Biocidal functionality can also be introduced into cellulose by condensing the hydroxyl groups on 3-trihydroxysilylpropyl-5,5-dimethylhydantoin (SPH) (Figure 6.2) with those on cellulose followed by chlorination of the amide nitrogen on the hydantoin ring with chlorine bleach . It was observed that a complete 5.7 log reduction of S. aureus could be obtained in a contact-time interval of 30-60 min. Likewise, a complete 5.9 log reduction of E. coli was observed in a contact-time interval of 60-120 min. The chlorine loading on the cotton cloth was 0.5-0.6% by weight in these experiments. For comparison purposes, cotton cloth was also treated with the quaternary ammonium compound dimethyloctadecyltrimethoxysilylpropylammonium chloride. In this case the log reductions of S. aureus and E. coli were only 1.8 and 2.5, respectively, in
H Y CH2CH2CH2-Si-OH
the same contact-time intervals as those tested for the samples treated with SPH. This comparison demonstrates conclusively the superiority of cellulose treated with N-halamines over that treated with biocidal quaternary ammonium salts. The chlorinated SPH-treated cloth is reasonably stable to loss of chlorine during dry storage. A loss from 0.62% to 0.54% Cl was observed over a 50-day period for the treated cloth stored in a non-airtight plastic bag. In standard washing tests it was found that cotton cloth treated with SPH and chlorinated with an initial chlorine loading of 0.61% retained 0.42% Cl after 5 machine washings, 0.41% after 10 washings, and 0.10% after 50 washings; thus the material still retained some biocidal functionality even after 50 machine washings.
The SPH compound has also been employed to treat commercial office envelope paper . In this case, a chlorine loading of 0.82% by weight was obtained. The chlorine content declined only to 0.78% over a 36-day period of storage in a vacuum desiccator. The paper completely inactivated S. aureus (5.4 logs) at a contact time of only 10 min.
Was this article helpful?