Microcapsules containing curable siloxanes

1. An aqueous suspension of silicate shell microcapsules wherein a first portion of the silicate shell microcapsules contain as a core Part A of a curable siloxane composition comprising;

a) an organopolysiloxane having at least two silicon-bonded alkenyl groups per molecule,

b) a hydrosilylation catalyst,

and a second portion of the silicate shell microcapsules contain as a core Part B of the curable siloxane composition comprising;

c) an organohydrogensiloxane having an average of greater than two silicon bonded hydrogen atoms (SiH) per molecule.

2. The aqueous suspension of claim 1 wherein Part B of the curable siloxane composition further comprises a) the organopolysiloxane having at least two alkenyl groups.

3. The aqueous suspension of claim 2 wherein the amount used of components a) and c) provides a molar ratio of the SiH units of the organohydrogensiloxane to the alkenyl groups in the organopolysiloxane that is from 1 to 4.

4. The aqueous suspension of claim 3 wherein the molar ratio of the SiH units of the organohydrogensiloxane to the alkenyl groups in the organopolysiloxane used in Part B of the curable siloxane composition is from 3 to 10.

5. The aqueous suspension of claim 1 wherein the organopolysiloxane having at least two alkenyl groups comprises at least two siloxane units represented by the average formula R 2 R m SiO (4-m)/2

wherein

R is a hydrocarbon group containing 1 to 20 carbon atoms,

R 2 is a monovalent alkenyl aliphatic group, and

m is zero to 2.

6. The aqueous suspension of claim 5 wherein the organopolysiloxane having at least two alkenyl groups has the average formula;

CH 2 ═CH(Me) 2 SiO[Me 2 SiO] x′ Si(Me) 2 CH═CH 2

CH 2 ═CH—(CH 2 ) 4 -(Me) 2 SiO[Me 2 SiO] X′ Si(Me) 2 -(CH 2 ) 4 —CH═CH 2 , or

Me 3 SiO[(Me) 2 SiO] x′ [CH 2 ═CH(Me)SiO] x″ SiMe 3

wherein Me is methyl, x′ >0, and x″ >2.

7. The aqueous suspension of claim 1 wherein the organohydrogensiloxane comprises the average formula;

(R 3 3 SiO 1/2 ) a (R 4 2 SiO 2/2 ) b (R 4 HSiO 2/2 ) c wherein

R 3 is hydrogen or R 4 ,

R 4 is a monovalent hydrocarbyl containing 1 to 10 carbon atoms,

a≧2, b≧0, c≧2.

8. The aqueous suspension of claim 7 wherein the organohydrogensiloxane is selected from a dimethyl, methyl-hydrogen polysiloxane having the average formula;

(CH 3 ) 3 SiO[(CH 3 ) 2 SiO] b [(CH 3 )HSiO] c Si(CH 3 ) 3

where b≧0, and c≧2.

9. The aqueous suspension of claim 1 wherein the hydrosilylation catalyst is an elemental platinum group metal having a concentration of 1 to 500 ppm in the curable siloxane composition.

10. The aqueous suspension of claim 1 wherein the silicate shell microcapsules are obtained by;

I) mixing an oil phase containing Part A or Part B of the curable siloxane composition and an aqueous solution of a cationic surfactant to form an oil in water emulsion,

II) adding a water reactive silicon compound comprising a tetraalkoxysilane to the oil in water emulsion,

III) polymerizing the tetraalkoxysilane at the oil/water interface of the emulsion to form a microcapsule having a core containing either Part A or Part B of the curable siloxane composition and a silicate shell,

IV) combining the microcapsules containing Part A of the curable siloxane composition with the microcapsules containing Part B of the curable siloxane composition.

11. The aqueous suspension of claim 10 wherein the tetraalkoxysilane is tetraethoxysilane.

12. The aqueous suspension of claim 10 wherein the water reactive silicon compound further comprises (CH 3 O) 3 SiCH 2 CH 2 CH 2 N + (CH 3 ) 2 (CH 2 ) 17 CH 3 Cl − .

13. A process for preparing a suspension of silicate shell microcapsules comprising;

preparing a first suspension of silicate shell microcapsules by

I) mixing an oil phase containing Part A of a curable siloxane composition comprising;

a) an organopolysiloxane having at least two alkenyl groups,

b) a hydrosilylation catalyst,

and an aqueous solution of a cationic surfactant to form an oil in water emulsion,

II) adding a water reactive silicon compound comprising a tetraalkoxysilane to the oil in water emulsion,

III) polymerizing the tetraalkoxysilane at the oil/water interface of the emulsion to form a microcapsule having a core containing the oil and

a silicate shell;

preparing a second suspension of silicate shell microcapsules by

I) mixing an oil phase containing Part B of a curable siloxane composition comprising;

c) an organohydrogensiloxane having an average of greater than two silicon bonded hydrogen atoms (SiH) per molecule

and an aqueous solution of a cationic surfactant to form an oil in water emulsion,

II) adding a water reactive silicon compound comprising a tetraalkoxysilane to the oil in water emulsion,

III) polymerizing the tetraalkoxysilane at the oil/water interface of the emulsion to form a microcapsule having a core containing the oil and

a silicate shell; and

mixing the first and second suspensions together.

14. The process of claim 13 wherein the weight ratio of the first suspension mixed with the second suspension varies from 0.9 to 1.1.