Reforming paper structure using an ionic liquid treatment to improve the specific surface area, moisture retention, and hydrophobicity

A method for treating cellulose paper using the ionic liquid 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) was developed. The treatment was intended to reform the paper structure. Filter paper was immersed in 20 g of molten [BMIM]Cl at 80 °C for 20–80 s and then washed with ethanol and distilled water. The treated paper was then immersed in tert-butyl alcohol before drying in a freeze dryer for 30 min. Next, polyethylene glycol (PG) and trichloromethylsilane were fixed to freeze-dried paper. The paper treated with [BMIM]Cl had a higher specific surface area than that not treated with [BMIM]Cl, and the specific surface area increased as the treatment time increased. The amount of PG fixed to the paper increased as the specific surface area of the paper increased, and PG improved moisture retention. The degree to which the moisture retention was improved was therefore related to the increase in the specific surface area caused by [BMIM]Cl treatment. Addition of trichloromethylsilane to the paper treated with [BMIM]Cl improved the hydrophobicity, and this was caused by the [BMIM]Cl treatment. Overall, [BMIM]Cl treatment was effective for reforming the paper structure and this improved the amount of functional material that could be fixed to the paper.