Recycling of superabsorbent polymer via hydrothermal microwave processing

Patent metadata

Field	Value
Publication number	US-11396587-B2
Application number	US-202016999139-A
Country	US
Kind code	B2
Filing date	Aug 21, 2020
Priority date	Aug 23, 2019
Publication date	Jul 26, 2022
Grant date	Jul 26, 2022

Abstract

Poly(acrylic acid)-based superabsorbent polymer (SAP) and H 2 O 2 in a feed is converted with microwave (MW) irradiation into poly(acrylic acid) (PAA) in the product. The MW total energy used to convert SAP into PAA is less than 50 MJ/kg SAP.

First claim

What is claimed is:

1. A method for degrading a superabsorbent polymer (SAP) to poly(acrylic acid) (PAA) comprising placing a feed into a reactor, irradiating said feed with microwave (MW) at a temperature, and producing a product comprising said PAA at a carbon yield; wherein said feed comprises said SAP at a concentration greater than about 3 wt % and hydrogen peroxide (H 2 O 2 ) at a concentration greater than about 0.5 wt % of said SAP concentration; wherein said feed has a residence time in said reactor between about 2 min and about 9 min; wherein said temperature is about 200° C.; wherein said carbon yield is greater than about 90%; and wherein said MW used to convert SAP to PAA requires a MW total energy of less than about 50 MJ/kg SAP.

2. The method of claim 1 , wherein said residence time is between about 4 min and about 6 min.

3. The method of claim 1 , wherein said residence time is about 5 min.

4. The method of claim 1 , wherein said SAP concentration is greater than about 5 wt %.

5. The method of claim 1 , wherein said SAP concentration is greater than about 10 wt %.

6. The method of claim 1 , wherein said MW total energy is less than about 12 MJ/kg SAP.

7. The method of claim 1 , wherein said MW total energy is less than about 6 MJ/kg SAP.

8. The method of claim 1 , wherein said SAP has degree of neutralization (DN) greater than about 50%.

9. The method of claim 1 , wherein said SAP has DN between about 65% and about 75%.

10. The method of claim 1 , wherein said carbon yield is greater than 95%.

11. The method of claim 1 , wherein said carbon yield is about 98%.

12. The method of claim 1 , wherein said PAA has a weight-average molecular weight less than about 1,000,000 g/mol.

13. The method of claim 1 , wherein said PAA has a weight-average molecular weight less than about 500,000 g/mol.

14. The method of claim 1 , wherein said PAA has a weight-average molecular weight less than about 200,000 g/mol.

15. The method of claim 1 , wherein said PAA has a polydispersity index (PDI) between about 4.5 and about 3.

16. The method of claim 1 , wherein said PAA has a PDI between about 4 and about 3.

17. The method of claim 1 , wherein said PAA has a PDI of about 4.2.

18. A method for degrading a superabsorbent polymer (SAP) to poly(acrylic acid) (PAA) comprising placing a feed into a reactor, irradiating said feed with microwave (MW) at a temperature, and producing a product comprising said PAA at a carbon yield; wherein said feed comprises said SAP at a concentration of about 20 wt % and H 2 O 2 at a concentration of about 0.1 wt %; wherein said feed has a residence time in said reactor of about 5 min; wherein said temperature is about 200° C.; wherein said carbon yield is about 98%; wherein said MW used to convert SAP to PAA requires a MW total energy of less than about 50 MJ/kg SAP; and wherein said PAA has a weight-average molecular weight less than about 1,000,000 g/mol.

19. The method of claim 18 , wherein said SAP has DN between about 65% and about 75%.

20. The method of claim 18 , wherein said PAA has a PDI of about 4.2.

21. The method of claim 18 , wherein said weight-average molecular weight of said PAA is less than about 500,000 g/mol.

Assignees

• Procter & Gamble

Inventors

• Banaszak Holl Mark Monroe
• Tanksale Akshat
• Ching Teck Wei
• Zhang Jing
• Collias Dimitris Ioannis
• Mcdaniel John Andrew
• Gilbertson Gary Wayne
• James Martin Ian
• Simonyan Arsen Arsenov

Classifications

• C08J2333/06

  of esters containing only carbon, hydrogen, and oxygen, the oxygen atom being present only as part of the carboxyl radical · CPC title

• C08J11/16 Primary

  by treatment with inorganic material (C08J11/14 takes precedence) · CPC title

• C08J2300/14

  Water soluble or water swellable polymers, e.g. aqueous gels · CPC title

• C08J7/123

  Treatment by wave energy or particle radiation (C08J7/18 takes precedence) · CPC title

• C08J2333/02

  Homopolymers or copolymers of acids; Metal or ammonium salts thereof · CPC title