1 Conversion of paper to film by ionic liquids: 1 manufacturing process and properties 2 Atsushi Tanaka 1 , Alexey Khakalo 1 , Lauri Hauru 2 , Antti Korpela 1 , Hannes Orelma 1* 3 1 VTT - Technical Research Centre of Finland Ltd, Biologinkuja 7, Espoo, Finland 4 2 University of Helsinki, P.O. Box 55 (A. I. Virtasen aukio 1), FI-00014 University of Helsinki 5 KEYWORDS 6 Cellulose, dissolution, paper, ionic liquid, all-cellulose composite 7 ABSTRACT 8 In this study, we investigate the “chemical welding” of paper with the ionic liquid (IL) 1-ethyl-3- 9 methylimidazolium acetate ([EMIM]OAc) using a two-step process. First, the IL is transported into 10 the structure of the paper as a water solution. Then, partial dissolution is achieved by activation 11 with heat, where the water evaporates and the surfaces of the fibres partially dissolve. The 12 activated paper is washed with water to remove IL, and dried to fuse fibre surfaces into each 13 other. The “chemically welded” paper structure has both elevated dry and wet strength. The 14 treatment conditions can be adjusted to produce both paper-like materials and films. The most 15 severe treatment conditions produce films that are fully transparent and their oxygen and grease 16