Incorporation of novel degradable oligoester crosslinkers into waterborne pressure sensitive adhesives: towards removable adhesives†
Waterborne pressure-sensitive adhesives (PSAs) containing degradable crosslinked chains that enable easy removability of the adhesive tape have been successfully synthesized. Symmetric and asymmetric degradable oligoester crosslinkers of variable chain length have been synthesized by ring opening polymerization (ROP) of ε-caprolactone and lactide. The oligoester crosslinkers have been incorporated into a conventional waterborne PSA formulation to demonstrate the possibility of introducing degradability by hydrolysis of crosslinking chains to PSAs. The adhesive films present good adhesive properties, but it is remarkable that when exposed to basic conditions their adhesion is substantially reduced within short times and hence the PSAs can easily be removed (much easier than if conventional crosslinkers are used). The degradation of the ester group of the crosslinkers is responsible for the loss of adhesion properties making this class of degradable waterborne PSAs excellent candidates as removable adhesives. These PSAs might have a strong impact on the sustainability of the cleaning process of glass bottles (or other substrates) by reducing the energy and solvent consumption.