GB718966A - Improved method of preventing set-off from freshly printed sheets - Google Patents

Abstract

718,966. Printing-machines. LEVEY CO., Inc., F. H. Jan. 19, 1953 [March 28, 1952], No. 1536/53. Class 100(2). Set-off preventing.-A method of preventing set-off from freshly printed surfaces consists in applying over the printed surface a coating of transparent film-forming solution, the solvent of which is volatile. The coating is applied as a continuous film all over the surface by non-wiping contact with the surface of a smooth roller, plate or blanket, e.g. of rubber or it may be applied locally over the inked portions only, e.g. by a gravure printing cylinder coated with the solution. The solvent for the film-forming material must not be a solvent for the ink. The film-forming material may consist of a resin or a plastic soluble in a suitable solvent and capable of forming a continuous thin film such as cellulose acetate, ethyl cellulose or carboxymethyl cellulose; ammonium casenite, rosin and rosin derivatives; shellac, maleic resins; latices such as aqueous emulsions of vinyl resins; polystyrene; polyacrylates, polymethacrylates; modified phenolics or other synthetic, natural or fossil resins. Sodium silicate may also be used. Compatible mixtures of any of these substances may be used. The solvent may be any of a large group of known low-boiling point volatile solvents capable of dissolving or dispersing the particular film-forming constituent selected, e.g. water; methyl, ethyl or propyl alcohols; mixtures of such alcohols and water; ethers such as monalkyl glycol ethers; esters such as ethyl acetate; ketones such as methyl ethyl ketone; toluene; naphtha or other volatile aliphatic or aromatic hydrocarbons. Examples of suitable solutions are given. The solvent may be dried more rapidly by the application of heat or a current of air especially when used on a web of wet print passing at high speed through a printing press.