Room temperature curable silicone sealant

Details Room temperature curable silicone sealant Room temperature curable silicone sealant

2001-01-19

2002-09-17

Dawson, Robert (Department: 1712)

Stock material or miscellaneous articles

Composite

Of silicon containing

C428S447000, C524S490000, C524S588000, C524S863000, C528S901000, C277S590000

Reexamination Certificate

active

06451440

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to one part, room temperature vulcanizable silicone sealants, and in particular to such sealants having both improved flowability and improved properties upon cure.
BRIEF DESCRIPTION OF THE RELATED ART
Silicone compositions that are storable under dry conditions and which, on exposure to moisture, cure to produce elastomers, are widely used as sealants and caulks in building and construction applications. These compositions are often referred to as one part, room temperature vulcanizable (“RTV”) compositions. They typically contain a moisture-curable polyorganosiloxane polymer, a filler, and a condensation cure catalyst. When used as sealants, they are typically packaged in a moisture impervious tube and applied to a substrate by extrusion from the packaging tube.
One approach to improving the performance properties of the elastomer formed from the sealant composition is to increase the amount of filler contained in the composition. However, increasing the filler content of the sealant composition also increases the viscosity of the composition, leading to difficulties in extrusion from the packaging. There accordingly remains a need in the art for a sealant composition having a viscosity that is sufficiently low to enable extrusion of the composition, but which does not at the same time limit the amount of filler that can be added to the composition.
SUMMARY OF THE INVENTION
The present invention relates to a curable silicone sealant composition comprising
a one-part, moisture-curable polysiloxane component comprising a mixture or reaction product of (i) a polysiloxane polymer having hydrolyzable substituent groups and (ii) a polyfunctional silicon compound having two or more hydrolyzable substituent groups,
a filler, and
a hydrocarbon fluid comprising, based on 100 parts by weight of the hydrocarbon fluid, greater than 40 parts by weight cyclic paraffinic hydrocarbons and less than 60 parts by weight noncyclic paraffinic hydrocarbons.
The composition is readily extrudable, and yet upon cure, exhibits improved tensile, elongation, and adhesive properties.
DETAILED DESCRIPTION OF THE INVENTION
In a preferred embodiment, the moisture-curable silicone sealant comprises, based on 100 parts by weight (“pbw”) of the sealant composition, from 20 pbw to 90 pbw, more preferably from 30 pbw to 75 pbw, even more preferably from 40 pbw to 60 pbw, of the moisture-curable organopolysiloxane polymer, from 1 pbw to 80 pbw, more preferably from 2 pbw to 78 pbw, even more preferably from 3 pbw to 65 pbw, of the filler, and from 1 pbw to 50 pbw, more preferably from 10 pbw to 40 pbw, even more preferably from 15 pbw to 35 pbw, of the hydrocarbon fluid.
The moisture-curable polysiloxane component comprises a mixture or reaction product of (i) a polysiloxane polymer having hydrolyzable substituent groups and (ii) a polyfunctional silicon compound having two or more hydrolyzable substituent groups. Suitable functional polysiloxanes comprises one or more silicone polymers or copolymers having structural units according to structural formula (I):
 R
a
SiO
4-a/2
  (I)
wherein each R is independently hydroxy, a hydrolyzable organic group, or a monovalent hydrocarbon radical, 0≦a≦4, and at least one R group per molecule is hydroxy or a hydrolyzable organic group, more preferably a hydroxy group.
Suitable hydrolyzable organic groups are those organic groups, for example, alkoxy, oximo, amino, aminoxy or acyloxy groups, that are capable of reacting under room temperature vulcanization conditions in the presence of moisture and a condensation cure catalyst to thereby allow moisture curing of the sealant composition.
Suitable monovalent hydrocarbon radicals include monovalent acyclic hydrocarbon radicals, monovalent alicyclic hydrocarbon radicals, and monovalent aromatic hydrocarbon radicals.
