A separable paper adhesive based on the starch―lignin composite

One major defect in paper adhesives is that it is difficult to remove the adhesive in waste paper. These adhesives can easily adhere to paper-making equipment, which hampers recycling. Herein, the hyperbranched polyester H102 is used to act as dispersant, and grafting copolymerization of lignin onto the starch backbone was carried out by initiation of free radicals to prepare a bio-based paper adhesive in water. The results show that the adhesive can achieve the best adhesion properties under m(H2O)/m(St) = 15:1, m(SLS)/m(St) = 0.15:1, m(APS)/m(St) = 0.02:1, and pH = 4 at 80 °C for 6 h. The addition of H102 stabilizes the performance of the adhesive and extends the shelf life. The feasibility was verified by Fourier transform infrared spectroscopy (FT-IR), Ultraviolet-visible Spectrophotometry (UV-vis), Thermogravimetric analysis (TG), X-ray diffraction (XRD) and rheological property analysis. Moreover, the as-prepared adhesive can be dissolved in H2O by heating, which is beneficial to improve the recovery and recycling of waste paper compared with the traditional adhesives.