Reinforced wiper blade for a windscreen wiper frame

Abstract

The invention relates to a wiper blade for a windscreen wiper frame, and to a wiper frame comprising said blade. At least one part of said blade comprises an elastomer-based material (i) containing natural rubber and ethylene-propylene-diene monomer (EPDM), which is vulcanized, and (ii) reinforcing fillers, characterized in that the reinforcing fillers comprise a pozzolan. The invention further relates to the use of the pozzolan in the production of such a blade.

Description

Reinforced wiper blade for windshield wiper blade

[0001] The invention relates to a wiper blade for a windshield wiper, in particular made partly from recycled materials.

[0002] Motor vehicles are commonly equipped with windshield wiper systems to wash and / or wipe the windshield and prevent the driver's view of their surroundings from being disturbed. The wiper blades of such a system are conventionally driven by arms performing a reciprocating angular movement. These blades rub against the outer surface of the window, for example the windshield, and evacuate the water by bringing it out of the driver's field of vision. In a conventional version, the blades are made in the form of articulated levers that hold the wiper blade at several points. In a more recent version called "flat blade" (for "flat blade"), the blades are made in the form of a semi-rigid assembly that holds the wiper blade along its entire length.

[0003] Generally speaking, a wiper blade is made of elastically deformable material based on an elastomer supplemented with additives, in particular to improve its mechanical properties, elasticity, resistance to wear, external aggressions or to facilitate the implementation of the manufacturing process. These may, for example, be reinforcing fillers, plasticizer, vulcanizing agent, agent for protection against UV radiation, oxidation, ozone and / or wear. These additives remain necessary to obtain a material with sufficient properties, in particular in terms of mechanical strength, sliding properties and without generating excessive noise to be used in the automotive industry to manufacture wiper blades.

[0004] Both the elastomer and the additives are, in most cases, petrochemical products. However, the growing desire to protect the environment and reduce CO2 emissions is leading to a reduction in the use of such petrochemical products.

[0005] In the rubber industry, natural rubber can be used as a base elastomer, which is highly effective in terms of its elasticity and intrinsic mechanical properties. Natural rubber is derived from rubber cultivation, making it a bio-sourced material. Combined with bio-sourced plasticizers, the use of natural rubber can significantly reduce the amount of petrochemical-derived materials.

[0006] It is thus possible to use an elastomer mixture based on natural rubber, in particular non-functionalized, and EPDM (ethylene-propylene-diene monomer).

[0007] However, the reinforcing fillers present in the additives are most often made up of carbon black.

[0008] In most wiper blade elastomer blends, the carbon black content is in the range of 25 to 30%.

[0009] Carbon black, also called furnace black or thermal black, is massively produced by the petrochemical industry, by incomplete combustion of hydrocarbons.

[0010] In order to reduce the environmental impact of the manufacture of windshield wiper blades, it is desirable to have wiper blades made entirely or partly from recycled or bio-sourced material.

[0011] It is also desirable to be able to use these materials in industrial processes, with controlled costs.

[0012] This material must, however, make it possible to obtain wiping blades whose mechanical and physical properties are suitable for wiping a motor vehicle window.

[0013] Replacing carbon black in reinforcing fillers is therefore delicate.

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

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

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

[0017] EP3546302 describes wiper blades for windshield wipers comprising a partially bio-sourced EPDM-based material. It may contain various fillers, such as kaolin.

[0018] EP3455107 describes wiping blades comprising as the only rubber a non-functionalized natural rubber and at least one bio-sourced plasticizer; the material may comprise a bio-sourced reinforcing filler, for example chosen from a mineral filler, wood fibers, cellulose, diatoms.

[0019] FR3048216 relates to a wiper blade for a windshield wiper comprising a material which comprises an elastomer and a reinforcing filler which is a kaolin.

