Abstract
A study was made on the reactions between polyvinyl alcohol (PVA) and Cibacron dyes in alkaline aqueous solutions.
The reaction of PVA with Cibacron Brilliant Yellow 3G under various conditions (temperature, basicity, concentrations of dye and PVA) always stopped at a very low degree of bonding (of dye to PVA). This low degree of bonding may be attributed to: (1) the loss of dye due to hydrolysis, (2) the phase separation of PVA caused by a neutral salt, alkali and dye, and (3) low reactivities of both the dye and PVA.
The degree of bonding increased with repeated reactions for Brilliant-Yellow 3G, -Red 3B and -Red B, though the degree of bonding reached. constant values after the given reaction times, The degree of bonding at balance between formation and rupture of the bond was taken as maximum. This maximum value became greater in the decreasing order of the molecular size of dye, suggesting that the steric hindrance of the dye molecule bonded to the neighboring hydroxyl groups influences apparently the maximum degree of bonding. These maximum values approximately coincided with values calculated on the assumption that two dye molecules on the chain are situated so far apart from each other that the distance dose not exceed its molecular length. A balancing between the bonding and the hydrolysis, a mutual repulsion between sulfonic groups, the random coiling of PVA chain in the solution, etc. are considered to be responsible for the low degree of bonding.
