The disclosed invention is directed to pulp fibers suitable for forming a wet-laid
paper product which include amino-functionality which is non-extractable in an
aqueous phase. The pulp fibers may be prepared by applying an amino-functional
additive to a fibrous web prior to the finishing operation at a pulp mill. The
fibrous web may then be repulped at a papermaking machine to form a paper web which
includes the amino-functionalized fibers of the present invention. A paper web
formed of the amino-functionalized fibers may display unique and/or improved reactivity
toward certain papermaking additives. For instance, the paper webs of the disclosed
invention may show dry tensile strength increases of greater than 40% when treated
with a permanent wet strength agent such as a polyamine epichlorohydrin wet strength
agent, whereas a paper web which does not include the amino-functionalized fibers
of the present invention may show less than a 20% increase in strength properties
when treated with the same strength agents.