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

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

[0022] This is why the present invention relates to a wiper blade for a windshield wiper, at least a portion of said blade comprising a material based on (i) elastomer containing natural rubber and ethylene-propylene-diene monomer (EPDM), vulcanized and (ii) reinforcing fillers, the reinforcing fillers comprising a pozzolan.

[0023] The invention also relates to the use of pozzolan in the manufacture of a wiper blade for a windscreen wiper, said blade comprising an elastomer-based material containing natural rubber and vulcanized ethylene-propylene-diene monomer (EPDM), and at least reinforcing fillers.

[0024] Pozzolan is a natural rock made up of basaltic or similar volcanic scoria (projections). It has a honeycomb structure.

[0025] Pozzolans generally correspond to substances which, in the presence of water, can combine with lime to produce very slightly soluble hydrates.

[0026] For the purposes of the invention, pozzolan refers to silico-aluminous substances such as fly ash from ancillary industrial processes such as those in cement works. This slag emanating during the process is recovered in the form of hard particle powder which can be reused as filler.

[0027] The pozzolans useful according to the invention can, for example, be produced by the combustion of shale coals burned in thermal power stations used in the production of cement.

[0028] Pozzolans are aluminosilicates. The composition of Al, O and Si elements can be determined by spectrometry, in particular by scanning microscope coupled to an Xmax 80N silicon energy-selective spectrometer. Pozzolans also contain, in smaller quantities, alkali or alkaline-earth metals, or transition metals; they contain in particular levels of Na, Mg, Fe, Au and calcium. An example of a pozzolan composition suitable for implementing the invention is shown in the figure.

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

[0030] Advantageously, the pozzolan particles have a spheroidal shape.

[0031] The pozzolan according to the invention is in the form of particles with an average size of approximately 4 µm to 5 µm, in particular approximately 4 µm. The average size of the pozzolan particles is preferably less than or equal to 5 µm, that is to say that 95% of the population of all the particles has a size less than or equal to 5 µm.

[0032] Particle size means 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 pozzolan particularly suitable for carrying out the invention is fly ash with CAS number 68131-74-8.

[0035] Pozzolan in the form of such particles can be used as a reinforcing filler in an elastomer-based material. It provides a reinforcing character, compared to a mixture of the same composition but not containing filler.

[0036] Surprisingly, significant amounts of pozzolan can be incorporated into rubber and EPDM-based materials without altering the elastic properties of said material. Indeed, it is known from the state of the art in the field of elastomer-based materials that while fillers can stiffen the materials, too large a quantity of fillers relative to the elastomer will certainly modify the rigidity of the material but to the detriment of elasticity. Also, the person skilled in the art knows that the quantity of filler must be at most equal to the quantity of elastomer.

[0037] The invention therefore relates in particular to wiper blades for windscreen wipers comprising a material having one or more characteristics defined above, and in which the material contains from 70 to 230 pce of pozzolan.

[0038] The quantities expressed in pce (parts per hundred of elastomer) – corresponding to phr (for “parts per hundred of rubber”) in English – are much higher than those acceptable for carbon black.

[0039] According to embodiments, the pozzolan may be present in the material at a rate of 100 to 160 pce.

[0040] The composition of the material can thus contain large quantities of fillers, which makes it possible to reduce the quantity of rubber / EPDM and therefore reduce production costs.

[0041] Thus, the study of the stress-elongation curves shows that a mixture loaded with 160 pce of pozzolan has a modulus 25% similar to that of a mixture with 50 pce of carbon black.

[0042] According to certain embodiments of the invention, the reinforcing fillers consist entirely of pozzolan.

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

[0044] Pozzolan can constitute from 40 to 100% by mass of the reinforcing fillers, in particular from 50 to 100% of the reinforcing fillers, in particular from 50 to 70%.

[0045] According to one embodiment, the material further comprises at least one agent chosen from plasticizers, UV protection agents, antioxidants and vulcanization agents, in particular from plasticizers and antioxidants.

