Wiper blade for a windscreen wiper

Abstract

Wiper blade for a windscreen wiper, at least one portion of said blade comprising a material based (i) on an elastomer containing natural rubber and ethylene-propylene-diene monomer (EPDM), and (ii) on at least one additive, characterized in that the additive is at least one biobased oil comprising free fatty acids and mono-, di- and triacylglycerols of fatty acids, said fatty acids having C28-C31 hydrocarbon chains and / or C34-C36 hydrocarbon chains. The invention also relates to the use of a modified biobased oil as plasticizer and to a method for preparing a wiper blade of a windscreen wiper.

Description

Wiper blade for windshield wiper blade

[0001] The invention relates to a wiper blade for a windshield wiper, in particular composed in part of bio-sourced materials, as well as methods for preparing such a wiper blade.

[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. This 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 efficient 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 fillers and plasticizers, the use of natural rubber can significantly reduce the amount of petrochemical-derived materials.

[0006] Application EP3546302 describes materials for windshield wiper blades in which the elastomer is composed of a mixture of natural rubber, in particular non-functionalized, and EPDM (ethylene-propylene-diene monomer) of bio-sourced origin.

[0007] WO2017 / 194776 describes wiper blades for windshield wipers comprising a natural rubber-based material and at least one plasticizer which is a bio-sourced vegetable oil, such as sunflower oil.

[0008] The use of these materials makes it possible to prepare wiper blades for which the amount of raw material of petroleum origin is reduced; the blades made from these materials have good characteristics in terms of mechanical strength and sliding properties.

[0009] Conventionally, the production of a blade from the mixture is obtained by shaping, either by compression in a mold or by extrusion through a die, before vulcanization begins. The materials are well suited to the manufacture of blades by a compression molding process, which involves vulcanization at a temperature of approximately 180°C.

[0010] A particular problem is encountered when using an extrusion preparation process. Indeed, the continuous temperature for the crosslinking reaction, for example in a salt bath, is around 200 – 210°C. At such temperatures, the bio-sourced oils present in the rubber mixture will generate fumes, in particular due to their high volatility.

[0011] The fumes generated will make the workshop environment dangerous. In addition, the flash point of the vegetable oil may be reached. At the flash point temperature, the amount of gas formed increases in pressure and can cause an ignition when it comes into contact with a heat source, such as an electric arc.

[0012] For rapeseed oil, for example, the flash point is just above 200°C, which is much too close to the salt bath temperature of 210°C. Using it would carry too great a risk of the salt bath catching fire.

[0013] It is therefore difficult to use bio-sourced vegetable oils in an extrusion process.

[0014] The mixtures of elastomer and vegetable oil described in the prior art are therefore generally used in compression molding processes, with more moderate temperature settings. The extrusion process is carried out from a material containing petroleum oils with a flash point temperature above 220°C.

[0015] There is therefore a need to have a composition comprising raw materials not derived from the petroleum industry, and in particular bio-sourced plasticizers, which do not have the drawbacks mentioned above and which are suitable for a manufacturing process by extrusion of windscreen wiper blades.

[0016] The inventors have now found that it is possible to use modified vegetable oils for the preparation of wiping blades in this type of process.

[0017] This is why the present invention relates to a wiper blade for a windscreen wiper, at least part of said blade comprising a material based on (i) elastomer containing natural rubber and ethylene-propylene-diene monomer (EPDM), and (ii) at least one additive, characterized in that the additive is at least one biosourced oil comprising C28-C31 hydrocarbon chains and / or C34-C36 hydrocarbon chains.

[0018] The invention also relates to the use of such a bio-sourced oil as a plasticizing agent in the composition of a wiper blade for a windshield wiper.

[0019] The invention also relates to a method for preparing a wiper blade for a windshield wiper comprising the preparation of a mixture of at least natural rubber, EPDM and a plasticizing agent which is such a biosourced oil containing C28-C31 hydrocarbon chains and C34-C36 hydrocarbon chains; it is followed by the extrusion of the mixture and then its vulcanization at a temperature greater than or equal to 200°C. The method then comprises a step of recovering the vulcanized material to constitute at least a portion of the wiper blade.

[0020] The invention finally relates to a wiping blade for a windscreen wiper blade capable of being obtained by such a method.

