Study on manufacturing hot water-resistant PVOH coated paper by gas grafting palmitoyl chloride (I) – Penetration of palmitoyl chloride during gas grafting of PVOH-coated paper

Abstract Gas grafting treatment with fatty acid chloride is a hydrophobization method based on the principle of forming ester bonds by reacting hydroxyl groups on the surface of hydrophilic substances with a gaseous fatty acid chloride. In order to increase the hydrophobization efficiency through gas grafting treatment, it is necessary to form an ester bond concentrated on the surface of the polyvinyl alcohol (PVOH) coating layer. When palmitoyl chloride, a fatty acid chloride, reacts with the hydroxyl groups of PVOH to form polyvinyl palmitate, the by-product hydrochloric acid promotes the dehydration of PVOH, causing discoloration while producing polyacetylene. Using this discoloration principle of polyene, it was estimated whether evaporated fatty acid chloride penetrated into the PVOH coating layer. The top layer was coated with PVOH having a saponification degree of 89 %, and the bottom layer was coated with PVOH having a saponification degree of 99 %. There was a difference in the discoloration according to the degree of saponification of PVOH, even the amount of palmitoyl chloride was small as much as 300 mg/m². It was confirmed that the vaporized fatty acid chloride during gas grafting treatment permeates the PVOH layer of 7 g/m² even in a very small amount.