Impact of Retention Polymers on Flocculation, Retention, Drainage and Sheet Formation, A Laboratory Study, 1994 Papermakers Conference Proceedings

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The effect of different polyacrylamide (PAM) polymers alone and together with bentonite on a filler-containing groundwood furnish was investigated. Flocculation was monitored on the fines fraction with a Photometric Dispersion Analyser. Filler and fines retentions were determined with a Britt-type jar (DDJ), and drainage with a Dynamic Drainage Analyser (DDA). Beta-formation of standard handsheets made with the same chemicals was also recorded. Flocculation monitoring showed that clay was flocculated with PAMs of both charge signs, while fibre fines were flocculated primarily by cationic PAM. The dosage levels needed for flocculation also differed, fibre fines needing higher doses. Bentonite increased flocculation with low cationic and anionic PAMs. The DDJ retention tests showed that low and, in particular, medium cationic charge PAMs were superior to high cationic PAM, which had lower molecular mass. Drainage with the DDA was unaffected by the use of medium and high cationic PAMs, but slowed down with low cationic PAMs and even more with anionic PAMs. Poorer handsheet beta-formation was experienced with those polymers that caused strong flocculation, e.g. anionic PAM + bentonite.