Recycling of superabsorbent polymer via UV irradiation in flow system

Patent metadata

Field	Value
Publication number	US-11154839-B2
Application number	US-201916548873-A
Country	US
Kind code	B2
Filing date	Aug 23, 2019
Priority date	Aug 23, 2019
Publication date	Oct 26, 2021
Grant date	Oct 26, 2021

Abstract

Poly(acrylic acid)-based superabsorbent polymer (SAP) in a feed stream is converted with UV irradiation into poly(acrylic acid) (PAA) in a flow system. The UV total energy used to convert SAP into PAA is less than about 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 flowing a feed stream comprising said SAP into a UV irradiation zone, irradiating said feed stream with UV, and producing a product stream comprising said PAA at the end of said irradiation zone; wherein said feed stream comprises said SAP at a concentration greater than about 1 wt %; wherein said feed stream has a residence time in said UV irradiation zone of less than about 120 s; and wherein said UV used to convert SAP to PAA requires a UV total energy of less than about 50 MJ/kg SAP.

2. The method of claim 1 , wherein said residence time is less than about 60 s.

3. The method of claim 1 , wherein said UV total energy is less than about 16 MJ/kg SAP.

4. The method of claim 1 , wherein said feed stream comprises SAP and water.

5. The method of claim 1 , wherein said feed stream comprises SAP and hydrogen peroxide.

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

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

8. The method of claim 1 , wherein said feed stream has a viscosity; wherein said product stream has a viscosity; wherein the ratio of the viscosity of the product stream to the viscosity of the feed stream is the viscosity ratio; and wherein the negative logarithm of said viscosity ratio is less than about 6.

9. The method of claim 1 , wherein said feed stream has a viscosity; wherein said product stream has a viscosity; wherein the ratio of the viscosity of the product stream to the viscosity of the feed stream is the viscosity ratio; and wherein the negative logarithm of said viscosity ratio is less than about 4.

10. The method of claim 1 , wherein said feed stream has a viscosity; wherein said product stream has a viscosity; wherein the ratio of the viscosity of the product stream to the viscosity of the feed stream is the viscosity ratio; and wherein the negative logarithm of said viscosity ratio is less than about 2.

11. The method of claim 1 , wherein said PAA has a weight-average molecular weight less than about 2,000,000 g/mol.

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 polydispersity index (PDI) less than about 4.

14. The method of claim 1 , wherein said PAA is used to produce a recycled SAP; said SAP comprises PAA at a concentration; and wherein said PAA concentration is less than about 30%.

15. The method of claim 1 , wherein said PAA is used to produce a recycled SAP; wherein said recycled SAP has an amount of extractables; and wherein said amount of extractables is less than about 15%.

16. The method of claim 1 , wherein said PAA is used to produce a recycled SAP; wherein said recycled SAP has a swelling ratio; and wherein said swelling ratio is greater than about 45 g/g.

17. A method for degrading a superabsorbent polymer (SAP) to poly(acrylic acid) (PAA) comprising flowing a feed stream comprising said SAP into a UV irradiation zone, irradiating said feed stream with UV, and producing a product stream comprising PAA at the end of said UV irradiation zone; wherein said feed stream comprises water and SAP at a concentration greater than about 1 wt %; wherein said feed stream has a residence time in said UV irradiation zone of less than about 120 s; wherein said UV used to convert SAP to PAA requires a UV total energy of less than about 16 MJ/kg SAP; and wherein said PAA has a weight-average molecular weight less than about 1,000,000 g/mol.

18. A method for degrading a superabsorbent polymer (SAP) to poly(acrylic acid) (PAA) comprising flowing a feed stream comprising said SAP into a UV irradiation zone, irradiating said feed stream with UV, and producing a product stream comprising PAA at the end of said UV irradiation zone; wherein said feed stream comprises water and SAP at a concentration greater than about 5 wt %; wherein said feed stream has a residence time in said UV irradiation zone of less than about 120 s; wherein said UV used to convert SAP to PAA requires a UV total energy of less than about 16 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 feed stream has a viscosity; wherein said product stream has a viscosity; wherein the ratio of the viscosity of the product stream to the viscosity of the feed stream is the viscosity ratio; and wherein the negative logarithm of said viscosity ratio is less than about 4.

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

21. The method of claim 18 , wherein said feed stream comprises SAP and hydrogen peroxide.

Assignees

• Procter & Gamble

Inventors

• Collias Dimitris Ioannis
• Mcdaniel John Andrew
• Gilbertson Gary Wayne
• James Martin Ian
• Simonyan Arsen Arsenov

Classifications

• C08J11/16

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

• C08L33/02

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

• B01J20/261

  obtained by reactions only involving carbon to carbon unsaturated bonds (macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds per se C08F) · CPC title

• C08J2300/16

  Biodegradable polymers · CPC title

• B01J20/3441 Primary

  Regeneration or reactivation by electric current, ultrasound or irradiation, e.g. electromagnetic radiation such as X-rays, UV, light, microwaves · CPC title