| The conventional hydrogen peroxide bleaching of cotton fabric is often carried out under alkaline conditions(pH > 11)at temperatures greater than 95 oC.Such a bleaching process causes not only extensive energy consumption but also severe fiber damage.N-[4-(triethylammoniummethylene)benzoyl]caprolactam chloride(TBCC)is a new kind of bleach activator,based on which an activated peroxide system can be established for low-temperature bleaching of cotton fabric under near-neutral pH condtions.In comparision to the conventional peroxide bleaching system,the TBCC-activated peroxide system has the advantages of energy saving and protecting fibers from chemical damage.However,TBCC is usually synthesized using a two-bath and two-step process.Firstly,4-chloromethylbenzoyl chloride and caprolactam were refluxed in toluene for 6 hours to result in 4-chloromethylbenzoylcaprolactam.Secondly,4-chloromethylbenzoylcaprolactam and triethylamine were refluxed in acetonitrile for 4 hours to give TBCC.Therefore,synthesizing TBCC is a long and complex process,consequently leading to a low product yield as well as a high cost.In the first chapter of this thesis,TBCC was synthesized in three steps on the conventional synthesis method.Firstly,4-chloromethylbenzoic acid was refluxed in thionyl chloride for 1.5 hours to result in 4-chloromethylbenzoyl chloride.Secondly,4-chloromethylbenzoyl chloride,caprolactam and trimethylamine were added to toluene,dichloromethane,ethyl acetate,acetonitrile or acetone at room temperature for 1-2 hours to obtain intermediate product CMBC with a yield over 80%.Thirdly,CMBC and triethylamine were refluxed in acetonitrile for 4 hours to give TBCC.In the second chapter of this thesis,a novel one-pot process was proposed for synthesizing TBCC by adding caprolactam,trimethylamine and 4-chloromethylbenzoyl chloride which was given by an acid chloride reaction in acetonitrile at the same time.The mixture was maintained at room temperature for 1-2 hours,and then was heated to reflux for 4 hours.After the temperature was reduced to 45 °C,sodium hydrogencarbonate was added to the system and stirred for 1 hour to give TBCC in a yield of 78.87% with an increase of up to 19.72% chemical yield compared with conventional synthesis method.The one-pot synthesis of TBCC has simplified the synthetic steps and reduced the synthetic cost.In comparison to the conventional synthesis process,TBCC synthesized using the new one-pot synthesis process could provided equivablent bleaching performance.A series of cationic bleach activators containing lactambased leaving groups of varying ring size was synthesized using one-pot process and confirmed by nuclear magnetic resonance spectroscopy and mass spectrometry.The low-temperature pretreatment of cotton fabric by combining enzyme desizing,enzymatic scouring and TBCC-activated peroxide bleaching in one bath was explored in the third chapter of this thesis.The cotton fabric was treated by one-bath one-step and one-bath multi-steps pretreatment process respectively.The effects of these pretreatment were investigated by measuring size residual,water absorbency and degree of whiteness of cotton fabric pretreated.Experimental results show that,the activity of amylase was inhibited in onebath one-step process result in the weakness of scouring and bleaching effect.In comparison with enzyme desizing and conventional peroxide bleaching,cotton fabric treated by one-bath two-step and one-bath three-step process had equivalent performance which can meet the requirements of dyeing and finishing.The one-bath pretreatment process of cotton fabric is carried out under near-neutral pH conditions at 50 °C,protecting the cotton fabrics effectively from chemical damage in high temperature and alkaline conditions.Compared with the threebath three-step pretreatment process,the one-bath one-step process shortens the process routine,reduces the energy consumption and proper sewerage. |
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