Improvements in or relating to the manufacture of coloured paper

851,546. Pigmented paper containing synthetic resins. IMPERIAL CHEMICAL INDUSTRIES Ltd. Dec. 12, 1958 [Dec. 23, 1957], No. 39870/57. Class 96. Pigments, e.g. azo pigments, phthalocyanine pigments, inorganic chrome and iron lakes, phospho-molybdic and phosphomolybdotungstic lakes of basic dyestuffs, or carbon black, are incorporated during the manufacture of paper in conjunction with a condensation product obtained by heating, in the absence of water, a polyalkylene polyamine with cyanamide, a derivative thereof, or a derivative of cyanocyanamide. The condensation product is preferably added to pulp slurry in the beater after the pigment has been added. The polyalkylene polyamines specified are diethylene triamine, triethylene tetramine, tetraethylene pentamine, bis - (# - aminohexyl)amine, 1: 2 - bis - (w - amino-hexyl amino)ethane, or a polymer of ethylene imine. Specified derivatives of cyanamide and cyanocyanamide are phenyl cyanamide, guanidine, dicyandiamide, phenyldicyandiamide, p - chlorophenyl - dicyandiamide, hexamethylene - bis - dicyandiamide, ethylenebis - dicyandiamide, guanylurea, biguanide, phenylbiguanide, or salts with weak acids of guanidine, guanyl urea, or biguanide. The condensation products, which should be employed in the form of their acid salts and may be used in conjunction with salts of copper, iron, cobalt, nickel, chromium, or zinc, are prepared by heating the ingredients together at a temperature of 70-200‹ C., optionally in the presence of an organic diluent as described in Specifications 522,539, 657,753 755,519, and 798,061; amounts of 2.5 to 25% of the weight of the pigment are suitable and may completely replace aluminium sulphate. According to an example, 20 parts of a 20% paste of copper phthalocyanine were mixed in a beater with 100 parts of air-dry, bleached α-cellulose pulp. 1 part of the condensation product of ethylenebis-dicyandiamide and diethylene triamine dissolved in water and acidified with dilute acetic acid was mixed in. A sheet of paper produced from this furnish was very much stronger in depth of shade than a sheet produced by use of an equal weight of aluminium sulphate instead of the condensation product.