Process for producing a dispersion-coated wiper rubber

Abstract

Method for producing a wiper rubber, in particular for a windscreen wiper, comprising the process steps: a) forming a wiper rubber base body (10; 100) from a natural and / or synthetic rubber and b) Coating at least a portion of the wiper rubber base body (10; 100) with a natural and / or synthetic rubber dispersion (40; 140), wherein the rubber dispersion (40; 140) contains at least one filler, and wherein the at least one filler is added to a reaction mixture for forming the rubber primary dispersion before or during a polymer formation reaction, and wherein the at least one filler is selected from the group consisting of polyethylene particles, in particular particles of ultra-high molecular weight polyethylene, and / or nanoclay, in particular exfoliated and / or exfoliable nanoclay.

Description

[0001] The present invention relates to a process for producing a dispersion-coated wiper rubber. State of the artDisclosure of the invention

[0002] Windshield wiper rubbers are used to ensure good visibility through a windshield in wet conditions.

[0003] The document DE 10 2009 000 072 A1 describes a wiper rubber which is at least partially provided with a powder coating of a highly pre-crosslinked natural and / or synthetic rubber powder, as well as a process for its production.

[0004] The document DE 10 2007 034 328 A1 describes a strand extrudate and a method for its production. The strand extrudate is formed from an elastomer material to which a coating of a polymer material is applied.

[0005] Further relevant prior art is provided by the documents US 4 912 803 A and DE 10 2009 000 072 A1. Disclosure of the invention

[0006] The present invention relates to a method for producing a wiper rubber, in particular for a wiper blade or a windscreen wiper, for example of a motor vehicle.

[0007] The inventive method according to claim 1 for producing a wiper rubber, in particular for a windscreen wiper, comprises the process steps: a) forming a wiper rubber base body (10; 100) from a natural and / or synthetic rubber and b) Coating at least a portion of the wiper rubber base body (10; 100) with a natural and / or synthetic rubber dispersion (40; 140), wherein the rubber dispersion (40; 140) contains at least one filler, and wherein the at least one filler is added to a reaction mixture for forming the rubber primary dispersion before or during a polymer formation reaction, and wherein the at least one filler is selected from the group consisting of polyethylene particles, in particular particles of ultra-high molecular weight polyethylene, and / or nanoclay, in particular exfoliated and / or exfoliable nanoclay.

[0008] Dispersion coating has the advantage of being a health- and environmentally friendly coating process. In particular, dispersion coating can be carried out with less protective measures and thus at a lower cost than other coating processes, such as powder coating and melt coating. Furthermore, dispersion coating can achieve not only a physical but also a chemical bond, thus providing a more stable bond between the coating and the wiper rubber base than with other coating processes, such as powder coating and melt coating. Furthermore, dispersion coating is advantageously a coating process suitable for in-line production.

[0009] By forming not only the wiper rubber base body but also the coating from a natural and / or synthetic rubber - and not, for example, from another, for example chemically incompatible and / or inelastic, polymer material - the bonding stability of the coating to the wiper rubber base body can advantageously also be improved and cracking in the coating can be avoided.

