PHYSICAL AND OPTICAL-PROPERTIES OF STEAM-EXPLODED LASER-PRINTED PAPER

Laser-printed paper was pulped by the steam-explosion process. A full- factorial experimental design was applied to determine the effects of key operating variables on the properties of steam-exploded pulp. The variables were addition level for pulping chemicals (NaOH and/or Na2SO 3), digester pressure, digester residence time,and addition level for dispersant. Steam explosion removed laser toners from the fibers and d ispersed the particles,as evidenced by the higher sheet brightness and opacity of exploded pulp compared with an unexploded control pulp. Ho wever, the fiber-bonding ability of exploded pulp was lower than that for unexploded pulp, as evidence by lower tensile index and relative b onded area. Zero-span breaking length of exploded pulp also was lower, indicating that explosive discharge damaged the fibers.