Reinforced wiper blade for windshield wiper frame

Abstract

The present invention relates to a wiper blade for a windscreen wiper frame and to a wiper frame comprising said blade. The invention relates to a wiper blade, at least a portion of which comprises an elastomer-based material (i) comprising natural rubber and a vulcanized ethylene-propylene-diene monomer (EPDM), and (ii) a reinforcing filler, characterized in that the reinforcing filler comprises pozzolan. The invention also relates to the use of volcanic ash in the manufacture of said blade.

Description

Field of the Invention

[0001] The present invention relates to a wiper blade for a windshield wiper frame, in particular made partly of recycled materials. Background Art

[0002] Motor vehicles are generally equipped with a windshield wiper system to clean and / or wipe the windshield and prevent interference with the driver's environmental vision. The windshield wiper frame of such a system is generally driven by an arm that performs an angled reciprocating motion. These wiper blades rub against the outer surface of the glass, such as the windshield, and remove water, clearing it from the driver's field of vision. In a conventional version, the wiper frame is designed as a hinged rocker that holds the wiper blade at several points. A more recent version, known as the "flat wiper blade", is in the form of a semi-rigid assembly that holds the wiper blade in place along its entire length.

[0003] Generally, wiper blades are made of an elastically deformable material based on an elastomer supplemented with additives, in particular to improve its mechanical properties, elasticity, abrasion resistance and resistance to external aggression, or to facilitate the implementation of the manufacturing process. Examples include reinforcing fillers, plasticizers, vulcanizing agents and reagents for preventing UV radiation, oxidation, ozone and / or abrasion. These additives are still necessary to obtain a material with sufficient properties, especially in terms of mechanical strength, sliding performance, and without generating excessive noise, for manufacturing wiper blades in the motor vehicle industry.

[0004] In most cases, both the elastomer and the additives are petrochemical products. However, the growing desire to protect the environment and reduce CO2 emissions has led to restrictions on the use of such petrochemical products.

[0005] In the rubber industry, natural rubber can be used as the base elastomer, having high performance in terms of its elasticity and inherent mechanical properties. Natural rubber comes from rubber plantations, making it a bio-based material. In combination with bio-based plasticizers, the use of natural rubber significantly reduces the proportion of petrochemical materials.

[0006] Elastomer blends based on natural rubber (notably non-functionalized) and EPDM (ethylene-propylene-diene monomer) can be used.

[0007] However, the reinforcing fillers present in the additives generally consist of carbon black.

[0008] In most elastomer blends for windshield wipers, the carbon black content is on the order of about 25% to 30%.

[0009] Carbon black, also known as furnace black or thermal black, is produced in large quantities by the petrochemical industry via incomplete combustion of hydrocarbons.

[0010] In order to reduce the environmental impact of windscreen wiper manufacturing, the wiper blade should be made entirely or partially from recycled or bio-based materials.

[0011] It is also desirable to be able to use these materials in an industrial process at a controlled cost.

[0012] However, such materials must enable the production of a wiper blade with mechanical and physical properties suitable for wiping motor vehicle windows.

[0013] Therefore, replacing carbon black in reinforcing fillers is a delicate matter.

[0014] Specifically, it is difficult to propose fillers of natural origin, such as silica or kaolin, which are equivalent in terms of reinforcing ability.

[0015] Similarly, plant-based fillers, such as wood or cellulose, have limited compatibility with elastomeric polymers, which limits their use.

[0016] Another way to reduce the carbon footprint of wiper blade manufacturing is to use recycled materials in the reinforcing filler.

[0017] EP3546302 describes a wiper blade for a windscreen wiper frame, which comprises a partially bio-based EPDM-based material. It may contain various fillers, such as kaolin.

[0018] EP3455107 describes a wiper blade which comprises non-functionalized natural rubber as the only rubber and at least one bio-based plasticizer; the material may comprise a bio-based reinforcing filler, such as selected from mineral fillers, wood fibres, cellulose and diatoms.

