Wiper rubber profile and method for production thereof, and use thereof

Abstract

The invention relates to a wiper rubber profile for a windscreen wiper, in particular for a windscreen wiper of a motor vehicle, wherein: the wiper rubber profile (10) has a wiper lip (12) for cleaning a glass surface; at least the wiper lip (12) is surface-coated with particles (22) of a thermoplastic polymer material; and the particles (22) of a thermoplastic polymer material have an average particle size (D50) of < 8µm.

Description

[0001] Description

[0002] title

[0003] Wiper rubber profile and method for its production and its use

[0004] The present invention relates to a wiper rubber profile and to a method for its production and its use according to the preamble of the independent patent claims.

[0005] State of the art

[0006] Typical vehicle windshields are made of glass and therefore have a hydrophilic surface with a surface energy of over 60 mN / m. Rainwater striking the windshield can therefore wet the glass surface thoroughly. When a rubber profile of a wiper blade is moved across such a water-wetted hydrophilic glass surface, a wiper lip of the rubber profile can glide on a thin film of water that forms, a so-called hydrodynamic lubricating film. This allows the rubber profile of the wiper blade to move across the windshield to be cleaned without annoying rattling or jerking.

[0007] However, motor vehicle windshields are sometimes intentionally coated with a highly hydrophobic coating to achieve a strong water-repellent effect. For this purpose, the windshield is treated with common waxes, for example, which reduce the surface energy of the windshield to values ​​of 30 mN / m or less. This makes the glass surface highly hydrophobic, causing raindrops to bead up and roll off. A similar effect can be observed when vehicles are cleaned in a car wash, as a chemical drip aid in the form of gloss dryers, hot waxes, and gloss waxes is always added at the end of the cleaning process. These drying aids reduce the surface energy of the cleaned body, including the vehicle windows.This allows rainwater to bead up and roll off easily, preventing a hydrodynamic film from forming when cleaning a windshield with a wiper. Instead, operating the wiper often results in an unwanted stick-slip behavior of the wiper blade or even the entire wiper arm, which manifests itself in a jerky or rattling movement of the wiper strip on the windshield.

[0008] In this context, it is known from DE 10125045 A1, DE 10 2009 026 914 A1, DE 102019200001 A1, and EP 1 561 656 A to provide the surface of a rubber profile of a wiper strip for windshield wipers with polymer granules. This friction-reducing material reduces the coefficient of friction of the corresponding rubber profile on a vehicle windshield to be cleaned. At the same time, the corresponding solid lubricants are consumed during use of the wiper strip. This is the case, for example, with the wiper strip shown in DE 10201900001 A1.

[0009] The principle of reducing the coefficient of friction also applies to hydrophobic vehicle windshields. However, cleaning hydrophobic windshields in particular continues to pose a major challenge when it comes to achieving low-friction and quiet operation of a corresponding wiper strip.

[0010] Disclosure of the invention

[0011] The present invention relates to a wiper rubber profile, a method for its production and its use with the characterizing features of the independent patent claims.

[0012] Advantages of the Invention According to the invention, a wiper rubber profile is provided which is suitable for windshield wipers, in particular for motor vehicles. The wiper rubber profile comprises a wiper lip which, for cleaning a motor vehicle windshield during operation, is in physical contact with the windshield. At least the wiper lip of the wiper rubber profile is provided on the surface with particles of a thermoplastic polymer material, wherein the particles of the thermoplastic polymer material have an average grain size D50 of <8 μm and in particular an average grain size D50 of 4 to 7.5 μm.

[0013] Although the use of polymer particles with a grain size of 0.1 pm and more is already known, the invention is based on the finding that when using thermoplastic polymer particles with an average grain size D50 of <8 pm, in particular from 4 to 7.5 pm, an unexpectedly significant improvement in the wiping behavior of a correspondingly equipped wiper rubber profile when cleaning even highly hydrophobic glass panes occurs compared to a possible use of thermoplastic polymer particles with a higher average grain size, for example of 11 pm.

[0014] In this way, wiper rubber profiles and appropriately equipped wiper strips or windscreen wipers can be provided that provide largely noise-free and sufficiently good wiping performance even on hydrophobic or hydrophobized glass panes.