[0046] In particular, it comprises at least one plasticizer. A plasticizer is a component that makes the material more flexible and / or easier to process for the manufacture of a wiper blade (made of elastomeric material). Generally speaking, plasticizers are often compositions comprising fatty acids, in particular mineral or vegetable oils.

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

[0048] The bio-sourced oil can be chosen from vegetable oils and / or fats but also from animal oils and / or fats, or a mixture of these.

[0049] The vegetable oil and / or fat is chosen in particular from sunflower oil, olive oil, rapeseed oil, linseed oil, coconut oil, castor oil, soybean oil and mixtures thereof. The bio-sourced plasticizing agent may in particular be sunflower oil.

[0050] The elastomer contains ethylene-propylene-diene monomer (EPDM), the EPDM being at least partly bio-sourced. The EPDM may thus comprise up to 70% bio-sourced ethylene, preferably between 40 and 60%.

[0051] For the purposes of the present invention, the term "bio-sourced" means a product that is not of fossil origin but is obtained from renewable resources. Where appropriate, it also means a biological process. "Fossil-based" means any product derived from petroleum or coal or petroleum or coal derivatives, in particular traditional fuel products derived from petrochemicals.

[0052] Bio-sourced ethylene can, for example, be produced from ethanol obtained from at least one plant material, the plant material being chosen in particular from sugar cane, beetroot, a woody plant or a mixture of these.

[0053] Such blends of natural rubber and EPDM are described in application EP3546302.

[0054] In particular, an elastomer made from a mixture of natural rubber and EPDM, half of which is produced from ethanol from sugar cane cultivation, will be used.

[0055] The composition may further contain one or more treatment promoters, including chemical base lubricants such as steric acid.

[0056] The wiper blade material can thus contain a rate of bio-sourced and recycled materials by weight of 75%, which reduces the rate of petroleum-based ingredients to less than 20% by weight.

[0057] According to one embodiment of the invention, the elastomer is vulcanized with peroxide. Such a vulcanization system is described in particular in EP3546302; it does not use sulfur, which involves the use of activators or accelerators that can be harmful to the environment. In this embodiment, the material of the wiper blade does not contain sulfur. Preferably, the material of the wiper blade also does not contain zinc oxide.

[0058] The wiper blades for windshield wipers having the characteristics and composition according to the present invention can in particular be obtained by extrusion of the material described in the present application.

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

[0060] The invention also relates to a windshield wiper blade comprising a wiping blade as defined above. Brief description of the figures

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

[0062] represents a wiping blade of a windshield wiper blade according to the invention

[0063] represents the elemental composition of a pozzolan determined by scanning electron microscope coupled with an Xmax 80N silicon energy selection spectrometer (energy 15 kV / 40s acquisition time)

[0064] represents the stress-elongation curves of material containing pozzolan or carbon black...

[0065] represents the stress-elongation curves of material containing pozzolan contents from 0 to 230 pce

[0066] According to the invention, the wiping blade 1 of a windscreen wiper blade according to the invention has an elongated shape and is intended to be carried by a body of the blade (not shown). The blade 1 comprises a lip 3 and a heel 5 which are connected by a hinge 7. The lip 3, heel 5, hinge 7 assembly forms a basic body of the blade 1.

[0067] The heel 5 allows the blade 1 to be hooked into the body of the wiper. The lip 3 is intended to be in contact with the outer surface of a window such as a windshield for wiping.

[0068] The hinge 7 is formed by a thin strip of material which gives the blade a certain flexibility and allows it to tilt when the direction of movement of the broom changes, in other words a forward and backward tilting movement of the lip.

[0069] Blade 1 is obtained by a conventional manufacturing process known to those skilled in the art.

[0070] Advantageously, at least a portion of the blade 1 comprises the material as described above, in particular the basic body of the blade comprises this material. It is thus possible to envisage embodiments in which, for example:

[0071] - only lip 3 includes the material,

[0072] - only heel 5 includes the material,

[0073] - the whole blade 1 includes the material.

