Method of preparing amine functional silicone microemulsions

A method of preparing a transparent amino-functional polyorganosiloxane microemulsion having an average particle size of from about 0.015 to about 0.050 microns, comprising the steps of:

• (A) forming an oil and surfactant mixture by blending:
• (1) 100 parts of an amino-functional polyorganosiloxane having an amino content of from about 0.6 to about 3.0 milliequivalents per gram and comprising:
• (a) R.sub.a Q.sub.b SiO.sub.(4-a-b)/2 units;
• and
• (b) R.sub.c SiO.sub.(4-c)/2 units;
• wherein the molar ratio of R.sub.a Q.sub.b SiO.sub.(4-a-b)/2 units to R.sub.c SiO.sub.4-c)/2 units ranges from about 1.2 to about 1:65, "a" is a number in the range of 0-2, "b " is a number in the range of 1-3, "a"+"b" is less than or equal to 3, "c" is a number in the range of 1-3, R is a monovalent hydrocarbon or substituted hydrocarbon radical having from 1 to about 6 carbon atoms, and q is a polar radical having the general formula --R.sup.1 NHZ, wherein R.sup.1 is a divalent linking group comprised of carbon and hydrogen atoms;
• carbon, hydrogen, and oxygen atoms;
• or carbon, hydrogen, and sulfur atoms;
• and Z is a radical selected from the group consisting of hydrogen atoms, alkyl radicals containing from 1 to 4 carbon atoms, and --CH.sub.2 CH.sub.2 NH.sub.2 radicals;
• and
• (2) from about 10 to about 60 parts by weight per 100 parts of (A)(1) of at least one surfactants, wherein at least one of the surfactants is insoluble in the amino-functional polyorganosiloxane;
• (B) dropwise adding water to the oil and surfactant mixture prepared in step (A), the water being added for a period of from about 5 to about 60 minutes in an amount ranging from about 5 to about 40 parts by weight based on the weight of the oil surfactant mixture, the mixture containing the oil and surfactant mixture and the water added thereto being agitated during the addition of the water such that a homogeneous mixture is formed of the water and the oil and surfactant mixture;
• (C) adding water to the homogeneous mixture formed in (B), the water being added in an amount such that the total amount of water added in (B) and (C) is in range of from about 500 to about 1000 parts by weight based on the weight of the mixture formed in (A);
• and
• (D) adding an acid selected from the group consisting of a lower aliphatic saturated carboxylic acid having from 1 to about 4 carbon atoms, HCl, H.sub.2 SO.sub.4, HNO.sub.3, HBr and Hl to the mixture formed in (C) in an amount sufficient to provide the mixture with a pH of from about 4 to about 7, the acid reacting with the amino-functional polyorganosiloxane (A)(1) to form a water-soluble salt.