As used herein, the term “monovalent acyclic hydrocarbon radical” means a monovalent straight or branched chain hydrocarbon radical, preferably containing from 1 to 20 carbon atoms per radical, which may be saturated or unsaturated and which may, optionally, be substituted, for example with one or more halo groups. Suitable monovalent acyclic hydrocarbon radicals include, for example, alkyl radicals, for example, methyl, ethyl, sec-butyl, tert-butyl, octyl, dodecyl, stearyl and eicosyl, haloalkyl, such as trifluoropropyl, alkenyl radicals, for example, ethenyl and propenyl, and alkynyl radicals, such as, for example, propynyl and butynyl.
As used herein, the term “alicyclic hydrocarbon radical” means a radical containing one or more saturated hydrocarbon rings, preferably containing from 6 to 10 carbon atoms per ring, per radical which may optionally be substituted on one or more of the rings with one or more alkyl groups, each preferably containing from 2 to 6 carbon atoms per group and which, in the case of two or more rings, may be fused rings. Suitable monovalent alicyclic hydrocarbon radicals include, for example, cyclohexyl and cyclooctyl.
As used herein, the term “monocyclic aromatic hydrocarbon radical” means a hydrocarbon radical containing one aromatic ring per radical, which may optionally be substituted on the aromatic ring with one or more alkyl groups, each preferably containing from 2 to 6 carbon atoms per group. Suitable monovalent aromatic hydrocarbon radicals include, for example, phenyl, tolyl, xylyl, 2,4,6-trimethylphenyl, and naphthyl.
In one preferred embodiment, the polysiloxane polymer comprises a mixture of two or more linear polymers or copolymers having the structural formula (II):
wherein each R
1
, R
2
, R
3
, R
4
, R
5
, R
6
, R
7
, R
8
, R
9
, and R
10
is independently a hydrolyzable organic group or a monovalent hydrocarbon radical, at least one of R
1
, R
2
, R
3
, R
4
, R
5
, R
6
, R
8
, R
9
and R
10
per molecule is hydroxy, or at least two of R
1
, R
2
, R
3
, R
4
, R
5
, R
6
, R
7
, R
8
, R
9
and R
10
per molecule are hydrolyzable organic groups, and x and y are each numbers selected to provide a polymer that exhibits a viscosity of from 5,000 to 500,000 centiPoise (“cp”) at 25° C.
In a preferred embodiment, each R
1
, R
3
, R
4
, R
5
, R
6
, R
7
, R
8
and R
9
is independently (C
1
-C
8
)alkyl, fluoroalkyl or phenyl and each R
2
and R
10
is hydroxyl, (C
1
-C
8
)alkyl, fluoroalkyl or phenyl.
Suitable polyfunctional organosilicone compounds are those that contain at least two hydrolyzable groups per molecule. Suitable polyfunctional organosilicone compounds can be silanes or partially hydrolyzed products of silanes and include, for example, vinyltrimethoxysilane, tetramethoxysilane, methyltriethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methylphenyldiethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, methyl(tri(methylethylketoximo)silane, ethyl(tri(N,N-diethylamino)silane, methyltriacetoxysilane, ethyltriacetoxysilane, methyltri(N-methylacetamido)silane, n-propylorthosilicate and ethylpolysilicate, as well as dimers and trimers of such compounds.
In a preferred embodiment, the polyfunctional organosilicone compound has the structural formula (III):
R
11
4
Si   (III)
wherein each R
11
is independently a hydrolyzable group or a monovalent hydrocarbon radical, provided that at least one R
11
is H, alkoxy or alkenyl and that at least two R
11
groups are hydrolyzable groups.
In one preferred embodiment, at least three R
11
substituents are each alkoxy, oximo, amino, aminoxy or acyloxy, more preferably alkoxy or acyloxy, even more preferably (C
1
-C
8
)alkoxy or (C
1
-C
8
)acyloxy, and the remaining R
11
substituent, if any, is (C
1
-C
8
)alkyl, (C
2
-C
8
)alkenyl, aryl or fluoroalkyl. Preferred polyfunctional organosilicone compounds include, for example, vinyltrimethoxysilane, tetramethoxysilane, methyltriethoxysilane, methyltriacetoxysilane, ethyltriacetoxysilane, tetraethoxysilane, methyltrimethoxysilane, di-t-butoxydiacetoxysilane, or mixtures thereof.
The relative quantities of each of the silicone-containing components is readily determined by one of ordinary skill in the art.

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