Mini-Encyclopedia of Papermaking Wet-End
Additives and Ingredients, their Composition, Functions, Strategies for Use
POLYETHYLENE OXIDE (PEO)
Composition: The ethylene oxide monomer is nothing more than an epoxide ring. Two corners of the molecule consist of -CH2- linkages. The third corner is an oxygen, -O-. In the presence of a catalyst the monomer forms a chain having the repeat unit -CH2-CH2-O-. The PEO products found to be most effective in various papermaking applications are those having very high molecular mass, much in excess of one million grams per mole. Factors that make PEO wet-end chemistry puzzling include (a) the fact that it can be used as a retention aid even though it is nonionic, (b) the fact that its performance is highly dependent on its shear history, and (c) the fact that it needs the presence of lignin or certain phenolic "cofactor" additives to achieve its best effect as a flocculant and retention aid. Observations of PEO behavior suggest that the molecular chains are initially tangled with each other and that this tangling is somehow essential for effective flocculation. PEO is usually received as dry granules. These need to be dispersed with care, using a dilution ratio of at least 100 and avoidance of excessive shear.
Function: Potent retention aid for high-yield pulps and for furnish to which a phenolic cofactor has been added; in theory it can be used as a formation aid for specialty applications where there is an insignificant amount of lignin or cofactor and where the drainage rate is not a concern.
Strategies for Use: Polyethylene oxide has been used as a retention aid since the 1970's in various Canadian newsprint mills and other applications with high-yield pulps. In most of these cases the retention efficiency is maximized by first adding various proprietary phenolic compounds that appear to interact with the PEO and allow it to bridge between the adjacent solid materials in the furnish. As noted above, attention needs to be paid to the make-down process, using plenty of dilution and avoiding excessive or prolonged hydrodynamic shear. On the paper machine PEO needs to be trialed in small steps, since overdose can be expected to produce large fiber flocs that hurt the uniformity of the paper. A great potential advantage of PEO is that it is not affected by conditions of anionic charge or electrical conductivity. In other cases it has been reported that addition of highly cationic materials to the furnish ahead of PEO can improve the overall retention and drainage. In principle PEO ought to work as a retention aid in a highly closed white water system. The ratio of cofactor to PEO usually needs to be maintained within an optimum range. The possibility of using PEO as a "formation aid" is listed here only as a matter of completeness. It is known that very high mass polyelectrolytes having little affinity for fibers can be used to improve the uniformity of non-woven fabrics. If this approach were used with cellulosic fibers in the production of paper, it would be expected to reduce dewatering rates significantly, requiring a reduction of machine speed.
Cautions: Consult the MSDS and supplier recommendations. PEO is not expected to be particularly hazardous.
PLEASE NOTE: Users of the information contained on these pages assume complete responsibility to make sure that their practices are safe and do not infringe upon an existing patent. There has been no attempt here to give full safety instructions or to make note of all relevant patents governing the use of additives. Please send corrections if you find errors or points that need better clarification.
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This page is maintained by Martin Hubbe, Associate Professor of Wood and Paper Science, NC State University, email@example.com .