Biodegradable slashing agents from soy protein for textile industry

Biodegradable sizing agents were developed from physically modified soy protein, acrylic-acid grafted soy protein and soymeal to substitute poly(vinyl alcohol) (PVA) sizes for high-speed weaving and reduce environmental pollution from textile desizing effluent. PVA is the best textile size due to its excellent film properties and adhesion to fibers. However, non-biodegradability of PVA leads to serious environmental issues. Till now, no biodegradable substitutes with size properties and cost-effectiveness comparable to PVA have been developed. In this research, sizing agents from physically modified soy protein, acrylic-acid grafted soy protein and soy meal were developed to substitute PVA size. The potential of using the soy protein based sizes for warp sizing in textile industry were investigated by tensile properties of size films, adhesion of sizes to yarns, abrasion resistance of sized yarns, industrial-scale weaving performance, desizing efficiency and biodegradability of sizing agent. Our research showed that soy protein based sizes had film elongation, adhesion to yarns and abrasion resistance similar or higher than commercial PVA sizes. Industrial weaving trial showed that, at lower add-on, physically modified soy protein sized cotton and polyester/cotton yarns had weaving efficiencies 13% and 3% higher than the PVA sized ones, and 39% and 10% higher than the modified starch sized ones. Physically modified soy protein sized polyester yarns had weaving efficiencies similar to the PVA sized ones. In addition, soy protein based sizes had a chemical oxygen demand value of 70 -109 mg/L after 5 days treatment in activated sludge, much lower than 398 mg/L of PVA, demonstrating that soy protein sizes were readily biodegradable