U.S. patent application number 10/874512 was filed with the patent office on 2005-12-29 for highly elastomeric and paintable silicone compositions.
Invention is credited to Beers, Melvin Dale, Feng, Ta-Min, Mishra, Steve S..
Application Number | 20050288415 10/874512 |
Document ID | / |
Family ID | 35506851 |
Filed Date | 2005-12-29 |
United States Patent
Application |
20050288415 |
Kind Code |
A1 |
Beers, Melvin Dale ; et
al. |
December 29, 2005 |
Highly elastomeric and paintable silicone compositions
Abstract
Highly elastomeric, curable, paintable silicone compositions are
provided. The paintable silicone compositions comprise an
organopolysiloxane, a silicone functional crosslinker, and an
organic polymer. The highly elastomeric, curable, paintable
silicone compositions have an elongation of at least 150% and are
useful as paintable sealants and caulks.
Inventors: |
Beers, Melvin Dale; (US)
; Feng, Ta-Min; (US) ; Mishra, Steve S.;
(US) |
Correspondence
Address: |
CALFEE HALTER & GRISWOLD, LLP
800 SUPERIOR AVENUE
SUITE 1400
CLEVELAND
OH
44114
US
|
Family ID: |
35506851 |
Appl. No.: |
10/874512 |
Filed: |
June 23, 2004 |
Current U.S.
Class: |
524/425 ;
524/492 |
Current CPC
Class: |
C08G 77/26 20130101;
C08L 83/04 20130101; C09D 183/04 20130101; C08G 77/18 20130101;
C08G 77/16 20130101; C08L 75/04 20130101; C08G 77/14 20130101; C08L
101/10 20130101; C08L 83/04 20130101; C09D 183/04 20130101; C08L
75/04 20130101; C08L 75/04 20130101; C08K 5/544 20130101; C08K
5/544 20130101; C08L 83/00 20130101; C08L 83/00 20130101; C08L
2666/04 20130101; C08L 2666/14 20130101; C08G 77/20 20130101; C08K
5/544 20130101; C08L 83/04 20130101; C08L 83/04 20130101; C08L
83/00 20130101 |
Class at
Publication: |
524/425 ;
524/492 |
International
Class: |
C08K 003/26; C08K
003/34 |
Claims
We claim:
1. A curable silicone composition comprising: organopolysiloxane,
silicone functional crosslinker; and organic polymer; wherein the
curable silicone composition, once cured, can be painted without
fish eyes; and wherein the curable silicone composition, once
cured, has an elongation of at least 150%.
2. The curable silicone composition of claim 1 wherein the curable
silicone composition, once cured has an elongation of at least
200%.
3. The curable silicone composition of claim 2 wherein the curable
silicone composition, once cured, has an elongation of at least
800%.
4. A curable silicone composition comprising: a) from 50% to 95%
(by weight, based on total polymer) organopolysiloxane polymer; b)
from 1% to 10% (by weight, based on organopolysiloxane) silicone
functional crosslinker; and c) from 5% to 50% (by weight, based on
total polymer) dispersed organic polymer.
5. The curable silicone composition of claim 4 wherein the curable
silicone composition comprises from 55% to 93% by weight
organopilysiloxane polymer.
6. The curable silicone composition of claim 5 wherein the curable
silicone composition comprises from 57% to 91% by weight
organopilysiloxane polymer.
7. The curable silicone composition of claim 4 wherein the curable
silicone composition comprises from 7% to 45% by weight organic
polymer.
8. The curable silicone composition of claim 7 wherein the curable
silicone composition comprises from 9% to 43% by weight organic
polymer.
9. The curable silicone composition of claim 4 wherein the
organopolysiloxane polymer has at least two reactive functional
groups on the polymer chain.
10. The curable silicone of claim 9 wherein the reactive functional
groups are selected from the group consisting of hydroxyl, alkoxy,
silicone alkoxy, acyloxy, ketoximo, amino, amido, aminoxy,
alkenoxy, alkenyl, enoxy and mixtures thereof.
11. The curable silicone composition of claim 10 wherein the
reactive functional groups are end groups.
12. The curable silicone composition of claim 4 wherein the organic
polymer is selected from the group consisting of silylated
polyurethane, non-silylated polyurethane, silylated allylic
terminated polyether, a polyether that contains a silicone
functional group, a silylated and non-silated acrylic functional
polymer, a silylated and non-silated butyl functional polymer, and
copolymers and mixtures thereof.
13. The curable silicone composition of claim 12 wherein the
elongation of the silicone composition, once cured, is at least
150%.
14. The curable silicone composition of claim 13 wherein the
curable silicone composition, once cured, can be painted without
the formation of fish eyes.
15. The curable silicone composition of claim 4 wherein the curable
silicone composition, once cured, passes a paint adhesion tape
test.