[0015] Advantageous embodiments of the present invention are the subject of the subclaims.

[0016] It is advantageous if the particles of a thermoplastic polymer material also have a particle size distribution D99 of <10 pm. Particles with a particle size distribution D99 of <10 pm and a mean grain size D50 of <8 pm, particularly between 4 and 7.5 pm, have the advantage of being very homogeneous particle powders, which, when applied to the surface of a wiper rubber profile, also lead to a very homogeneous coating. This has a positive effect on the resulting wiping pattern of the wiper rubber profile on the surface to be cleaned.

[0017] It is also advantageous if the particles of a thermoplastic polymer material have a ratio of the particle size distribution D99 to the average grain size D50 (D99 / D50) <1.3. Particles with a ratio of the particle size distribution D99 to the average grain size D50 (D99 / D50) <1.3 have the advantage that they are particle powders with even greater homogeneity, which lead to an even more homogeneous coating when applied to the surface of a wiper rubber profile. In particular, even with an advantageously high degree of coverage of the surface of the wiper rubber profile with particles of a thermoplastic material of >50%, it is still guaranteed that there is only a minor stacking of particles on the surface of the wiper rubber profile. This also has a positive effect on the resulting wiping pattern of the wiper rubber profile on a surface to be cleaned.

[0018] It is also advantageous if the thermoplastic polymer material is polyethylene, with ultra-high molecular weight polyethylene (UHMW-PE) being particularly preferred. However, high-density polyethylene (HDPE) is also suitable. The particular advantage of these materials is that they already have a low dry friction coefficient, even as solid material. Thus, when used in particle form, they lead to a reduction in the friction coefficient of the correspondingly coated areas of a wiper rubber profile.

[0019] Furthermore, it is advantageous if the particles of a thermoplastic polymer material form a monolayer on the surface of the wiper lip, as this ensures optimal wiping behavior of a wiper strip containing the rubber profile while at the same time ensuring maximum flexibility of the same.

[0020] According to a further advantageous embodiment of the present invention, the particles of a thermoplastic polymer material form a binder-free coating, which is in particular in direct physical contact with a rubber material of the wiper lip. This enables simplified production of the rubber profile, while at the same time ensuring that the surface properties of the rubber profile are not negatively influenced by the sliding friction properties of a possible binder material.

[0021] It is also advantageous if the wiper rubber profile, which has a head section for holding the wiper rubber profile to a wiper strip and a wiper lip for cleaning a glass surface, as well as a tilting web that connects the wiper lip and the head section, is coated with the thermoplastic polymer particles only in the area of ​​the wiper lip. It is particularly advantageous if the wiper lip is only partially coated with the thermoplastic polymer particles in areas that face a glass surface to be cleaned. The advantage is that the partial coating of wiper rubber profiles represents a process-related advantage and a cost saving with regard to the surface-coating polymer particle material to be used.

[0022] In addition, it is advantageous if the wiper rubber profile is made of an elastomer material in the form of ethylene-propylene-diene terpolymer (EPDM), ethylene-propylene copolymer (EPM), natural rubber (NR), chloroprene rubber (CR) or butadiene rubber (BR) or mixtures thereof. EPM and EPDM are particularly preferred as elastomer materials.

[0023] According to a particularly advantageous embodiment of the present invention, a corresponding wiper rubber profile is produced by first producing an extruded profile, for example, by extrusion. This extruded profile is provided with particles of a thermoplastic polymer material with an average grain size of <8 pm, in particular between 4 and 7.5 pm, and then vulcanized. The particles of a thermoplastic polymer material can be applied before vulcanizing the extruded profile.

[0024] It is particularly advantageous if the particles of a thermoplastic polymer material are applied using an aerosol or an electrostatic fluidized bed process. In both cases, thin coatings with a high particle coverage rate on the surface of the elastomer material of the wiper rubber profile are guaranteed. If the particles of a thermoplastic polymer material are applied before vulcanization of the extruded profile, the particles of a thermoplastic polymer material applied to the surface also bond with the surface of the extruded profile during vulcanization.

[0025] Short description of the drawing

[0026] Advantageous embodiments of the present invention are shown in the drawing and explained in more detail in the following description of the figures.

