WIPER BLADE FOR A WINDSCREEN WIPER FRAME

Abstract

The invention concerns a wiper blade (1) for a windscreen wiper frame, at feast a portion of said blade (1) comprising a material made from natural rubber and at least one additive, characterised in that said additive is at least a bio-sourced plasticiser and in that said blade comprises, as the only rubber, said natural rubber in the vulcanised state, said vulcanised rubber being obtained by vulcanising a non-functionalised natural rubber. The invention also concerns a windscreen wiper frame comprising such a wiper blade and a wiper system comprising such a windscreen wiper frame.

Claims

1. A wiper blade for a windshield wiper, at least part of said blade comprising: a material based on natural rubber and at least one additive, wherein said additive is at least one biosourced plasticizer; and as the only rubber, said natural rubber in the vulcanized state, said vulcanized rubber being obtained by vulcanization of a nonfunctionalized natural rubber.

2. The wiper blade as claimed in claim 1, wherein the plasticizer is a biosourced oil.

3. The wiper blade as claimed in claim 2, wherein the difference between the solubility parameter of said biosourced oil and the solubility parameter of said natural rubber, measured in (cal/cm.sup.3).sup.1/2, is less than or equal to 2 (cal/cm.sup.3).sup.1/2.

4. The wiper blade as claimed in claim 3, wherein the solubility parameter of said biosourced oil is between 8.2 and 8.4 (cal/cm.sup.3).sup.1/2.

5. The wiper blade as claimed in claim 1, wherein said biosourced oil is selected from vegetable oils and/or fats, animal oils and/or fats, or a mixture thereof.

6. The wiper blade as claimed in claim 1, wherein said additive is moreover a biosourced reinforcing filler.

7. The wiper blade as claimed in claim 6, wherein said biosourced reinforcing filler is selected from a mineral filler, wood fibers, cellulose, diatoms, or a mixture thereof.

8. The wiper blade as claimed in claim 7, wherein said mineral filler is an aluminum silicate.

9. The wiper blade as claimed in claim 1, wherein more than 90 wt % of said material is of biosourced origin.

10. The wiper blade as claimed in claim 1, wherein said blade part comprising said material is a basic body of said blade.

11. The wiper blade as claimed in claim 1, wherein said additive is a biosourced protective agent against UV radiation.

12. The wiper blade as claimed in claim 1, wherein said additive is a nonbiosourced antioxidant and/or a nonbiosourced vulcanizing agent.

13. The wiper blade as claimed in claim 1, said blade comprising a single grade of natural rubber.

14. A windshield wiper comprising a wiper blade as claimed in claim 1.

15. A wiping system comprising a windshield wiper as claimed in claim 14.

Description

DESCRIPTION OF THE FIGURES

[0039] The invention will be better understood, and other aims, details, features and advantages of the invention will become clearer from the detailed explanatory description given hereunder, of at least one embodiment of the invention given as a purely illustrative and nonlimiting example, referring to the appended FIG. 1, which is a schematic sectional view of a wiper blade according to one embodiment of the invention.

DETAILED DESCRIPTION

[0040] The wiper blade 1 according to the invention comprises a material based on:

[0041] natural rubber, and

[0042] at least one additive.

[0043] The additive is for example a biosourced plasticizer.

[0044] A plasticizer is a component for making the material more flexible and/or easier to use for manufacturing a wiper blade. Generally, piasticizers are often oils. Here, according to the invention, the plasticizer is a biosourced oil.

[0045] The biosourced oil is selected so that the difference between the solubility parameter of the biosourced oil measured in (cal/cm.sup.3).sup.1/2 and the solubility parameter of natural rubber is less than or equal to 2 (cal/cm.sup.3).sup.1/2, or even less than or equal to 1.5 (cal/cm.sup.3).sup.1/2, or even less than or equal to 1 (cal/cm.sup.3).sup.1/2, or even less than or equal to 0.5 (cal/cm.sup.3).sup.1/2.

[0046] The solubility parameter of natural rubber is 8.3 (cal/cm.sup.3).sup.1/2.

[0047] In other words, the solubility parameter of the biosourced oil is close to the solubility parameter of natural rubber. This ensures that the biosourced oil (or a mixture of biosourced oils) selected is compatible with and has good affinity for natural rubber, i.e. the oil will mix properly with natural rubber.

