Process for preparing agglomerate-free nanoscalar iron oxide particles with a hydrolysis resistant coating

• US 6,183,658 B1
• Filed: 10/09/1998
• Issued: 02/06/2001
• Est. Priority Date: 04/10/1996
• Status: Expired due to Term

• Current Assignee: Leibniz-Institut für Neue Materialien gGmbH (INM)
• Original Assignee: Institut Fur NEUE Materialien GEM GmbH
• Inventors: Schiestel, Thomas, Lesniak, Christoph, Schmidt, Helmut, Nass, Rüdiger
• Primary Examiner(s): Koslow, C. Melissa
• Application Number:
  US09/171,065
• Time in Patent Office: 851 Days
• Field of Search: 428/405, 427/600, 427/601, 427/220, 252/62.56, 252/62.54, 252/62.52, 106/460, 106/456
• US Class Current: 252/62.56
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01G 49/02 Oxides; Hydroxides C01G49/0018 takes precedence
• CPC Class Codes: C01P 2004/64 Nanometer sized, i.e. from 1-100 nanometer
• CPC Class Codes: C01P 2006/80 Compositional purity
• CPC Class Codes: C01P 2006/90 Other properties not specified above
• CPC Class Codes: C09C 1/24 Oxides of iron
• CPC Class Codes: C09C 3/006 Combinations of treatments provided for in groups C09C3/04 - C09C3/12
• CPC Class Codes: C09C 3/045 Agglomeration, granulation, pelleting
• CPC Class Codes: C09C 3/12 Treatment with organosilicon compounds C09C3/006 takes precedence
• CPC Class Codes: Y10T 428/2995 Silane, siloxane or silicone coating

Abstract

A process for preparing an agglomerate-free suspension of nanosize iron-containing oxide particles coated in a stable manner comprises preparing an aqueous suspension of nanosize iron-containing oxide particles which are partially or completely in the form of agglomerates; adding a trialkoxysilane and a water-miscible polar organic solvent which has a boiling point at least 10° C. higher than the boiling point of water; treating the resulting suspension with ultrasound until at least 70% of the particles present are in the range of ±20% of the average particle diameter; removing the water by distillation under the action of ultrasound; and separating the non-disintegrated agglomerates.

Claims

1. A process for producing an-agglomerate-free suspension of stably coated nanosize iron-containing oxide particles, comprising the following steps in the order indicated:

(1) preparing an aqueous suspension of nanosize iron-containing oxide particles which are partly or completely present in the form of agglomerates;

(2) adding (i) a trialkoxysilane which has a hydrocarbon group which is directly bound to Si and to which is bound at least one group selected from amino, carboxyl, epoxy, mercapto, cyano, hydroxy, acrylic, and methacrylic, and (ii) a water-miscible polar organic solvent whose boiling point is at least 10°

C. above that of water;

(3) treating the resulting suspension with ultrasound until at least 70% of the particles present have a size within the range from 20% below to 20% above the mean particle diameter;

(4) removing the water by distillation under the action of ultrasound; and

(5) removing the agglomerates which have not been broken up.

2. A process according to claim 1, comprising, following step (5), the additional step (6) of deionizing the suspension.

3. A process according to claim 2 wherein step (6) comprises dialyzing the suspension.

4. A process according to claim 1 wherein the iron-containing oxide particles contain iron and from 0 to 70 metal atom % of at least one metal selected from the group consisting of Zn, Cu, Co, Ni and Mn.

5. A process according to claim 4 wherein the iron-containing oxide particles contain from 0 to 35 metal atom % of at least one metal selected from the group consisting of Zn, Cu, Co, Ni and Mn.

6. A process according to claim 1 wherein the iron-containing oxide particles are pure iron oxide particles in which the Fe(II)/Fe(III) ratio is from 1:

1 to 1;

3.

7. A process according to claim 1 wherein a trialkoxysilane having at least one amino group is used in step (2).

8. A process according to claim 1 wherein the polar organic solvent in step (2) has at least one hydroxyl group.

9. A process according to claim 8 wherein the polar organic solvent has at least two hydroxyl groups.

10. A process according to claim 9 wherein the polar organic solvent is selected from the group consisting of ethylene glycol, propylene glycol, glycerol, trimethylolpropane, diethylene glycol and mixtures of these.

11. A process according to claim 1 wherein step (3) is carried out at a temperature of from 50 to 100°

C.

12. A process according to claim 1 wherein step (4) is carried out under reduced pressure and a temperature of not more than 80°

C.

13. A process according to claim 1 wherein step (5) is carried out by means of gravity.

14. A process according to claim 13 wherein step (5) is carried out by centrifugation.

15. A process according to claim 1 wherein the iron-containing oxide particles are superparamagnetic iron oxide particles.

16. A process for producing agglomerate-free stably coated nanosize iron-containing oxide particles, comprising preparing an agglomerate-free suspension of stably coated nanosize iron-containing oxide particles by the process of claim 1 followed by removing the liquid medium from the suspension.

17. A process according to claim 16, wherein the iron-containing oxide particles are superparamagnetic iron oxide particles.

18. An agglomerate-free suspension of stably coated nanosize iron-containing oxide particles prepared by the process of claim 1.

19. Agglomerate-free stably-coated nanosize iron-containing oxide particles prepared by the process of claim 16.

20. Agglomerate-free nanosize iron-containing oxide particles provided with a hydrolysis-resistant coating based on aminosilane.