Abstract
In order to study the reaction of the U. F. precondensates in the finishing bath during the pre-drying, the change of pH and relative viscosity (ηr) of the finishing bath at 75°C were observed obtaining the following results.
1. Both pH and ηr, are remarkably influenced by the catalyst type used. Of course these influences become least in case of no catalyst and indeed there appear but a little change after two hours. When the catalyst AC is used, there is no appreciable degree of difference as in the cace no catalyst is used. Catanitto, NH4Cl and D. A. P. decrease pH and increase ηr greatly until the bath becomes turbid by the white precipitates after short time.
2. If the precondensates are methylated, the stability of the bath can be improved and both pH and ηr vary very slowly.
3. There exists no linear relation between pH and ηr.
Next, we estimated F% and M% at 75°C for the finishing bath consisted of methylated dimethylol urea. F% means the extent of producing formaldehyde and M% that of forming methylene linkage. The influences of catalyst on pH and ηr, were similar to the above effects.
When Catanitto, NH4Cl and D. A. P. are used as catalyst, though F% did not reach 25%, M% amounted to about 70% resulting the total extent of reaction (T%) to 90_??_97%.
