Preventing Discoloration of Poly(vinyl alcohol)-Coated Paper Hydrophobized by Gas Grafting with Palmitoyl Chloride

Gas grafting with fatty acid chloride (FAC) is a simple and ultrafast paper treatment, which produces only hydrochloric acid as a byproduct. In this study, poly­(vinyl alcohol) (PVOH)-coated paper was treated by gas grafting with palmitoyl chloride, and the effects of temperature, time, and concentration of palmitoyl chloride on discoloration were investigated. The grafting efficiency expressed by the water absorption capacity (Cobb size) and the amount of grafted FAC increased with increasing temperature, reaction time, and concentration of palmitoyl chloride. However, discoloration of PVOH was inevitable at high temperature and long reaction time, and under excessive FAC dosage. PVOH was converted into polyene via dehydration by the acid catalyst at high temperature. Calcium carbonate applied to PVOH coating for preventing discoloration of the PVOH-coated paper could neutralize gaseous hydrochloric acid. Unfortunately, the hydrophobicity decreased slightly with an increase in the calcium carbonate blending ratio due to the additional consumption of FAC. The grafting efficiency could be improved without discoloration if the blending ratio was appropriately controlled based on the specific surface area of the calcium carbonate particles.