Challenging the impossible: Extending the shelf-life of polyester-based PU dispersions

 
Thermo-activated waterborne adhesives based on polyurethane dispersions are an established technology, providing strong and elastic bonding with superior hot tear strength. This feature makes PUD-based adhesives the technology of choice for highly demanding and dynamically loaded applications in the automotive, furniture and particularly in the footwear industries. The principle of thermal activation is based on the use of semi-crystalline polyester backbones. However, the resulting PUD is prone to suffer from hydrolytic degradation limiting the shelf life of adhesives based on those materials. Several ways are known to improve the storage stability of polyester based dispersions. First of all, it is important to strictly control temperature and pH during storage. Improvements in shelf life have also been achieved by addition of polycarbodiimides as hydrolysis stabilizers. Since storing conditions in the field are not always well controlled and polycarbodiimides are a costly additive, there is still demand for economically attractive solutions to improve the shelf life of such versatile adhesives. During the talk, we will introduce a new technology that significantly improves the shelf life of polyester-based PU dispersions providing superior initial hot tear resistance over a prolonged storage time in economically attractive conditions.