Polypropylene terephthalate is used to keep dirt solubilised after it has been washed off the textile and to prevent it from re-depositing. The surface active agents in the formula will remove dirt, but once this dirt has been dissolved into the washing water it still comes into contact with the garments and may settle back again once the rinsing cycle begins. The function of this soil release polymer is to make sure dirt stays in the washing water and is removed in the rinsing process.
This particular polymer has a similar structure to the better known variant which is used in packaging, but differs from it by being water soluble. It is petrochemically based, but fully biodegradable. We specifically exclude phthalates from our Ecover formulas. We also choose packaging materials that do not contain phthalates.