[0048] Thus, the solubility parameter of the biosourced oil is between 7 and 10 (cal/cm.sup.3).sup.1/2, and preferably between 8 and 9 (cal/cm.sup.3).sup.1/2.

[0049] The biosourced oil is for example selected from vegetable oils and/or fats but also from animal oils and/or fats, or a mixture thereof.

[0050] Advantageously the vegetable oil and/or fat is selected from sunflower oil, olive oil, colza oil, linseed oil, coconut oil, castor oil, soybean oil. Preferably, it is a mixture of sunflower oil and colza oil.

[0051] The animal oil and/or fat is selected from fish oils.

[0052] These biosourced oils are known to have a solubility parameter between 8.2 and 8.4 (cal/cm.sup.3).sup.1/2. As examples, solubility parameters for a selection of oils are given in the following table:

TABLE-US-00001 sunflower oil 8.2 (cal/cm.sup.3).sup.1/2 olive oil 8.4 (cal/cm.sup.3).sup.1/2 colza oil 8.3 (cal/cm.sup.3).sup.1/2 linseed oil 8.4 (cal/cm.sup.3).sup.1/2 coconut oil 8.4 (cal/cm.sup.3).sup.1/2

[0053] According to the invention, the use of nonfunctionalized natural rubber as the only rubber of the wiper blade, in combination with one or more biosourced oils that have a solubility parameter between 8.2 and 8.4 (cal/cm.sup.3).sup.1/2, makes it possible to obtain a wiper blade that is environmentally friendly, easy to manufacture, and whose mechanical and physical properties are very suitable for wiping a motor vehicle window glass.

[0054] Preferably, the material further comprises a biosourced reinforcing filler as an additive.

[0055] The reinforcing filler makes it possible to improve the mechanical properties of the rubber. Notably it makes it possible to improve the breaking strength and/or abrasion performance of the wiper blade 1.

[0056] The biosourced reinforcing filler is for example selected from a mineral filler, wood fibers, cellulose, diatoms, or a mixture thereof. Preferably, it is a mixture of mineral filler and wood fibers.

[0057] These types of reinforcing fillers make it possible to improve the mechanical properties of natural rubber, while limiting the use of carbon black of nonbiosourced origin that is used conventionally as a reinforcing filler of elastomers in the motor vehicle sector.

[0058] The mineral filler is preferably an aluminum silicate, such as a kaolin. Kaolin means a mineral species rich in aluminum silicates, in particular rich in hydrated aluminum silicates such as kaolinite. It may also be calcined kaolin.

[0059] Advantageously, the material comprises:

[0060] between 30 and 45 wt % of natural rubber, preferably between 35 and 40 wt %,

[0061] between 35 and 55 wt % of biosourced reinforcing filler, preferably between 40 and 50 wt %, and

[0062] between 1 and 10 wt % of biosourced plasticizer, preferably between 4 and 7 wt %.

[0063] The material may also comprise one or more additives that are generally known by a person skilled in the art, notably for improving the mechanical properties, elasticity, wear resistance, resistance to external aggressive factors or else to improve the implementation of the method.

[0064] It may be a vulcanizing agent, or a protective agent against UV radiation, oxidation, ozone and/or wear, for example. The additives are of biosourced origin so that more than 90 wt % of the material is of biosourced origin, preferably more than 95 wt %, or even more than 96 wt %.

[0065] In other words, less than 10 wt % of the material is of nonbiosourced origin, preferably less than 5 wt %, or even less than 4 wt %.

[0066] Advantageously, the nonbiosourced products are products of fossil origin, notably from petrochemistry.

[0067] Thus, the material comprises as additive at least one biosourced protective agent against UV radiation. This protective agent is, for example, a metal oxide selected from titanium dioxide, zinc oxide, or a mixture thereof.

[0068] The metal oxide may be combined with an acid, such as stearic acid and/or palmitic acid. On reacting with the metal oxide, the acid forms a salt that makes it possible to dissolve the metal oxide in the mixture.

[0069] The material further comprises nonbiosourced additives. They may be at least one nonbiosourced antioxidant and/or at least one nonbiosourced vulcanizing agent.

[0070] The antioxidant is selected, for example, from diphenyl amines, paraphenylenediamines, or a mixture thereof.

[0071] The vulcanizing agent is selected, for example, from thiuram, thiazole, sulfenamide, or a mixture thereof. Preferably, it is a mixture of thiuram, thiazole and sulfenamide. Any other antioxidant and/or any other vulcanizing agent known by a person skilled in the art may be envisaged.

