| 摘要 |
Aqueous coating compositions comprising (1) a water-soluble methylolated derivative of a water-soluble homopolymer or copolymer of acrylamide or methacrylamide capable of yielding an insoluble, cross-linked product on heating, and (2) an inert inorganic pigment may be coated on base surfaces, e.g. paper, and the coating is insolubilized by heating to form planographic printing surfaces. Specified copolymers are those of acrylamide and methacrylamide, acrylamide and methacrylic acid, and methacrylamide and methacrylic acid. Specified pigments are clay, diatomaceous earth, fuller's earth, zinc oxide, calcium carbonate, satin white, calcium silicate, barium sulphate and titanium dioxide. The acrylamide polymer may be methylolated by reacting with formaldehyde in an aqueous medium in the presence of sodium carbonate at a pH of about 10. The cross-linking may be effected in the presence of a catalyst, e.g. zinc acetate, chromate, chloride or borate, or ammonium chloride, phosphate or dichromate. |
