| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing deinked wastepaper pulp with high whiteness and high quality by significantly reducing dirt of deinked pulp produced from printed wastepaper including some neutral newspaper with low deinking properties.SOLUTION: The present invention provides a method for pulping printed wastepaper by a combination of a disintegration step, a dust removal step, a bleaching step, a dispersion step, a floatation step, and a washing/dewatering step, wherein, a disintegration step is set as a treatment step in an alkaline region of pH 10.0 or more and 12.5 or less, a pre-stage floatation step is set as a treatment step in a neutral area of pH 6.0 or more and 9.0 or less, a bleaching step is set as a treatment step in an alkaline region of pH 10.0 or more and 12.0 or less, and a post-stage floatation step is set as a treatment step in a neutral area of pH 6.0 or more and 9.0 or less. The method can provide printed wastepaper pulp in which the number of dirt of 0.004-5.0 mmis 5000-35000/mor less, and ISO whiteness is 65%-85%.SELECTED DRAWING: None |
