Polyorganosiloxane compositions with metal based N-heterocyclic carbene condensation reaction catalysts and methods for the preparation thereof
A complex prepared by combining a metal compound and an N-heterocyclic carbene has catalytic activity for condensation reaction of polyorganosiloxane compositions. The composition includes the complex, a silanol functional compound having an average per molecule of one or more silicon bonded hydroxy moieties.
1. A composition formed by mixing:
(A) a catalytically effective amount of a reaction product prepared by a method comprising combining
i) a metal compound, where the metal compound is selected from a titanium compound and a zinc compound, and
ii) an N-heterocyclic carbene; and
(B) a silanol functional compound having an average, per molecule, of one or more silicon bonded hydroxy moieties; and
where ingredient (A) catalyzes condensation reaction of the hydroxy moieties of ingredient (B).
2. The composition of claim 1 , where the metal compound is a zinc(II) compound.
3. The composition of claim 1 , where the metal compound is selected from dialkyl zinc compounds, diaryl zinc compounds, zinc dihalides, zinc dialkoxides, zinc diesters, and zinc(II) bis(trialkylsilyl)amides.
4. The composition of claim 2 , where the zinc(II) compound is selected from bis-(pentamethylcyclopentadienyl)zinc, diethyl zinc, zinc dibutoxide, zinc diacetylacetonate, and ZnCl 2 .
5. The composition of claim 1 , where the N-heterocyclic carbene has general formula (I):
where Q is a nitrogen atom (N) or a carbon atom (C); subscript x is 0 when Q is N, and subscript x is 1 when Q is C; one of R 51 and R 52 is an alkyl group and the other of R 51 and R 52 is selected from the group consisting of an alkyl group, an hydroxy functional group, a carboxylic acid functional group, and a substituted or unsubstituted hydroxy functional aromatic group; and R 53 and R 54 are each independently selected from a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group or an aralkyl group, with the proviso that R 53 and R 54 may optionally bond together to form a fused ring structure.
6. The composition of claim 1 , where the N-heterocyclic carbene is an imidazole based N-heterocyclic carbene ligand of formula (II):
where subscript x is 1, one of R 51 and R 52 is an alkyl group and the other of R 51 and R 52 is selected from the group consisting of an alkyl group, an hydroxy functional group, a carboxylic acid functional group, and a substituted or unsubstituted hydroxy functional aromatic group; and R 53 and R 54 are each independently selected from a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group or an aralkyl group.
7. The composition of claim 1 , where the N-heterocyclic carbene is an imidazole based N-heterocyclic carbene ligand of formula (III):
where one of R 51 and R 52 is an alkyl and the other of R 51 and R 52 is selected from the group consisting of an alkyl group, an hydroxy functional group, a carboxylic acid functional group, and a substituted or unsubstituted hydroxy functional aromatic group; and R 60 , R 61 , R 62 , and R 63 are each independently selected from a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group or an aralkyl group.
8. The composition of claim 7 , where each dashed line indicates a double bond, R 60 , R 61 , R 62 , and R 63 are each independently selected from hydrogen or an alkyl group selected from methyl, ethyl, propyl or butyl.
9. The composition of claim 1 , where the N-heterocyclic carbene is prepared by a method comprising combining an azolium salt with a base.
10. The composition of claim 9 , where the azolium salt is selected from the group consisting of an azolium halide and an azolium borate.
11. The composition of claim 9 , where the base is selected from the group consisting of cesium salts, KH, K(N(SiMe 3 ) 3 ) 2 , NaOH, KOH, pyridine, lithiumdiisopropylamide, potassium t-butoxide, NaH, or LiN(SiMe 3 ) 2 .
12. The composition of claim 1 , where ingredient (A) comprises a complex of the general formula [ML n ][X] y , where M is Zn or Ti, each L is selected from the group consisting of a halogen atom, a monovalent hydrocarbon group, an amino group, a silyl amide group, a carboxylate ester group, a hydrocarbonoxy group, and a N-heterocyclic carbene ligand, with the proviso that at least one L is the N-heterocyclic carbene ligand, and subscript n is 1 to the maximum number of attachment points to M regardless of the denticity or hapticity of the substituent for L, X is an unbound anion species to make the overall charge of the complex zero, and subscript y is 0 to 2 when M is Zn and subscript y is 0 to 4 when M is Ti.
13. The composition of claim 12 , where ingredient (A) is a complex selected from the group consisting of:
a cis isomer of any one of complexes 1, 2, 3, 4, and 5, and a mixture of two or more of cis and trans isomers of complexes 1, 2, 3, 4, and 5.
14. The composition of claim 1 , where ingredient (B) comprises an organosiloxane block copolymer comprising:
40 to 90 mole percent disiloxy units of formula [R 71 2 SiO 2/2 ],
10 to 60 mole percent trisiloxy units of formula [R 72 SiO 3/2 ],
0.5 to 35 mole percent silanol groups [≡SiOH];
where:
each R 71 and R 72 is independently a hydrocarbon group of 1 to 30 carbon atoms or a halogenated hydrocarbon group of 1 to 30 carbon atoms;
where:
the disiloxy units [R 71 2 SiO 2/2 ] are arranged in linear blocks having an average of from 10 to 400 disiloxy units [R 71 2 SiO 2/2 ] per linear block,
the trisiloxy units [F1 72 SiO 3/2 ] are arranged in non-linear blocks having a molecular weight of at least 500 g/mole, and at least 30% of the non-linear blocks are crosslinked with each other, each linear block is linked to at least one non-linear block; and
the organosiloxane block copolymer has a weight average molecular weight of at least 20,000 g/mole.
15. The composition of claim 1 , further comprising a filler.
16. The composition of claim 15 , where the filler comprises a phosphor.
17. The composition of claim 1 , further comprising a crosslinker.
18. The composition of claim 17 , where the crosslinker is an alkoxysilane or a polyorganohydrogensiloxane.
19. A method comprising: exposing to moisture, a composition formed by mixing:
(A) a catalytically effective amount of a reaction product prepared by a method comprising combining
i) a metal compound, where the metal compound is selected from a titanium compound and a zinc compound, and
ii) an N-heterocyclic carbene; and
(B) a silanol functional compound having an average, per molecule, of one or more silicon bonded hydroxy moieties; and
where ingredient (A) catalyzes condensation reaction of the hydroxy moieties of ingredient (B); thereby preparing a reaction product.