[0021] Indeed, bio-sourced oils, in particular oils of vegetable origin, having been treated to modify their physicochemical characteristics can be used in extrusion manufacturing processes, at high temperatures.

[0022] The vegetable oil 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 oil modified according to the invention may in particular be sunflower oil.

[0023] Treatments may include filtration, oligomerization, hydrogenation and / or distillation steps.

[0024] The oils suitable for implementing the invention consist of a mixture of hydrocarbon compounds with long linear and branched chains with typical molecular weights of C20, C30 and up to C36.

[0025] In particular, the oil contains C30 triacontane chains (melissic acid) and C36 hexatriacontane chains (hexatriacontyl acid).

[0026] The structure can be characterized by means of gas chromatography coupled with mass spectrometry (GC / MS). The modified bio-sourced oil useful according to the invention contains a mixture of hydrocarbon compounds with long linear chains, therefore of the alkane type; the mixture advantageously contains from 10 to 34% of C28-C31 chains and from 90 to 64% of C34 to C36 chains, in particular from 10 to 30% of C28-C31 chains, and in particular a ratio of 1 third of C28 to C31 (including C30 triacontane) and 2 thirds of C34 to C36 (including C36 hexatriacontane).

[0027] Advantageously, the ratio between C28-C31 chains and C34-C36 chains is 1:2.

[0028] Preferably, the oil of biosourced origin useful as a plasticizer according to the invention is essentially free of free fatty acids or triglycerides, that is to say that the content of these components in the oil is less than or equal to 0.1%, in particular less than or equal to 0.01%.

[0029] This type of oil or transformed plasticizer is characterized by a low quantity of unsaturations, which can be measured by the iodine index method according to the NF EN ISO 3961 or NF EN 14111 method.

[0030] The iodine value is correlated with the amount of unsaturations. Indeed, the higher the amount of iodine adsorbed by an oil, for example, the more it reflects a high amount of unsaturations, because iodine, through a chemical reaction, binds to the unsaturations during the experiment. Conversely, an oil composed entirely of saturated fatty acids will have an iodine value of zero.

[0031] The iodine value of the oil is less than 40, in particular is from 0.4 to 10, preferably from 0.5 to 2, preferably less than or equal to 1.5 and more preferably less than or equal to 0.9.

[0032] In particular, the iodine index of the bio-sourced plasticizer according to the invention is of the order of 0.9. This level is almost that of a Polyalphaolefine type plasticizer commonly used for the formulation of rubbers for windshield wiper blade applications (example Durasyn 166 / INEOS) which is characterized by an iodine index of 0.1, or of the premium quality stearic acid usually used and validated, with an iodine index of 0.4.

[0033] This characterization demonstrates that the chemical transformation has had a considerable effect on the vegetable oils used as raw material, which are usually characterized by much higher iodine index levels, for example sunflower oil, of the order of 127, or palm oil, one of the oils considered to be among the most saturated, of the order of 50 iodine index. For comparison, the iodine index of rapeseed oil is 97 to 107.

[0034] The oil is perfectly compatible with rubbers and EPDM, characterized by a Hildebrand solubility parameter of the order of 14 to 16 (J / cm 3 ) 1 / 2 This value is very close to that of natural rubber (NR) and EPDM respectively of 16.6 and 15.8 J / cm 3 )1 / 2.

[0035] Advantageously, the pour point (for point) of the oil is less than or equal to -15°C, and in particular the pour point is -25°C. Indeed, the oil must remain fluid at low temperature.

[0036] The flash point is above 270°C

[0037] The boiling point is above 400°C

[0038] In terms of consistency, the oil behaves similarly to a vegetable oil and can have a dynamic viscosity level of around 50 to 60cSt at 40°C according to DIN ISO3104.

[0039] Advantageously, the modified oil is substantially free of residual sterols, vitamins or fatty acids.

[0040] The invention relates in particular to a method for preparing a wiper blade for a windshield wiper which comprises

[0041] a) the preparation of a mixture comprising at least natural rubber, EPDM and a plasticizing agent which is a bio-sourced oil containing C28-C31 hydrocarbon chains and C34-C36 hydrocarbon chains as defined in this description,

[0042] b) extrusion of the mixture obtained followed by its vulcanization, at a temperature greater than or equal to 200°C,

[0043] (c) recovering the vulcanized material to constitute at least part of the wiper blade.

