Crosslinkable organopolysiloxane compositions
Hydrosilylative crosslinking compositions containing an aliphatically unsaturated compound which is the reaction product of an alkali metal siliconate and a chlorosilane and a coupler having two silicon bond hydrogen atoms have high compression and damping characteristics when cured.
1 . A hydrosilylation-crosslinkable composition, comprising:
(A) at least one aliphatically unsaturated organopolysiloxane produced by reaction of
(i) alkali metal salts of silanol(s) of the formula
R a R 1 b (OH) 3-p Si(OM) p (II)
and/or condensation products thereof,
with the proviso that in component (i) the average molar ratio of alkali metal:silicon is 0.10 to 2.00,
with (ii) chlorosilanes of formula
R 7 r R 8 R 9 t SiCl (III),
wherein
M is an alkali metal cation,
R and R 7 independently of one another are alkyl radicals,
R 8 are identical or different and represent monovalent hydrocarbon radicals having aliphatic carbon-carbon multiple bonds,
R 1 and R 9 independently of one another are identical or different and are aromatic hydrocarbon radicals free from aliphatic carbon-carbon multiple bonds,
a is 0 or 1,
b is 0 or 1, with the proviso that a+b=1,
p is 1, 2 or 3,
r is 0, 1, 2 or 3 and
t is 0, 1 or 2, with the proviso that r+t=2,
with the proviso that siliconate component (i) and/or the chlorosilanes (ii) of formula (III) comprise at least one aromatic hydrocarbon radical free from aliphatic carbon-carbon multiple bonds,
(B) one or more organosilicon compounds having two Si-bonded hydrogen atoms and
(C) at least one catalyst which promotes addition of Si-bonded hydrogen onto an aliphatic multiple bond and wherein the composition comprises unconverted reactants (i) and (ii), and the unconverted reactants are present in an amount less than 0.5% by weight of the composition, or the aliphatically unsaturated organopolysiloxane (A) comprises a 3 or 4 membered cyclic ring.
2 . The composition of claim 1 , wherein in the production of component (A), 1.0 to 20.0 mol equivalents of chlorosilanes (ii) are employed per mol equivalent of siliconate component (i).
3 . The composition of claim 1 , wherein organopolysiloxanes (A) have an average of 9 to 25 silicon atoms.
4 . The composition of claim 1 , wherein organopolysiloxane(s) (A) are those having the average formula
[R a R 1 b SiO 3/2 ] m [R 7 r R 8 R 9 t SiO 1/2 ] n (I),
wherein R, R 1 , R 7 , R 8 , R 9 , a, b, r and t are as defined above and
m is ≥0.50 and ≤0.70 and
n is ≥0.30 and ≤0.50,
with the proviso that in formula (I) the sum of b+t≠0 and the sum of m+n is 1.
5 . The composition of claim 1 , wherein at least one coupler (B) is an organosilicon compound containing units of formula
R 4 e H f R 5 g SiO (4-e-f-g)/2 (IV),
wherein
R 4 are identical or different and represent monovalent or divalent, SiC-bonded, optionally substituted, aliphatically saturated hydrocarbon radical,
R 5 are identical or different and represent monovalent or divalent, SiC-bonded, optionally substituted, aliphatically saturated aromatic hydrocarbon radicals,
e is 0, 1, 2 or 3,
f is 0, 1 or 2 and
g is 0, 1 or 2,
with the proviso that e+f+g≤4 and two Si-bonded hydrogen atoms are present per molecule.
6 . The composition of claim 5 , wherein coupler (B) contains, per molecule, at least one radical R 5 which is a divalent, SiC-bonded, aliphatically saturated aromatic hydrocarbon radical which connects two units of formula (IV) to one another.
7 . The composition of claim 1 , wherein the composition comprises:
(A) at least one aliphatically unsaturated organopolysiloxane produced by reaction of
component (i) with component (ii) optionally in the presence of organic solvent (iii) and optionally in the presence of an auxiliary base (iv), wherein the product mixture is optionally worked up in water, filtered and devolatilized,
(B) at least one organosilicon compound having two Si-bonded hydrogen atoms and
(C) at least one catalyst which promotes addition of Si-bonded hydrogen onto aliphatic A multiple bond,
optionally (D) inhibitor(s),
optionally (E) further constituents, and
optionally (F) solvent(s).
8 . A process for producing the composition of claim 7 , comprising mixing the individual components together.
9 . The process of claim 8 , wherein directly after the reaction of component (i) with chlorosilanes (ii), optionally in organic solvent (iii) and optionally in the presence of an auxiliary base (iv), component (A) is subjected to aqueous workup, devolatilized, and subsequently mixed with organosilicon component (B) and the optionally employed components inhibitor (D), further constituents (E) and solvent (F) in any desired sequence followed by addition of component (C), optionally as a mixture with component (D) or (F).
10 . A molded article produced by crosslinking a composition of claim 1 .