Preparation of AKD and modified PAM mixtures and their neutral sizing performances

Polyvinylamine (PVAm) is a linear, cationic, water soluble polymer. It has a lot of highly active amido groups linked directly to the carbon chains, and its molecular weight and charge density can be adjusted accordingly. Therefore, the study on the synthesis and application of PVAm as a potential polymer for improving paper-machine runnability, strengthening different paper grades, fixing the anionic trash and dealing with waste-water is worthy both theoretically and practically. In this paper, PVAm was prepared by Hofmann degradation of polyacrylamide (PAM), and mixed with alkyl ketene dimmer (AKD) to make a stable emulsion-based neutral sizing agent with good flow ability and sizing performance. The sizing agent had good retention and sizing during neutral sizing. The sizing experiments showed that when adding 0.3% dosage of the sizing agent, sizing degree was 35 s before aging but it increased as high as 55 s after aging. Moreover, paper properties was also improved clearly: the breaking length increased by 6.1% and the folding endurance was improved by 300%.