[0019] FR3048216 relates to a wiper blade for a windscreen wiper frame, the wiper blade comprising a material comprising an elastomer and a reinforcing filler, which is kaolin.

[0020] Arayapranee W. et al. (J. Appl. Polym. Sci. 2008, 1165 - 1174) describe blends of natural rubber and EPDM with fillers such as rice husk ash. Summary of the Invention

[0021] Surprisingly, in the context of the present invention, it has been found that ash from industrial processes can be used in rubber formulations to replace all or part of the reinforcing filler, imparting mechanical properties similar to those of carbon black.

[0022] To this end, a subject of the present invention is a wiper blade for a windshield wiper frame, at least a part of said blade comprising a material based on (i) an elastomer containing natural rubber and ethylene-propylene-diene monomer (EPDM) in vulcanized form, and (ii) a reinforcing filler, said reinforcing filler comprising pozzolan.

[0023] The subject of the present invention is also the use of pozzolan in the manufacture of a wiper blade for a windshield wiper frame, said blade comprising an elastomer-based material containing natural rubber and ethylene-propylene-diene monomer (EPDM) in vulcanized form, and at least a reinforcing filler.

[0024] Pozzolan is a natural rock composed of basalt volcanic slag or slag with a similar composition. It has a honeycomb structure.

[0025] Pozzolan is generally a substance that can combine with lime in the presence of water to obtain a very slightly soluble hydrate.

[0026] For the purposes of the present invention, the term "pozzolan" refers to aluminosilicate substances such as fly ash from auxiliary industrial processes (such as those used in cement factories). The slag released during this process is recovered in the form of a hard granular powder, which can be reused as a filler.

[0027] The pozzolan used according to the present invention can, for example, be sourced from the combustion of shale coal burned in a thermal power plant and used in the manufacture of cement.

[0028] Pozzolan is an aluminosilicate. The composition of the elements Al, O and Si can be determined by spectrometry, in particular by a scanning microscope coupled with an Xmax 80N silicon energy-selective spectrometer. Pozzolan also contains smaller amounts of alkali metals or alkaline earth metals or transition metals; they significantly contain levels of Na, Mg, Fe, Au and calcium. Examples of pozzolan compositions suitable for the present invention are shown in Figure 2 in.

[0029] For the implementation of the present invention, the pozzolan preferably used is pozzolan in the form of amorphous particles; preferably, at least 90% of the pozzolan particles according to the present invention are in amorphous form.

[0030] Advantageously, said pozzolan particles have a spherical shape.

[0031] The pozzolan according to the present invention is in the form of particles with an average size of about 4 μm to 5 μm, especially about 4 μm. The average size of the pozzolan particles is preferably less than or equal to 5 μm, i.e. 95% of all particle populations have a size less than or equal to 5 μm.

[0032] The term "particle size" refers to the largest dimension of the particle, if it has an irregular shape.

[0033] The average particle size is determined by methods known to those skilled in the art, such as laser diffraction.

[0034] A particularly suitable pozzolan for use in the present invention is fly ash having CAS number 68131-74-8.

[0035] This volcanic ash in particulate form can be used as a reinforcing filler in elastomer-based materials. It imparts reinforcing properties compared to a mixture of the same composition but without any filler.

[0036] Surprisingly, large amounts of volcanic ash can be incorporated into rubber and EPDM based materials without changing the elastic properties of said materials. In particular, it is known from the prior art in the field of elastomer-based materials that, although fillers can stiffen the material, an excess of fillers relative to the elastomer will certainly change the stiffness of the material, but to the detriment of elasticity. As known to those skilled in the art, the amount of filler must at most be equal to the amount of elastomer.

[0037] A subject of the invention is therefore in particular a wiper blade for a windscreen wiper frame, comprising a material having one or more of the characteristics defined above, and wherein said material contains 70 to 230 phr of pozzolan.

[0038] The amounts expressed in phr (parts per hundred rubber) are much higher than the acceptable amounts for carbon black.

[0039] According to certain embodiments, the pozzolan may be present in the material in a proportion of 100 to 160 phr.

