Patent Application
20080034526
One exemplary embodiment of the invention is depicted in the drawing and described in greater detail in the following description.
The head portion 1 or the flexible segment 2 is preferably manufactured of EPDM (ethylene propylene diene terpolymer), EPR (ethylene propylene copolymer), CR (chloroprene), NR (natural rubber), BR (polybutadiene), SBR (styrene butadiene rubber) or IR (polyisoprene) or mixtures of said substances. The wedge 3 and/or the wiper lip 4 are manufactured of a rubber material, which contains a copolymer based on isoprene. The copolymer can be a copolymer of isoprene and butadiene for example. However, one or more other monomers that can be copolymerized with isoprene can be used instead of butadiene. In addition, the wedge 3 or the wiper lip 4 can contain as further constituents of the rubber material, e.g., natural rubber, polybutadiene or another of the types of rubber cited as the material for the top portion 1 or the flexible segment 2. Furthermore, in order to better anchor the flexible segment 2 in the wedge 3, it is possible to manufacture a region 5 of the wedge 3 adjacent to the flexible segment 2 from the same material as the flexible segment 2. It is also possible to manufacture the wedge 3 from the rubber material of the top portion 1 or of the flexible segment 2 or from another rubber material, which differs from that of the top portion 1 or the wiper lip 4.
The material selection for the wedge 3 or the wiper lip 4 is based on the notion of combining rubber types that cross-link at a slow speed like polybutadiene and rubber types that cross-link quickly such as natural rubber with one another via copolymerization in one molecule strand so that a uniformly cross-linking rubber material is generated in the process. The constituent amounts of the monomers used for copolymerization can be adapted appropriately to the conditions required for the concrete application purpose.
Since natural rubber per se is already present as a polymer, one can fall back as a substitute on the isostructural monomer isoprene and copolymerize it with one or more monomers of another structure or composition.
The rubber material also contains a homogenizing agent if necessary, which guarantees a better intermixing of the various rubber types or fractions in the crude rubber material. At the same time, it produces a stabilization of the overall crude rubber material as a stable dispersion of filler materials and auxiliary agents in the crude rubber mass. Aromatic or aliphatic resins are used as homogenizing agents for example.
The rubber material also contains at least one filler material. The filler material is preferably formed from carbon black. So-called furnace black is used as carbon black for example. However, using a mixture of furnace black and thermal black has proven to be advantageous. While furnace black generally has a relatively fine granulation and with high filler contents produces namely an abrasion-resistant, but relative hard rubber material, thermal black has a coarse granulation, which also with high filler contents only produces a small increase in the hardness of the rubber material.
The constituent amounts of the two types of carbon black are preferably selected such that the highest possible filler content that is favorable for processing the rubber material is achieved, but on the other hand, so that the overall hardness of the hardened rubber material does not get too high since the system would otherwise be brittle and no longer capable of wiping for example.
A particularly high filler content can be achieved if a softening agent is also added to the rubber material since in this way the brittleness of the rubber material that increases with an increasing filler content can be counteracted effectively. Synthetic softening agents such as mineral oils are suitable as softening agents for example.
Normally, desiccants are added to the crude rubber material when manufacturing rubber materials. If these types of desiccants are dispensed with, the moisture contained in the base materials produces, during extrusion or vulcanization, a porous surface of the rubber profile being produced in this manner. A common desiccant that is used in rubber materials is calcium oxide for example. It forms calcium hydroxide upon contact with the moisture contained in the rubber material. However, problems can arise when calcium oxide is used, if there is crystallization of the resulting calcium hydroxide.
For this reason, the rubber material under discussion is manufactured without the addition of calcium oxide. In order to achieve a sufficiently good surface quality of the generated profile nevertheless, the moisture content of the base materials required to produce the rubber material is checked and if necessary they are stored separately under the exclusion of moisture. In addition, the vulcanization of the crude rubber material is performed with the shortest possible reaction time. A vulcanization system based on peroxides is particularly suited for this.
An example of an exemplary embodiment of a rubber material A for manufacturing a top portion 1 and a rubber material B for manufacturing a flexible segment 2, a wedge 3 or a wiper lip 4 of a wiper blade or their composition related to 100 parts by weight of elastomer (phr) is listed in the following:
Manufacturing the rubber material takes place in that first one or more types of rubber are added to the extruder with the filler material(s), the homogenizing agent and additional auxiliary processing agents and undergo intensive mixing there. Alternatively, the base materials can also be added to a mixer, be mixed there and, e.g., be compression molded or be fed to a injection molding process.
A profile strand is produced in this way, wherein to produce wiper rubbers for windshield wipers said strand has the form of double strand in which two wiper rubber individual strands are connected to one another in the longitudinal direction of the double strand in region of the wiper lip. The produced double strand is fed, e.g., to a salt bad or a furnace for vulcanization and vulcanized there at a temperature of approx. 205° C. Surface modification takes place as needed in a further step, e.g., via graphitizing, halogenation, painting or coating. Afterwards, the vulcanized elastomer profile is then cut in the longitudinal direction.
As an alternative, it is possible to purposefully modify only specific surface sections of a wiper blade. Therefore, using appropriate process management with targeted covering of regions of the wiper blade that are not being modified, only the wiper lip that comes into contact with the surface being cleaned can be modified or additionally or alternatively a guide groove of the wiper blade with which the wiper blade can be inserted into a corresponding wiper blade holder.
| Number | Date | Country | Kind |
|---|---|---|---|
| 103 56 942.1 | Dec 2003 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/DE04/02540 | 11/18/2004 | WO | 00 | 5/9/2007 |
