Recovery method for organic acid, and production method for recycled pulp

Patent metadata

Field	Value
Publication number	US-11021839-B2
Application number	US-201816759482-A
Country	US
Kind code	B2
Filing date	Jul 26, 2018
Priority date	Nov 1, 2017
Publication date	Jun 1, 2021
Grant date	Jun 1, 2021

Abstract

The purpose of the present disclosure is to provide a recovery method for an organic acid. The recovery method makes it possible to efficiently recover an organic acid that is included in a deactivating aqueous solution that includes excrement. This recovery method has the following features. A method for recovering an organic acid that deactivates a highly water-absorbent polymer that is included in used absorbent articles, the method being characterized by including: a deactivation step (S1) in which the highly water-absorbent polymer is immersed in a deactivating aqueous solution that includes an organic acid and has a prescribed pH and the highly water-absorbent polymer is deactivated; a highly water-absorbent polymer removal step (S2) in which the deactivated highly water-absorbent polymer is removed from the deactivating aqueous solution; a pH adjustment step (S3) in which the deactivating aqueous solution is adjusted to a prescribed pH; a concentration step (S4) in which the deactivation step (S1), the highly water-absorbent polymer removal step (S2), and the pH adjustment step (S3) are repeated using deactivating aqueous solution that has gone through the pH adjustment step (S3) and the organic acid in the deactivating aqueous solution is concentrated; and an organic acid recovery step (S6) in which the organic acid is recovered from the deactivating aqueous solution.

First claim

The invention claimed is:

1. A method of recovering an organic acid which inactivates superabsorbent polymers included in a used absorbent article, the method comprising:
(1) an inactivation step of immersing the used absorbent article or superabsorbent polymers obtained from the used absorbent article in an inactivation aqueous solution which has a predetermined pH and includes an organic acid to form a first solution that includes the inactivation aqueous solution and inactivated superabsorbent polymers;
(2) a superabsorbent polymer removal step of removing the inactivated superabsorbent polymers from the first solution produced by step (1) to form a second solution that includes the inactivation aqueous solution;
(3) a pH adjustment step of adjusting the pH of the second solution produced by step (2) to form a regenerated inactivation solution having a predetermined pH;
a concentration elevation step of repeating at least once steps (1)-(3) by circulating the regenerated inactivation solution produced by step (3) to the inactivation step (1) to produce a concentration elevation solution; and
recovering organic acid from the concentration elevation solution.

2. The method according to claim 1 , wherein
in the pH adjustment step, the second solution is adjusted to have the predetermined pH by adding an organic acid, removing a pH raising substance which raises pH, or a combination of the adding and the removing.

3. The method according to claim 2 , wherein
the organic acid is an organic acid which includes a carboxyl group.

4. The method according to claim 1 , wherein
the concentration elevation step further includes a sterilization step of sterilizing the regenerated inactivation aqueous solution.

5. The method according to claim 4 , wherein
in the sterilization step, the regenerated inactivation aqueous solution is sterilized by using ozone, chlorine dioxide, hydrogen peroxide, ultraviolet light, radiation, or any thereof.

6. The method according to claim 4 , wherein
in the sterilization step, the regenerated inactivation aqueous solution is sterilized by using ozone and deep ultraviolet light.

7. A method of producing recycled pulp fibers from a used absorbent article while elevating a concentration of and recovering an organic acid which inactivates superabsorbent polymers, the method comprising:
(1) an inactivation step of by immersing a material which includes pulp fibers and superabsorbent polymers derived from the used absorbent article in an inactivation aqueous solution which has a predetermined pH and includes an organic acid to form a first solution that includes the inactivation aqueous solution and inactivated material;
(2) a material extraction step of extracting the inactivated material from the first solution produced by step (1) to form a second solution that includes the inactivation aqueous solution;
(3) a recycled pulp fiber formation step of obtaining the recycled pulp fibers from the inactivated material extracted in step (2);
(4) a pH adjustment step of adjusting the pH of the second solution produced by step (2) to form a regenerated inactivation solution having a predetermined pH;
a concentration elevation step of repeating at least once steps (1)-(4) by circulating the regenerated inactivation solution produced by step (4) to the inactivation step (1) to produce a concentration elevation solution; and

recovering organic acid from the concentration elevation solution.

8. The method according to claim 7 , wherein
in the pH adjustment step, the second solution is adjusted to have the predetermined pH by adding an organic acid, removing a pH raising substance which raises pH, or a combination of the adding and the removing.

9. The method according to claim 8 , wherein the organic acid is an organic acid which includes a carboxyl group.

10. The method according to claim 7 , wherein
the concentration elevation step further includes a sterilization step of sterilizing the regenerated inactivation aqueous solution.

11. The method according to claim 10 , wherein
in the sterilization step, the regenerated inactivation aqueous solution is sterilized by using ozone, chlorine dioxide, hydrogen peroxide, ultraviolet light, radiation, or any combination thereof.

12. The method according to claim 10 , wherein
in the sterilization step, the regenerated inactivation aqueous solution is sterilized by using ozone and deep ultraviolet light.

Assignees

• Unicharm Corp

Inventors

• Konishi Takayoshi
• Hiraoka Toshio
• Kato Takashi
• Ishikawa Yoshihide
• Kurita Noritomo

Classifications

• B09B3/35

  Shredding, crushing or cutting · CPC title

• B09B3/38

  Stirring or kneading · CPC title

• B09B2101/67

  Diapers or nappies · CPC title

• B09B3/70

  Chemical treatment, e.g. pH adjustment or oxidation (involving an extraction step B09B3/80) · CPC title

• A61F5/44 Primary

  Devices worn by the patient for reception of urine, faeces, catamenial or other discharge (absorbent pads, e.g. sanitary towels, A61F13/15; drainage appliances for wounds A61M27/00); Colostomy devices · CPC title