[0040] Thus, the material composition can contain a large amount of filler, making it possible to reduce the amount of rubber / EPDM and thus reduce production costs.

[0041] Thus, studies of stress-strain curves indicate that a mix containing 160 phr of pozzolan has a similar 25% modulus as a mix containing 50 phr of carbon black.

[0042] According to certain embodiments of the present invention, the reinforcing filler consists entirely of pozzolan.

[0043] According to other embodiments, the reinforcing fillers of the material contain other components, and they may in particular contain carbon black.

[0044] The pozzolan may constitute from 40 to 100% by mass of the reinforcing filler, in particular from 50 to 100% by mass of the reinforcing filler, in particular from 50 to 70%.

[0045] According to one embodiment, the material further comprises at least one reagent selected from plasticizers, UV stabilizers, antioxidants, and vulcanizing agents, particularly reagents selected from plasticizers and antioxidants.

[0046] In particular, it includes at least one plasticizer. A plasticizer is a component used to make the material more flexible and / or easier to process for manufacturing a wiper blade (made of elastomeric material). Generally, a plasticizer is usually a composition including fatty acids, particularly mineral oil or vegetable oil.

[0047] In particular, a bio-based plasticizer will be used, preferably bio-based oil.

[0048] The bio-based oil may be selected from vegetable oils and / or fats, but may also be selected from animal oils and / or fats, or mixtures thereof.

[0049] Vegetable oils and / or fats are particularly selected from sunflower oil, olive oil, rapeseed oil, linseed oil, coconut oil, castor oil, soybean oil, and mixtures thereof. The bio-based plasticizer may particularly be sunflower oil.

[0050] The elastomer contains ethylene-propylene-diene monomer (EPDM), and the EPDM is at least partially bio-based. The EPDM may thus include up to 70% bio-based ethylene, preferably between 40% and 60%.

[0051] For the purposes of the present invention, the term "bio-based" refers to products that are not of fossil origin but are obtained from renewable resources. Where applicable, it also refers to biological processes. The term "fossil-based" refers to any product derived from petroleum or coal or derivatives of petroleum or coal, particularly conventional fuel products derived from petrochemicals.

[0052] For example, bio-based ethylene can be made from ethanol obtained from at least one plant material, particularly selected from sugarcane, beets, woody plants, or mixtures thereof.

[0053] This blend of natural rubber and EPDM is described in patent application EP3546302.

[0054] In particular, an elastomer made from a blend of natural rubber and EPDM will be used, half of which is made from sugarcane ethanol.

[0055] The composition may further comprise one or more processing aids, particularly chemical lubricants such as stearic acid.

[0056] The wiper blade material can thus contain up to 75% by weight of bio-based and recycled materials, thereby reducing the proportion of petroleum-based components to less than 20% by weight.

[0057] According to an embodiment of the present invention, the elastomer is vulcanized with peroxide. This vulcanization system is described in particular in EP3546302; it does not use sulfur, which means that activators or accelerators that may be harmful to the environment are used. In this embodiment, the wiper blade material does not contain any sulfur. Preferably, the wiper blade material also does not contain any zinc oxide.

[0058] A wiper blade for a windshield wiper frame having the characteristics and composition according to the present invention can be obtained in particular by extruding the material described in this patent application.

[0059] According to another embodiment, the windshield wiper blade is obtained by molding the above material.

[0060] The subject of the present invention is also a windshield wiper frame comprising a wiper blade as defined above. Description of the Drawings

[0061] The present invention will be better understood by reading the following description given by way of example only and with reference to the accompanying drawings, in which:

[0062] Figure 1 A wiper blade of a windshield wiper frame according to the present invention is shown.

[0063] Figure 2 The elemental composition of the volcanic ash determined using a scanning electron microscope coupled with an Xmax 80N silicon energy-selective spectrometer (acquisition time: energy 15 kV / 40 s) is shown.

[0064] Figure 3 The stress-strain curves of materials containing volcanic ash or carbon black are shown.