[0027] Figure 1 shows the schematic cross section of a wiper rubber profile according to a first embodiment of the present invention,

[0028] Figure 2 is a photographic plan view of a wiper rubber profile according to an embodiment,

[0029] Figure 3 is a photographic plan view of a wiper rubber profile according to the embodiment of the invention of a wiper rubber profile shown in Figure 1,

[0030] Figure 4 shows photographic top views of a wiper rubber profile according to the embodiments according to Figures 1 and 2 with coatings of different degrees of coverage in comparison,

[0031] Figure 5 is a graphical representation of the degree of coverage by coatings of wiper rubber profiles depending on the type of particles used in the coating, particularly with regard to coatings according to Figure 4,

[0032] Figure 6 shows photographic images of wiping patterns produced using wiper rubber profiles with surface coatings according to Figure 4, and Figure 7 shows a graphical evaluation of the wiping patterns shown in Figure 6 with regard to the wiping quality achieved.

[0033] Character description

[0034] Figure 1 shows a schematic sectional view of a wiper rubber profile 10 according to an embodiment of the present invention. The wiper rubber profile 10 comprises a wiper lip 12, which is partially provided with a coating 11 of particles of a thermoplastic polymer material. The wiper lip 12 is connected, for example, via a tilting web 14 to a head part 13 of the wiper rubber profile, wherein the head part 13 serves, for example, to hold the wiper rubber profile on a wiper strip (not shown) of a windshield wiper. Alternatively, it is also possible to provide the entire wiper lip 12 with a coating 11 of particles of a thermoplastic polymer material or even to provide the wiper rubber profile 10 as a whole with such a coating 11.

[0035] The wiper rubber profile 10 can be made of one or more elastomer materials, with particularly suitable elastomer materials being ethylene-propylene-diene terpolymer (EPDM), ethylene-propylene copolymers (EPM), natural rubber (NR), chloroprene rubber (CR), or butadiene rubber (BR), as well as mixtures thereof. For producing the coating 11 from particles of a thermoplastic polymer material, for example, particles made of polyethylene are suitable, with ultra-high molecular weight polyethylene (UHMW-PE), high molecular weight polyethylene (HMW-PE), or high-density polyethylene (HDPE) being particularly suitable.

[0036] The particular advantage of the wiper rubber profile 10 according to the invention is that thermoplastic polymer particles are selected for the coating 11, the average grain size of which D50 is <8 pm. While a beneficial friction-reducing effect can already be demonstrated for thermoplastic polymer particles with a grain size of 10 pm or more, an unexpectedly strong beneficial effect with regard to the sliding friction and wiping properties of the wiper rubber profile 10 occurs when the average grain size falls below 8 pm. This is further illustrated by the photographic views of experimentally produced wiper rubber profile surfaces shown in Figures 2 and 3, as well as by experimental data.

[0037] Figure 2 shows a light micrograph of a wiper rubber profile provided with a coating 11, which has been coated with thermoplastic polymer materials in the form of UHMW-PE with an average particle diameter D50 of 12 μm. It can be seen that the corresponding particles 22 cover a large part of the surface, with noticeable open spaces 24 remaining uncoated between the particles. These uncoated open spaces 24 come into direct contact with a corresponding glass surface when the wiper rubber is used to clean it and often generate annoying squeaking noises or rattling when moving across the corresponding glass pane, for example due to a so-called stick-slip effect.

[0038] Especially on hydrophobic or partially hydrophobic windscreens, the uneven running of the wiper rubber profile and thus the corresponding wiper blade becomes noticeable through disturbing noises.

[0039] If the packing density, i.e., the number of particles per unit area of ​​the wiper rubber surface, is increased beyond the level shown in Figure 2, the remaining free surfaces 24 on the surface of the wiper rubber profile decrease, but at the same time, the flexibility of the wiper lip also decreases. As a result, the dynamic sealing effect of the wiper lip on the glass surface to be cleaned is lost, resulting in streaking during wiping, thus resulting in poor wiping quality.

