US 4,711,928 AGranted

Moisture cured one-part RTV silicone sealant

AssigneeDow Corning Corporation

InventorsChi-long Lee, Myron T. Maxson

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Abstract

A method of producing a one-part silicone elastomeric sealant which has improved shelf life and an economical process of manufacture is disclosed. The method mixes a diorganovinylsiloxy endblocked polydiorganosiloxane, reinforcing filler, and a silazane. This reinforced base is then converted by reacting with a silane of the formula H[SiR.sub.2 OSiR.sub.2 CH.sub.2 CH.sub.2 ].sub.b SiR.sub.a (OR").sub.3-a where R is methyl, ethyl, propyl, phenyl or trifluoropropyl, R" is methyl or ethyl, a is 0 or 1, and b is 0 or 1 using a platinum catalyst. The result is a base containing an alkoxy functional polymer. This base is then mixed with alkoxy functional silane crosslinker and titanium catalyst to yield a composition which is stable in the absence of moisture for long periods of time in storage, but cures to an elastomer upon exposure to moisture. The improved shelf life is due to the presence of alkylene radicals between the penultimate silicon atom and the last silicon atom of the polymer.

Claims8

Dependent claims

A method of producing a one-part silicone sealant stable in the absence of moisture which cures on exposure to moisture having an in situ treated filler comprising

(A) mixing
(1) 100 parts by weight of a diorganovinylsiloxy endblocked polydiorganosiloxane where the viscosity of the siloxane is from 0.5 to 500 Pa.s at 25.degree. C.,
(2) from 5 to 100 parts by weight of a reinforcing filler having a surface area of from about 50 to 400 m.sup.2 /g, and
(3) from 0.5 to 4.0 parts by weight of a silazane of the formula (RR"'MeSi).sub.2 NH, where R is methyl, ethyl, propyl, phenyl, or trifluoropropyl, R'" is methyl or vinyl, and where, if vinyl is present, the ratio of methyl to vinyl is from 1:1 to 50:1, for each 10 parts of filler (2),
(B) heating the mixture to a temperature of 175.degree. C., with a nitrogen, purge over the container to treat the filler,
(C) cooling, then adding
(4) sufficient silane of the formula
H[SiR.sub.2 OSiR.sub.2 CH.sub.2 CH.sub.2 ].sub.b SiR.sub.a (OR").sub.3-a
where R is methyl, ethyl, propyl, phenyl or trifluoropropyl, R" is methyl or ethyl, a is 0 or 1, and b is 0 or 1, to give a ratio of 1 to 3 mols of silane per mol of vinyl radical in polydiorganosiloxane (1),
(5) from 1 to 50 parts by weight of platinum per million parts by weight of polydiorganosiloxane (1) as platinum catalyst, then heating for from 30 to 60 minutes at a temperature of from 65.degree. C. to 125.degree. C., then
(D) applying a vacuum and cooling to room temperature, then
(E) admixing in the absence of moisture,
(6) from 3 to 15 parts by weight of a crosslinker of the formula
R'.sub.a Si(OR").sub.4-a
where R' is methyl or phenyl, R" is methyl or ethyl, and a is 0 or 1 and
(7) from 0.2 to 2.0 parts by weight of a titanium catalyst, and
(F) storing the mixture in the absence of moisture.

14 more elements

Dependencies are inferred from the claim text.

Facts

Application: 06/835,578Filed 3 Mar 1986
Granted: 8 Dec 1987
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

C09K 3/1018
Characterised by the chemical nature of one of its constituents: macromolecular compounds having one or more carbon-to-silicon linkages
C08G 77/50
In which at least two but not all the silicon atoms are connected by linkages other than oxygen atoms: by carbon linkages
C08K 5/54
Use of organic ingredients: silicon-containing compounds
C09K 2003/1056
Materials or components characterised by specific properties: moisture-curable materials