[0044] Such modified vegetable oils can be used in bi-material synthesis processes.

[0045] The process may in particular include a peroxide vulcanization step.

[0046] The material additive may further comprise at least one agent chosen from fillers, antioxidants and vulcanizing agents.

[0047] According to one embodiment of the invention, the EPDM is at least partly bio-sourced. The EPDM can thus comprise up to 70% bio-sourced ethylene, preferably between 40 and 60%.

[0048] 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.

[0049] 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.

[0050] Such blends of natural rubber and EPDM are described in application EP3546302.

[0051] 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.

[0052] Advantageously, the material comprises:

[0053] between 30 and 45% by weight of natural rubber, preferably between 35 and 40% by weight,

[0054] between 10 and 20% by weight of at least partly bio-sourced EPDM, preferably between 15 and 20% by weight,

[0055] between 35 and 55% by weight of reinforcing filler, preferably between 40 and 45% by weight, and

[0056] between 1 and 10% by weight of plasticizer, preferably between 2 and 5% by weight.

[0057] The wiper blade material can contain more than 50% and up to 85% recycled and / or bio-sourced material.

[0058] The composition may further contain one or more treatment promoters, including chemical base lubricants such as stearic acid. Brief description of the figures

[0059] 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:

[0060] represents a wiping blade of a windshield wiper blade according to the invention

[0061] 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.

[0062] 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.

[0063] 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.

[0064] Blade 1 is obtained by a conventional manufacturing process known to those skilled in the art.

[0065] 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:

[0066] - only lip 3 includes the material,

[0067] - only heel 5 includes the material,

[0068] - the whole blade 1 includes the material.

[0069] 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.

[0070] The wiping blade 1 may thus comprise a single-layer or multi-layer coating. The coating covers the base body of the blade 1.

[0071] Example 1: Preparation of a composition

[0072] 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. The quantities are indicated as a percentage by weight and in phr (parts per hundred of rubber) corresponding, in French, to pce (parts per hundred of elastomer).

[0073] The following formula was produced in a 130 litre Krupp industrial mixer, which delivered approximately 120 kg of raw mix in the form of a continuous strip for feeding the extruder.

[0074] formulapce%Natural Rubber50 - 8030 – 48EPDM50 – 2030 - 12Carbon black4527Oil modified according to the invention*6 – 103.5 – 6Anti-O20,70.5Desiccant53treatment promoter21.2Peroxide crosslinking agent53

[0075] The treatment promoter / anti-dispersant agent is a mixture of fatty alcohol, fatty acid and fatty acid ester, such as Aflux® 42 marketed by Lanxess.

[0076] The antioxidant used in this example is 2,2,4-Trimethyl-1,2-dihydroquinoline.

[0077] *the oil used is the product marketed under the name Vivaspes 10227®

[0078] A slide is then prepared as follows.

[0079] The composition is introduced into an extruder heated to 60-90°C in order to sufficiently fluidify the material; the fluidized mixture is then forced to pass through a die which will give it the geometry of the final part.

[0080] The profile coming out of the die is then vulcanized in a salt bath, 20 to 30m long, in the presence of NaNO3 / NaNO2 or NaNO3 / KNO3 salt brought to a temperature of 210°C.

[0081] The profile is pulled and forced by immersion in this fluidized salt bed, to pass through the oven for a sufficiently long time, of the order of 1 minute 30 seconds so that at the exit of this type of tunnel, the rubber is cooked, that is to say vulcanized.

[0082] This operation is obviously carried out with the hood closed to avoid any emissions due to the vulcanization of the rubber.

[0083] But if the hood is temporarily lifted to observe the behavior of the profile when immersed in the salt bath, it can be seen that no smoke is generated when passing through the salt bath at 210°C. Example 2

[0084] The material properties are evaluated.

[0085] The following properties are evaluated

[0086] Mooney ML Consistency: Determines the consistency of the raw material for good extruder shaping ability, according to ISO289 standard

[0087] Shore A: Rubber hardness according to ISO868. In order to remove water from the windshield, a significant scraping force is required. The hardness of rubbers for wiper blade applications should be in the range of 55 to 70 Shore A points.

