Textile processing

Control of metal ions is critical in several textile processing steps. Dequest® phosphonates and polymers, with their excellent ability to control both hardness and heavy metal ions, should be considered in any process where metal ions may interfere. Dequest has primarily investigated the utility of phosphonates and polymers in two critical processes : textile scouring and peroxide bleaching of textiles.

The scouring process uses hot alkaline solutions to remove natural and other impurities from textile fabrics. If impurities are not removed, they will negatively affect subsequent bleaching, dyeing, printing or finishing operations. Dequest® phosphonates and polymers are used in scouring to remove iron and water hardness ions ; this results in better fabric whiteness, prevention of staining due to iron deposits and prevention of fabric damage during bleaching caused by embedded copper or iron fragments.

Hydrogen peroxide, commonly used to bleach textiles, is easily decomposed in the presence of very low levels of heavy metals. Loss of peroxide and bleaching efficiency results, and in textile applications, the presence of metal particles on the fabric can cause pinholing due to the excessive rate of local decomposition of the peroxide. Very low levels of phosphonates can sequester the metal ions, preventing this decomposition. Also, since silicates are sometimes used in bleaching to stabilize the peroxide and buffer the solutions, the addition of phosphonates can help to prevent the scale build-up common in silicate systems.