Forming clear gel and transparent film by reacting alumina hydrate with vinyl alcohol-vinyl acetate copolymer
AssigneeAluminum Company of America
InventorsWilly M. Balaba, Gary J. DiFranco
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Abstract
A stable gel is formed by reacting alumina hydrate sol and a vinyl alcohol-vinyl acetate copolymer in an aqueous solution having pH less than about 7 to form a polymeric sol and then transforming the sol to a gel. The copolymer preferably comprises polyvinyl acetate that is about 85-99% hydrolyzed. The gel is drawn into a thin layer and water is removed to form a thin, substantially crack-free film. The film makes a stable, generally transparent insulating material.
Claims19
A method for preparing a stable gel comprising alumina hydrate combined with a water-soluble partially hydrolized polyvinyl acetate polymer, said method comprising
- (a) preparing a sol comprising a colloidal dispersion of alumina hydrate in an aqueous medium,
- (b) mixing said sol with a water-soluble partially hydrolyzed polyvinyl acetate polymer comprising about 85-99% vinyl alcohol groups,
- (c) reacting said alumina hydrate with said copolymer in an aqueous solution having a pH of less than about 7, thereby to form a polymeric sol comprising alumina hydrate combined with the said polymer, and
- (d) transforming the polymeric sol to a stable gel by eliminating the aqueous dispersion medium.
A stable gel prepared in an aqueous solution having a pH less than about 7, said gel being the reaction product of an alumina hydrate sol and a water-soluble partially hydrolyzed polyvinyl acetate polymer comprising about 85-99% vinyl alcohol groups.
A transparent, thin, crack-free film formed by the steps of
- (a) forming a polymeric sol by reacting an alumina hydrate sol and a water-soluble partially hydrolyzed polyvinyl acetate polymer in an aqueous solution containing a water-soluble plasticizer and having pH less than 7, wherein said solution contains at least 10 wt. % of a polymer comprising about 85-99% vinyl alcohol groups,
- (b) transforming the sol to a gel by eliminating the aqueous dispersion medium,
- (c) drawing the gel into a thin layer, and
- (d) removing any remaining water from the thin layer, thereby to form a thin film.
Dependencies are inferred from the claim text.