Electrostatic paper base and method of making the same

Claim 1

A method for the preparation of a paper base suitable for electrostatic masters for lithographic printing comprising the steps of (a) applying to at least one side of a paper substrate a thin coating of a barrier coating composition which comprises (1) an aqueous medium, (2) a film-forming amount of a synthetic, organic, polymeric, thermoplastic, water-resistant, film-forming resin which is solid at ordinary temperatures, and which has a glass transition temperature less than 115° C., said film forming resin also having labile hydrogen-containing groups reactive with an ammonium zirconyl complex, (3) less than 35% by weight (dry basis) of inorganic particulate material, (4) the ratio of resin to inorganic particulate material being at least 2:1; (b) cross-linking the resin in said coating with an ammonium zirconyl complex; (c) passing said paper through a dryer operating at a temperature such that the temperature of said paper substrate and coating is elevated above said resin glass transition temperature; and (d) positioning said coated paper following drying in successive layers; (e) said coating composition being rendered non-blocking by cross-linking with the ammonium zirconyl complex whereby fusion of the successive layers is obviated.

Claim 2

A method for the preparation of a paper base suitable for electrostatic masters for lithographic printing comprising the steps of (a) applying to at least one side of a paper substrate a thin coating of a barrier coating composition which comprises (1) an aqueous medium, (2) a film-forming amount of a synthetic, organic, polymeric, thermoplastic, water-resistant, film-forming resin which is solid at ordinary temperatures, and which has a glass transition temperature less than 115° C., said film forming resin also having labile hydrogen-containing groups reactive with an ammonium zirconyl complex, (3) less than 35% by weight (dry basis) of inorganic particulate material, (4) the ratio of resin to inorganic particulate material being at least 2:1; (b) cross-linking the resin in said coating with an ammonium zirconyl complex; (c) passing said paper through a dryer operating at a temperature such that the temperature of said paper substrate and coating is elevated above said resin glass transition temperature; and (d) positioning said coated paper following drying in successive layers; (e) said coating composition being rendered non-blocking by cross-linking with the ammonium zirconyl complex whereby fusion of the successive layers is obviated.