The use of lignin in emulsion-based pressure-sensitive adhesives

Abstract

Pressure sensitive adhesive (PSA) films were produced by in situ seeded semi-batch emulsion polymerization of butyl acrylate (BA) and methyl methacrylate (MMA) in the presence of varying amounts of lignin. Two types of Kraft lignin, water-soluble and non-water soluble, were used in this study. Lignin was modified using acrylation (methacryloyl chloride), maleation (maleic anhydride) and acetylation (acetyl bromide and acetic acid) to promote its miscibility with the BA and MMA monomers and encourage its incorporation into the polymer matrix. For the case of the maleated lignin, maximum incorporation of 10 wt% was achieved whereas, for the acrylated lignin case, a maximum of 5 wt% was attained. Lignin was shown to decrease latex viscosity in all cases. At a lignin loading of 1 wt% (relative to the amount of monomer) a tack and shear strength of the PSA films increased significantly while the peel strength remained constant. Thus, maleated lignin was shown to be an effective, renewable modifier for emulsion-based PSA properties.