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 Contributor Abstract 

Stephen F. Nelsen

   65th Birthday Symposium
Madison, Wisconsin
June 3-4, 2005

 

Glen Cunkle

Ciba Specialty Chemicals, 540 White Plains Rd, Tarrytown, NY  10591

Inhibition of Brightness Reversion of Mechanical Pulps

Paper containing lignin (e.g. newsprint) is highly susceptible to yellowing when exposed to light, especially near ultraviolet light (300-400nm).  Several mechanisms have been proposed to account for this photo-instability and they all invoke phenoxy radicals as key intermediates which are furthered oxidized to form yellow chromophores.  This discoloration restricts the use mechanical pulps (i.e. paper pulps which still contain lignin) to low value, short life cycle products.  If the light stability of lignin could be significantly improved, the possible uses of mechanical pulps would be greatly expanded.

 

We have developed an efficient chemical additive approach to stabilizing lignin containing pulp against loss of brightness due to the adverse effect of UV radiation.  We have found that hindered amine nitroxides or preferentially the colorless hydroxylamines, even when added at low concentrations, produce dramatic improvement in the light stability of mechanical pulps.

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Last Updated: May 12, 2005 (P.M. Gannett)