[0040] If significantly smaller particles with an average grain size D50 <8 pm are used, a significantly improved surface of a wiper rubber profile can be achieved. This can be seen in Figure 3. Figure 3 shows an optical micrograph of a wiper rubber profile 10 provided with a coating 11, wherein particles 22 of a thermoplastic polymer material in the form of UHMW-PE particles are used. It can be seen that the remaining free surfaces 24 have decreased significantly compared to Figure 2 and thus only minor contact between uncoated free surfaces 24 and a glass surface to be cleaned can occur. In particular, on partially hydrophobic or fully hydrophobic windshields, the experiment shows significantly less stick-slip behavior and thus significantly less noise generation.

[0041] The dynamic sealing effect of the wiper lip is maintained, and the wiping quality remains sufficiently high. This unexpectedly high and previously unattainable effect of a wiper rubber profile with low noise and simultaneously high wiping performance represents a significant advancement in wiper rubber profiles, especially for cleaning hydrophobic glass surfaces.

[0042] At the same time, the particles of a thermoplastic polymer material form, for example, a monolayer on the surface of the wiper lip 12 or a coating 11 with a layer thickness of 4 - 15 pm. The coating 11 is, for example, binder-free, i.e., without the addition or use of an additional binder, and is in direct physical contact with the rubber material of the wiper lip 12.

[0043] The wiping behavior of both embodiments of coated wiper rubber profiles according to Fig. 2 and Fig. 3 were subjected to a test according to the following exemplary embodiments.

[0044] Examples of implementation

[0045] The preparation of an appropriate windshield, the appropriate

[0046] Tests with coated wiper rubber profiles according to Figure 2 or according to the embodiment of the invention according to Figure 3 were carried out as follows:

[0047] 1) Apply Rain-X™ to the entire windshield surface of a vehicle according to the manufacturer's instructions. Allow 15 minutes for drying.

[0048] 2) Determine the hydrophobicity of the disc by measuring the contact angle with water at five different positions. The contact angle should be 90 + 10° (this corresponds to a highly hydrophobic disc, and water beads strongly off).

[0049] 3) Installation of the wiper blades on the driver and passenger side

[0050] 4) Continuous, large-area spraying of the windscreen with water (approx. 800 ml / minute) during the entire test period

[0051] 5) Starting up the wiper system, slow wiping in motor level 1

[0052] 6) After 30 seconds of continuous wiping, the wiper blade running behavior on the driver and passenger side is assessed or measured with regard to a possible chatter amplitude (this manifests itself in rattling, jerking or shaking of the wiper blades during operation).

[0053] 7) The chatter amplitude can be determined, for example, using acceleration sensors attached to the wiper blades. Another option is image analysis using a high-speed camera.

[0054] Table 1 shows the corresponding test results of wiper rubber profiles coated with UHMW-PE polyethylene particles with different average particle sizes when wiping windshields pretreated according to the procedure described above.

[0055] Table 1

[0056] In summary, it can be seen that when using a wiper rubber profile according to the present invention, which has been coated with thermoplastic polymer particles with an average grain size D50 <8 pm, an unexpectedly high effect can be achieved with regard to the noise development during wiping processes on a hydrophobized windshield.

[0057] In addition, further test coatings were prepared on wiper rubber profiles according to the embodiment shown in Figure 1 and comparatively according to the embodiments of the invention shown in Figure 2, which were coated with polyethylene particles made of UHMW-PE with first and second average particle sizes with different degrees of coverage of the surface of the wiper rubber profile with particles.

[0058] Figure 4 shows corresponding first wiper rubber profiles with a coating containing first particles A, which have a particle size distribution D50 of 11 pm and D99 of 17 pm and a ratio D99 / D50 of 1.5, and corresponding second wiper rubber profiles with a coating containing second particles B, which have a particle size distribution D50 of 6 pm and D99 of 8 pm and a ratio D99 / D50 of 1.3. For comparison, surface images of wiper rubber profiles coated with a coating containing particles A and B are shown, respectively, at different degrees of coverage of the respective wiper rubber profile with particles A and B, respectively, of 40, 45, 50, 55 and 60%.

[0059] It can be seen that, in general, coatings containing particles B, with a comparable degree of coverage of the surface of a wiper rubber profile coated therewith, show a significantly more uniformly structured surface than surfaces of wiper rubber profiles coated with coatings containing particles B.

