Silicone composition for elastomer foam
Organopolysiloxane compositions are described that are crosslinkable by polyaddition and that can produce a silicone elastomer foam (or “silicone foam”) having a low density, i.e. a density of less than 0.20 g/cm 3 , and having good mechanical properties and a good fire resistance.
1 . An organopolysiloxane composition X that is a precursor of a silicone foam M, the composition X comprising:
a. from about 40% to about 80% by weight of at least one organopolysiloxane A exhibiting, per molecule, at least two C 2 -C 6 alkenyl groups bonded to the silicon,
b. from about 1% to about 20% of at least one organopolysiloxane B exhibiting, per molecule, at least two SiH units,
c. from about 2 to about 400 ppm by weight a catalytically effective amount of at least one hydrosilylation platinum catalyst C,
d. from about 0.3% to about 2.5% by weight of at least one porogenic agent D, which is water or an aqueous emulsion,
e. at least about 3% by weight, with respect to the total amount of the composition X, of at least one inorganic filler E, which is a fumed silica, the specific surface of which is from about 100 m 2 /g to about 300 m 2 /g,
f. at least 6% by weight, with respect to the total amount of the composition X, of at least one inorganic filler F, which is a ground quartz, and
g. from about 0.4% to about 5% by weight of at least one heat-resistance additive J,
wherein the ratio by weight of the quartz F to the fumed silica E is from about 1.5 to about 4; and
wherein the silicone foam M obtained by crosslinking and/or curing of the organopolysiloxane composition X has a limiting oxygen index of more than 33.
2 . The organopolysiloxane composition X as claimed in claim 1 , wherein the amount of inorganic filler E is from about 3% to about 14% by weight of said composition X.
3 . The organopolysiloxane composition X as claimed in claim 1 , wherein the amount of inorganic filler F is from about 6% to about 25% by weight of said composition X.
4 . The organopolysiloxane composition X as claimed in claim 1 , wherein the ratio by weight of the quartz F to the fumed silica E is from about 1.6 to about 3.6.
5 . The organopolysiloxane composition X as claimed in claim 1 , further comprising an organopolysiloxane gum G comprising at least two C 2 -C 6 alkenyl groups bonded to the silicon.
6 . The organopolysiloxane composition X as claimed in claim 1 , further comprising an inhibiter I.
7 . The organopolysiloxane composition X as claimed in claim 1 , comprising:
a. from about 40% to about 80% by weight of at least one organopolysiloxane A exhibiting, per molecule, at least two C 2 -C 6 alkenyl groups bonded to the silicon,
b. from about 1% to about 20% by weight of at least one organopolysiloxane B exhibiting, per molecule, at least two SiH units,
c. from about 2 to about 400 ppm by weight of platinum metal,
d. from about 0.3% to about 2.5% by weight of a porogenic agent D, which is water or an aqueous emulsion,
e. from about 3% to about 14% by weight of at least one inorganic filler E, which is a fumed silica, the specific surface of which is from about 100 m 2 /g to about 300 m 2 /g,
f. from about 6% to about 25% by weight, with respect to the total amount of the composition X, of at least one inorganic filler F, which is a ground quartz,
g. from about 0.4% to about 5% by weight of at least one heat-resistance additive J,
h. from about 0 to about 3000 ppm by weight of a crosslinking inhibiter I, and
i. from about 0% to about 4% by weight of a diorganopolysiloxane gum G comprising at least two C 2 -C 6 alkenyl groups bonded to the silicon.
8 . A two-component system P, that is a precursor of the organopolysiloxane composition X as defined in claim 1 and comprising the constituents A, B, C, D, E, F and J, wherein said two-component system P comprises two separate parts P1 and P2 that are to be mixed to form the organopolysiloxane composition X and comprising said constituents, and in that one of the parts P1 or P2 comprises the catalyst C and the porogenic agent D and does not comprise the organopolysiloxane B.
9 . The organopolysiloxane composition X as claimed in claim 1 , wherein the at least one organopolysiloxane B exhibits, per molecule, at least three SiH units.
10 . The organopolysiloxane composition X as claimed in claim 7 , wherein the at least one organopolysiloxane B exhibits, per molecule, at least three SiH units.