Catalysis of the reaction of urea–formaldehyde precondensates on cellulose

The reaction of dimethylol urea on cotton cellulose at 150°C. has been studied with NH4Cl and Na2CO3 as catalysts. With the ammonium salt, 0.2 mmole/g. precondensate was required to attain the maximum level of fixed resin, while maximum resistance to hydrolysis by dilute acid required 0.3–0.4 mmole/g. The acid resistance is attributed to the crosslinking of the fiber, which is primarily responsible for the changes produced in resilience and other physical properties. The application of monomethylol urea with NH4Cl does not lead to changes in acid resistance or physical properties such as are attributed to crosslinking. Catalysis with Na2CO3 does not appear to lead to crosslinking with dimethylol urea, since the treated cellulose remains soluble in cuprammonium hydroxide. There is very little difference in the effectiveness of monomethyl and dimethylol ureas for changing physical properties when they are applied with the alkaline catalyst. It is suggested that the curing step with Na2CO3 leads to further condensation through methylene ether linkages rather than to reaction with the cellulose substrate.