Process for producing superabsorbents

Patent metadata

Field	Value
Publication number	US-12220686-B2
Application number	US-201917289287-A
Country	US
Kind code	B2
Filing date	Nov 4, 2019
Priority date	Nov 14, 2018
Publication date	Feb 11, 2025
Grant date	Feb 11, 2025

Abstract

The invention relates to a process for producing superabsorbent polymer particles, comprising polymerization of a monomer solution, wherein the monomer solution comprises partly neutralized acrylic acid formed by continuous mixing of acrylic acid and an aqueous solution of a base, the apparatus for preparing the partly neutralized acrylic acid comprises a vessel (B), and the feed line to vessel (B) ends inside vessel (B) below the liquid Level of the partly neutralized acrylic acid.

First claim

The invention claimed is:

1. A process for producing superabsorbent polymer particles, comprising polymerizing of a monomer solution, comprising
a) partly neutralized acrylic acid,
b) at least one crosslinker, and
c) at least one initiator,
drying a resulting polymer gel, optionally grinding and classifying a resulting dried polymer gel and optionally thermally post-crosslinking and cooling resulting polymer particles, wherein the partly neutralized acrylic acid is formed by continuous mixing of acrylic acid, an aqueous solution of a base, and optionally water, an apparatus for preparing the partly neutralized acrylic acid comprises a ring line (R), a vessel (B), a heat exchanger (W), and a pump (P), and a feed line to vessel (B) ends inside vessel (B) below a liquid level of the partly neutralized acrylic acid.

2. The process according to claim 1 , wherein the feed line to vessel (B) ends from 0.05 to 0.5 m above the bottom of the vessel (B).

3. The process according to claim 1 , wherein an outlet of vessel (B) is in a center of the bottom of vessel (B) and a horizontal distance of a center of the feed line to vessel (B) from the center of the bottom of vessel (B) is from 0.50 to 1.50 m.

4. The process according to claim 1 , wherein the feed line to vessel (B) has a cylindrical shape and a diameter from 0.1 to 0.5 m.

5. The process according to claim 1 , wherein an inner volume of the vessel (B) is from 10 to 50 m 3 .

6. The process according to claim 1 , wherein a filling level of the vessel (B) is from 10 to 80%, wherein the filling level is a quotient of a volume of partly neutralized acrylic acid in vessel (B) and an inner volume of the vessel (B).

7. The process according to claim 1 , wherein
a residence time of the partly neutralized acrylic acid in vessel (B) is from 20 to 80 minutes, wherein the residence time is a quotient of a volume of partly neutralized acrylic acid in vessel (B) and a feed per minute to the apparatus for preparing the partly neutralized acrylic acid.

8. The process according to claim 1 , wherein the vessel (B) has a cylindrical shape having a diameter d and a torispherical bottom, and the torispherical bottom has a dish having a radius r 1 of 0.8 to 1.0 d and a toroidal shaped knuckle having a radius r 2 of 0.1 to 0.154 d.

9. The process according to claim 1 , wherein the diameter d of the cylindrical part of the vessel (B) is from 1 to 5 m.

10. The process according to claim 1 , wherein the base for neutralization is sodium hydroxide, sodium hydrogen carbonate, sodium carbonate, potassium hydroxide, potassium hydrogen carbonate, and/or potassium carbonate.

11. The process according to claim 1 , wherein a degree of neutralization of the partly neutralized acrylic acid is from 40 to 85 mol-%.

12. The process according to claim 1 , wherein a solids content of the partly neutralized acrylic acid is from 40 to 50% by weight.

13. The process according to claim 1 , wherein
a temperature of the partly neutralized acrylic acid is from 20 to 70° C.

14. The process according to claim 1 , wherein from 75 to 98% of the partly neutralized acrylic acid is recycled via the ring line (R).

Assignees

• Basf Se

Inventors

• Peterson Monte Alan
• De Kaey Ronny
• Possemiers Karl
• Schroeder Juergen
• Funk Ruediger
• Weismantel Matthias

Classifications

• C08F2810/20

  leading to a crosslinking, either explicitly or inherently · CPC title

• C08F120/06

  Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof · CPC title

• B01J2219/1945

  toroidal · CPC title

• B01J2219/1943

  cylindrical · CPC title

• B01J2219/00166

  controlling the residence time inside the reactor vessel · CPC title