[0010] The subdivision of the wiper rubber into wiper rubber base body and coating, or the multi-step, particularly two-step, production of the latter, also has the advantage that the wiper rubber base body can be made from a material with different properties than the coating. For example, the wiper rubber base body, which requires significantly more material than the coating, can be made from a cost-effective material such as ethylene propylene diene rubber (EPDM). In contrast, more cost-intensive or expensive materials, namely polymers and fillers such as nanoparticle fillers, are also used in (very) small quantities for the coating. Due to the comparatively low material usage for the coating, the overall material costs can even be reduced, even when more cost-intensive materials are used in the coating.Furthermore, dividing the wiper rubber into a wiper rubber base and a coating allows the materials of the sections to be optimized for their respective functions. The wiper rubber base, for example, can be made of a material with good dimensional stability, such as the cost-effective ethylene propylene diene rubber (EPDM), while the coating material can be optimized for high abrasion resistance, particularly surface hardness, a low coefficient of friction, and / or the minimization of running noise, for example, noise caused by friction-induced vibrations.For example, the coating material can be equipped with a higher crosslinking density and thus with lower flexibility or higher hardness, for example, a Shore hardness of approximately 90, than the material of the wiper rubber base body, which can be designed with a Shore hardness of approximately 65, for example, in particular without negatively affecting the overall flexibility of the wiper rubber. In addition, the coating material contains special fillers optimized for friction reduction or improved wiping quality and / or noise minimization. In contrast, the material of the wiper rubber base body dispenses with such specialized and usually expensive fillers and, if necessary, simpler, more readily available, and / or more cost-effective fillers can be used.In addition, the rubber dispersion coating advantageously makes it possible to dispense with a graphite coating, which conventionally tends to form water spots and / or streaks and generally only results in a poor immediate wiping quality.

[0011] According to the invention, the rubber dispersion is a primary dispersion.

[0012] A primary dispersion can be understood in particular as a dispersion which is produced by a polymer formation reaction, for example by emulsion polymerization or suspension polymerization, directly from monomers and in particular not by dispersing a (otherwise produced) polymer, in particular rubber, (secondary dispersion).

[0013] A primary dispersion can advantageously exhibit higher chemical reactivity than a secondary dispersion, which can have a beneficial effect on the stability of the coating's bond to the wiper rubber base. Furthermore, a primary dispersion can potentially produce a more uniform and / or thinner coating. Furthermore, a primary dispersion can achieve an exfoliating and / or anti-agglomeration effect on fillers, as explained in more detail below, which can have a beneficial effect on the properties of the coating and thus of the wiper rubber.

[0014] According to the invention, the rubber dispersion contains at least one filler.

[0015] According to the invention, the at least one filler is added to a reaction mixture for forming the rubber primary dispersion before or during a polymer formation reaction. This has the advantage that a particularly fine distribution of the filler in the dispersion can be achieved and agglomeration of filler particles can be avoided. This, in turn, makes it possible to achieve a particularly uniform coating and / or improve an effect caused by the filler on the properties of the coating or the wiper rubber, in particular the wiping properties. This is particularly advantageous when using nanoparticle fillers, since agglomeration, which is particularly undesirable with nanoparticle fillers, can be reduced or even avoided, and optionally an (additional) exfoliating effect on nanoparticle filler particles, such as nanotubes and / or phyllosilicates, can be achieved.

[0016] The reaction mixture for forming the rubber primary dispersion can comprise, in particular, a liquid, for example, water, monomers and optionally oligomers, as well as additives such as surfactants and / or protective colloids. The polymer formation reaction can be initiated, in particular, by adding an initiator, for example a water-soluble one, to the reaction mixture, thus allowing the onset of the polymerization reaction to be specifically controlled—for example, by setting it to a time after or during the filler addition.

[0017] According to the invention, the at least one filler is selected from the group consisting of polyethylene particles, in particular particles of ultra-high molecular weight polyethylene, and / or nanoclays (nanoclays, nanoclay minerals), in particular exfoliated and / or exfoliable nanoclay.

[0018] Optionally, an additional filler is selected from the group consisting of nanoparticle fillers, high-density polyethylene particles, polytetrafluoroethylene particles (PTFE articles), and mixtures thereof; in one embodiment, carbon nanotubes, in particular exfoliated carbon nanotubes, are selected as the additional filler.

[0019] These comparatively expensive fillers can improve the properties of the coating or wiper blade, particularly the wiping quality and / or wiping behavior, for example, with regard to reducing running noise. Their use in the coating dispersion allows for the use of small amounts of material, thus keeping overall material costs low.

[0020] A nanoparticle filler can be understood, in particular, as a filler which, at least when used as a filler within a polymer matrix, is at least substantially in the form of nanoparticles. In particular, a nanoparticle filler can be understood as both a filler which already comprises, or is at least substantially formed from, separated or exfoliated nanoparticles prior to introduction into the polymer matrix, as well as an exfoliable filler which can only be converted into nanoparticles in the rubber dispersion by exfoliation / separation.

