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 having a formula
[(R 2 SiO (2-a)/2 ) s (OZ) a ][(RSiO (3-b)/2 ) (1-s) (OZ) b ]
where s and 1-s represent mole fractions of the siloxy units,
s is from 0 to 0.6, a is from 0 to 2, b is from 0 to 2,
with the proviso that a+b is from 0.10 to 2.00
R is a monovalent organic group having 1-30 carbon atoms,
Z is hydrogen or an alkyl group having 1-4 carbon atoms,
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, and the hydroxy terminated polydiorganosiloxane is present and is selected from a hydroxy terminated polydimethylsiloxane.
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 where R is n-octyl or methyl, and Z is hydrogen or methyl.
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 .