Objective In order to solve the environmental problems such as formaldehyde release of melamine-urea formaldehyde resin for finish foil, the technology research on preparation of formaldehyde-free finish foil by formaldehyde-free water-based impregnating adhesive and coating was carried out.

Method Quaternized nanocellulose-modified waterborne acrylate emulsion was used as impregnating adhesive to prepare impregnated paper, and rollers were used to apply acrylic paints on its surface to prepare finish foil. X-ray photoelectron spectroscopy (XPS), thermogravimetric analyzer and mechanics test machine were used to analyze the changes of surface chemical groups and element content, thermal stability and tensile properties of finish foil.

Result The results showed that the longitudinal tensile strength and elongation at break of finish foil increased by 4.2 times and 3.2 times compared with base papers, respectively. In addition, finish foil could be folded at any angle with excellent flexibility. The formaldehyde emission of finish foil was 0.12 mg/L, which met the requirement of formaldehyde emission value ≤ 0.3 mg/L for F^☆☆☆☆ limit according to F star rating of Japanese standard. It refers to the strictest level of formaldehyde emission tested by the desiccator method in the world. XPS analysis showed that the surface chemical structure and element content of finish foil changed compared with base paper. The surface hydrophobicity of finish foil was improved after being treated with acrylic adhesives and coating. From the thermogravimetric analysis, finish foil showed a slight decrease in thermal stability compared with base paper. In addition to surface abrasion resistance and hardness, the impact resistance, resistance to dry heat, resistance to damp heat, water resistance and resistance to pollution corrosion of finish foil-topped panels all met the requirements of GB/T 15102—2017 Surface decorated fiberboard and particleboard with paper impregnated thermosetting resins and GB/T 37005—2018 Paint finishing wood-based panels.

Conclusion The finish foil enhanced by quaternized nanocellulose has good environmental and mechanical properties.