[0074] If necessary, all or part of the surface of the blade 1 may also be treated in such a way as to modify it, for example by graphitization, plasma treatment, halogenation, ion implantation and / or deposition of a coating. Such a treatment makes it possible to reinforce the mechanical, wiping and / or wear resistance properties of the blade.

[0075] The wiping blade 1 may thus comprise a single-layer or multi-layer coating. The coating covers the base body of the blade 1.

[0076] Example 1: Preparation of a composition

[0077] An example of a formulation of material used for the manufacture of a wiping blade in accordance with the invention is given here for illustrative purposes.

[0078] Ingredientsphr%PEFC-certified natural rubber7032EPDM 50% bio-sourced3014N5502210Pyroblack*3014Ultrafine A13014Vegetable oil209Calcium oxide83.7Antioxidant agent0.70.3Processing agent31.4Peroxide20.9

[0079] Pyroblack is a recycled black made from the pyrolysis of recycled used tires.

[0080] The tested formula is based on natural rubber + EPDM. Ultrafine A1 is a pozzolan whose composition is shown in figure 2, with an average particle size of 4 microns.

[0081] The process agent or treatment promoter / anti-dispersant agent is a mixture of fatty alcohol, fatty acid and fatty acid ester, such as Aflux® 42 marketed by Lanxess.

[0082] The antioxidant used in this example is 2,2,4-Trimethyl-1,2-dihydroquinoline

[0083] The material is prepared using a standard 24D extrusion and salt bath process.

[0084] The extrusion resulted in a smooth-looking K106 profile.

[0085] The roasting time (Scorch t5) at 130°C is 15.4 minutes

[0086] Vulcanization kinetics were measured according to ISO3417 RPA Vulcanization Def. 0.5° / Freq. 100 cpm – 210°C / 10' - T0+1 day

[0087] ts2 (min) 0.27

[0088] t90 (min) 0.62

[0089] Tensile strength measurements or tensile test were carried out according to ISO 37 at 500 mm / min.

[0090] The elongation of the material subjected to 50% elongation after 72 hours at 85°C (50% elongation set in English) was measured according to ISO 2285.

[0091] The material properties are shown in the table below

[0092] Mooney Viscosity ML(1+4)100°C (pts)46Mooney Scorch t5 / 130°C (min)15.4RPA Vulcanization Def. 0.5° / Freq. 100S'mini (dNm)1.41S'maxi (dNm)14.88Ts2 (min)0.27T90 (min)0.62BLADE ProfileK106density1.17Modulus 50% (MPa)1.6Modulus 100% (MPa)3.3Strength at break (Mpa)8Elongation at break (%)205varModulus 50% at 7d85°C(%)-950% Elongation Set 72h at 85°C (%)20

[0093] Example 2

[0094] To evaluate the performance of using ultrafine pozzolan as a reinforcing filler, several rubber blends were made with the same formulation, but varying only the type of filler

[0095] The formulations tested are as follows

[0096] Made from natural rubber;

[0097] The protection system is composed of diphenylamine and antiozonant amino products;

[0098] Conventional sulfur vulcanization with ZnO / stearic acid activators and MBTS / TMTD accelerators

[0099] The ultrafine pozzolan filler has a reinforcing character compared to a mixture of the same formulation (NR sulfur vulcanization) but without filler. The results are shown in figure number 3.

[0100] For example, we note a level of 25% Modulus (which corresponds roughly to the deformation rate of the hinge of a windscreen wiper blade encountered either statically or in operation) of the order of 0.6 to 0.9MPa compared to only 0.3MPa in an unfilled mixture.

[0101] The rubber compound is capable of supporting high load rates, so that a compound loaded at 160phr for example will have made it possible to reach the level of a compound at 50phr of black in terms of moduli.

[0102] Example 3

[0103] The performance of elastomeric material containing varying levels of pozzolan was measured.

