Repulpable PSAs

The PSA formulator can also take advantage of plasticizers. For example, polyether-based plasticizers have both good low-temperature flexibility and good hydrophilicity. Using these properties, acrylic PSAs have been formulated with these types of plasticizers to obtain high adhesion to food packages stored under refrigerated conditions [102]. Similarly, polyether plasticized acrylics have been used to make repulpable PSAs [103]. 

For some applications, such as for repulpable type PSAs, it may be advantageous to incorporate high levels of acrylic acid because this makes the polymer more hydrophilic. At the same time, high levels of acid also improve the water-dispersibility of the adhesive, especially at higher pH where the acid groups are converted to the more water-soluble neutralized salt form. Since the high level of acid increases the of the resulting polymer, a non-tacky material results. To make the adhesive pressure sensitive, the polymer can be softened with water-dispersible or soluble plasticizers, such as polyethers [68]. 

Other than the hydrocarbon elastomers and acrylics, and to a smaller degree silicones, little success commercially has attended efforts to utilize other polymers for PSAs. The patent literature describes a number of water solubles, suitably crosslinked, as the base ingredient for repulpable adhesives on paper backings used to splice rolls during papermaking operations. The patent literature also reveals efforts to utilize polyurethanes, polyurethane-acrylic hybrids, ionomers, and polyester block elastomers, among others, but only repulpable adhesives have reached the marketplace. Two systems that have achieved mentionable commercial success are described below. 

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