Colloidal dispersion and redispersible composition in the form o

Details Colloidal dispersion and redispersible composition in the form o Colloidal dispersion and redispersible composition in the form o

1998-04-13

2000-03-07

Williamson, Michael A.

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Cosmetic, antiperspirant, dentifrice

424489, A61K 700

Patent

active

060336773

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a colloidal dispersion and a redispersible composition in the form of a colloidal dispersion, based on cerium oxide.
2. Description of the Related Art Including Information Disclosed under 37 C.F.R. 1.97 and 1.98
Dispersions of cerium compounds are used in numerous applications. There may be mentioned in particular use in heterogeneous catalysis and, especially, catalysis for treatment of exhaust gases from internal combustion engines (catalysis for automobile post-combustion). These dispersions can also be used as an anticorrosion coating agent or in cosmetics.
However, the use of these dispersions is limited by a certain instability over a period of time, leading to sedimentation. Furthermore, the cost of transportation of these dispersions is always increased by the fact that it is necessary to transport, in addition to the active element, the liquid phase in which this is in suspension.
As a result, it is of particular interest to be able to have available either stable dispersions or solid products which are capable of being redispersed to give a colloidal suspension.
In addition, the known processes for the preparation of these dispersions allow only suspensions having a very acid pH, that is to say generally less than 5, to be obtained.
Thus, in the applications which have been mentioned above, and in particular in the case of cosmetics, it is important to be able to have available colloidal dispersions having less acid pH values.
A first object of the invention is therefore the preparation of a stable colloidal dispersion of cerium oxide which has, in particular, a high pH.


BRIEF SUMMARY OF THE INVENTION

A second object of the invention is to obtain a solid composition based on cerium oxide, which is redispersible in the form of a colloidal dispersion.
For this purpose, the colloidal dispersion of cerium oxide in a liquid phase, according to the invention, is characterised in that it also comprises at least one additive chosen from: .beta.-position;
The invention also relates to a redispersible composition in the form of a colloidal dispersion, characterised in that it comprises a cerium oxide and at least one additive chosen from: .beta.-position;
The invention furthermore relates to a process for the preparation of a colloidal dispersion of cerium oxide, characterised in that at least one additive chosen from: or .beta.-position; material.


DETAILED DESCRIPTION OF THE INVENTION

The dispersions according to the invention have the advantage in particular of being stable for at least several months up to pH values of the order of 7.5.
Other characteristics, details and advantages of the invention will also become more completely apparent on reading the description which follows, as well as the various concrete but non-limiting examples intended to illustrate the invention.
In the description which follows, the expression colloidal dispersion of a cerium compound means any system made up of fine solid particles of colloidal dimensions based on cerium oxide and/or hydrated cerium oxide (cerium hydroxide) in suspension in a liquid phase, it also being possible for the said species, where appropriate, to contain residual amounts of bonded or adsorbed ions, such as, for example, nitrate, acetate, citrate or ammonium ions. It can be seen that such dispersions can contain the cerium either totally in the form of colloidal particles or both in the form of ions and in the form of colloidal particles.
In addition, it is mentioned here that the mean diameter of the colloidal particles is to be understood as meaning the mean hydrodynamic diameter of the latter, as determined by quasi-elastic diffusion of light in accordance with the method described by Michael L. McCONNELL in the review Analytical Chemistry 53, no. 8, 1007, A, (1981).
As indicated above, the colloidal dispersion of the invention is characterised by the presence of an additive, which can first be chosen from .beta.-diketones. These are, in particular, co

REFERENCES:
patent: 4886624 (1989-12-01), Gradeff et al.

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