Compositions: coating or plastic – Coating or plastic compositions – Corrosion inhibiting coating composition
Patent
1993-05-27
1995-05-16
Green, Anthony J.
Compositions: coating or plastic
Coating or plastic compositions
Corrosion inhibiting coating composition
106 1411, 106 1441, 106 1442, 106 1444, 523402, 523406, 523459, C09D 510
Patent
active
054156890
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The invention relates to an anticorrosive zinc-containing undercoating agent for steel surfaces.
It is known to use zinc dust and/or zinc flakes as a corrosion-inhibiting pigment in organic undercoating agents. The undercoating agents consist essentially of a synthetic resin which is dissolved in an organic solvent in order to have a soft consistency during use. Aromatic hydrocarbons, like xylol, are primarily considered as organic solvents. The undercoating agent is stored in its liquid form in closed containers and is delivered in this manner. For a specified use, it is directly applied to the previously cleaned steel surface. By evaporating the solvent, the mixture hardens and forms a solid closed layer in which the zinc dust is contained in a finely distributed form. When moist air penetrates into the undercoating, mainly basic zinc carbonate (4ZnO.CO.sub.2.4H.sub.2 O) forms on the zinc flakes, which results during an increase in volume and in an increase in the density of the undercoating and protects the steel surface lying therebelow from destruction. A further anticorrosive effect is due to the cathodic protective action of the zinc dust pigment.
Considerable amounts of organic solvents are emitted into the surrounding air during the application of the known zinc dust undercoating agents. In order to avoid this disadvantage, it is known (EP-A-0 385 880) to use, in a two-component corrosion-inhibiting agent as the first reaction component, a powder-like or flake-like zinc, which is dispersed in an organic liquid containing a water-free, water-emulsifiable epoxy resin binding agent, and a second reaction component (component B) consisting of a water-diluted or water-dissolved polyamine hardener, which reaction components can be mixed with one another to form a viscous hardenable coating compound. The component A also contains a glycolether as a water-soluble organic solvent and silicic acid of a crystaline or amorphous consistency. The glycolether has obviously the function of improving the water emulsibility of the epoxy resin binding agent. The hardening of the coating compound will be delayed on the other hand because of the softening characteristic of the glycolether. The coating compound remains therefore sticky until complete hardening so that in a dusty environment, surface contamination must be feared during the drying process.
Starting out from this, the basic purpose of the invention is to improve the known undercoating agent of the above-disclosed type such that the undercoating agent dries quicker.
In order to achieve this, the invention suggests that the organic liquid of the first reaction component (component A) contains a synthetic resin additive which is liquidy and/or dissolved in an organic solvent, which speeds up the drying process of the coating compound by evaporation of the organic solvent or by reaction with the second reaction component or with oxygen.
The synthetic resin additive of the invention has mainly the purpose of speeding up the drying by evaporating the organic solvent or by reacting with the hardener or with oxygen. Thus, the synthetic resin forms a type of a structure holding the system together and results in a surface drying as long as the reaction of the epoxy resin binding agent with the polyamine has not concluded.
As synthetic resins can be considered aldehyde resins and phenolic resins, epoxy group, a carboxyl group and an isocyanate group,
In as far as the synthetic resins contain a portion of an organic solvent, such portion is only a fraction of the portion of the solvent in known two-component under-coating agents.
The epoxy resin binding agent contains preferably bisphenol A-resins and/or bisphenol AF-resins.
The undercoating agent of the invention has according to a preferred embodiment of the invention the following composition:
Component A bisphenol A and/or bisphenol AF; resins, like hydrocarbon resin; powder or zinc flakes; sulfate and/or mica;
Component B wetting agents.
The water contained in the component B complete 14 or partial
REFERENCES:
patent: 3408318 (1968-10-01), Madison
patent: 3944712 (1976-03-01), Kurcz
patent: 3998771 (1976-12-01), Feneis, Jr. et al.
patent: 4476260 (1984-10-01), Salensky
patent: 4544688 (1985-01-01), Anderson et al.
patent: 5001173 (1991-03-01), Solensky et al.
Epikote-Harze, Deutsche Farben-Zeitschrift (pp. 463-470) by Von Dr. L. Korfhage (1955) no month.
Petrikat Axel
Wekenmann, deceased Guido
Zipperlen, nee Harenz Sabine
Green Anthony J.
Sika Chemie GmbH
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