Facile Synthesis of a Novel, Low Fabric Damage and Cost-Effective Bleach Catalyst for Cotton Fabric: 1,4-Dimethylpiperazine Manganese Complex

Abstract

The application of hydrogen peroxide bleaching catalysts in cotton fabric bleaching can effectively reduce the temperature and time of the bleaching process, thereby reducing energy consumption. Conventional hydrogen peroxide bleaching catalysts such as manganese complex (Mn–Me₃TACN) with the ligand of 1,4,7-trimethyl-1,4,7-triazacyclononane introduced by Unilever can achieve satisfactory whiteness at low bleaching temperatures. However, Mn–Me₃TACN can result in severe chemical damage to fibers and the ligand 1,4,7-trimethyl-1,4,7-triazacyclononane is very expensive, which greatly inhibit the commercial application of the conventional bleaching catalysts. In this work, a novel and cost-effective manganese complex (Mn-DMPP) with the ligand of 1,4-dimethylpiperazine for cotton fabric bleaching is reported. The physicochemical properties of synthesized complex are characterized and the bleaching performance of Mn-DMPP is evaluated in terms of H₂O₂ decomposition and the whiteness index, tensile strength retention, and capillary effect of the bleached fabric. After bleaching at 70 °C for 45 min, the whiteness of the fabric bleached with Mn-DMPP is 76.55, and the tensile strength retention is 87.77%. Under the same testing conditions, the whiteness of the fabric bleached with Mn–Me₃TACN is 76.79, and the tensile strength retention is 82.3%. Compared with conventional catalyst Mn–Me₃TACN, the cotton fabric bleached with the Mn-DMPP at low temperature shows higher tensile strength retention at similar whiteness levels. Therefore, Mn-DMPP is an effective catalyst for the low-temperature bleaching of cotton fabric with hydrogen peroxide. It has competitive advantages in reducing bleaching production costs and protecting fibers from severe chemical damage.