GB747801A - Improvements in or relating to photo-sensitive silver halides - Google Patents

Abstract

Light-sensitive silver halides are prepared by precipitation from an aqueous solution containing 1 to 30 per cent (by weight of the halide) of a non-ionic surface active dispersing agent containing at least 6 intralinear oxyalkylene groups of 2 to 3 carbon atoms and a hydrophobic group including a hydrocarbon group of at least 8 carbon atoms containing an alkyl radical of at least 4 carbon atoms. The precipitation may be carried out with dilute solutions of soluble inorganic halides such as ammonium bromide or potassium chloride or iodide, and aqueous solutions of water soluble silver salts such as the nitrate, sulphate, sulphamate, nitrate, acetate or mixtures thereof. The precipitating solutions may contain 1-20 per cent by weight of the water of water miscible organic solvents such as alcohols, e.g. methanol, ethanol, or glycerol. Suitable dispersing agents are condensation products of an alkylene oxide or poly alkylene oxide with a water insoluble organic compound having an active or replaceable hydrogen atom attached to a non-carbon atom, (O,S or N), such as aliphatic monohydric alcohols (C8 to C18), oleyl alcohol, fatty acids (C12 to C18), oleic acid, abietic acid, alkyl phenols such as octyl-, decyl- and diisobutyl-phenol, saturated aliphatic primary amines and amides such as lauric, stearic, palmitic and oleic acid amides. The preferred non-ionic dispersing agents are condensation products of at least 10 moles of ethylene oxide with one mole of a monohydric alcohol of at least 10 carbon atoms or an alkyl phenol. Suitable dispersing agents may also be obtained by reacting a lower polymer of an alkylene oxide instead of the monomer with an alcohol, mercaptan amine, amide or phenol. The reaction product of the alkylene oxide and the replaceable-hydrogen containing compound may be condensed with formaldehyde. According to a typical example, a solution of ammonium bromide, potassium iodide and a 10 per cent aqueous solution of the condensation product of 1 mole of sperm oil alcohols (C14 to C18) and 20 moles of ethylene oxide are mixed with an aqueous silver nitrate solution (solutionized with 20 per cent aqueous ammonia), After stirring for 10 seconds the mixture is allowed to stand and ripen at 30 DEG C. for 2 hours. The halide grains are separated and washed. The ripening may be at 25 to 50 DEG C. for a period of half to 4 hours. The washed grains may be dispersed in aqueous solutions of protective colloids such as gelatine, casein, albumin, polyvinyl alcohol, acetals, polyamides or cellulose derivatives to prepare photographic emulsions. Such emulsions may also be prepared by adding the protective colloid directly to the ripened dispersion of silver halides without isolating or working the grains, the resulting emulsion may be gelled and shredded and washed free of soluble salts. Thus silver halide precipitated in the presence of a condensation product of 1 mole of oleyl alcohol and 20 mole of ethylene oxide can be mixed after decanting supernatant liquid with an aqueous solution of a mixed benzaldehyde/sodium o sulphobenzaldehyde polyvinyl acetal to produce a photographic emulsion containing silver halide grains of 0.2 to 0.4 microns. Cetal betaine may be added to improve spreading characteristics. Other condensation products referred to are those obtained from condensing 16 moles of ethylene oxide with octodecyl alcohol, 15-20 moles of propylene oxide with diisobutylphenol, 6 to 10 moles of propylene oxide with dodecyl alcohol, 12 moles of ethylene oxide with oleic acid, 10 to 20 moles of ethylene oxide with stearic acid, 40 moles of ethylene oxide with stearic acid, 20 moles of ethylene oxide with propylene glycol monostearate, 15 moles of ethylene oxide with 1 mole of amides of coconut oil acids or abietic cid. Specifications 358,114 and 598,477 [Group IV], are referred to.