[0021] Nanoparticles can be understood as particles which have a size in the nanometer range, in particular of less than or equal to 1000 nm, for example of less than or equal to 100 nm, optionally of less than or equal to 25 nm, at least in one spatial direction.

[0022] Before being introduced into the polymer matrix, a nanoparticle filler, particularly an exfoliable one, may optionally also comprise larger particles, for example, with a layered structure, for example, with an average particle size of less than or equal to 20 µm, in particular less than or equal to 10 µm. Particles with a layered structure may, for example, have an average particle size of less than or equal to 10 µm before being introduced into the polymer matrix and, within the layered structure, may comprise layers with layer thicknesses in the nanometer range, for example, of approximately 1 nm. These layers are then separated from one another within the polymer matrix when used as a filler, forming layered or platelet-shaped nanoparticles.

[0023] However, it is also possible for a nanoparticle filler to comprise, or at least essentially consist of, separated or exfoliated nanoparticles even before being introduced into the polymer matrix. This can be achieved, for example, by an exfoliating pretreatment, such as an organic modification.

[0024] By means of these particularly expensive fillers mentioned above, the properties of the coating or the wiper rubber, in particular the wiping quality and / or the wiping behavior, for example with regard to minimizing running noise, can be particularly significantly improved, whereby their use in the coating dispersion can not only minimize material costs, but also - due to the agglomeration-inhibiting and / or exfoliating / separating effect explained above - improve the effect achievable by these fillers.

[0025] A nanoclay can be understood in particular as a material which comprises or is formed from a, in particular mineral, layered silicate, for example montmorillonite, bentonite, kaolinite, hectorite and / or halloysite, which comprises (exfoliated / separated) nanoparticles and / or can form nanoparticles (is exfoliable / separable to nanoparticles).

[0026] Montmorillonite nanoclays, for example, can have aluminum silicate layers with layer thicknesses of about 1 nm, which are stacked to form a multilayer system of about 10 µm in size and which, when introduced into a polymer matrix, separate from each other and form layer-like or platelet-like nanoparticles with a high aspect ratio (nm × µm).

[0027] Halloysite nanoclays, on the other hand, can be formed in the form of two-layer aluminum silicate nanotubes, for example with an average size of about 15 nm x about 1000 nm.

[0028] In addition, nanoclays can be used in an organically modified form, for example to provide (directly) exfoliated / separated nanoparticles and / or to effect or improve exfoliation / separation within the polymer matrix.

[0029] For example, in the form of a quaternary alkylammonium bentonite salt, bentonite can be advantageously used as an organically modified nanoclay.

[0030] In a further embodiment, the wiper rubber base body is formed in process step a) by extrusion, in particular in the form of a wiper rubber base body strand. Extrusion is advantageously a process that can be manufactured in-line.

[0031] The wiper rubber base body can, in particular, comprise a wiper lip, a tilting rib, and a fastening section. The wiper lip can, in particular, be connected to the fastening section via the tilting rib. In the ready-to-use wiper rubber, the wiper lip can, in particular, have two side surfaces and an end surface. Wiping edges can, in particular, be formed between the side surfaces and the end surface.

[0032] In principle, it is possible to form a single profile or a single profile strand in process step a), in which the wiper lip is formed directly in the ready-to-use form (two side surfaces, one end surface and two wiping edges).

[0033] Preferably, however, the wiper rubber base body in process step a) is formed in the form of a double profile, in particular a double profile strand. A double profile can be understood as a body that corresponds to the shape of two wiper rubbers connected at the future end faces of the wiper lips. By separating, for example, cutting, in particular in the longitudinal direction of the double profile, two individual profiles or individual profile strands can be formed from such a double profile, the wiper lip end faces of which are formed by the separating or cutting surfaces.

