has a thickness of at most 20 microns, preferably at most 10 microns.

8. Part according to any one of claims 1 to 7, characterized in that the amount of said nanoparticles is at most 0.1% by weight relative to the total weight of polymer profile.

9. A method of manufacturing a part as defined in claims 1 to 8, said method comprising the following steps: i. preparing the composition comprising nanoparticles of crystalline structure of the fullerene and / or nanotube type, and ii. covering the profile, made of rubber or elastomer, with the composition, to form the surface layer, so as to obtain said piece.

10. The method of claim 9, characterized in that in step i, the composition further comprises a polymeric binder.

11. The method of claim 10, characterized in that in step i, the amounts of nanoparticles and polymeric binder are respectively between 40 and 80% by weight of the composition and between 20 and 60% by weight of the composition .

12. The method of claim 10 or 11, characterized in that the polymeric binder is selected from polyurethanes, silicones, polyacrylates and polyacrylonitriles, or their mixture.

13. Method according to any one of claims 9 to 12, characterized in that it further comprises the following steps:

dispersing the composition in a liquid medium, before step ii, and

14. The method of claim 13, characterized in that the liquid medium is water or an organic solvent.

15. The method of claim 13 or 14, characterized in that in step i, the composition further comprises a dispersing agent.

16. Method according to any one of claims 9 to 12, characterized in that step ii. is carried out by a dry method of recovery.

17. Method according to any one of claims 9 and 13 to 15, characterized in that step ii. is carried out by a wet coating process.

18. Use of the part according to claims 1 to 8 as wiper blade for motor vehicle wiper blade.

19. The use of the part according to claim 1 to 8 as a glazed surface liner for a motor vehicle door.