[0060] This is not least due to the fact that surface coatings containing particles B, even at high coverage levels, are significantly less likely to form a coating that deviates from a monolayer of particles on the surface of the wiper rubber profile, showing areas that correspond to a double or multiple layer of particles on the surface of the wiper rubber on top of each other.

[0061] This is illustrated, for example, in Figure 5. Figure 5 shows a plot of the degree of coverage of the surface of a wiper rubber profile with particles A, B and C, where the particles C here have a particle size distribution D50 of 11 pm, D99 of 19 pm and a ratio D99 / D50 of 1.7. The plot of the degree of coverage is shown over the respective split as a percentage of the proportion of particles A, B, C that are present in a monolayer on the surface of the respective wiper rubber profile and particles A', B', C' that are arranged in a double or multiple layer on the surface of the wiper rubber profile.

[0062] As a result, it can be seen from Figure 5 that in coatings containing particles C, these are present up to a coverage of 45% essentially in the form of a monolayer on the surface of a wiper rubber profile, in coatings containing particles A, these are present up to a coverage of 50% essentially in the form of a monolayer on the surface of a wiper rubber profile, and in coatings containing particles B according to the invention, these are present up to a coverage of 55% essentially in the form of a monolayer on the surface of a wiper rubber profile.

[0063] It has been shown that coatings on wiper rubber profiles according to the invention containing particles B form a substantially homogeneous monolayer without the formation of multilayer regions up to a high coverage of 55%. The particular advantage is that a high degree of particle coverage effectively prevents a sticking effect of the rubber surface of the wiper rubber profile directly on a glass surface to be cleaned, which would otherwise lead to squeaking noises when the wiper rubber profile is moved across the surface to be cleaned.The effective prevention of the formation of multi-layered regions deviating from a monolayer of particles B up to a coverage of 55% results in a very good wiping pattern on glass surfaces that are cleaned with a wiper rubber profile of the type according to the invention, since multi-layered regions in a coating of a wiper rubber profile lead to streaking during the wiping process due to their relative elevation.

[0064] Corresponding results of wiping tests on glass surfaces of the type described above are shown in Figure 6. Thus, first wiping tests were carried out with first wiper blades containing first wiper rubber profiles with coatings containing particles A and second wiping tests were carried out with second wiper blades containing second wiper rubber profiles with coatings containing particles B.

[0065] From Figure 6 it can be seen that in wiping tests with wiper blades containing first wiper rubber profiles with coatings containing particles A, streaks can be seen in the wiping pattern from a coverage level of 55%, whereas in wiping tests with the second wiper blades containing second wiper rubber profiles with coatings containing particles B, no streaking can be observed even at this and a higher coverage level of 60%.

[0066] An evaluation of the wiping tests according to Figure 6 is shown in Figure 7. This evaluation shows the wiping quality in the form of a rating number on a scale of 0 - 10 over a coverage level corresponding to the respective coating. The criteria for the rating number are the number and type of detectable wiping errors in relation to their position in the field of vision of a potential driver and in relation to whether these wiping errors disappear again quickly or remain permanently detectable. Figure 7 shows that in wiping tests with wiper blades containing first wiper rubber profiles with coatings containing particles A, the rating number of the wiping pattern drops sharply from a coverage level of 55%, whereas in wiping tests with the second wiper blades containing second wiper rubber profiles coated with particles B, a consistently high rating number is maintained even at this and a higher coverage level of 60%.

[0067] The test results show that wiper rubber profiles which are surface-coated with particles of a thermoplastic polymer material which have an average grain size D50 of <8 pm, preferably an average grain size D50 of 4 to 7.5 pm, and also preferably an average grain size D99 of <10 pm, in particular a ratio of the average grain sizes of D99 / D50 <1.3, show unexpectedly positive properties when used in wiper blades of windscreen wipers.

[0068] The production of a wiper rubber profile according to Figure 1 is carried out, for example, by coating an extruded profile which is produced by extrusion, in particular before its vulcanization.