[0034] Preferably, in process step b), the rubber dispersion is applied to at least one area of ​​the side surfaces of the wiper lip (of the single profile or double profile), in particular those areas that form the (future) wiping edges. These areas have a particularly significant effect on the wiping quality and wiping properties of the wiper blade during use.

[0035] In the case of a single profile, the end face between the two side surfaces of the wiper lip can also be coated with the rubber dispersion in process step b).

[0036] Since separation preferably occurs after process step b) and consequently, in the case of a double profile, no end faces are yet formed during the coating of process step b), the end faces of the wiper lips can, in particular, be uncoated in the case of a double profile. However, the side surface areas of the wiper lip, which later (after separation) form the wiping edges and are essentially responsible for the wiping quality or wiping properties of the wiper rubber, can also be easily coated in the case of production using a double profile. Production using a double profile can advantageously significantly increase, for example, approximately double, the number of wiper rubbers that can be produced per unit of time.

[0037] In another embodiment, the coating in process step b) is carried out by spraying the rubber dispersion. In particular, process step b) can be carried out by spray coating. This advantageously allows a uniform coating to be achieved in an in-line process.

[0038] Preferably, the wiper rubber base body is unvulcanized during coating with the natural and / or synthetic rubber dispersion in process step b). The wiper rubber base body can, in particular, be co-vulcanized and / or crosslinked together with the coating in process step d), which is explained in more detail below. This not only has the advantage of consolidating process steps and thus shortening production time, but can also have a beneficial effect on the stability of the bond between the coating and the wiper rubber base body and the uniformity of the coating, for example, by preventing cracking in the coating.

[0039] In a further embodiment, the method further comprises process step c): drying the coated wiper rubber base body. Drying can, in particular, remove the liquid, for example, water, from the rubber dispersion coating. Drying in process step c) can, in particular, be carried out using a drying process suitable for in-line production, for example, using infrared radiation.

[0040] In a further embodiment, the process further comprises process step d): (Co-)vulcanization of the dried, coated wiper rubber base body. It has proven advantageous to remove any liquid from the coated wiper rubber base body before vulcanization, or to dry it, in order to achieve the most uniform and defect-free coating possible. Vulcanization in process step d) can advantageously also be carried out in an in-line production process, for example, in a salt bath.

[0041] Furthermore, the method can comprise process step e): separating, in particular cutting, the wiper rubber base body into individual wiper rubbers. The separation in process step e) can also be carried out in a process capable of in-line production. After separation, the wiper rubbers are ready for use and can be packaged, which can be carried out in a process step f). If the wiper rubber base body is formed in the form of a double profile or double profile strand in process step a), the double profile or double profile strand can be separated into individual profiles in process step e). This can be done, for example, by separating, in particular cutting, along the double profile and, if appropriate, transversely to the double profile strand.

[0042] In-line processes can advantageously reduce overall manufacturing costs.

[0043] Since both process steps a) and b) as well as process steps c), d) and / or e) and optionally f) can be carried out in in-line production processes, it is possible to produce wiper rubbers cost-effectively by an in-line process chain, for example one which can be carried out entirely in-line.

[0044] In a further embodiment, the wiper rubber base body in process step a) is formed from chloroprene rubber (CR) and / or ethylene propylene diene rubber (EPDM).

[0045] In particular, the wiper rubber base body can be made of ethylene propylene diene rubber (EPDM). The use of ethylene propylene diene rubber advantageously achieves particularly clear visibility during wiping. Furthermore, ethylene propylene diene rubber is advantageously cost-effective and exhibits good dimensional stability.

[0046] In a further embodiment, a natural rubber (NR), chloroprene rubber (CR) and / or ethylene-propylene-diene rubber (EPDM) dispersion is used in process step b).

[0047] In a special embodiment, the rubber dispersion (or coating) and the wiper rubber base body are made of a natural and / or synthetic rubber of the same type, for example, EPDM on EPDM, NR on NR. This advantageously allows for a particularly stable bond between the coating and the wiper rubber base body.