[0065] Figure 4 The stress-strain curves of materials with a volcanic ash content ranging from 0 to 230 phr are shown. Detailed Description

[0066] According to Figure 1 , the wiper blade 1 of the windshield wiper frame according to the present invention has an elongated shape and is intended to be carried by a wiper blade body (not shown). The wiper blade 1 includes a lip 3 and a heel 5, and the lip 3 and the heel 5 are connected by a hinge 7. The assembly of the lip 3, the heel 5 and the hinge 7 forms the base of the wiper blade 1.

[0067] The heel 5 allows the wiper blade 1 to be hooked into the wiper blade body. The lip 3 is designed to contact the outer surface of a window (such as a windshield) to wipe it.

[0068] The hinge 7 is formed by a thin strip of material, which gives the wiper blade a certain flexibility and allows the wiper blade to tilt when the movement direction of the wiper changes, in other words, the lip tilts back and forth.

[0069] The wiper blade 1 is obtained by conventional manufacturing processes known to those skilled in the art.

[0070] Advantageously, at least a part of the wiper blade 1 comprises the material as described above; notably, the substrate of the wiper blade comprises this material. Embodiments can thus be envisaged, in which for example:

[0071] - only the lip 3 comprises the material,

[0072] - only the heel 5 comprises the material,

[0073] - the entire wiper blade 1 comprises the material.

[0074] If desired, all or part of the surface of the wiper blade 1 can also be treated in order to modify it, for example by graphitization, plasma treatment, halogenation, ion implantation and / or coating. Such treatment enhances the mechanical, wiping and / or wear resistance of the wiper blade.

[0075] The wiper blade 1 can thus comprise a single-layer or multi-layer coating. The coating covers the substrate of the wiper blade 1.

[0076] Example 1: Preparation of the composition

[0077] For illustrative purposes, an example of a material formulation for manufacturing a wiper blade according to the invention is given here.

[0078] [Table 1]

[0079]

[0080] Pyroblack is recycled carbon black derived from the pyrolysis of recycled used tyres.

[0081] The formulations tested were based on natural rubber + EPDM. Ultra-fine A1 is a volcanic ash, the composition of which is as Figure 2 shown, with an average particle size of 4 microns.

[0082] The processing aid or processing accelerator / anti-dispersant is a mixture of fatty alcohols, fatty acids and fatty acid esters, such as Aflux® 42 sold by Lanxess.

[0083] The antioxidant used in this example was 2,2,4-trimethyl-1,2-dihydroquinoline.

[0084] The material was prepared using standard 24D extrusion and salt bath processes.

[0085] Extrusion produced a smooth K106 profile.

[0086] The scorch time (scorch t5) at 130 °C is 15.4 minutes

[0087] Sulfuration kinetics was measured according to standard ISO3417 RPA vulcanization Def. 0.5° / frequency 100 cpm–210 °C / 10'-T0 + 1 day

[0088] ts2 (min) 0.27

[0089] t90 (min) 0.62

[0090] Tensile tests were measured at 500 mm / min according to standard ISO 37

[0091] The elongation rate (elongation set at 50% elongation) of the material that has undergone 50% elongation after 72 hours at 85 °C was measured according to standard ISO 2285

[0092] The properties of the material are shown in the following table

[0093] [Table 2]

[0094]

[0095] Example 2

[0096] To evaluate the performance of using ultrafine pozzolan as a reinforcing filler, several rubber compounds were produced with the same formulation, but only changing the type of filler

[0097] The formulations tested were as follows

[0098] Based on natural rubber

[0099] The protective system consists of diphenylamine, amine products and anti-ozonants

[0100] Conventional sulfur vulcanization with ZnO / stearic acid activator and MBTS / TMTD accelerator

[0101] Compared with the unfilled mixture (NR sulfur vulcanization) with the same formulation, the ultrafine pozzolan filler has a reinforcing effect. The results are as Figure 3 shown

[0102] For example, the 25% modulus level (which roughly corresponds to the deformation rate of the hinge of a windshield wiper blade encountered in static or operation) is on the order of 0.6 to 0.9 MPa, while the compound without the filler is only 0.3 MPa

[0103] The rubber compound can withstand a high filler content, such that for example, a compound loaded to 160 phr will reach the level of a compound containing 50 phr carbon black in terms of modulus

[0104] Example 3

[0105] The properties of elastomeric materials containing different levels of volcanic ash were measured.

