Compositions – Solids with solution or dispersion aids
Reexamination Certificate
2001-12-05
2004-11-02
Metzmaier, Daniel S. (Department: 1712)
Compositions
Solids with solution or dispersion aids
C516S033000, C106S287190, C106S447000, C423S611000, C524S131000, C524S497000, C424S059000
Reexamination Certificate
active
06811723
ABSTRACT:
The present invention relates to an organic sol and a solid compound based on titanium oxide and an amphiphilic compound and their preparation processes.
Colloidal sol or dispersions of titanium oxide in organic media are known. However, the preparation processes of these sols are complex from an industrial point of view. A first class of processes uses compounds sensitive to water such as titanium alkoxides. Another class generally involves the preparation of an aqueous sol in the first instance and secondly bringing this aqueous sol into contact with an organic phase in order to transfer the titanium oxide into the organic phase. Such an operating method is not suitable for preparing sols in polar phases which are miscible with water. There is therefore a requirement for simpler processes which also provide access to sols with varying characteristics.
A subject of the present invention is to provide such processes and such organic sols.
For this purpose, the organic sol according to the invention is characterized in that it comprises titanium oxide particles; an organic liquid phase and at least one amphiphilic compound chosen from the polyoxyethylenated alkyl ether phosphates.
The invention also relates to a process for the preparation of such a sol which, according to a first variant, is characterized in that said amphiphilic compound and the organic liquid phase are mixed together, then the titanium oxide particles are dispersed in the mixture obtained. According to a second variant, the process is characterized in that a mixture of titanium oxide particles and at least one said amphiphilic compound are mixed together and said mixture is dispersed in the organic liquid phase.
The sols according to the invention have the advantage of being able to exist in a wide range of solvents, polar or non-polar solvents.
Other characteristics, details and advantages of the invention will appear more fully on reading the following description and the various concrete but non-limitative examples intended to illustrate it.
In the remainder of the description, the expression sol or colloidal dispersion of titanium oxide designates any system constituted by fine solid particles of colloidal dimensions based on titanium oxide suspended in a liquid phase, said types also being optionally able to contain residual quantities of linked or adsorbed ions such as for example chlorides, sulphates, nitrates, acetates, citrates, ammoniums or organic bases such as diethylamine. It should be noted that in such dispersions, the titanium may either be totally in the form of colloids or simultaneously in the form of ions and in the form of colloids.
The particles of the sol according to the invention can be based on titanium dioxide with a mainly anatase crystal structure. “Mainly” means that the content of the anatase titanium dioxide particles is higher than 50% by mass. Preferably, the particles have an anatase content greater than 80%. The degree of crystallization rate and the nature of the crystalline phase are measured by XR diffraction.
These particles can also be of rutle structure.
The average diameter of these particles in the sol is generally at most 250 nm, preferably at least 15 nm, even more preferentially between 20 and 70 nm. It is specified here that the average diameter of the particles or colloids must be understood as designating the average hydrodynamic diameter of the latter, and as determined by quasi-elastic diffusion of light according to the method described by Michael L. Mc Connell in the Journal Analytical Chemistry 53, no. 8, 1007 A, (1981).
The particles of the sol according to the invention generally have a BET specific surface area of at least 200 m
2
/g, preferably at least 250 m
2
/g.
By BET specific surface area is meant the specific surface area determined by nitrogen adsorption according to the ASTMD 3663-78 standard based on the BRUNAUER-EMMETT-TELLER method described in the periodical “The Journal of the American Society”, 60, 309 (1938). In order to measure the specific surface area of the particles according to the invention, when they are in the form of a dispersion, it is essential to follow the measurement protocol which consists of eliminating the liquid phase from the dispersion then drying the particles under vacuum at a temperature of 150° C. for at least 4 hours.
According to two variants of the invention, the titanium oxide particles of the sol can comprise a coating. Before the following description of these two variants, it can be specified here that in both cases, the particles have an average diameter generally of at most 100 nm, preferably at least 25 nm, even more preferentially comprised between 50 and 70 nm. These coated particles also generally have a BET specific surface area of at least 70 m
2
/g, preferably at least 100 m
2
/g.
In the first or these variant, the titanium oxide particles are at least partially coated with a layer of at least one metallic or silicon oxide, hydroxide or oxyhydroxide. For this first variant, reference can be made to Patent Application EP-A-880564 the teaching of which relating to the description of the product and its method of preparation is incorporated here by way of reference. These metallic oxides, hydroxides or oxyhydroxides can in particular be chosen from SiO
2
, ZrO
2
, aluminium, zinc, titanium or tin oxides, hydroxides or oxyhydroxides in simple or mixed form. By mixed is understood a metallic compound based on at least two of the aforementioned elements (silicoaluminates, etc.).
In general, the ratio by weight of the metallic oxides, hydroxides or oxyhydroxides to the titanium dioxide is at most 60% by weight. This ratio is a function of the use for which the particles are intended. Preferably, when the particles are used in a cosmetic application, this ratio is 25%, even more preferentially at most 20%.
This quantity of metallic oxide, hydroxide or oxyhydroxide is measured on the particles in dispersion by X-ray fluorescence.
According to a particular embodiment of the invention, the particles are at least partially covered with a layer of silica and/or an aluminium oxide, hydroxide or oxyhydroxide in simple or mixed form.
According to another embodiment, the particles are covered with a layer of silica and aluminium hydroxide or oxyhydroxide with an SiO
2
content of 30% by weight and an Al
2
O
3
content of 15% by weight with respect to the titanium dioxide.
According to more particular embodiment, the particles are covered with a layer of silica and aluminium hydroxide or oxyhydroxide with an SiO
2
content of 15% by weight and an Al
2
O
3
content of 5% by weight with respect to the titanium dioxide.
According to the second of these variants, the titanium oxide particles are at least partially covered with a first layer of at least one compound of cerium and/or iron, and a second layer of least one metallic or silicon oxide, hydroxide or oxyhydroxide. For this second variant, reference can be made to Patent Application WO-A-98/01392 the teaching of which relating to the description of the product and its preparation method are incorporated here by way of reference.
The compounds present in the first aforementioned layer are precursors of cerium or iron oxide, i.e. they are thermally decomposable to cerium or iron oxide. They may be cerium or iron salts.
Particles covered with a cerium compound are preferred. The ratio by weight of the cerium compound(s) to the titanium dioxide is preferably at most 6% by weight, expressed in CeO
2
. This ratio can be optimized as a function of the size of the particles. Thus, It has been observed that for particles of 25 nm diameter, the optimum cerium content was 5.5% by weight, expressed in CeO
2
, with respect to the titanium dioxide, similarly for particles of 45 nm diameter, this content is 4.5%; for particles of 60 nm diameter, this content is 3%, and for particles of 80 nm diameter, this content is 2%.
The particles of this second variant are also at least partially covered with a second layer based on at least one metallic oxide, hydroxide or oxyhydroxid
Aupaix Nicole
Chane-Ching Jean-Yves
Burns Doane Swecker & Mathis L.L.P.
Metzmaier Daniel S.
Rhodia Chimie
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