Wiping rubber for wiper blades in windshield wipers

Abstract

The invention relates to a wiping rubber for wiper blades in windshield wipers, comprising a profile body formed of an elastomer or rubber material, at least partially having a surface coating. The surface coating (22) comprises carbon fibers (24).

Claims

1. A windshield wiper blade comprising a profile formed from an elastomer material or from a rubber material, where the profile has at least partially a surface coating, characterized in that the surface coating (22) comprises carbon fibers (24), characterized in that the carbon fibers (24) have been partially carbonized but not fully carbonized, and characterized in that the length of the carbon fibers (24) is <1 mm.

2. The wiper blade as claimed in claim 1, characterized in that the carbon fibers (24) are derived from cellulose or PAN.

3. The wiper blade as claimed in claim 1, characterized in that the carbon fibers (24) are ferro- or paramagnetic.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) One embodiment of the present invention is illustrated in the figures and is described in more detail in the description below.

(2) FIG. 1 is a cross-sectional diagram of a wiper rubber in a first embodiment of the present invention, and

(3) FIG. 2 is a diagram of the chemical reactions proceeding during crosslinking of the surface coating of the wiper rubber.

DETAILED DESCRIPTION

(4) FIG. 1 depicts a wiper rubber of a wiper blade for windshield wipers in a first embodiment of the present invention. The wiper rubber 10 here encompasses a wiper stock 12, the main function of which consists in the fixing of the wiper rubber to a windshield-wiper-blade holder, not shown. To this end, the wiper rubber 10 has a cavity 14 which is enclosed by rubber material and is oriented in the longitudinal direction of the wiper rubber, and serves for introduction of a wiper-blade holder. The wiper rubber 10 also has a wiper lip 16, the wiper edge 18 of which comes into contact with a surface requiring cleaning. By way of example, there is a tiltable web 20 connecting the wiper stock 12 to the wiper lip 16, where this permits inclination of the wiper lip 16 with respect to the wiper stock 12, as a function of the direction of wiping of the windshield wiper.

(5) By way of example, the wiper rubber 10 has been manufactured from a suitable elastomer or rubber material, examples being natural rubber (NR), polychloroprene (CR), EPDM, isoprene (IR), polybutadiene (BR), styrene-butadiene (SBR), acrylonitrile-butadiene (NBR), mixtures of acrylonitrile-butadiene with PVC, and mixtures of the abovementioned rubber materials with one another.

(6) In order in particular to allow the mechanical properties of this type of wiper rubber to be influenced advantageously, it preferably has a surface coating 22 at least in the areas which come into contact with a surface requiring cleaning.

(7) By way of example, the surface coating 22 here can merely cover the lateral faces of the wiper lip 16 while omitting the wiper edge 18, as shown in FIG. 1. However, it is also possible to provide a surface coating 22 over the entire wiper lip 16 and, if appropriate, also to apply this coating at least partially on the surface of the tiltable web 20 and/or of the wiper stock 12.

(8) In the invention, the surface coating 22 encompasses, as lubricant, a filler encompassing fibers. The fibers are carbon fibers, preferably only partially carbonized. If the carbonization process is only partial, a certain number of functional groups remain on the surface of the fiber. If the partially carbonized carbon fibers are based on polyacrylonitrile (PAN) or on cellulose or on cellulose derivatives, hydroxide, amide, imide, and/or nitrile groups remain on the surface of the carbon fibers after the partial carbonization process. This permits secure fixing of the carbon fibers on the surface of the wiper rubber material by way of their functional groups, using a reactive resin. The chemical linkage of the partially carbonized carbon fibers to the surface of the wiper rubber 10 markedly increases the wear resistance of the surface coating 22.

(9) The length of the carbon fibers used is preferably by way of example smaller than 1 mm, preferably smaller than 200 m, and in particular from 3 to 100 m.

(10) A coating solution is used for the coating of the wiper rubber material, and encompasses carbon fibers and, for example, a resin component as binder. The coating solution is preferably used in the form of a two-component system and to this end preferably comprises a suitable hardener. The proportion of carbon fibers in the coating solution is by way of example from 10 to 70% by weight. The resin component used in the coating solution comprises by way of example a resin based on a cyanate ester which comprises di-, tri-, or oligocyanates.

(11) By way of example, the coating solution is applied to the wiper rubber by means of a transfer roll or by means of dipping or spraying. In the case of the wiper rubber 10 shown in FIG. 1, the coating preferably takes place on both sides of the wiper lip region. To this end, the wiper rubber profile is first extruded or, respectively, injection-molded or compression-molded in the form of a tandem profile with a connection at the wiper edges 18. The coating solution is applied after the wiper rubber profiles have been vulcanized and separated.

(12) Once the coating solution has been applied, a drying or crosslinking process takes place, the chemical principles of which are illustrated in FIG. 2. The figure is a diagram of a carbon fiber 24 which has functional groups in the form of hydroxide groups on the surface. In the example shown in FIG. 2, these react with a diisocyanate with elimination of water, thus chemically fixing the fiber 24 to the cyanate-ester-based binder matrix.

(13) In another embodiment, it is possible to render the carbon fibers ferro- or paramagnetic. To this end, these are given a prior, preferably thin, coating of a ferro- or paramagnetic material, for example by means of PVD or CVD. If an electromagnetic field is applied to the wiper rubber during or after the application of the coating solution and in particular prior to the hardening of the same, the concentration of carbon fibers 24 present in the coating solution increases at the surface of the resultant layer 22, and the carbon fibers are usually oriented perpendicularly with respect to the surface of the wiper rubber. This method can achieve a further reduction of the resistance of the surface coating 22 to friction.

(14) Examples are given below of the constitutions of coating solutions, the application of which on a wiper rubber gives a coating that markedly reduces friction.

(15) TABLE-US-00001 Embodiment 1 2 3 4 Proportion in Proportion in Proportion in Proportion in Component % by wt. % by wt. % by wt. % by wt. Carbon fibers 10.0 15.0 18.0 21.0 Polyacrylate 9.0 6.6 Polyester 6.6 Melamine 2.8 10.0 hardener Isocyanate 1.7 3.7 hardener Thickener 2.0 3.0 (solution) Butyl glycol 14.0 14.0 Water 50.5 52.0 (demineralized) Xylene 22.5 22.0 Methoxypropyl 22.5 22.0 acetate N-Butyl acetal 25.7 25.9

(16) The wiper rubber of the invention can advantageously be used in windshield wipers for motor vehicles, rail vehicles, or aircraft, and also for surface cleaning in the context of chemical processes. It is also possible to use it as seal material for door seals or window seals.