Colloid systems and wetting agents; subcombinations thereof; pro – Continuous liquid or supercritical phase: colloid systems;... – Aqueous continuous liquid phase and discontinuous phase...
Patent
1998-04-06
1999-08-17
Lovering, Richard D.
Colloid systems and wetting agents; subcombinations thereof; pro
Continuous liquid or supercritical phase: colloid systems;...
Aqueous continuous liquid phase and discontinuous phase...
3661761, 3661801, 516 76, 516929, B01J 1300, B01F 920
Patent
active
059385812
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for preparing an emulsion consisting of droplets of a phase A, dispersed in a phase B, the phases A and B being immiscible.
The process of the invention is more particularly useful for preparing monodispersed emulsions.
The process of the invention is also applicable to the preparation of emulsions with a low surfactant content.
Many emulsification techniques are known at the present time. Among the most common, mention may be made of microfluidization and ultrasonication techniques.
Microfluidization consists of the high-pressure spraying of a liquid jet consisting of two immiscible fluids onto a solid wall. The turbulences and cavitations thus induced lead to the dispersion of one fluid in the other.
Ultrasonication allows the dispersion of a given fluid in another fluid which forms the continuous phase which is not dispersible in the first. By this process, a mixture of the two fluids is subjected to high-intensity ultrasonic vibrations which create the cavitation phenomena leading to the dispersion of one fluid in the other.
European patent applications EP 442,831 and EP 517,987 moreover disclose processes for preparing monodispersed emulsions of the oil-in-water or magnetizable polymer-in-water type. These processes comprise steps consisting in:
a) adjusting the content of oil or of polymer, respectively, of a polydispersed primary stable emulsion to a value of between 1 and 40% by weight;
b) increasing the surfactant concentration of the polydispersed primary emulsion so as to obtain two phases, a so-called liquid phase in which the oil droplets or the polymer droplets, respectively, are free, and a so-called solid phase in which the droplets are combined;
c) separating the liquid phase from the solid phase; and
d) optionally repeating operations a) to c) above as many times as necessary to obtain the monodispersed emulsion.
These processes involve the fractionation of a starting primary emulsion by successive creaming operations.
It goes without saying that these first two long and tiresome processes are not readily industrializable.
The invention proposes a process for preparing an emulsion starting from a simple primary emulsion consisting of two immiscible phases, this process being particularly suitable for industrial application and particularly easy to carry out.
More specifically, the invention provides a process for preparing a secondary emulsion consisting of droplets of a phase A, dispersed in a phase B, A being immiscible in B, starting with a polydispersed primary emulsion of identical formulation and consisting of droplets of the said phase A dispersed in the said phase B, the droplets of the secondary emulsion having a diameter in all cases which is less than the diameter of the droplets of the primary emulsion, characterized in that the starting primary emulsion is viscoelastic and in that the said starting primary emulsion is subjected to a controlled shear such that the same maximum shear is applied to the entire emulsion.
In the context of the present invention, the term primary emulsion is understood to refer to the starting emulsion used to produce the target emulsion, which is referred to as the secondary emulsion.
It will be noted that, according to the invention, the formulations of the starting primary emulsion and of the secondary target emulsion are identical, which, in other words, means that these emulsions contain the same ingredients in equal amounts.
According to a preferred embodiment of the invention, the primary emulsion is simple: in this case, it consists of a homogeneous first phase dispersed in a homogeneous second phase, known as the continuous phase, the said first and second phases by definition being immiscible.
However, it is possible to carry out the process of the invention starting with a double emulsion consisting of droplets of a given emulsion or a given dispersion in a homogeneous continuous phase.
As an example of double emulsions, mention may be made of emulsions of water-in-oil-in-water type.
Starting with such d
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Advances in Chemistry Series 231, "Emulsions-Fundamentals and Applications in the Petroleum Industry", L.L. Schramm, Editor, Am. Chem. Soc., Washington, D.C (1992), pp. 134-136.
Bibette Jerome Michel
Mason Thomas
Centre National de la Recherche Scientifique (C.N.R.S.)
Lovering Richard D.
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