Paper base planographic printing plates

1,148,577. Paper-base planographic printing plates. APPLETON COATED PAPER CO. 12 May, 1966, No. 21041/66. Heading B6C. [Also in Division B2] A planographic printing plate comprises a paper base with a dried, insolubilized coating layer providing the printing surface, the coating being formed from an aqueous dispersion of 5 to 10 parts by weight of a protective colloid of polyvinyl alcohol or hydroxyethylated starch; 0À3 to 10 parts by weight of a mixture containing 55 to 85% ethyl acrylate, 45 to 20% acrylonitrile and 0À5 to 4% methacrylic acid; 18 to 60 parts by weight of inert mineral pigment; 0À2 to 5 parts by weight of melamine formaldehyde resin or melamine resin in combination with melamine formaldehyde resin, or a sufficient quantity of any other formaldehyde donor to insolubilize the protective colloid; and from 1À5 to 30 parts by weight of a mixture containing 1 to 4 parts of zinc acetate and at least 1 part of aluminium chloride or ferric chloride or chromium chloride. The inert pigment is preferably kaolin clay. The plate is made by coating the paper base web with the aqueous dispersion, and then drying; the opposite side of the paper base may be coated to prevent curl and impart dimensional stability.