16. A curable silicone composition comprising: a) from 50% to 95%
(by weight based on total polymer weight) organopolysiloxane
polymer; b) from 1% to 10% by weight silicone functional
crosslinker; and c) an organic polymer or oligomer, wherein the
organic polymer or oligomer is selected from the group consisting
of silylated polyurethane, silylated allylic terminated polyether,
polyether having a silicone functional group, silylated acrylic
multipolymer, butyl functional polymer, and combinations thereof;
wherein the ranges of organic polymer (by weight based on total
polymer) are from 15% to 50% for silylated polyurethane; from 15%
to 50% for non-silylated polyurethane; from 15% to 50% for
silylated allylic terminated polyether; from 15% to 50% silylated
allylic terminated acrylic polyether; from 15% to 50% for polyether
having a silicone functional group; from 10% to 50% for silylated
and non-silylated acrylic multipolymer; and from 5% to 50% for
silylated and non-silylated butyl functional polymer.
17. The curable silicone composition of claim 16 wherein the
organopolysiloxane has a molecular weight in the range from 20,000
to 100,000 grams/mole.
18. The curable silicone composition of claim 16 wherein the
organopolysiloxane has at least two reactive groups and an organic
polymer selected from the group consisting of silylated
polyurethane, non-silylated polyurethane, silylated allylic
terminated polyether, a polyether that contains a silicone
functional group, a silylated acrylic functional polymer, a
non-silylated acrylic functional polymer, a silylated acrylic
functional polymer, a non-silylated acrylic functional polymer, and
mixtures thereof.
19. The curable silicone composition of claim 18 wherein the
reactive groups are selected from end groups, pendant groups, and
combinations thereof.
20. The curable silicone composition of claim 16 wherein the
silicone crosslinker is selected from the group consisting of
oximes, alkoxysilanes, epoxyalkylalkoxysilanes, amido silanes,
aminosilanes, enoxysilanes, tetraethoxysilanes,
methyltrimethoxysilane, vinyltrimethoxysilane,
glycidoxypropyltrimethoxsilane, vinyltris-isopropenoxysilane,
methyltris-isopropenoxysilane, methyltris-cyclohexylaminosilane,
methyltris-secondarybutylaminosilane, condensation cure catalysts,
and combinations thereof.
21. The curable silicone composition of claim 20 wherein the
crosslinker is an oxime crosslinker.
22. The curable silicone composition of claim 21 wherein the oxime
crosslinker is selected from vinyltris-methylethylketoximosilane,
methyltris-methylethylketoximosilane, and combinations thereof.
23. The curable silicone composition of claim 16 wherein the
silicone composition is selected from the group consisting of
1-part curable compositions, 2-part curable compositions, and
combinations thereof.
24. The curable silicone composition of claim 16 wherein the
polyorganosiloxane is selected from the group consisting of
thermally curing systems and room temperature curing systems.
25. The curable silicone composition of claim 16 wherein the
composition comprises an extrusion or an in situ cured system.
26. The curable silicone composition of claim 16 further comprising
from 0.01% to 2% (by total weight) catalyst.
27. The curable silicone composition of claim 26 wherein the
catalyst is selected from the group consisting of metal salts of
carboxylic acids, organotitanates, platinum complexes, peroxides,
and combinations thereof.
28. The curable silicone composition of claim 27 wherein the
catalyst comprises metal salts of carboxylic acids selected from
the group consisting of dibutyltindilaurate, dibutyltindiacetate,
dimethyltindi-2-ethylhexanoate, and combinations thereof.
29. The curable silicone composition of claim 27 wherein the
catalyst comprises organotitanates selected from the group
consisting of tetrabutyltitanate, tetra-n-propyltitanate,
diisopropoxydi(ethoxyacetoace- tyl)titanate,
bis(acetylacetonyl)diisopropyl titanate and combinations
thereof.
30. The curable silicone composition of claim 27 wherein the
catalyst comprises a platinum complex.
31. The curable silicone composition of claim 27 wherein the
catalyst comprises a peroxide.
32. The curable silicone composition of claim 16 further comprising
from 3% to 60% (by total weight) reinforcement agents,
semi-reinforcing agents, or combinations thereof.
33. The curable silicone composition of claim 32 wherein the
reinforcement agent is selected from the group consisting of
hydrophobic treated fumed silicas, untreated fumed silicas,
hydrophobic precipitated calcium carbonates, ground calcium
carbonates, talc, zinc oxides, polyvinyl chloride powders, soft
acrylic polymers and combinations thereof.
34. The curable silicone composition of claim 16 further comprising
from 0.5% to 2% (by total weight) adhesion promoter.
35. The curable silicone composition of claim 16 wherein the
tensile elongation, once cured, is at least 150%.
36. The curable silicone composition of claim 35 wherein the
tensile elongation, once cured is at least 200%.
37. The curable silicone composition of claim 36 wherein the
tensile elongation, once cured is at least 800%.
