Diperfluoroalkylethyl phosphate (DPFP), one of the representative water-soluble fluorine-containing compounds for giving oil-penetration resistance to paper, was added to pulp slurries in combination with a cationic polymer, polyamideamine-epichlorohydrin (PAE) resin or poly(diallyldimethyl-ammonium chloride) (PDADMAC). Mechanisms of the development of water- and oil-penetration resistances were investigated for the handsheets prepared from these pulp slurries. Anionic DPFP molecules were retained to cationic sites of PAE or PDADMAC on pulp fibers through electrostatic interactions in the pulp slurries. The handsheets prepared with PAE had clearly higher sizing degree than those with PDADMAC at the same DPFP addition levels as well as at the same DPFP contents in the handsheets. Regarding oil-penetration resistance, however, both handsheets prepared with PAE-DPFP and PDADMAC-DPFP showed similar degrees at the same DPFP retentions. Heat-treatment is essential for improving sizing degree of the DPFP-handsheets. When aqueous solutions of DPFP and either PAE or PDADMAC are mixed, PAE/DPFP or PDADMAC/DPFP precipitates are formed through ionic bonds between these two compounds in water. Then, these PAE/DPFP and PDADMAC/DPFP precipitates were prepared without pulp fibers, and these mixtures before and after heat-treatment were subjected to some analyses to explain the results obtained for the DPFP-handsheets. FT-IR and solid-state 31P-NMR analyses of the model compounds indicated the formation of phosphoric ester bonds to some extent between DPFP and PAE in the mixture after heat-treatment; the ionic bonds between cationic azetidinium groups and anionic phosphate groups present in the PAE/DPFP mixture turned in part to phosphoric ester bonds. If phosphoric ester bonds are formed between DPFP and PAE molecules in the PAE-DPFP-handsheets, the improvement of sizing degree for the handsheets by heat-treatment are explainable in terms of the transformation of hydrophilic ionic bonds to less hydrophilic phosphoric ester bonds between PAE and DPFP retained in the handsheets by heat-treatment.
All Science Journal Classification (ASJC) codes
- General Materials Science