Establishment Of Novel Activated Peroxide Systems For Low-temperature Scouring And Bleaching

Conventional bleaching with hydrogen peroxide (H2O2) is often undertaken underalkaline conditions at temperatures greater than95oC. This not only consumes significantamounts of energy, but also leads to fiber damage. An activated peroxide system can beestablished by incorporating a so-called bleach activator with H2O2. The reaction of bleachactivator with H2O2leads to a peracid which is a more effective oxidant agent and responsiblefor low-temperature bleaching. Hence, the activated peroxide system has advantages inreducing energy consumption and environment impact.This project was carried out in two stages. In the first stage, a novel activated peroxidesystem was established for bleaching of cotton fabric at60oC by incorporatingN-[4-(triethylammoniomethyl)benzoyl]caprolactam chloride (TBCC) and sodium bicarbonate(NaHCO3) into H2O2solution. Experimental results showed that the TBCC/H2O2/NaHCO3system was effective for improving the degree of whiteness, reducing the fiber damage, andimproving the water absorbency of cotton fabric. X-ray photoelectron spectroscopy (XPS)was applied to analyze the surface elemental composition of cotton greige fabric before andafter treatment. C1s XPS spectra and quantitative analysis revealed that theTBCC/H2O2/NaHCO3system improved the water absorbency of cotton fabric by removinghydrophobic matters as well as by oxidizing coloring matters and cellulose. The hexaneextractions and scanning electron microscopy images indicated that the TBCC/H2O2/NaHCO3system removed the hydrophobic matters from cotton fabric and improved the waterabsorbency to some extent.In the second stage, a novel series of bleach activators was proposed to be synthesizedfrom vitamin B3(nicotinic acid) and be applied for cotton bleaching. The niacin-based bleachactivators had been confirmed by NMR analysis (1H and13C) and time of flight massspectrometry (TOFMS). The activation performance of niacin-based activators had beentested through the bleaching process of cotton greige fabric. The niacin-based activatedperoxide system had a relatively good bleaching performance under the conditions of50oCand pH=7.2. The CIE WI of cotton greige fabric after treatment could be improved to above50. Among the niacin-based bleach activators, N-nicotinoylbutyrolactam provided the bestbleaching performance, and the CIE WI of cotton greige fabric after treatment was above55.The reaction of niacin-based activators and H2O2was monitored using high performanceliquid chromatography-mass spectrometry (LC-MS). The results showed that the lactam ringgroup of the bleach activator opened to form alkyl peroxyacids while the whole lactam groupwas not cleaved as a leaving group to form nicotinoyl peroxyacid. It is speculated that thismight be the reason why the performance of the niacin-based activators had been limited.Therefore, future work needs to focus on investigating the reaction mechanism.