Stock material or miscellaneous articles – Composite – Of silicon containing
Patent
1996-10-28
1998-06-16
Cameron, Erma
Stock material or miscellaneous articles
Composite
Of silicon containing
428451, 428492, 427387, 4274121, B05D 508
Patent
active
057667713
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
It is known that elastomers are polymer materials with rubber-elastic behavior which at room temperature can be stretched to a multiple of their normal length, with this being practically fully reversible, and which, specifically because of this property, have been used in many different technical applications. In addition to the elastic behavior, the frictional resistance frequently is also a decisive factor which in some applications, e. g., for motor vehicle tires and shoe soles, should be as high as possible but in other applications as low as possible, e. g., as rubber for wipers.
Wiper blades must meet high, partially contrary demands. On the one hand, they must be hard and sturdy enough to withstand the mechanical stresses under the prevailing operating conditions as long as possible without damage. But on the other hand, they must be elastic enough to transmit a contact pressure onto the pane over the entire surface that is wiped, which pressure should be as constant as possible. Furthermore, during wet friction and, in particular, during dry friction, the frictional resistance vis-a-vis glass should be as small as possible so that, on the one hand, the mechanical stress on the wiper is as small as possible and the wiper can be operated with as little energy as possible and, on the other hand, the stick-slip effect is prevented, i. e., uneven rubbing during wiping, especially of the dry pane. It is known that the frictional resistance can be reduced through aftertreatments of the rubber, for example, by dusting on solid substances such as talc or zinc stearate or by a chemical aftertreatment, for example, with a halogen, sulfuric acid or potassium permanganate. Chlorination with elemental chlorine is among the most widely used aftertreatment processes. It is, however, associated with health and safety risks, it is not reproducible to a satisfactory degree, and it is also accompanied by a deterioration of physical and chemical properties, for example, reduced ozone resistance, earlier material fatigue and increased wear.
Furthermore, it is known that the frictional resistance can be reduced or the sliding properties improved in that the surfaces are coated. This process is primarily applied to elastomers in which the chlorination fails, e. g., to ethylene-propylene-diene copolymers. The coating may be comprised of soft formulations of the said copolymers, but it is based to a great extent on fluoroorganic compounds, e. g., polytetrafluorethylene, which distinguishes itself because of excellent sliding characteristics. Perfluorinated polymers, however, adhere very poorly to the substrates so that optionally expensive pretreatments are required to ensure good adhesion. Furthermore, perfluorinated polymers are soft. Therefore, their surface is easily damaged which considerably impairs the functioning of the respective component, e. g., of a wiper blade or a seal.
Nass et al. (Synthesis and Properties of Transparent ZrO.sub.2 Containing p. 258 et seq.) have described a method wherein a sol generated from 3-methacryloxysilane, zirconium propylate and methacrylic acid is used as coating agent. By way of radical polymerization, a stabilizing organic network is formed in addition to the inorganic skeleton. The zirconium is tied into both. But these inorganic-organic polymers, also identified as ormocers (organically modified ceramics), are relatively brittle and their adhesion on rubber surfaces is not satisfactory. Also, zirconium propylate is a relatively expensive raw material.
ADVANTAGES OF THE INVENTION
The hard-elastic coatings according to the invention considerably reduce the frictional resistance of elastomers vis-a-vis glass for both dry friction and wet friction, they have good adhesion to rubber surfaces, they are highly elastic and sufficiently resistant to abrasion. Therefore, they are eminently suited for the coating of wiper blades made of rubber. The coatings reduce the frictional resistance of non-chlorinated rubber to levels which correspond to those of chl
Gerhard Volker
Gross Frank
Leutsch Wolfgang
Merkel Wilfried
Schmidt Helmut
Cameron Erma
Robert & Bosch GmbH
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