Diatomite Modified With Alkyl Ketene Dimer For Hydrophobicity of Cellulosic Paper

Multi-functionalization of papermaking chemicals is one of its main developing strategies. Fillers and internal sizing agents are often mutually restricted in practice. Therefore, it is feasible to prepare a new papermaking chemical by combining its functions. A process of diatomite modified with Alkyl ketene dimer (AKD) was developed in this study. The modified diatomite (AD) can concurrently play the role of mineral filler and sizing agent in the papermaking process. With the equal dosage of AKD, the AD had better sizing and retention performance than the commercial AKD emulsion in the case of cationic polyacrylamide (CPAM) and the CPAM/ bentonite retention system. The sizing mechanism of the AD can be interpreted as numerous hydrophobic sites and micro-surface structure of the paper sheet caused by the AD. Since the ester linkages were not detected in FT-IR spectra of the paper sheet filled by the AD, the chemical reaction may not be indispensable for its sizing performance. What’s more, an interesting “sticky” hydrophobicity phenomenon was observed when filling with AD. The approach in this study to prepare the “sticky” hydrophobic paper sheet can find its applications in some non-traditional application fields of cellulosic paper.

Structure Optimization of Cellulose Nanofibers/Poly(Lactic Acid) Composites by the Sizing of AKD

Recently, cellulose nanofibers (CNF) are used as one novel fillers to reinforce poly(lactic acid) (PLA) matrix and form PLA green nanocomposites. In the present work, alkyl ketene dimer (AKD) was used as the sizing of CNF to improve the interfacial compatibility between the hydrophilic CNF and the hydrophobic PLA. The interactions between the AKD and CNF were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), which showed the formation of ketone ester structure between AKD and the hydroxyl groups of CNF. Thermo gravimetric analysis (TGA) showed the little reduced thermal stability of the AKD-CNF/PLA composites. The AKD-CNF/PLA morphology has rough surfaces due to the incorporation of cellulose nanofibers. The mechanical properties of AKD-CNF/PLA were tested by tensile testing, which discovered more AKD-CNF content enhances stress–strain performance. The highest tensile strength of composites was obtained for PLA with 5.0 wt.% AKD-cellulose, which is almost nine times higher than that of the pure PLA.

Effects of hydrophobic sizing on paper dry and wet-strength properties: A comparative study between AKD sizing of NBSK handsheets and rosin sizing of CTMP handsheets

Alkyl ketene dimer (AKD) and rosin sizing are used in papermaking to decrease paper’s tendency to absorb liquid water. Earlier information regarding the effects of internal sizing on paper dry strength is not consistent. In the present laboratory study, AKD sizing of handsheets made from Nordic bleached softwood pulp (NBSK), and rosin sizing of handsheets made from Nordic hardwood chemi-thermomechanical pulp (CTMP) were done via an internal sizing method, and by immersing handsheets in aqueous sizing agent dispersion. In the study, AKD sizing had no significant effect on the dry strength of NBSK handsheets. The result corresponds to practical experiences of papermakers. However, both AKD sizing methods resulted in a substantial and long-lasting increase of handsheet wet-strength. Unlike internal AKD sizing of NBSK handsheets, rosin internal sizing of CTMP handsheets resulted in decreased handsheet dry strength. The decrease indicates that, under the conditions present during the experiment, rosin sizing agents interfered with interfiber hydrogen bonding of CTMP fibers. Given that, in practice, no such undesired effects have been commonly linked to rosin sizing, the observed effect may be specific to sheet-making conditions. However, the effect of rosin sizing on strength properties and their variation cannot be ruled out completely.

Synthesis and Characterization of Hydrophobically Modified Xylans

Xylan is a major type of hemicellulose that has attracted a lot of research and development activities. It is often derivatized in order to improve its properties. In the literature, hydrophobic modification of polymers is often used to produce surfactant-like materials and associative thickeners. In this work, we have derivatized xylan with alkyl ketene dimer (AKD) and two types of alkenyl succinic anhydrides (ASAs). The xylan-AKD derivatives have been made at 90 °C, using dimethyl sulfoxide as solvent and 4-dimethylaminopyridine as promoter. Samples with degrees of substitution (DS) up to 0.006 have been produced. The xylan-ASA derivatives have been synthesized at 120 °C in dimethyl sulfoxide with DS up to 0.105–0.135. The structures of these products have been confirmed with NMR and FT-IR. These xylan derivatives increase the structural diversity of xylan and provide additional options for people seeking to use hydrophobically modified polysaccharides in their applications.