Polyethylene oxide (PEO) technology is widely used in retention systems, mainly in newsprint production - by papermakers in Canada, Sweden, South Africa, and Japan. Kemira’s PAPEO technology incorporates the latest in PEO chemistry, combining a patented cofactor, or enhancer, with a proprietary PEO polymer.
”PEO is one of the industry’s ’survivors’, and has been in use since the 1970s,” says Marco Polverari.
“It has had something of a mixed reputation, however, largely because of early mill trials that pointed to it being a problematic and unreliable chemical. And once perceptions form, they are difficult to erase.
”Over the last 10 years, however, its reputation has grown stronger and stronger, as PEO-based retention aid systems have proved both viable and effective. With closed white water systems and the increasing use of deinked pulp, mills today are looking for the optimum chemical balance for their processes - and PEO has been shown to be the best choice for many newsprint and specialty mills.”
Researchers in Canada first started investigating the effectiveness of PEO in the 1970s. Initial mill trials on newsprint grades produced unsatisfactory results, however, with PEO only delivering benefits in about half the cases studied.
Polverari believes the reason for this was the poor understanding of wet-end chemistry at the time and shortcomings in chemical engineering.
”Mills usually tried to use too much PEO in an effort to reap quick results. Unfortunately, they were employing conventional makedown equipment, which not only resulted in imprecise chemical dissolution, but also caused havoc with mills’ delicate chemical balance.
”Important parameters such as injection velocity, dilution rates, and delivery points were not given the attention they needed. Small wonder then that mills complained about consistency problems with their newsprint.”
Solving the enhancer problem
Another major problem was the use of ineffective enhancer technology, and the failure to use any enhancer at all in some cases. An enhancer is essential to create bonding sites on the fines and fibers, which the PEO molecule can use as anchors when bridging fines and fibers together.
Phenolic resin was used as an enhancer quite early on, but it never proved a complete solution. Basic research at McGill University and the Paprican Pulp and Paper Research Institute in Canada, with significant contributions from Kemira, broke new ground around 1990.
”This research highlighted the importance of better additional enhancers. Working together with Paprican, Kemira developed an extremely efficient and stable enhancer technology.
”Our current PAPEO products have a shelf-life 10 times superior to phenolic resin, and they are not effected by headbox concentrations of calcium ions, or by the detrimental substances carried over by deinked pulp, such as sodium silicate.”
Technological enhancements have also solved the problem of delivering PEO-based chemicals precisely.
”Kemira’s sophisticated makedown system monitors a host of parameters, such as mix times, equilibrium dosage, polymer dispersion, and total dilution rates. And being a totally automated system, it’s very user-friendly as well.”
Kemira Solutions 3/2005
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