Formaldehyde → Melamine formaldehyde

Beteiligte Stoffe

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In 95 parts of water was dissolved 5 parts of a partial sodium salt of poly(vinylbenzenesulfonic acid) (VERSA, TL500; manufactured by National Starch Co.). Aqueous sodium hydroxide solution was added thereto to adjust the pH to 4.0. 100 Parts of diisopropylnaphthalene containing 6.8% 2-anilino-3-methyl-6-di-n-butylaminofluoran dissolved therein as an electron-donating achromatic dye, and 15% 1,2-bis[p-bis(p-methoxyphenylamino)phenoxy]ethane as the compound of the present invention was emulsified into 100 parts of the 5% aqueous solution of the partial sodium salt of poly(vinylbenzenesulfonic acid) to obtain an emulsion having a particle diameter of 4.0 μm. On the other hand, a mixture of 6 parts of melamine, 11 parts of 37 wt% aqueous formaldehyde solution, and 30 parts of water was stirred with heating at 60° C. to obtain a clear aqueous solution of a melamine-formaldehyde prepolymer. This aqueous solution was mixed with the emulsion obtained above. The pH of the mixture was adjusted to 6.0 with aqueous phosphoric acid solution with stirring, and the resulting liquid was heated to 65° C. and kept being stirred for 6 hours. The capsule dispersion thus obtained was cooled to room temperature and its pH was adjusted to 9.0 with aqueous sodium hydroxide solution.

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