Patent ID: 7385001

Claim:
A method of making a silicone oil-in-water emulsion comprising the steps of: (i) forming a homogeneous oil phase containing a silicone gum, a silicone rubber, a silicone elastomer, a silicone resin, or a mixture thereof; the silicone in the homogeneous oil phase having a viscosity of at least 100,000,000 (100 million) centistoke (mm 2 /s) to 5,000,000,000 (5 billion) centistoke (mm 2 /s); (ii) mixing one or more surfactants with the homogeneous oil phase; (iii) adding water to the homogeneous oil phase to form a water-in-oil emulsion containing a continuous phase and a dispersed phase, the water being added in an amount of about 0.5-10 percent by weight based on the weight of the silicone in the homogeneous oil phase; (iv) applying high shear to the water-in-oil emulsion in a twin-screw extruder having a length to diameter L/D ratio of at least 15, to cause inversion of the water-in-oil emulsion to an oil-in-water emulsion; and (v) diluting the oil-in-water emulsion by the addition of water; the method being carried out in the absence of a solvent other than solvents present in the silicone gum, silicone rubber, silicone elastomer, or silicone resin in (i).