Complete drying method for hydrogels

• US 6,641,064 B1
• Filed: 04/25/2001
• Issued: 11/04/2003
• Est. Priority Date: 10/27/1998
• Status: Expired due to Term

• Current Assignee: BASF AG (BASF SE)
• Original Assignee: BASF AG (BASF SE)
• Inventors: Klotzsche, Helmut, Stüven, Uwe, Herfert, Norbert, Schliwa, Rudolf, Dentler, Joachim
• Primary Examiner(s): Rosenbaum, Mark
• Application Number:
  US09/807,447
• Time in Patent Office: 923 Days
• Field of Search: 241/24.28, 241/25, 241/29, 241/30, 241/80
• US Class Current: 241/24.28
• CPC Class Codes: B01J 20/26 Synthetic macromolecular compounds
• CPC Class Codes: B01J 20/30 Processes for preparing, regenerating, or reactivating
• CPC Class Codes: B29B 13/06 by drying B29B13/08 takes precedence ; drying moulded articles or half products B29C37/0092
• CPC Class Codes: C08F 6/008 Treatment of solid polymer wetted by water or organic solvents, e.g. coagulum, filter cakes
• CPC Class Codes: C08J 2300/14 Water soluble or water swellable polymers, e.g. aqueous gels
• CPC Class Codes: C08J 3/00 Processes of treating or compounding macromolecular substances
• CPC Class Codes: C08J 3/12 Powdering or granulating
• CPC Class Codes: F26B 1/005 by means of disintegrating, e.g. crushing, shredding, milling the materials to be dried F26B17/102, F26B17/103 take precedence

Abstract

Hydrogel particles are produced by a drying step followed sequentially by precomminuting, grinding, separating, and further drying of coarse particles.

Claims

1. A process for drying a hydrogel, which comprises the following successive steps:

a) drying said hydrogel by contact or convective drying

b) precomminuting the contact or convectively dried hydrogel

c) grinding the precomminuted hydrogel using a coarse or crusher roll mill

d) separating off the moist resilient hydrogel particles which have a water content of more than 10% by weight

e) afterdrying said moist resilient hydrogel particles.

2. A process as claimed in claim 1, wherein said drying of said hydrogel is effected using a can dryer or a belt dryer.

3. A process as claimed in claim 1, wherein said precomminuting of the dried material is effected using a knuckle-type crusher.

4. A process as claimed in claim 1, wherein said grinding of the precomminuted dried material using a coarse or crusher roll mill is effected using a nip setting such that the dry particles have an average diameter of 0.1-10 mm after grinding.

5. A process as claimed in claim 1, wherein the moist resilient particles are separated off using a sieve vibrating at a frequency of 10 to 50 Hz to an amplitude of 1-10 mm and at an inclination of from 5 to 45°

with regard to the horizontal.

6. A process as claimed in claim 1, wherein the moist particles which have been separated off are added to the hydrogel to be dried.

7. A process as claimed in claim 1, wherein the moist particles separated off are directed into a separate dryer for afterdrying.