[0048] In another embodiment, the rubber dispersion has a higher crosslinker content than the rubber of the wiper rubber base body. This advantageously allows for a higher degree of crosslinking and thus a higher hardness of the coating, which can have a beneficial effect, among other things, on the abrasion resistance and / or the coefficient of friction of the coating and thus on the wiping properties and wiping quality of the wiper rubber. The desired overall flexibility of the wiper rubber can be provided by the material of the wiper rubber base body.

[0049] With regard to further technical features and advantages of the method according to the invention, reference is hereby explicitly made to the explanations in connection with the wiper rubber produced according to the invention as well as to the figures and the figure description.

[0050] A further subject of the present disclosure is a wiper rubber, or rather, a wiper blade for a windshield wiper, for example, of a motor vehicle. The wiper rubber can be manufactured using a method according to the invention.

[0051] The wiper rubber comprises a wiper rubber base body made of a natural and / or synthetic rubber, wherein the wiper rubber base body is at least partially provided with a natural and / or synthetic rubber dispersion coating.

[0052] The dispersion coating can in particular be formed from a rubber primary dispersion.

[0053] The dispersion coating comprises at least one natural and / or synthetic rubber and at least one filler.

[0054] The dispersion coating may in particular comprise natural rubber (NR) and / or chloroprene rubber (CR) and / or ethylene propylene diene rubber (EPDM).

[0055] The above applies to the at least one filler or an additional filler. Drawings

[0056] Further advantages and advantageous embodiments of the method according to the invention are illustrated by the drawings and explained in the following description. It should be noted that the drawings are for descriptive purposes only and are not intended to limit the invention in any way. They show: Fig. 1 is a schematic perspective view of an embodiment of a wiper rubber manufactured according to the invention; and Fig. 2 a diagram illustrating an embodiment of a method according to the invention.

[0057] Fig. Figure 1 shows a wiper blade with a wiper blade base body 10 made of natural and / or synthetic rubber. The wiper blade base body has a wiper lip 11, a tilting rib 12, and a fastening section 13. The wiper lip 11 is connected to the fastening section 13 via the tilting rib 12. The wiper lip 11 has two side surfaces 11a, 11b and an end surface 11c. The wiping edges 11d, 11e are formed between the side surfaces 11a, 11b and the end surface 11c.

[0058] Fig. 1 shows that the regions of the side surfaces 11a, 11b of the wiper lip 11, which form the wiping edges 11d, 11e, are provided with a natural and / or synthetic rubber dispersion coating 40. The dispersion coating 40 may optionally comprise a higher degree of crosslinking than the wiper rubber base body 10 and / or fillers, in particular different fillers than the wiper rubber base body 10. For example, the dispersion coating 40 may comprise nanoparticle fillers, such as carbon nanoparticle fillers, for example, carbon nanotubes, and / or nanoclays, and / or particles of ultra-high molecular weight polyethylene (UHMW-PE particles) and / or polytetrafluoroethylene particles (PTFE particles).

[0059] Fig. 1 further shows that, in the embodiment shown therein, the entire side surfaces of the wiper lip 11 and the tilting web 12 are provided with the dispersion coating 40. In addition, in the Fig. In the embodiment shown in Figure 1, the fastening section 13 is also partially provided with the dispersion coating 40. The end face 11c of the wiper lip 11, however, is uncoated.

[0060] Such a wiper rubber can be produced by an embodiment of the method according to the invention using a double profile, which is within the scope of Fig. 2 is explained.

[0061] Fig. 2 illustrates that in a method step a) a wiper rubber base body 10,10';100 in the form of a wiper rubber base body double profile strand 10,10';100 is formed by extrusion from a natural and / or synthetic rubber. Fig. 1 shows that the double profile 10,10';100 is designed in the form of two wiper rubbers, the wiper rubber base bodies 10,10' of which each have a wiper lip 11,11', a tilting web 12,12' and a fastening section 13,13' and which are connected to one another at the later end faces of the wiper lips 11,11'.