[0088] Mechanical properties are measured in tensile / elongation mode according to the ISO37 standard, which provides access to the characteristics of moduli at 100% elongations (Modulus 100%) and properties up to break, i.e. resistance at break or modulus at break and elongation at break. These last two values ​​represent the ultimate properties of rubber, which are commonly expressed in rubber manufacturing.

[0089] Modulus 100% (MPa) is a measurement related to the stiffness of the rubber blade but under elongation

[0090] Var IRHD a 7d / 85°C (pts) is measured according to ISO48. Following prolonged exposure to hot air at 85°C, rubber tends to stiffen or soften.

[0091] We want to guarantee a stable level of hardness depending on aging; the variation must not be more than 3 hardness points.

[0092] varResistance at break a 7d85°C (%) and varElongation at break a 7d85°C (%) are measured according to ISO37. These data allow us to evaluate the second consequence of hot air aging by measuring the loss of resistance at break.

[0093] Elongation set = measurement of residual deformation after exposure to hot air at 85°C for 72 hours and under 50% constant elongation, according to NF ISO 2285. At the end of the 72-hour stay, the length of the specimen is measured. This has lengthened compared to the initial length. Good properties correspond to the smallest possible difference.

[0094] The results are presented in the table below

[0095] Propriétés mélange caoutchoucValeur de référenceNormeTestcaoutchoucML(1+4)100°C (pts)50.5ISO289Shore A (pts)61ISO868Modulus 100% (MPa)3.7ISO37Resistance at break (MPa)>=812Elongation at break (%)>=200230var IRHD a 7d / 85°C (pts)< + / - 3-2ISO48varResistance at break a 7d85°C (%)>=-20-13ISO37varElongation at break a 7d85°C (%)>=-20050% Elongation Set 72h at 85°C (%)14ISO2285

Claims

Wiper blade for a windscreen wiper, at least a portion of said blade comprising a material based on (i) an elastomer containing natural rubber and ethylene-propylene-diene monomer (EPDM), and (ii) at least one additive, characterized in that the additive is at least one bio-sourced oil comprising C28-C31 hydrocarbon chains and / or C34-C36 hydrocarbon chains. Wiper blade for windscreen wiper according to claim 1, characterized in that the ratio between the C28-C31 chains and the C34-C36 chains is 1:

2. Wiper blade for windscreen wiper according to any one of claims 1 or 2, characterized in that the oil contains chains of the C30 triacontane type and of the C36 hexatriacontane type. Wiper blade for windscreen wiper according to any one of claims 1 to 3, characterized in that the iodine index of the oil is less than 40, in particular is from 0.4 to 10, preferably less than or equal to 1.

5. Wiper blade for a windscreen wiper according to any one of claims 1 to 4, characterized in that the oil has a Hildebrand solubility parameter of 14 to 16 (J / cm 3 ) 1 / 2 . Wiper blade for windscreen wiper according to any one of claims 1 to 5, characterized in that the oil has a pour point less than or equal to -15°C. Wiper blade for windscreen wiper according to any one of claims 1 to 6, characterized in that the oil is a modified bio-sourced oil which contains from 10 to 34% of C28-C31 chains and from 90 to 64% of C34 to C36 chains. Wiper blade for windscreen wiper according to any of claims 1 to 7, characterized in that the additive further comprises at least one agent chosen from fillers, antioxidants and vulcanizing agents. Wiper blade for windscreen wiper according to any one of claims 1 to 8, characterized in that the EPDM contains up to 70% bio-sourced ethylene. Use of a bio-sourced oil comprising C28-C31 hydrocarbon chains and / or C34-C36 hydrocarbon chains, as defined in any one of claims 1 to 7, as a plasticizing agent in the composition of a wiper blade for a windshield wiper. A method of preparing a wiper blade for a windscreen wiper, characterized in that it comprises:a) the preparation of a mixture comprising at least natural rubber, EPDM and a plasticizing agent which is a bio-sourced oil comprising C28-C31 hydrocarbon chains and / or C34-C36 hydrocarbon chains as defined in any one of claims 1 to 7,b) the extrusion of the mixture obtained followed by its vulcanization, in particular peroxide vulcanization, at a temperature greater than or equal to 200°C,c) the recovery of the vulcanized material to constitute at least part of the wiper blade. Wiper blade for a windshield wiper blade obtainable by the method according to claim 11.

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