Improvements in processes of making a coated paper base adapted to receive a sensitized emulsion for instance as used in lithographic printing

摘要

577,832. Planographic printing plates. TOLAND, W. C., and BASSIST, E. Dec. 8, 1942, No. 17462. Drawings to Specification. [Class 98 (ii)] [Also in Group VIII] Coated paper, adapted to be further coated with a light-sensitive emulsion and used as a planographic printing plate, is made by covering the paper on both sides with a urea-formaldehyde resin of the type which first sets to a partly dried state having affinity for aqueous mixtures, but becomes water-repellent when fully dried and hardened, applying to one or both sides of the paper an aqueous suspension of a colloidal coating material suitable to form the water-receptive non-printing portions of the printing plate while the resin coatings are in a partly dried state,. and allowing the two coatings to dry together to firmly bond the outer coating to the urea-formaldehyde resin while the latter hardens to a water-repellent condition. Kraft paper, parchment paper or , fibreboard sized or impregnated with polyvinyl alcohol, rosin, or gelatin is coated on both sides with an aqueous suspension or solution of a urea-formaldehyde resin containing a hardening agent such as. hexamethylene tetramine, partly dried and, if desired, hot-calendered without curing the resin to the water-insoluble stage. The paper is then coated on one side with an aqueous suspension of a colloidal material, e.g. polyvinyl alcohol, gelatin, glue, gum arabic, or albumen with or without a filler such as clay, and dried. The paper may be conditioned by restoring, moisture thereto by keeping in a moist atmosphere which may be under pressure. Specification 547,517 is referred to.