Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1987-05-29
1990-12-04
Lipman, Bernard
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
5253264, 525342, 525360, 525367, 525371, 525383, C08F 842
Patent
active
049754955
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for the modification of the surface of polytetrafluoroethylene or of copolymers consisting mainly of polytetrafluoroethylene by the action of a volatile and easily hydrolyzable compound on the one heated surface of the polymer and of moisture, as well as to molded elements thus modified and their use.
Polytetrafluoroethylene and copolymers containing it in preponderant amounts are especially used for the manufacture of molded elements, for example for coating of metals, because of their excellent mechanical and chemical properties. Polytetrafluoroethylene is to a large degree chemically inert and is not affected by most organic solvents. Only fluorine-containing hydrocarbons will cause polytetrafluoroethylene to swell without, however, destroying it. Especially the adhesion and wetting characteristics of polytetrafluoroethylene do not change after treatment with fluorine hydrocarbons. Decomposition reactions occur if basic fluorine or chlorotrifluoride come into contact with polytetrafluoroethylene at higher temperatures and under pressure. In regard to anorganic fluorides, e.g. uranium hexafluoride, however, polytetrafluoroethylene is completely stable (see Kunststoffhandbuch, "Fluorhaltige Polymerisate" [Handbook of Plastics, "Fluorine-containing Polymers"], Vol. 11, Chapter 4, p. 271, Carl-Hanser Verlag, Munchen).
This chemically inert behavior makes the modification of the surface of polytetrafluoroethylene extraordinarily difficult. However, it is often desirable to make the surfaces of products made of polytetrafluoroethylene hydrophilic and thereby to improve their wettability with polar fluids, such as water. Often the adhesive or adhesive properties in regard to organic coating are sought to be influenced by modification of the surface. This is of special interest when constructing multi-layered combination materials. Further, the ability to accept dye, the anti-static behavior and certain electrical properties, such as surface resistance, are improved or changed by hydrophilation.
It is known to apply to the surfaces of products made of polytetrafluoroethylene hydrophilating substances, such as non-ionogenic wetting agents, cation-active anti-static preparations or anion-active compounds. However, these do not adhere to the surface of the polytetrafluoroethylene and thus can be washed off. But a permanent modification of the surface properties of products made of polytetrafluoroethylene is desired.
It is further known to treat the surface of polytetrafluoroethylene oxidatively by corona discharge or by the effect of a chromic-sulfuric acid mixture. However, such treatment only affects the outer boundary of the surface, is expensive, negatively affects sewage disposal and in general gives little satisfaction. The same is true for treatment with sodium in liquid ammonia or other solvents with the additional disadvantage that the etching effect is reduced by UV radiation and the effects of heat.
A method for the activation of the surface of polymers made of fluorocarbon is described in U.S. Pat. No. 2,898,229. In the course of this method the articles, for example made of polytetrafluoroethylene, are first heated to a surface temperature of approximately 150.degree. C. without the surface of the polymer being materially affected. The heated surface then is brought into contact with the vapor of a volatile and easily hydrolyzable compound of silicon, titanium or germanium in the presence of moisture. Cited in this patent as examples of such volatile and easily hydrolyzable compounds are titanium tetrachloride, germanium tetrachloride and silicon tetrachloride as well as tetraisopropyl titanate. Treatment is preferably with the vapor of the volatile compound.
It is stated in the patent that these compounds react with the moisture present on the surface of the articles with the formation of oxides. The treated articles lose their customary slipperiness. Stickers will adhere to the treated surface in contrast to the untreated surface. Adhesion of epoxy resins to the sur
REFERENCES:
patent: 2898229 (1959-08-01), Herr et al.
patent: 3122445 (1964-02-01), Osborn
patent: 3442700 (1969-05-01), Yoshioka et al.
patent: 3666741 (1972-05-01), Leibecki
Karunaratna Mihal
Nottelmann Heinz
Rossbach Volker
Windeln Johannes
Lipman Bernard
Rossbach Volker
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