[0072] According to FIG. 1, the wiper blade 1 of a windshield wiper according to the invention has an elongated shape and is intended to be carried by a body of the wiper (not shown). The blade 1 comprises a lip 3 and a heel 5, which are connected by a hinge 7. Together, the lip 3, heel 5, and hinge 7 form a basic body of the blade 1.

[0073] The heel 5 makes it possible to hook the blade 1 in the body of the wiper. The lip 3 is intended to be in contact with the outside surface of a window glass such as a windshield, for wiping it.

[0074] The hinge 7 is formed by a thin strip of material, which gives the blade some flexibility and allows the latter to flip over during a change in direction of movement of the wiper, in other words the lip has a movement of flipping to and fro.

[0075] The blade 1 is obtained by a conventional method of manufacture known by a person skilled in the art.

[0076] Advantageously, at least part of the blade 1 comprises the material as described above, notably the basic body of the blade comprises this material. We may thus envisage embodiments in which, for only the lip 3 comprises the material.

[0077] only the heel 5 comprises the material,

[0078] the whole blade 1 comprises the material.

[0079] If necessary, all or part of the surface of the blade 1 may also be treated so as to modify it, for example by graphitization, plasma treatment, halogenation, ion implantation and/or deposition of a coating. This treatment makes it possible to reinforce the mechanical properties, wiping properties and/or wear resistance of the blade.

[0080] The wiper blade 1 may thus comprise a coating of the monolayer or multilayer type. The coating covers the basic body of the blade 1.

EXAMPLE

[0081] An example of a formulation of material used for making a wiper blade 1 according to the invention is given here for purposes of illustration, but the invention is not in any way limited to this. The units are in phr (parts per hundred of rubber).

TABLE-US-00002 Formulation phr Natural rubber 100 Kaolin 120 Wood fiber 5 Sunflower oil 5 Colza oil vulcanized with mineral sulfur 10 Diphenyl amine 3 Paraphenylenediamine 4 Titanium dioxide 10 Palmitic acid and stearic add 0.8 Zinc oxide 7.5 Vulcanizing system 5.25 (thiuram/thiazole/sulfenamide)

[0082] The vulcanization kinetics of this example of material was investigated. The measurements were performed according to standard ISO 3417. The results are as follows:

TABLE-US-00003 Vulcanization properties Smin. 2.8 dNm Smax. 17 dNm t.sub.s2 1.5 min t.sub.90 2.7 mm Vulcanization 5 min at 165 C.

[0083] Vulcanization takes 5 minutes at 165 C.

[0084] The Mooney viscosity of this material was also measured according to standard ISO 289. It is 54 Mooney units. From the viewpoint of application, the material can be used for an industrial process by molding or by extrusion with a mixing process with a short cycle time of the order of 4 to 8 min.

[0085] Tests were also carried out for testing the properties of this material, notably the mechanical properties.

[0086] The initial hardness of the material is 64 IRHD (international rubber hardness degrees). Hardness measurement was performed according to standards ISO 48 and ISO 188.

[0087] The measurements of tensile strength or tensile test were performed according to standard ISO 37 at 500 mm/min. The results are summarized in the following table:

TABLE-US-00004 Initial properties Tensile stress at 100% or Modulus 100% 2.5 MPa Breaking strength 10 MPa Elongation at rupture 465%

[0088] The elongation of the material subjected to elongation of 50% after 22 hours at 70 C. (50% elongation set) is 9%. It was measured according to standard ISO 2285.

[0089] The elasticity is 67% and is accompanied by a hysteresis effect of 28%. The elasticity was measured according to standard DIN53512 and the hysteresis effect was determined according to standard NFT 46002.

[0090] These properties are at the level of those of a conventional compound of nonbiosourced origin, notably based on carbon black as reinforcing filler, and nonbiosourced piasticizers.

[0091] Thus, in this example, the combination of two biosourced reinforcing fillers, kaolin and wood fiber, was used, replacing the conventional carbon black. This combination of reinforcing fillers was used together with a combination of two biosourced plasticizers, sunflower oil and colza oil. This double combination made it possible to obtain a material comprising less than 5 wt % of nonbiosourced additives that still has the mechanical properties necessary for use in wiper blade manufacture.

[0092] It should be noted that variant embodiments are of course possible and that the present invention is not limited just to wiper blades comprising the material of the formulation given as an example.