Process for preparing cross-linked acrylic elastomers

Claim 1

A process for preparing a pulverulent, ionically cross-linked acrylic elastomer, which can be compressed to a homogeneous and essentially clear elastic material by pressing at 20° to 250° C. comprising: (i) preparing a solution of a mixture of monomers comprising: (A) a mixture of a chloride, carbonate, organocarboxylate, acetylacetonate, or alcoholate zirconium compound and at least one acid selected from the group consisting of acrylic acid, and methacrylic acid, said compound and said at least one acid being present in amounts such that a zirconium salt product is formed upon heating wherein more than half of the valences of said zirconium are bound to the anion formed from said unsaturated carboxylic acid; and (B) at least one alkyl ester of acrylic acid having 1 to 20 carbon atoms in the alkyl group, or an alkyl ester of methacrylic acid having 5 to 20 carbon atoms in the alkyl group in a substantially anhydrous organic solvent selected from the group consisting of aliphatic hydrocarbons, aromatic hydrocarbons and alcohols which does not dissolve or swell said cross-linked acrylic elastomer, the proportion of the zirconium ion of said salt in said monomer mixture being 0.1 to 15% by wt. of the monomer mixture and the proportion of component B being chosen so that the glass transition temperature of said elastomer is less than 30° C.; (ii) polymerizing said monomer mixture by a free radical process with heat to form a pulverulent polymer; and (iii) precipitating and separating said pulverulent polymer.