Method of fractionating oxidic nanoparticles by crossflow membrane filtration

Inactive Publication Date: 2009-05-28
EVONIK OPERATIONS GMBH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Benefits of technology

[0022]Surprisingly it has been found that through the method of the invention, build-up of a cake layer

Problems solved by technology

Even small fractions of relatively coarse particles or of agglomerates may adversely affect the properties of the composites.
Whereas, in the case of particles in the micrometer range, separation of relatively coarse particles can be achieved via sedimentation, centrifugation or screen filtration, these methods are of only limited utility in the case of nanoparticles.
If the nanoparticles are in a dispersion, coarser particles may possibly also be separated off via sedimentation or centrifugation, but in this case the extreme surface-area and time requirements, along with the batch operating regime, are so disadvantageous that these methods can in practice be of virtually no importance.
Similarly, techniques such as size exclusion chromatography (SEC) or gel electrophoresis are unsuited to relatively large quantities.
Cake-forming filtration, accordingly, cannot be used to classify particle dispersions.
The limits on this method are that only very dilute dispersions can be treated and that the classifying effect has

Method used

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  • Method of fractionating oxidic nanoparticles by crossflow membrane filtration
  • Method of fractionating oxidic nanoparticles by crossflow membrane filtration
  • Method of fractionating oxidic nanoparticles by crossflow membrane filtration

Examples

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[0037]The tests below were performed on a 30% dispersion of titanium dioxide in water, as may be prepared, for example, by a process which is described in DE 10204470 A1. The dispersion used has a D50 value of approximately 0.09 μm and also a D90 value of approximately 0.2 μm; that is, 50% of the particles have a diameter less than or equal to 0.9 μm, and 90% have a diameter less than or equal to 0.2 μm.

[0038]The following commercially available membranes from Millipore were used:

[0039]Test 1: polytetrafluoroethylene membrane with a pore diameter of 1 μm

[0040]Test 2: polytetrafluoroethylene membrane with a pore diameter of 0.45 μm

[0041]Test 3: polytetrafluoroethylene membrane with a pore diameter of 0.2 μm

[0042]The stirrer speed was 1264 min−1 in each case. This corresponds to an average cross-flow velocity of approximately 9 m / s.

[0043]As shown in FIG. 2, the particle size distribution was measured both before (measurement series with angular measurement points) and after (measureme...

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Abstract

A method of fractionating a dispersion of oxidic nanoparticles wherein at least one step of the method is a membrane crossflow filtration step, the flow of the dispersion over the membrane being brought about by means of driven rotating parts; and dispersions of oxidic nanoparticles that are obtainable by the method.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a method of fractionating dispersions of oxidic nanoparticles by membrane filtration. It further relates to dispersions of oxidic nanoparticles that are obtained by the method of the invention.[0003]2. Description of the Background[0004]Recent years have seen a steady increase of interest, from both academia and industry, in nanoscale particles, in other words particles with a diameter of less than 1 μm, since the properties of nanoparticles have caused them to be ascribed great potential in respect of applications in, for example, electronics, optics, and chemical products. Of particular interest in this context are particles whose diameter is in the range below 100 nm. It is here, usually, that the effects known as “nano-effects” occur, quantum effects for example, which can be attributed to factors that include the influence of the large particle surface area. With these particles, mo...

Claims

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Application Information

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IPC IPC(8): B32B5/16B01D61/00B01D61/14C01F17/00C01B33/12C01G9/02C01G30/00C01G19/02C01G25/02C01F7/02C01G23/04B01D65/02
CPCB01D61/142Y10T428/2982B01D2311/165B01D2315/02B01D2315/16B01D2317/025C01G1/02C01G15/00C01G19/02C01G23/006C01G23/047C01G25/02C01G30/005C01P2004/04C01P2004/61B01D61/147B01D61/146B01D61/149
Inventor WURSCHE, ROLANDBAUMGARTEN, GOETZLORTZ, WOLFGANGKROELL, MICHAEL
Owner EVONIK OPERATIONS GMBH
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