[0106] Formulation used: natural rubber vulcanized by sulfur, using an industrially common system: sulfur + 2 accelerators

[0107] The type of protection system is commonly used in the formulation of windshield wiper blades.

[0108] The mixture was vulcanized under industrial cycle time conditions of 4' / 170 °C.

[0109] The filler contents are shown in the table below. They correspond to the percentages of ultrafine volcanic ash in the range of 37.8% to 66.8%.

[0110] [Table 3]

[0111]

[0112] The tensile elongation curves are shown in Figure 4 in.

[0113] Two antagonistic effects can be clearly seen when increasing the filler content in the mixture.

[0114] In the range of 0 to 100%: This is an increase in stiffness or modulus - the grey and black curves (maximum value for ultrafine A1 - 230 phr) are significantly higher than the curve obtained for the product without any filler.

[0115] Low modulus measurements can be supplemented by hardness measurements according to standard NF ISO 48 - 1, which shows that 70 phr is the minimum acceptable value for a rubber with sufficient rigidity to obtain a Shore A hardness of 51 pts in order to ensure water tightness relative to the water in contact with the windshield. Below this value, the rubber lip may be crushed, thus allowing a water film to pass when the wiper frame moves.

[0116] Between 500% - 650%: This corresponds to the range of the boundary properties of the rubber, indicating an improvement in the breaking strength when the filler content is 70 phr (17.3 MPa) compared to the unfilled compound (12.9 MPa), but the performance level decreases with the increase in stiffness.

[0117] Specifically, the compound with 130 phr is much harder than the unfilled compound (Shore A values of 56 vs 35 respectively) and has the same level of breaking strength (12.5 vs 12.9 MPa).

[0118] Finally, when exceeding this content to reach 230 phr, it approaches the brittle limit of the rubber compound at 7.5 MPa. Admittedly, the stiffness increases with the filler content, but this is at the expense of the boundary properties.

Claims

1. A wiper blade for a windshield wiper frame, at least a part of said blade comprising a material based on (i) an elastomer containing natural rubber and vulcanized ethylene-propylene-diene monomer (EPDM), and (ii) a reinforcing filler, characterized in that, said reinforcing filler comprises volcanic ash.

2. The wiper blade for a windshield wiper frame according to claim 1, characterized in that, said material contains 70 to 230 phr of volcanic ash.

3. The wiper blade for a windshield wiper frame according to at least one of claims 1 or 2, characterized in that, said volcanic ash is in the form of amorphous particles.

4. The wiper blade for a windshield wiper frame according to at least one of claims 1 to 3, characterized in that, said volcanic ash is in the form of particles with an average size of 4 to 5 μm.

5. The wiper blade for a windshield wiper frame according to at least one of claims 1 to 4, characterized in that, said reinforcing filler contains 50% to 100% by mass of volcanic ash.

6. The wiper blade for a windshield wiper frame according to at least one of claims 1 to 5, characterized in that, said material further comprises at least one reagent selected from plasticizers and antioxidants.

7. The wiper blade for a windshield wiper frame according to at least one of claims 1 to 6, characterized in that, said material contains at least one bio-based plasticizer.

8. The wiper blade for a windshield wiper frame according to at least one of claims 1 to 7, characterized in that, said elastomer is vulcanized with peroxide.

9. Use of volcanic ash according to any one of the preceding claims in the manufacture of a wiper blade for a windshield wiper frame, said wiper blade comprising an elastomer-based material containing natural rubber and vulcanized ethylene-propylene-diene monomer (EPDM), and at least a reinforcing filler.

10. A windshield wiper frame comprising a wiper blade according to any one of claims 1 to 8.

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