Method for recovering pulp fiber from used sanitary product and recycled pulp obtained thereby

Patent metadata

Field	Value
Publication number	US-10260199-B2
Application number	US-201515512443-A
Country	US
Kind code	B2
Filing date	Aug 7, 2015
Priority date	Sep 22, 2014
Publication date	Apr 16, 2019
Grant date	Apr 16, 2019

Abstract

Pulp fiber containing little ash is effectively recovered from a used sanitary product containing the pulp fiber and a polymer absorbent. The method according to the present invention comprises: a step for treating the used sanitary product with an ozone-containing gas and thus decomposing and removing at least a portion of the polymer absorbent in the used sanitary product; and a step for stirring the used sanitary product, that has been treated with the ozone-containing gas, in water or an aqueous solution containing an antiseptic and thus decomposing the used sanitary product into constituents. If required, the method may further comprise a step for separating the pulp fiber from the decomposition product obtained by the decomposition step.

First claim

The invention claimed is:

1. A method for recovering pulp fiber from a used sanitary product including pulp fiber and a polymer absorbent, comprising the steps of:
treating the used sanitary product with an ozone-containing gas to decompose and remove at least a portion of the polymer absorbent in the used sanitary product which decomposed and removed portion of the polymer absorbent is gasified and removed as carbon dioxide, wherein a product of the ozone concentration of the ozone-containing gas and the treatment time with the ozone-containing gas is 500 to 12,000 m −3 ·g·min, and
stirring the used sanitary product that has been treated with the ozone-containing gas, in a disinfectant-containing aqueous solution or in water to decompose the used sanitary product into its constituent elements.

2. The method according to claim 1 , wherein the ozone concentration of the ozone-containing gas is 50 to 200 g/m 3 .

3. The method according to claim 2 , wherein the treatment time with the ozone-containing gas is 10 to 60 minutes.

4. The method according to claim 2 , wherein the used sanitary product is treated with the ozone-containing gas to decompose and remove at least 90% of the polymer absorbent in the used sanitary product.

5. The method according to claim 2 , wherein the disinfectant is sodium hypochlorite, chlorine dioxide, acidic electrolyzed water, ozone water, acidic ozone water or organic acid-containing ozone water.

6. The method according to claim 3 , wherein the used sanitary product is treated with the ozone-containing gas to decompose and remove at least 90% of the polymer absorbent in the used sanitary product.

7. The method according to claim 3 , wherein the disinfectant is sodium hypochlorite, chlorine dioxide, acidic electrolyzed water, ozone water, acidic ozone water or organic acid-containing ozone water.

8. The method according to claim 1 , wherein the treatment time with the ozone-containing gas is 10 to 60 minutes.

9. The method according to claim 8 , wherein the used sanitary product is treated with the ozone-containing gas to decompose and remove at least 90% of the polymer absorbent in the used sanitary product.

10. The method according to claim 8 , wherein the disinfectant is sodium hypochlorite, chlorine dioxide, acidic electrolyzed water, ozone water, acidic ozone water or organic acid-containing ozone water.

11. The method according to claim 1 , wherein the used sanitary product is treated with the ozone-containing gas to decompose and remove at least 90% of the polymer absorbent in the used sanitary product.

12. The method according to claim 11 , wherein the disinfectant is sodium hypochlorite, chlorine dioxide, acidic electrolyzed water, ozone water, acidic ozone water or organic acid-containing ozone water.

13. The method according to claim 1 , wherein the disinfectant is sodium hypochlorite, chlorine dioxide, acidic electrolyzed water, ozone water, acidic ozone water or organic acid-containing ozone water.

14. The method according to claim 1 , further comprising a step of separating the pulp fiber from the decomposition product obtained by the decomposing step.

15. The method according to claim 1 , comprising a step of separating apart at least a portion of the elements composing the used sanitary product and/or breaking up a portion of the used sanitary product before the step of treating the used sanitary product with an ozone-containing gas to decompose and remove at least a portion of the polymer absorbent in the used sanitary product.

16. The method according to claim 1 , further comprising a step of drying the pulp fiber, the step of drying the pulp fiber resulting in dried pulp fiber having a moisture content of 5 to 13%.

17. The method according to claim 16 , wherein the pulp fiber is dried at a temperature of 100 to 200° C.

Assignees

• Unicharm Corp

Inventors

• Konishi Takayoshi
• Hiraoka Toshio
• Kameda Noritomo
• Ichiura Hideaki
• Nakaoka Hiroko

Classifications

• B29L2031/4878

  Diapers, napkins · CPC title

• B29B2017/0289

  Washing the materials in liquids · CPC title

• C08J11/10

  by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation (depolymerisation to the original monomer C07) · CPC title

• D21C5/022 Primary

  Chemicals therefor · CPC title

• B29B17/02

  Separating plastics from other materials · CPC title