Single-shaft extruder and use of a single-shaft extruder, and method for altering morphology of a superabsorbent polymer, specifically an SAP polymer gel, using a single-shaft extruder

Patent metadata

Field	Value
Publication number	US-11560456-B2
Application number	US-201716470270-A
Country	US
Kind code	B2
Filing date	Dec 15, 2017
Priority date	Dec 21, 2016
Publication date	Jan 24, 2023
Grant date	Jan 24, 2023

Abstract

A single-screw extruder for changing a morphology of superabsorbent polymer gel. The single-screw extruder has an input aperture, a channel, a screw and an output aperture. The screw in the invention has a first pitch value of a pitch of the screw flights along the conveying zone of the channel and, following in conveying direction, has a second pitch value of the pitch of the screw flights along the conveying zone of the channel, where the second pitch value is smaller than the first pitch value.

First claim

The invention claimed is:

1. A single-screw extruder ( 10 ) for changing a morphology of a superabsorbent polymer gel (SAP polymer gel) ( 24 ), having:
an input aperture ( 36 ) for the introduction of SAP polymer gel ( 24 ),
connected to the input aperture ( 36 ), a channel ( 16 ),
arranged in the channel ( 16 ), a screw ( 12 ) for conveying, and changing the morphology of, the SAP polymer gel ( 24 ) and
connected to the channel ( 16 ), an output aperture ( 30 ) for the discharge of the SAP polymer gel ( 44 ) with changed morphology,
where the screw ( 12 ) has a shank ( 13 ) and has screw flights ( 14 ) arranged on the shank ( 13 ) and is arranged and configured to convey the SAP polymer gel ( 24 ) from the input aperture ( 36 ) to the output aperture ( 30 ) by means of the screw flights ( 14 ),
where the channel ( 16 ) has an input zone ( 26 ) arranged at, or in the vicinity of, the input aperture ( 36 ), an output zone ( 28 ) arranged at, or in the vicinity of, the output aperture ( 30 ), and a conveying zone ( 18 ) extending along the channel ( 16 ) from the input zone ( 26 ) to the output zone ( 28 ),
wherein
the screw ( 12 ) has a first pitch value (G 1 ) of a pitch (G) of the screw flights ( 14 ) along the conveying zone ( 18 ) of the channel ( 16 ) and, following in conveying direction ( 20 ), has a second pitch value (G 2 ) of the pitch (G) of the screw flights ( 14 ) along the conveying zone ( 18 ) of the channel ( 16 ), and where the second pitch value (G 2 ) is smaller than the first pitch value (G 1 ), where the pitch (G) of the screw flights ( 14 ) decreases along the conveying zone ( 18 ) of the channel ( 16 ), and additionally,
a shank diameter (d) of the shank ( 13 ) of the screw ( 12 ) increases along the channel ( 16 ) in the conveying direction, where the ratio d/D of shank diameter (d) to external screw flight diameter (D) increases along the channel ( 16 ).

2. The single-screw extruder ( 10 ) according to claim 1 , where the screw ( 12 ) has, along the channel ( 16 ), at least three different pitch values (G 1 , G 2 , G 3 , G 4 ) of the screw flights ( 14 ).

3. The single-screw extruder ( 10 ) according to claim 2 , wherein the output aperture ( 30 ) has a die ( 34 ) with perforations wherein the perforations are provided in 5% to 66% of the area of the die ( 34 ).

4. The single-screw extruder ( 10 ) according to claim 1 , with at least one pitch value (G 1 , G 2 , G 3 , G 4 ) of the screw flights ( 14 ) between 30 mm and 800 mm.

5. The single-screw extruder ( 10 ) according to claim 1 , with a value of a flight land width (e) of the screw flights ( 14 ) is between 4 mm and 80 mm.

6. The single-screw extruder ( 10 ) according to claim 1 , where at least one value of a channel depth (H) between the shank ( 13 ) of the screw ( 12 ) and a wall of the channel ( 16 ) is between 25 mm and 500 mm.

7. The single-screw extruder ( 10 ) according to claim 1 , with a value of an external screw flight diameter (D) between 60 mm and 1000 mm.

8. The single-screw extruder ( 10 ) according to claim 1 , with at least one value of a shank diameter (d) between 25 mm and 500 mm.

9. The single-screw extruder ( 10 ) according to claim 1 , with a ratio d/D of shank diameter (d) to external screw flight diameter (D) between 0.4 and 0.6.

10. The single-screw extruder ( 10 ) according to claim 1 , where the pitch (G) decreases along the conveying zone ( 18 ) from a pitch value (G 1 ) of 500 mm in the vicinity of the input zone ( 26 ) to a pitch value (G 4 ) of 350 mm in the vicinity of the output zone ( 28 ).

