PURPOSE: To efficiently separate a heat-sensitive recording material layer, obtain pulp of high whiteness and suppress the drain COO load to the minimum by disaggregating waste paper of a heat-sensitive recording chart and then bleaching the disintegrated waste paper with a chlorine-based and an oxygen-based bleaching agents in many stages.
CONSTITUTION: Waste paper of a heat-sensitive recording chart is disaggregated and the resultant pulp suspension is then bleached with a chlorine-based bleaching agent and/or an oxygen-based bleaching agent in many stages. Chlorine, sodium hypochlorite, hypochlorous acid and chlorine dioxide are preferred as the chlorine-based bleaching agent. Hydrogen peroxide and oxygen are preferred as the oxygen-based bleaching agent. For example, the sequence of treatments with chlorine, alkali extraction, hypochlorous acid and chlorine dioxide, etc., is cited as the multistage bleaching process. Furthermore, a drum washer having relatively large outflow of ash content or microfiber is preferred as a washer used in the multistage bleaching process.
NISHIMURA TAKAAKI
KITAO OSAMU