[0062] Fig. 2 further shows that in a process step b) at least a part 11, 11', 12, 12' of the wiper rubber base body double profile strand 10, 10'; 100 is coated 40, 40', 140 with a natural and / or synthetic rubber dispersion 240. The rubber dispersion 240 is sprayed from nozzles 200 onto the side surfaces of the wiper lips 11, 11' and the tilting webs 12, 12' and partly onto the fastening sections 13, 13' of the wiper rubber base body double profile strand 10, 10'; 100, of which 200 are in Fig. 2, however, only one, namely an upper nozzle 200, is shown graphically. However, the nozzles 200 do not have to be arranged as in Fig. 2 shown above and below the wiper rubber base body double profile strand 10,10';100, but can also be arranged to the side of the wiper rubber base body double profile strand 10,10';100, which then, however, should not be aligned horizontally, but vertically (not shown).

[0063] Fig. 2 illustrates that in a process step c) the dispersion-coated wiper rubber base body 10,10',40,40';100,140 is then dried, for example by means of infrared radiation.

[0064] Fig. Figure 2 further illustrates that, in a subsequent process step d), the dried, coated wiper rubber base body 10, 10', 40, 40'; 100, 140 is vulcanized, for example, in a salt bath. In this case, the wiper rubber base body 10, 10'; 100 and the dispersion coating 40, 40'; 140 can, in particular, be co-vulcanized.

[0065] Subsequently, the wiper rubber base body double profile strand 10, 10', 40, 40'; 100, 140 can be separated, in particular cut, into individual wiper rubbers in a further process step e) not shown. The separation or cutting can be carried out in the longitudinal direction of the double profile to form two individual profile strands, as well as transversely to the strand direction to obtain individual wiper rubbers, which are then Fig. 1 shown an uncoated wiper lip end surface at the separating or cutting surface.

Claims

[1] Method for producing a wiper rubber, in particular for a windscreen wiper, comprising the process steps: a) forming a wiper rubber base body (10; 100) from a natural and / or synthetic rubber and b) Coating at least a portion of the wiper rubber base body (10; 100) with a natural and / or synthetic rubber dispersion (40; 140), wherein the rubber dispersion (40; 140) contains at least one filler, and wherein the at least one filler is added to a reaction mixture for forming the rubber primary dispersion before or during a polymer formation reaction, and wherein the at least one filler is selected from the group consisting of polyethylene particles, in particular particles of ultra-high molecular weight polyethylene, and / or nanoclay, in particular exfoliated and / or exfoliable nanoclay. [2] The method of claim 1, wherein an additional filler is selected from the group consisting of nanoparticle fillers, high density polyethylene particles, polytetrafluoroethylene particles, and mixtures thereof. [3] Method according to claim 2, wherein carbon nanotubes, in particular exfoliated carbon nanotubes, are selected as additional filler. [4] Method according to one of claims 1 to 3, wherein the wiper rubber base body (10; 100) is formed in method step a) by extrusion, in particular in the form of a wiper rubber base body strand. [5] Process according to one of claims 1 to 4, wherein the coating in process step b) is carried out by spraying the rubber dispersion. [6] Method according to one of claims 1 to 5, wherein the wiper rubber base body (10; 100) in process step a) is formed from ethylene-propylene-diene rubber and / or chloroprene rubber, in particular ethylene-propylene-diene rubber, and wherein in process step b) an ethylene-propylene-diene rubber, chloroprene rubber and / or natural rubber dispersion is used. [7] Method according to one of claims 1 to 6, wherein the rubber dispersion (40;140) has a higher crosslinker content than the rubber of the wiper rubber base body (10;100). [8] A method according to any one of claims 1 to 7, wherein the method further comprises the steps of: c) drying the coated wiper rubber base body (10,40;100,140) and d) vulcanizing the dried, coated wiper rubber base body (10,40;100,140), in particular wherein the drying in process step c) is carried out by infrared irradiation and wherein the vulcanizing in process step d) is carried out in a salt bath.

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