Formaldehyde → Melamine formaldehyde

Participants

Reaction Conditions

Reaction Steps

Five parts of a partial sodium salt of polyvinylbenzene sulfonic acid (produced by National Starch Co., trade name: VERSA, TL 500, average molecular weight: 500,000) was added with stirring to 95 parts of water heated up to about 80° C., and dissolved therein over a period of about 30 minutes. Then, the hot solution was cooled, and the pH was determined to be 2-3. The solution was adjusted to pH 4.0 by the addition of a 20 wt% aqueous solution of sodium hydroxide. Then, 100 parts of diisopropylnaphthalene, in which the electron-donating colorless dye set forth in Table 1 under Example 1 was dissolved as a color former in a concentration of 3.5%, was dispersed into 100 parts of the foregoing 5% aqueous solution of the partial sodium salt of polyvinylbenzenesulfonic acid in the form of an emulsion having a mean particle diameter of 4.5 microns. Separately, 6 parts of melamine, 11 parts of a 37 wt% aqueous solution of formaldehyde and 30 parts of water were admixed and heated to 60° C. with stirring. After the lapse of 30 minutes, a transparent aqueous mixture composed of melamine, formaldehyde and a melamine/formaldehyde initial condensate was obtained. The pH of the aqueous mixture was between 6 and 8. This transparent aqueous mixture is hereinafter called the initial condensate solution. The initial condensate solution obtained in the above-described manner was admixed with the foregoing emulsion, and then the mixture was adjusted to pH 6.0 by addition of a 3.6 wt% phosphoric acid solution, followed by 360 minutes of stirring at 65° C. The thus prepared capsule containing solution was cooled to room temperature, and adjusted to pH 9.0 by addition of a 20 wt% sodium hydroxide solution.

Provenance & Evidence