| 摘要 |
PURPOSE: Provided is a new pigment for making colored finely divided particles based on amino formaldehyde resin which has particles of substantially uniform particle size and spherical or irregular shape and shows excellent dispersibility and superior opacity. CONSTITUTION: The process for producing dyed finely divided particles comprises, in combination, the steps of: reacting in aqueous medium at a pH of 6-9 a member selected from the group consisting of either urea or benzoguanamine or a mixture of 100-0% by weight of urea and 0-100% by weight of benzoguanamine with formaldehyde in a ratio of 1 mol of the former to 1.3-3 moles of the latter to prepare an aqueous liquid of a soluble and fusible prepolymer; mixing this water-containing prepolymer with an organic solvent having a boiling point below 80 deg.C and being completely mixable with water in a ratio of 70-30% by weight of prepolymer and 30-70% by weight of organic solvent, dyeing said mixture with a single fluorescent dye or a combination of several dyes; introducing with high shear the dyed resin-containing mixture into an aqueous solution of protective colloid consisting of 92-98.5 % of water, 1-3% of water-soluble polymer, 0-3% of a nonionic surfactant or a mixture of non-ionic and ionic surfactants and 0.5 -2.0% of acidic curing catalyst at a reaction temperature in the range from 70-100 Deg.C, and thereafter; and separating the hardened resin from the suspension followed by drying and deaggregating the dried hardened resin.
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