Repellents fiber-reactive

The chemistry of fiber-reactive dyeing of cellulose has also been considered for producing durable water repellency. Monochlorotriazines and dichloro-... 

In analogy to vinyl sulfone fiber-reactive dyes, water repellents with the vinyl sulfone function have been patented [42]. The /3-hydroxyethylsulfate group, which, in the presence of alkali forms the reactive vinyl sulfone intermediate, functions as a water-solubilizing group and gives the water repellent an amphiphilic character until reacted with alkali. 

Water repellents with a chlorotriazine or vinyl sulfone functional group react with cellulose in the presence of alkali. Therefore, they are not compatible with cross-linking reactants requiring acid catalysis for the reaction with cellulose. This limitation, in addition to the cost, is one of several reasons why fiber-reactive chemistry developed for dyes has not been successfully adaptable to repellent finishing. 

Acetylation methods have been used for many years to improve some properties of wood cellulose such as moisture repellency, dimensional stability and resistance to environmental degradation. Their use for improving the properties of natural fibers has increased significantly in the last decade or so. The methods are based on the reaction of lignocellulosic material with acetic anhydride at elevated temperature, with or without a catalyst. The acetic anhydride reacts with the more reactive hydroxyl groups according to the equation [36],... 

Schuyten and co-workers [19] reinvestigated the reaction and confirmed that stearamidomethylpyridinium chloride reacts with cellulose to the extent of 1-2% of the weight of the fabric. This indicated that the reaction is restricted to the surface of the fibers. However, methylolstearamide did not react with cellulose, in contrast to the conclusions by Davis. Schuyten and co-workers concluded, therefore, that the quaternary stearamidomethylpyridinium salt itself is the reactive species. Distearamidomethane formed during curing is deposited on fibers and also contributes to nonpermanent repellency. 

---