Takayoshi Konishi, Kanonji, Japan; Toshio Hiraoka, Kanonji, Japan; and Noritomo Kurita, Kanonji, Japan.
Assigned to Unicharm Corporation, Ehime, Japan.

Filed: 5/10/18
Issued: 10/3/23

A method of manufacturing recycled pulp fibers from pulp fibers of used hygiene products, comprising steps of: a preparation step of preparing a treatment tank which includes a liquid mixture supply port, and a treatment liquid discharge port and an ozone containing gas supply port that are arranged below the liquid mixture supply port, a liquid mixture supply step of supplying a liquid mixture which includes super absorbent polymers and the pulp fibers that derive from a plurality of types of used hygiene products and water, from the liquid mixture supply port to the treatment tank, an ozone containing gas supply step of supplying ozone containing gas from the ozone containing gas supply port to a treatment liquid in the treatment tank, wherein the ozone concentration in the ozone containing gas is 40 to 200 g/m3 to cause the decomposition of the superabsorbent polymers, a recycled pulp fibers formation step of forming the recycled pulp fibers by bleaching the pulp fibers, while dissolving at least a portion of the super absorbent polymers in the treatment liquid, by, in the treatment tank, raising the ozone containing gas while the super absorbent polymers and the pulp fibers sink towards the bottom of the tank so as to make the ozone containing gas come into contact with the super absorbent polymers and the pulp fibers, and a treatment liquid discharge step of discharging the treatment liquid which includes the recycled pulp fibers from the treatment liquid discharge port, wherein the recycled pulp fibers have ΔYI of 0 to 10 with respect to a standard white board.