Case Number 101046 - Method for obtaining an Organic-Solvent-Free Stable Silane Solution
Contact: Geoffrey Pinski
Description: Organofunctional and non-organofunctional silanes have been demonstrated by UC researchers to be powerful agents to prevent corrosion of metals. Many different metals can be effectively protected against a range of different types of corrosion, such as stress corrosion cracking, pitting, corrosion fatigue cracking, uniform corrosion, etc.
Although silanes are easy to handle and apply, they often have the limitation that they come in the form of alkoxy esters which have to be hydrolyzed first before they can be applied to the metal. The ester is often insoluble in water so that a large amount of an organic solvent has to be added to solubilize them. Even after dilution of the hydrolyzed silane with water to the working strength, which can now often be done with water, the organic solvent content is still high, typically of the order of 50 vol.-%. Any application where large volumes of silane solutions are to be used, such as in coil coating operations, for instance, the alcohol-containing mixtures cannot be used for environmental and safety reasons. Another limitation of the silanes is that the hydrolysis process is rather slow. It may take many hours for hydrolysis to be complete.
All of these problems are solved if the silanes of interest in corrosion engineering are first converted to a different type of ester which hydrolyzes in pure water instantaneously. Such a process is the topic of this invention. It has been demonstrated to work and can be carried out on a large scale.
The silane is ready for use immediately, is 100% hydrolyzed and non-condensed, and the solution contains no alcohol. Special additives to the aqueous solution are used which increase the stability of the silane solution considerably. The converted silane is stable if it is kept in closed containers. Many silanes that are commercially available from vendors can be converted by the process.
It can be carried out on a continuous basis, so that it can be done in the background in a plant where the converted silane is used in a metal-finishing operation. The byproducts of the process are ethanol or methanol, which can be sold separately.
The availability of this process will increase the environmental compliance of silane treatments which will stimulate their acceptance in metal-finishing industries.