Method for the hydrosilylation of a siloxane photocatalysed by a polyoxometalate compound

1. A process for hydrosilylation between a siloxane compound (A) comprising at least one hydrogen atom bonded to a silicon atom and an unsaturated compound (B) comprising at least one alkene function and/or at least one alkyne function, wherein said process is catalyzed by a photocatalyst chosen from polyoxometalates.

2. The process as claimed in claim 1 , wherein said photocatalyst is a decatungstate.

3. The process as claimed in claim 1 wherein said siloxane compound (A) is a polyorganosiloxane comprising at least one unit of formula (I):

H d Z e SiO (4-(d+e))/2   (I)

in which:

Z represents a monovalent radical other than a hydrogen atom,

d and e represent integers, d being 1 or 2, e being 0, 1 or 2 and (d+e) being 1, 2 or 3;

and optionally other units of formula (II):

Z f SiO (4-f)/2   (II)

in which:

Z has the same meaning as above, and

f represents an integer between 0 and 3.

4. The process as claimed in claim 3 , wherein, in formula (I), the symbol d is 1 and Z represents a monovalent radical chosen from the group consisting of an alkyl group having 1 to 8 carbon atoms, which is optionally substituted with at least one halogen atom, and an aryl group.

5. The process as claimed in claim 1 , wherein said unsaturated compound (B) comprises one or more alkene functions and/or one or more alkyne functions, and from 2 to 40 carbon atoms.

6. The process as claimed in claim 1 , wherein said unsaturated compound (B) is chosen from the group consisting of:

non-polymeric unsaturated organic compounds,

polyorganosiloxane compounds comprising at least one alkene function and/or at least one alkyne function,

and mixtures thereof.

7. The process as claimed in claim 6 , wherein said unsaturated compound (B) is a non-polymeric unsaturated organic compound chosen from the group consisting of:

acetylene;

C 1 to C 4 alkyl acrylates and methacrylates;

acrylic or methacrylic acid;

alkenes, optionally octene and optionally 1-octene;

allyl alcohol;

allylamine;

allyl glycidyl ether;

piperidine allyl ether, optionally sterically hindered piperidine allyl ether;

styrenes, preferentially alpha-methylstyrene,

1,2-epoxy-4-vinylcyclohexane,

allyl chloride;

chloroalkenes, optionally allyl chloride; and

fluoroalkenes, optionally 4,4,5,5,6,6,7,7,7-nonafluoro-1-heptene.

8. The process as claimed in claim 6 , wherein said unsaturated compound (B) is chosen from polyorganosiloxane compounds comprising at least one unit of formula (V):

Y g L h SiO (4-(g+h))/2   (V)

in which:

Y represents a linear or branched radical containing between 2 and 12 carbon atoms, having at least one alkene function and/or at least one alkyne function, and optionally at least one heteroatom;

L represents a monovalent radical not comprising an alkene or alkyne function;

g and h represent integers, g being 1, 2 or 3, h being 0, 1 or 2 and (g+h) being 1, 2 or 3;

and optionally comprising other units of formula (VI):

L i SiO (4-i)/2   (VI)

in which:

L has the same meaning as above, and

i represents an integer between 0 and 3.

9. The process as claimed in claim 1 , wherein the siloxane compound (A) comprising at least one hydrogen atom bonded to a silicon atom and the unsaturated compound (B) comprising at least one alkene function and/or at least one alkyne function are one and the same bifunctional compound.

10. The process as claimed in claim 9 , wherein said bifunctional compound is a polyorganosiloxane comprising at least one unit of formula (I):

H d Z e SiO (4-(d+e))/2   (I)

in which:

Z represents a monovalent radical other than a hydrogen atom;

d and e represent integers, d being 1 or 2, e being 0, 1 or 2 and (d+e) being 1, 2 or 3;

and at least one unit of formula (V):

Y g L h SiO (4-(g+h))/2   (V)

in which:

Y represents a linear or branched radical containing between 2 and 12 carbon atoms, having at least one alkene function and/or at least one alkyne function, and optionally at least one heteroatom;

L represents a monovalent radical not comprising an alkene or alkyne function;

g and h represent integers, g being 1, 2 or 3, h being 0, 1 or 2 and (g+h) being 1, 2 or 3;

and optionally other units of formula (VII):

W j SiO (4-d)/2   (VII)

in which:

W represents a monovalent radical other than a hydrogen atom and not comprising an alkene or alkyne function, and

j represents an integer between 0 and 3.

11. The process as claimed in claim 1 , which comprises irradiating the photocatalyst with UV or visible light, the wavelength of which is between 300 nm and 500 nm.

12. The process as claimed in claim 1 , which is carried out in a homogeneous solution.

13. The process as claimed in claim 1 , which is carried out by heterogeneous catalysis.

14. A composition comprising:

a siloxane compound (A) comprising at least one hydrogen atom bonded to a silicon atom,

an unsaturated compound (B) comprising at least one alkene function and/or at least one alkyne function, and

a photocatalyst chosen from polyoxometalates.

15. The composition of claim 14 , wherein said photocatalyst is a decatungstate.

16. The composition of claim 14 , wherein said photocatalyst is tetrabutylammonium decatungstate.

17. The process of claim 1 , wherein said photocatalyst is tetrabutylammonium decatungstate.

18. A product formed by the irradiation of a composition of claim 14 , with UV or visible light, the wavelength of which is between 300 nm and 500 nm.

19. The composition of claim 4 , comprising 0.05 to 5% of the photocatalyst.