Aqueous emulsions of silicone resins
View Patent ↗Aqueous emulsions of a silicone resin are disclosed that provide a solid silicone resineous coating upon removing water from a film of the emulsion. The silicone resin emulsions are useful for treating various substrates for imparting water resistance/repellence and improving wear/weather protective properties. In particular, they are useful for rendering mineral-based building materials water-resistant, and also as binders in paints.
1. An aqueous emulsion comprising;
A) 1-70 weight percent of a silicone resin comprising a formula
[(CH 3 ) 2 SiO 2/2 ] d [(CH 3 )SiO 3/2 ] e [(C 8 H 17 )SiO 3/2 ] f
wherein d may vary from 0.1 to 0.3,
e may vary from 0.7 to 0.9,
f may vary from 0.01 to 0.04
and having a viscosity of from 1 to 4000 mPa·s at 25° C,
B) 0- 40 weight percent of a hydroxy terminated polydiorganosiloxane,
C) 0.5-20% based on the weight components A) and B) of a polyvinyl alcohol emulsifier,
D) 0.001-5% based on the weight of the emulsion of a water soluble salt, wherein the emulsion provides a solid coating upon removing water from a film of the emulsion.
2. The emulsion of claim 1 wherein the emulsion composition is free of organosilanes and has a pH of 7 to 11.
3. The emulsion of claim 1 wherein B) the hydroxy terminated polydiorganosiloxane is present and is selected from a hydroxy terminated polydimethylsiloxane.
4. The emulsion of claim 1 wherein D) the water soluble salt is an alkali metal, alkaline earth metal or ammonium salt.
5. The emulsion of claim 1 wherein D) the water soluble salt is sodium hydrogen carbonate or sodium carbonate.
6. A method for preparing a solid coating comprising;
I) forming a film of the emulsion composition according to claim 1 on a surface,
II) removing water from the film to form the solid coating.
7. The solid coating prepared according to the method of claim 6 .
8. A coating composition comprising the emulsion composition of claim 1 .