Preparation And Application Of High Efficiency Hydrogen Peroxide Bleaching Catalyst Used For Cotton Knitted Fabric Under Low Temperature

Conventional hydrogen peroxide bleaching process used to finish cotton knitted fabric is usually related to high temperature, high energy consumption, serious fabric damage and other disadvantages. Therefore, developing for high efficiency hydrogen peroxide bleaching catalyst to reduce energy consumption and improve the quality of textiles is imperative.Fe-TAML(ferric combined with big four amide formation complexes) is a green and high efficiency hydrogen peroxide catalyst, which is used in pulp bleaching. By adding small amounts of Fe-TAML, decomposing of the same amount of lignin under H2O2 can be performed at lower temperatures(from 90 ℃ down to 20 ℃) within a shorter period of time( reduced from 6h to 1h). So far, there are few literatures about the cotton knits bleaching by using Fe-TAML.In this paper, Fe-TAML was introduced to bleach cotton knitted fabric at the low temperature. A series novel hydrogen peroxide catalyst of macrocyclic four amide type was synthesized. These novel catalysts can promote hydrogen peroxide decomposition, which effectively improve the whiteness of cotton after bleaching.Meanwhile, the energy was greatly saved and the finishing effect of fabric was also improved.Firstly, the second generation TAML(macrocyclic tetralactams) was selected as target ligands to synthesize. Based on the four-step synthetic route of the second generation TAML in literature, 4-nitro-2-phenylenediamine was used as raw materials.After BOC protection, amidation, removal of the BOC protecting, and the formation of the ring, the yield of third step can be increased from 90 % to 95.2%. The products structure were characterized by FTIR and 1HNMR. Subsequently, the TAML wascoordinate with iron salts, manganese salts, cobalt salts, and copper salts respectively.Four types of the metal complex were received. The complex structure of Fe-TAML,Mn-TAML, Co-TAML, and Cu-TAML were determined by using FTIR. The corresponding thermal stabilities of them were measured by using TGA.The above four kinds of metal complexes were used in low temperature pretreatment of knitted cotton fabric. The most suitable catalyst was selected under70℃. And then the optimum process parameters of the low temperature hydrogen peroxide bleaching pretreatment were investigated, including the dosage of hydrogen peroxide, bleaching temperature, catalyst concentration, and bleaching solution p H.The cotton bleaching whiteness, wetting ability, and bursting strength were also studied. By combing single factor experiment with orthogonal experiment, the optimal process is as follows: 10 g/l 30% H2O2, 5μmol/l Cu-TAML, 1 g/l refining agent concentration, p H 10.5, under 70 ℃, the whiteness of knitted cotton fabric can reach 72.89%.Finally, the bleach effects of conventional cotton knitted fabric pretreatment was compared with above optimal process by testing the wetting ability and bursting strength difference of cotton knitted fabric. In addition, the whiteness of the fabric finished by Cu-TAML catalyst, commercially available activator and catalyst were compared under 70℃ respectively. The results show that the whiteness of the fabric finished by Cu-TAML is as the same as commercially available hydrogen peroxide catalyst, but better than that of the conventional hydrogen peroxide activator.