Process of forming dry strength paper with cationic resin, polyacrylamide resin and alum complex and paper thereof

摘要

Paper of high dry strength but low wet strength comprises water-laid cellulose fibres bonded together by a complex of a synthetic dry-strength polymer anionic by virtue of a content of acrylic, methacrylic or itaconic acid residues, a salt of tervalent aluminium and a non-thermo-setting cationic synthetic resin that cannot impart wet-strength. The anionic polymer is water-soluble or water-dispersible and may be fixed on the fibres by the action of the aluminium salt and the cationic synthetic resin in aqueous suspension, which is thereafter sheeted and dried. The three agents may be added to the suspension in any sequence, or the cationic synthetic resin and aluminium salt can be added together. The anionic polymer may be a copolymer of acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, an alkyl acrylate, an alkyl methacrylate or an alkyl vinyl ether with acrylic or methacrylic acid, or a condensate of a lower alkylene oxide with a polymer of acrylic acid, methacrylic acid or itaconic acid or with a copolymer of one of these acids or its salt with an ester of acrylic, methacrylic, itaconic, maleic, fumaric or citraconic acid and an alcohol such as methyl, butyl, octyl, dodecyl or cyclohexyl alcohol or a vinyl or vinyloxyalkyl ester of acetic or propionic acid, ethyl or butyl vinyl ether, acrylamide or methacrylamide. The aluminium salt may be alum, aluminium chloride or aluminium nitrate. The cationic synthetic resin may be polyethylenimine polyvinylamine; or condensation products of adipic acid, tetraethylene-pentamine and epichlorohydrin; methylamine, ethylendiamine and epichlorohydrin; methylamine, ammonia and epichlorohydrin; ethylene dichloride and 3, 3sv-iminobispropylamine; adipic acid and tetraethylenpentamine; diethylenetriamine and ethylene dichloride; ethylene diamine and epichlorohydrin; or ammonia and epichlorohydrin; or a quaternized polyacrylamide or a Hoffman degradation product of a polyacrylamide or an acrylamide-vinylpyridine copolymer. The anionic polymer may be fixed at a neutral or alkaline pH, e.g. 6-8. A size may be added with the anionic polymer and fixed by the aluminium salt. This size may be a rosin size, wax size, stearic anhydride, octadecyl keten dimer or octadecyl isocyanate. Alternatively, a cationic emulsion of a hydrophobic organic cellulose-reactive size, e.g. that prepared by reacting triethylene-tetramine with stearic acid and solubilizing with acetic acid, or a higher aliphatic amine-epichlorohydrin size, may be added with the cationic synthetic resin.