Particle-Stabilised Emulsions

Abstract

The invention relates to water-in-oil (W/O) or oil-in-water (O/W) emulsions containing an oil phase of at least one water-insoluble constituent; an aqueous phase; pyrogenic silica at the oil-water interface, the pyrogenic silica partially silylated such that non-silylated surface silanol groups remaining are between 95% and 5% of initial silanol groups, the equivalent of 1.7 to 0.1 surface SiOH groups per nm 2 , a surface energy gamma-s-D of 30 to 80 mJ/m 2 , and a specific BET surface area between 30 and 500 m 2 /g; and optionally other substances, such as pigments or preservatives. The inventive emulsions have a mean particle size of the dispersed phase, of between 0.5 μm and 500 μm, and are of low viscosity.

1 .- 9 . (canceled)  
   
   
       10 . An emulsion of the water-in-oil (W/O) or oil-in-water (O/W) type, comprising: 
 A) an oil phase comprising at least one liquid substantially water-insoluble component;    B) an aqueous phase;    C) pyrogenic silica at an oil-water interface of the oil phase and the aqueous phase, the pyrogenic silica partly silylated such that the content of non-silylated surface silanol groups on the silica surface is from not more than 95% to not less than 5% of the silanol groups of the starting silica, or from 1.7 to 0.1 SiOH groups per nm2 of silica surface, the dispersion fraction of the surface energy gamma-s-D being from 30 to 80 mJ/m 2  and the specific BET surface area being from 30 to 500 m 2 /g;    wherein the emulsions having a mean particle size of the disperse phase of from 0.5 μm to 500 μm and a relative viscosity η r  in the range of from 1 to 10 6 , the relative viscosity being defined as the quotient η/η 0  where η is the measured viscosity of the emulsion at 25° C. and a shear rate D=10 s −1 , and η 0  is the viscosity of the pure homogeneous phase, and wherein the relative viscosity of the emulsion obeys the formula η rel =(1−Φ/0.74) −([η]·0.74) , Φ being the phase volume of the disperse phase and └η┘ being a form factor from 2.5 to 100.    
   
   
       11 . The emulsion of  claim 10 , in which the volume of any phase in dispersion depleted by creaming, sedimentation, or phase separation is less than 10% of the total volume.  
   
   
       12 . The emulsion of  claim 10 , wherein at least one dispersed phase component comprises an organopolysiloxane.  
   
   
       13 . The emulsion of  claim 10 , wherein at least one dispersed phase component comprises an epoxy resin.  
   
   
       14 . A process for the preparation of a product emulsion of  claim 10 , comprising preparing a highly concentrated finely divided dispersion of the pyrogenic silica in the liquid which forms the homogeneous phase in the emulsion in a first step; preparing a highly viscous preemulsion comprising the total amount of disperse phase and the highly concentrated finely divided dispersion of pyrogenic silica prepared in the first step in the liquid which forms the homogeneous phase in the emulsion in a second step, the volume of dispersion used being such that the total amount of pyrogenic silica required in the product emulsion is present; and the remaining homogeneous phase is slowly metered in in a third step.  
   
   
       15 . A coating material, adhesive or sealant comprising an emulsion of  claim 10 .  
   
   
       16 . A cleaning or cleansing agent comprising an emulsion of  claim 10 .  
   
   
       17 . A water repellent, adhesion promoter, release agent, paper coating or foam control agent comprising an emulsion of  claim 10 .  
   
   
       18 . A W/O/W or O/W/O multiple emulsion which contains an emulsion of  claim 10 .  
   
   
       19 . A stability analyzer, comprising a flat-bed scanner having a sample holder for holding transparent measuring cells positioned perpendicularly to the scanner lamp, a tilted mirror which deflects the light of the scanner lamp laterally onto the measuring cells, and an evaluation apparatus for evaluating light received by the flat-bed scanner sensor.