2010-Improved Bleaching Efficiency using Cationic Bleach Activators

Improved Bleaching Efficiency using Cationic Bleach Activators

Changhai Xu, North Carolina State University


Hydrogen peroxide bleaching is traditionally carried out under alkaline conditions at high
temperature over 95 °C. This process involves high energy cost and gives rise to fiber damage.
By adding a bleach activator, hydrogen peroxide is converted into a more kinetically active peracid in situ that bleaches at a lower temperature, thereby saving energy and reducing fiber damage.
In the past decade, bleach activators have been reported in a considerable number of research papers to enhance the bleaching performance of hydrogen peroxide for industrial textile bleaching. Tetraacetylethylenediamine (TAED) and nonanoylbenzene sulphonate (NOBS) are two commercially important bleach activators. Many activated peroxide systems reported for industrial textile bleaching are based on these two bleach activators.
However, TAED has poor solubility in water and its bleaching effectiveness is insufficient at temperatures below 50 °C.
NOBS is superior to TAED to conduct an efficient bleaching system under certain conditions but the pernonanoic acid may be converted into unwanted diacylperoxide at low pH. Cationic bleach activators (CBA) are a class of quaternary ammonium peracid precursors.
They have excellent solubility in water and potential affinity towards negatively charged substrates due to their quaternary ammonium cations. An exemplified CBA is N-[4-
(triethylammoniomethyl)benzoyl]caprolactam chloride (TBCC) that gives better bleaching performance than NOBS.
A drawback of TBCC is that it is unstable in aqueous solution and must be stored in solid
form and dissolved immediately before use. A recent study found that N-[4-(triethylammoniomethyl)benzoyl]butyrolactam chloride (TBBC) has enhanced hydrolytic stability without substantial loss of bleaching efficiency. An activated peroxide system based on TBBC has been developed for bleaching regenerated bamboo fiber. This system has been shown to be effective under neutral pH conditions at 50 °C with significant reduction of fiber damage by comparison with conventional peroxide bleaching.
The purpose of the present study is to investigate the sorption behavior of TBBC on cellulosic fibers and develop a TBBC activated peroxide system for cotton bleaching with improved efficiency.