Dispersion process

摘要

Hydrophobic substances, particularly hydrophobic additive for photographic layers such as couplers may be dispersed in an aqueous medium in a two-or more-stage process using an oil-former. In a main dispersion stage the total quantity of the hydrophobic substance is dispersed in the aqueous medium without oil-former or with only part of the total quantity of oil-former. The residual portion of oil-former is dispersed in the aqueous medium without hydrophobic substance in at least one further dispersion stage preceding or following the main dispersion stage. The oil-former used is preferably a compound or a mixture of compounds selected from triaryl phosphates, dialkyl phthalates, monoesters of alpha -substituted succinic acid or of hydrogenated phthalic acids and aliphatic or cycloaliphatic alcohols of at least 10 carbon atoms. The process yields dispersions of improved stability of digestion.