Response surface methodology for optimizing heat sealing self-adhesive process of lignin-based waterborne polyurethane

To develop high-performance and environmentally friendly coating materials for self-adhesive heat-sealable paper, lignin-based waterborne polyurethane emulsion (ALWPU) was prepared by replacing 20 wt% of PPG with AlCl 3 demethylated modified lignin (AL), and used as self-adhesive coatings for kraft wrapping paper. The surface structure and physical properties of coated paper with different coating weights of ALWPU and water-based polyurethane (WPU) with AL were investigated, and the effects of heat pressing time, pressure and temperature on the T-peel strength and shear strength of self-adhesive paper were discussed and the heat-sealing process parameters were optimized by response surface methodology. The results indicated that at the same coating weight, the ALWPU coated paper exhibited significantly superior stiffness, burst strength, tear strength, dry/wet tensile strength, weather resistance, and thermal stability compared to the uncoated paper and WPU coated paper. When the coating weight was 8 g·m −2 , the coated paper with ALWPU exhibited a maximum T-peel strength of 10.6 N·cm −1 when the heat pressing time, pressure and temperature were respectively 3.3 min, 2.1 MPa, and 55°C, and the ALWPU coated paper achieved maximum shear strength of 5.8 MPa when the heat pressing time, pressure and temperature were respectively 3.3 min, 2.1 MPa and 50°C. This research provided a new insight for the high-value utilization of lignin and also provided a novel approach for efficient heat-sealing self-adhesion of paper packaging materials.