11. The single-screw extruder ( 10 ) according to claim 1 , where the screw ( 12 ) has, along the channel ( 16 ), a smallest pitch value (G 4 ) that is at most between 20% and 80% of a largest pitch value (G 1 ) along the channel ( 16 ).

12. The single-screw extruder ( 10 ) according to claim 1 , where the screw ( 12 ) has, along the channel ( 16 ), a smallest value of a shank diameter (d 2 ) that is at most between 20% and 80% of a largest value of a shank diameter (d 1 ) along the channel ( 16 ).

13. The single-screw extruder ( 10 ) according to claim 1 , where the single-screw extruder ( 10 ) is configured to produce an SAP polymer gel ( 24 ) with a desired morphology that increases the water absorption and/or the absorption rate of the dried SAP particles, and wherein the SAP gel ( 24 ) in the form of SAP gel particles is dried and ground to give dried SAP particles, wherein the water absorption and/or the absorption rate of the dried SAP particles is increased.

14. The single-screw extruder ( 10 ) according to claim 1 , characterized by at least one mixing-element arrangement ( 49 ) with at least one mixing element which protrudes into the channel ( 16 ) of the single-screw extruder and which is configured for the mixing of the SAP polymer gel ( 24 ).

15. The single-screw extruder ( 10 ) according to claim 14 , where the mixing-element arrangement ( 49 ) has a pin arrangement ( 48 ) comprising at least one pin ( 48 . 1 , 48 . 2 ) extending into an internal space ( 17 ) of the channel ( 16 ), and has at least one cutout ( 50 ) along the screw flights ( 14 ), the at least one pin ( 48 . 1 , 48 . 2 ) extending into the at least one cutout ( 50 ) of the screw flights ( 14 ) when the screw flights ( 14 ) are rotated during operation, rotation of the shank ( 13 ) of the screw ( 12 ) therefore being possible without contact between the pin ( 48 . 1 , 48 . 2 ) and the screw flights ( 14 ).

16. The single-screw extruder ( 10 ) according to claim 1 , where the channel ( 16 ) has at least two pins ( 48 ) arranged along the channel ( 16 ) in the conveying direction ( 20 ) and separated from one another by a mixing-element separation (K), and there is positive or negative correlation between a value of the mixing-element separation (K 1 , K 2 , K 3 , K 4 ) and a pitch value (G 1 , G 2 , G 3 ) of the pitch (G) of the screw flights ( 14 ).

17. The single-screw extruder ( 10 ) according to claim 16 , where
the negative correlation between the mixing-element separation (K) and the pitch (G) is such that a larger value of the mixing-element separation (K 1 , K 2 , K 3 , K 4 ) is provided when a smaller pitch value (G 1 , G 2 , G 3 ) is provided, and a smaller value of the mixing-element separation (K 1 , K 2 , K 3 , K 4 ) is provided when a larger pitch value (G 1 , G 2 , G 3 ) is provided, or
the positive correlation between the mixing-element separation (K) and the pitch (G) is such that a larger value of the mixing-element separation (K 1 , K 2 , K 3 , K 4 ) is provided when a larger pitch value (G 1 , G 2 , G 3 ) is provided, and a smaller value of the mixing-element separation (K 1 , K 2 , K 3 , K 4 ) is provided when a smaller pitch value (G 1 , G 2 , G 3 ) is provided.

18. A process for changing the morphology of the superabsorbent polymer gel (SAP polymer gel) ( 24 ) with a single-screw extruder ( 10 ) according to claim 1 comprising:
introducing the SAP polymer gel ( 24 ) from a polymerization process ( 38 ) into the single-screw extruder ( 10 ),
operating the single-screw extruder ( 10 ) in order to change the morphology of the SAP polymer gel ( 24 ) and
discharging the SAP polymer gel ( 44 ) with changed morphology from the single-screw extruder ( 10 ) to a drying process ( 46 ).

19. The process according to claim 18 , wherein the single-screw extruder ( 10 ) has a drive motor ( 40 ) and/or a heating device ( 42 ),
where the drive motor ( 40 ) is configured to rotate the shank ( 13 ) of the screw ( 12 ) at up to 150 revolutions per

Assignees

• Basf Se

Inventors

• Haag Monica
• Deuerlein Stephan
• Krauss Roland
• Klock Volker
• Barthel Holger

Classifications

• B29C48/397

  using a single screw · CPC title

• C08J3/075 Primary

  Macromolecular gels · CPC title

• B29C48/535

  with thread pitch varying along the longitudinal axis · CPC title

• B29B7/826

  Apparatus therefor · CPC title

• B29C48/022

  characterised by the choice of material · CPC title