| 摘要 |
<p>1,146,117. Treating microcapsules. FUJI SHASHIN FILM K.K. 7 April, 1967 [9 April, 1966], No. 16035/67. Heading B8C. [Also in Division D2] In a process for producing pressure-sensitive copying paper comprising an electron-accepting paper support coated with a microcapsule dispersion of a colourless electron-donating organic compound encapsulated in gelatine or gum arabic, which is hardened by reaction with formaldehyde, free remaining formaldehyde is removed from the dispersion before it is used to coat the support, by reaction with urea or sodium sulphite, to protect workers from the effects of formaldehyde fumes at the drying stage of the coated paper. When urea is added at a pH of 3 to 5 or 8 to 12, 30‹ to 60‹ C., in the proportion of 1 to 3 moles per mole of residual formaldehyde, after 4 hours, and sodium sulphite at pH of 6 to 8, room temperature, 1 to 1-5 moles per mole of residual formaldehyde after two hours a crystalline addition product is formed. In the case of sodium sulphite, acetic acid is added to keep the pH below 10, as NaOH formed in the reaction increases the #H.</p> |
