Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-02-02
2001-08-07
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S791000, C524S588000
Reexamination Certificate
active
06271299
ABSTRACT:
FIELD OF THE INVENTION
This invention is curable liquid silicone rubber compositions that are useful as fire resistant sealants.
BACKGROUND OF THE INVENTION
Organosiloxane compositions that cure to yield crosslinked silicone rubber sealants by the reaction of polyorganosiloxanes containing at least two reactive groups per molecule with organosilicon compounds containing at least three reactive groups per molecule as the crosslinker are known. The reactive ingredients of these compositions are typically packaged in two containers with the crosslinker in one container and a reaction catalyst in a second container. The curing reaction occurs when the contents of the two containers are mixed.
Many approaches to flame resistance depend on the addition of several ingredients, including oxide fillers and platinum. For example, Wolfer et al. in U.S. Pat. No. 5,008,317 describe flame retardant and arc resistant silicone elastomers which contain an additive obtained by mixing a vinyl-rich polydiorganosiloxane, a metal oxide selected from titanium dioxide, zirconium dioxide, zinc oxide, Ce(III) oxide, Ce(IV) oxide, platinum, and an organosilicon compound having a basic nitrogen bonded to the silicon. DeLaTorre et al. in U.S. Pat. No. 4,102,852, describe a self-extinguishing room temperature vulcanizable silicone rubber composition comprising a silanol end-stopped polydiorganosiloxane polymer, a metal oxide filler, an alkoxy functional cross-linking agent, carbon black, platinum, and a titanium chelate catalyst.
SUMMARY OF THE INVENTION
The present inventors have discovered that curable organosiloxane compositions comprising a liquid polyorganosiloxane having at least two reactive groups selected from the group consisting of an alkoxy, a hydroxy, an alkenyl or alkynyl group; crosslinking agent, catalyst, reinforcing filler, and wollastonite, cure to form silicone rubber sealants having unexpectedly improved fire resistance properties. These cured silicone rubber sealants have very low heat release and form hard char structures on burning. The compositions of the present invention are useful in sealing constructions to prevent the passage of flames and air and other vapors.
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Alvarez Khristopher Edward
Shephard Kiersten Lynn
Boley William F.
Dow Corning Corporation
Moore Margaret G.
Warren Jennifer S.
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