Curable polyorganosiloxane composition for use as an encapsulant for a solar cell module

1. A curable polyorganosiloxane composition for the use as an encapsulant, said composition consisting of:

(A) at least one polyorganosiloxane having at least two unsaturated hydrocarbyl residues,

(B) at least one polyorganohydrogensiloxane having at least seven Si atoms, wherein the molar ratio of SiH-groups to all Si-atoms in the polyorganohydrogensiloxane is ≧0.7,

(C) at least one hydrosilylation catalyst,

adhesion promoter (D1), wherein (D1) is a compound of formula (3c):

and ring position isomers thereof, and

and

adhesion promoter (D2), wherein (D2) is at least one organosilane, comprising at least one alkoxy silyl group, selected from compounds of the formula (4):

X—(CR 6 2 ) e —Y—(CH 2 ) e SiR d (OR 3 ) 3−d   (4)

wherein

X is selected from the group consisting of halogen, unsaturated aliphatic group with up to 14 carbon atoms, epoxy-group-containing aliphatic group with up to 14 carbon atoms, cyanurate-containing group, and an isocyanurate-containing group,

Y is selected from the group consisting of a single bond, a heteroatomic group selected from —COO—, —O—, —S—, —CONH—, —HN—CO—NH—,

e is 0, 1, 2, 3, 4, 5, 6, 7, or 8, and may be identical or different,

R may be the same or different, and is selected from optionally substituted alkyl with up to 30 carbon atoms, optionally substituted aryl with up to 30 carbon atoms, poly(C 2 -C 4 )-alkylene ether with up to 1000 alkylene oxy units, the groups R being free of aliphatic unsaturation,

R 3 is selected from H (hydrogen) and alkyl radicals having 1 to 6 carbon atoms, and may be identical or different,

R 6 is selected from hydrogen and R,

d is 0, 1, or 2,

(E) at least one reinforcing filler,

and optionally auxiliary or conventional additives selected from the group consisting of stabilizers against hot air, oils, solvents, process aids, mold release agents, wetting agents, pigments, functional fillers for increased heat or electrical conductivity, low surface or inert fillers, extenders for extended volume, natural or synthetic fibers, blowing agents, anti-microbial agents, fungicides, additives for increasing mildew resistance, opaque non-transparent fillers, plasticizers, release oils, hydrophobicizing oils, and inhibitors for controlling the crosslinking reaction,

wherein the molar ratio of the total of SiH groups in component (B) to the total of the unsaturated hydrocarbyl residues in component (A) in the formulation is between 0.7 and 4.

2. The curable polyorganosiloxane composition according to claim 1 , wherein the encapsulant is for a photovoltaic module.

3. The curable polyorganosiloxane composition according to claim 1 , wherein component (A) is a compound of formula (1):

R 1 a R 3−a SiO[R 2 SiO] m [R 1 RSiO] n SiR 1 a R 3−a   (1)

wherein R is selected from optionally substituted alkyl with up to 30 carbon atoms, optionally substituted aryl with up to 30 carbon atoms, or poly(C 2 -C 4 )-alkylene ether with up to 1000 alkylene oxy units, the groups R being free of aliphatic unsaturation,

wherein R 1 is selected from aliphatic or aromatic groups with up to 30 carbon atoms, comprising C═C-group-containing groups (alkenyl groups) or C≡C-group-containing groups (alkinyl groups), optionally comprising one or more O- or F-atoms,

a=0-3

m=0-2000

n=0-500.

4. The curable polyorganosiloxane composition according to claim 1 , wherein component (B) is a compound of formula (2a):

H a1 (R) 3−a1 Si[RHSiO] x [R 2 SiO] y [RR 1 SiO] z Si(R) 3−a1 H a1   (2a)

wherein R is selected from optionally substituted alkyl with up to 30 carbon atoms, optionally substituted aryl with up to 30 carbon atoms, or poly(C 2 -C 4 )-alkylene ether with up to 1000 alkylene oxy units, the groups R being free of aliphatic unsaturation,

wherein R 1 is selected from aliphatic or aromatic groups with up to 30 carbon atoms, comprising C═C-group-containing groups (alkenyl groups) or C≡C-group-containing groups (alkinyl groups), optionally comprising one or more O- or F-atoms, a1 is 0-1, and

7≦x+y+z<1000.

5. Curable polyorganosiloxane composition according to claim 4 , wherein R comprises at least one phenyl group.

6. Curable polyorganosiloxane composition according to claim 1 , wherein component (C) is at least one transition metal compound, wherein the transition metal is selected from group consisting of nickel, ruthenium, rhodium, palladium, osmium, iridium, and platinum.

7. Curable polyorganosiloxane composition according to claim 1 , wherein component (E) is selected from silica having a BET-surface of at least 150 m 2 /g.

8. Curable polyorganosiloxane composition according to claim 1 , said composition comprising:

100 parts by weight of component (A),

0.1 to 200 parts per weight of component (B),

0.5 to 1000 ppm of component (C), wherein component (C) is at least one transition metal compound, based on the amount of the transition metal in the component (C) and based on the total of components (A) and (B),

0.01 to 5 parts by weight of component (D),

up to 50 parts by weight of component (E).

9. A photovoltaic module comprising the cured polyorganosiloxane composition according to claim 1 .

10. A photovoltaic module comprising the cured polyorganosiloxane composition according to claim 2 .

11. A photovoltaic module comprising the cured polyorganosiloxane composition according to claim 3 .

12. A photovoltaic module comprising the cured polyorganosiloxane composition according to claim 4 .

13. A photovoltaic module comprising the cured polyorganosiloxane composition according to claim 5 .

14. A photovoltaic module comprising the cured polyorganosiloxane composition according to claim 6 .

15. A photovoltaic module comprising the cured polyorganosiloxane composition according to claim 7 .

16. A photovoltaic module comprising the cured polyorganosiloxane composition according to claim 8 .