Study On Application Of Cotton Knitted Fabric Bleaching At Low Temperature With New Activator

The traditional hydrogen peroxide bleaching process of cotton knitted fabrics has the problems of high water and energy consumption,low efficiency,severe damage to cotton fibers and waste of resources on high temperature.In this study,based on the previous research of our team,two new low temperature hydrogen peroxide bleach activators were used.In order to reduce the bleaching temperature,improve the whiteness of the fabric and reduce the strength loss,technological conditions in hydrogen peroxide bleaching of cotton knitted fabrics were studied.This process is helpful for realization of energy-saving emission reduction and cleaner bleaching production process in the dyeing and finishing industry.By adding BEA-212（the main component isα-pentaacetyl glucose（PAG））and HPC（the main component is O-phthalic anhydride（PA））to the solution containing hydrogen peroxide,based on these two kinds of novel activators could react with hydrogen peroxide to produce more oxidizing peroxyacids under alkali condition,the purpose of reducing the bleaching temperature of cotton knitted fabrics can be achieved.Firstly,we detect the fluorescence intensity of pure PAG and PA in the H₂O₂/NaOH system.The generation of hydroxyl radicals（HO·）in the system could be characterized.The test results show that both PAG and PA can promote H₂O₂ to produce HO·;the optimal detection condition of HO·fluorescence intensity in PAG/H₂O₂/NaOH system and PA/H₂O₂/NaOH system is:the optimal dosage of PAG and PA is 150μL and 100μL,respectively.It is speculated that the existence of HO·may contribute to the realization of low temperature bleaching.Secondly,the low temperature activator BEA-212 which containing PAG and the low temperature activator HPC which containing PA were used to construct the low temperature bleaching system BEA-212/H₂O₂/NaOH system and HPC/H₂O₂/NaOH system,these two kinds of systems were used to bleach cotton knitted fabric（the original fabric whiteness is-18.92 and the original fabric strength is 508.7 N）.The results show that the best process conditions for using BEA-212/H₂O₂/NaOH low-temperature bleaching system are:activator BEA-212 of2.0g/L,NaOH of 4.0g/L,H₂O₂ of 15.0g/L,the bleaching temperature is 75℃and the bleaching time is 60 min.After bleaching,the whiteness of cotton knitted fabric is 61.97 and the burst strength is 413.1N.All meet the requirements of enterprises,the requirements of enterprises（Whiteness requirement:more than 60,and the burst strength requirement:more than 380N）.The best process conditions using HPC/H₂O₂/NaOH low-temperature bleaching system are:activator HPC of 1.0g/L,NaOH of 4.0g/L,H₂O₂ of 15.0g/L,bleaching temperature is 75℃,and the bleaching time is 60 min.After bleaching,the whiteness of cotton knitted fabric is 64.09 and the burst strength is 404.1N.Compared with the traditional high-temperature bleaching process（using H₂O₂/NaOH system with the temperature of 98℃）,the bleaching temperature can be reduced by 23℃under the premise of meeting the production requirements of the enterprise.For the more,the purpose of energy saving and emission reduction is achieved.The study found that the fabrics treated by the two novel systems have good strength retention.And the HPC/H₂O₂/NaOH system is much more helpful to improve the whiteness of the fabric.Finally,in order to further broaden the scope of application of the HPC/H₂O₂/NaOH low- temperature bleaching system,a systematic study is conducted on the bleaching process of cotton knitted fabrics（the original fabric whiteness is 6.59 and the original fabric strength is553.4N）.To determine the appropriate range of process conditions,a single factor experiment was used;design two response values（fabric whiteness and burst strength）three factors（dosage of HPC,dosage of NaOH and dosage of H₂O₂）three-level response surface experiment based on single factor experiment.The best process conditions of HPC/H₂O₂/NaOH low temperature bleaching system could be obtain:activator HPC of 0.78g/L,H₂O₂ of 9.50g/L,NaOH of 3.48g/L（TF-122 of 2.0g/L,defoamer of 0.2 g/L,the bleaching temperature is 75℃,time is 60 min and the bath ratio is 1:20）.The whiteness of the cotton knitted fabric after bleaching is 68.92,and the bursting strength is 410.6 N;both meet the production requirements of the enterprise.Through the above research data,a regression model is further proposed and verification experiments are carried out.The results show that the optimized regression model is consistent with the actual situation,and the regression model is credible.