[0104] Formula used: based on natural rubber vulcanized with sulfur according to a system commonly used in industry: sulfur + 2 accelerators

[0105] Protection system of the type traditionally used for windshield wiper blade formulas.

[0106] The mixtures are vulcanized under industrial cycle time conditions 4' / 170°C

[0107] The filler rates are shown in the table below. They correspond to percentages of ultrafine pozzolan from 37.8% to 66.8%.

[0108] phrNatural Rubber100100100100100100Ultrafine A1070100130160230Antioxidant1.51.51.51.51.51.5Antiozonant 1222222Antiozonant 2222222ZnO444444Stearic Acid0.80.80.80.80.80.8Sulfur0.750.750.750.750.750.75Accelerator Thiuram1.51.51.51.51.51.5Accelerator MBTS222222Shore A (pts)355153566068Tensile Strength (MPa)12.917.313.212.59.97.5

[0109] The tensile elongation curves are shown in figure number 4.

[0110] We can clearly see the two opposing effects that we observe when we increase the charge rate in a mixture.

[0111] In the range 0 to 100%: this is the increase in stiffness or modulus – the curves in gray and the one in black (max of Ultrafine A1 – 230phr) are significantly higher than the curve obtained for the product not containing filler.

[0112] Low modulus measurements can be supplemented by hardness measurements according to NF ISO 48-1 which show that 70phr is the minimum acceptable to obtain a sufficiently rigid rubber with a hardness of 51pts Shore A, in order to guarantee the sealing property with regard to water in contact with the windscreen. Below this value, the lip of the rubber would risk being crushed and letting a film of water pass through when the wiper moves.

[0113] Between 500 – 650%: area corresponding to the limiting properties of rubber, the improvement in breaking strength is highlighted when the loading rate is 70phr (17.3 MPa) compared to the unloaded mixture (12.9 MPa), but the performance level decreases when the stiffness level increases.

[0114] In fact, the 130phr mixture, much more rigid than the unfilled mixture (resp. 56 shore A versus 35), is found at the same level of breaking strength (12.5 versus 12.9 MPa).

[0115] Finally, when we exceed this rate to reach 230phr we approach the limit of brittleness of the rubber mixture at 7.5 MPa. Certainly the rigidity increases with the load rate, but this is to the detriment of the properties at the limits.

Claims

Wiper blade for a windshield wiper, at least a portion of said blade comprising a material based on (i) elastomer containing natural rubber and ethylene-propylene-diene monomer (EPDM), vulcanized and (ii) reinforcing fillers, characterized in that the reinforcing fillers comprise a pozzolan. Wiper blade for windscreen wiper according to claim 1, characterized in that the material contains 70 to 230 pce of pozzolan. Wiper blade for a windscreen wiper according to at least one of claims 1 or 2, characterized in that the pozzolan is in the form of amorphous particles. Wiper blade for a windscreen wiper according to at least one of claims 1 to 3, characterized in that the pozzolan is in the form of particles with an average size of 4 to 5 µm. Wiper blade for a windscreen wiper according to at least one of claims 1 to 4, characterized in that the reinforcing fillers contain from 50 to 100% by mass of pozzolan. Wiper blade for windscreen wiper according to at least one of claims 1 to 5, characterized in that the material further comprises at least one agent chosen from plasticizers and antioxidants. Wiper blade for windscreen wiper according to at least one of claims 1 to 6, characterized in that the material contains at least one bio-sourced plasticizing agent. Wiper blade for a windscreen wiper according to at least one of claims 1 to 7, characterized in that the elastomer is vulcanized with peroxide. Use of pozzolan as defined in one of the preceding claims, in the manufacture of a wiper blade for a windshield wiper, said wiper blade comprising an elastomer-based material containing natural rubber and ethylene-propylene-diene monomer (EPDM), vulcanized and at least reinforcing fillers. A windscreen wiper blade comprising a wiping blade as defined in any one of claims 1 to 8.

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