[0069] For example, a suspension containing thermoplastic polymer particles or, preferably, an aerosol containing thermoplastic polymer particles can be used, which is applied to the extruded profile before it is vulcanized. Furthermore, it is possible to apply the thermoplastic polymer particles using an electrostatic powder coating process or a fluidized bed process. In principle, it is also possible to apply the thermoplastic polymer particles after the rubber extrudate has been vulcanized. In this case, however, additional thermal treatment of the coated wiper rubber profile may still be required to achieve thermal bonding of the polymer particles to the surface of the wiper rubber profile.

[0070] Due to the extremely small particle size of the thermoplastic polymer particles used, the use of particles with a particle size distribution D50 of < 4 pm with decreasing particle size is increasingly associated with problems in the application of such particles to a surface of a wiper rubber profile to be coated, which may lead to an inhomogeneous surface quality of the coating formed from the thermoplastic particles on the surface of a wiper rubber profile and thus to a wiping pattern of lower quality.

[0071] The wiper rubber profile according to the invention can be used advantageously in windscreen wipers for motor vehicles or rail vehicles.

Claims

Claims 1 . A wiper rubber profile for a windscreen wiper, in particular for a windscreen wiper of a motor vehicle, wherein the wiper rubber profile (10) has a wiper lip (12) for cleaning a glass surface, characterized in that at least the wiper lip (12) is superficially coated with particles (22) of a thermoplastic polymer material, wherein the particles (22) of a thermoplastic polymer material have an average grain size D50 of <8 pm.

2. Wiper rubber profile according to claim 1, characterized in that the particles (22) of a thermoplastic polymer material have an average grain size D50 of 4 to 7.5 pm.

3. Wiper rubber profile according to claim 1 or 2, characterized in that the particles (22) of a thermoplastic polymer material have an average grain size D99 of <10 pm.

4. Wiper rubber profile according to one of claims 1 to 3, characterized in that the particles (22) of a thermoplastic polymer material have a ratio of the average grain sizes D99 / D50 <1.

3.

5. Wiper rubber profile according to one of the preceding claims, characterized in that the thermoplastic polymer material comprises a polyethylene, in particular an ultra-high molecular weight polyethylene (UHMW-PE), or a high-density polyethylene (PE-HD).

6. Wiper rubber profile according to one of the preceding claims, characterized in that the particles (22) of a thermoplastic Polymer material forms a monolayer on the surface of the wiper lip (12).

7. Wiper rubber profile according to one of the preceding claims, characterized in that the particles (22) of a thermoplastic polymer material form a binder-free coating (11).

8. Wiper rubber profile according to one of the preceding claims, characterized in that the particles (22) of a thermoplastic polymer material form a coating (11), wherein the particles (22) are in direct physical contact with the rubber material of the wiper lip (12).

9. Wiper rubber profile according to one of the preceding claims, characterized in that the wiper rubber profile (10) comprises a head part (13) for holding the wiper rubber profile (10) on a wiper strip and a wiper lip (12) for cleaning a glass surface and a tilting web (14) for connecting the wiper lip (12) to the head part (13) of the wiper rubber profile (10), wherein the wiper lip (13) is coated on the surface with the particles (22) of a thermoplastic polymer material.

10. Wiper rubber profile according to claim 9, characterized in that the wiper lip (12) is only partially coated with particles (22) of a thermoplastic polymer material in an area facing a glass surface to be cleaned. 11 . Wiper rubber profile according to one of the preceding claims, characterized in that the wiper rubber profile (10) is made of an elastomer material in the form of ethylene-propylene-diene terpolymer (EPDM), ethylene-propylene copolymer (EPM), natural rubber (NR) and / or butadiene rubber (BR) or mixtures thereof.

12. A method for producing a wiper rubber profile according to one of the preceding claims, comprising the steps: (a) Extrusion of an extruded profile made of an elastomer material, (b) applying particles of a thermoplastic polymer material with an average grain size (D50) <8 pm, (c) Vulcanizing the extruded profile.

13. The method according to claim 12, characterized in that the application of particles of a thermoplastic polymer material takes place in a dispersion or by means of an electrostatic fluidized-bed process.

14. Use of a wiper rubber profile according to one of claims 1 to 11 in windscreen wipers for motor vehicles or rail vehicles.

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