Characteristics of High Yield Pulp (HYP) and Their Effects on the Wet-end Chemistry of the Papermaking Process, 2008 PAPERCON Conference

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Some of the recent findings are summarized on understanding the characteristics of HYP and its effect on the wet-end operations of the papermaking process in the production of printing and writing paper, including internal sizing and filler retention. Compared with bleached kraft pulp (BKP), HYP pulp contains more fines, lignin and anionic trash, as well as more carboxylic and sulfonic groups that impart HYP fibres a higher charge density. Due to these differences in physical and chemical properties between HYP and BKP, substituting HYP for BKP may have some impacts on the wet-end chemistry of the papermaking process. Generally, HYP has higher response to both AKD and rosin ester sizing than BKP due to the higher anionic group content and self-sizing capability, although HYP fines and anionic trash can affect the sizing adversely. The addition of cationic polymers, such as PEI, can eliminate the negative effect of HYP anionic trash on internal sizing and filler retention.