38. The curable silicone composition of claim 16 wherein the
organic polymer is a silylated polyurethane polymer, wherein the
silylated polyurethane polymer is derived by the steps of a)
reacting a diisocyanate compound with a polyol to form an
intermediate, wherein the intermediate is selected from
isocyantates and hydroxyl terminated polyurethane prepolymers; and
b) silylating the intermediate.
39. The curable silicone composition of claim 38 wherein
intermediate is silylated with an organo functional silane having
one or more hydrolyzable groups.
40. The curable silicone composition of claim 39 wherein the
hydrolyzable group is selected from the group consisting of
(OCH.sub.3).sub.3, (OCH.sub.2CH.sub.3).sub.3, oximo, enoxy,
isopropenoxy, 5and combinations thereof.
41. The curable silicone composition of claim 39 wherein the organo
functional silane is of the formula: R"--X--Si--R'wherein R' is
selected from the group consisting of (OCH.sub.3).sub.3,
(OCH.sub.2CH.sub.3).sub.3- , CH.sub.3(OCH.sub.3).sub.2, or
CH.sub.3(OCH.sub.2CH.sub.3).sub.2, other hydrolyzable groups such
as oximo substituents, enoxy, and isopropenoxy; R" is selected from
the group consisting of amino, ureido, mercapto, isocyanato, and
epoxy; and X is C.sub.1 to C.sub.8.
42. The curable silicone composition of claim 38 wherein the
molecular weight of the polyurethane prepolymer intermediate ranges
from 5,000 to 50,000 g/mol.
43. The curable silicone composition of claim 38 wherein the
polyurethane prepolymer intermediate has a NCO:OH ratio in the
range from 1.4:1 to 3:1 or an OH:NCO ratio in the range from 1.4:1
to 3:1.
44. The curable silicone composition of claim 16 wherein organic
polymer is a silylated allylic terminated polyether; wherein the
silylated allylic terminated polyether is derived from the reaction
of a vinyl alkyl terminated polyol with a hydride functional
silane.
45. The curable silicone composition of claim 44 wherein the
hydride functional silane is selected from the group consisting of
triethoxysilane, trimethoxysilane, methyldiethoxysilane,
methyldimethylsilane and combinations thereof.
46. The curable silicone composition of claim 16 wherein the
organic polymer is a polyether having a silicone functional
group.
47. The curable silicone composition of claim 46 wherein the
silicone functional group is a hydrolyzable silane group.
48. The curable silicone composition of claim 46 wherein the
polyether having a silicone functional group has a molecular weight
that ranges from 2,000 to 50,000 g/mole.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a unique family of one and
two component highly elastomeric vulcanizable paintable silicone
sealants and extrusions exhibiting high elongation characteristics
combined with excellent adhesion and weathering resistance. They
can be designed to have a wide range of properties ranging from low
modulus to high strength self-adhering curable room temperature
vuclanizable (RTV) silicone compositions exhibiting superior
paintability and adhesion characteristics while maintaining the
outstanding weathering resistance of silicone elastomers.
BACKGROUND OF THE INVENTION
[0002] Silicone compositions are widely used in the construction
industry as well as other industrial applications, such as
automotive, electronics, aerospace and consumer markets because
these materials possess self-bonding adhesion properties to several
types of substrates such as glass, metal, ceramics, fabrics, wood,
leather, plastics and paper. In addition, superior properties such
as low temperature flexibility, high-temperature stability, good
electrical insulation and resistance to chemicals and UV resistance
are inherent in silicone-based products. Thus, silicone extrusions
are widely used in a variety of applications. A disadvantage of
cured silicone compositions, however, is that they are considered
to be unpaintable. The low surface energy of the silicone prevents
latex or oil based paints to wet the surface of the cured silicone.
The paint tend to shrink away from the silicone surface leaving a
poor surface appearance commonly referred to in the industry as
"fish eyes."
[0003] Attempts to improve paintability of silicone compounds have
been made by adding inorganic fillers to the uncured silicone. For
example, silicone sealants have been formulated with the addition
of acicular, i.e. needle-like, calcium carbonate to the
polyorganosiloxane. In such sealants, the acicular particles become
oriented on the surface of the sealant during curing. The surface
of the cured sealant has improved paintability, but the addition of
the acicular calcium carbonate results in other problems such as
low elasticity. The generally high loading of calcium carbonate
necessary to achieve improved paintability deleteriously affects
the elasticity of the silicone sealant such that its tensile
elongation is lower than desired.
[0004] Plasticizer can be added to counter the negative effect of
calcium carbonate on the extensibility of the silicone. However,
plasticizers detract from the paintability of the silicone
sealant.
[0005] It is desirable to provide a curable silicone composition
that, once cured, is paintable by many types of coatings. It is
also desirable to provide silicone extrusions, sealants, adhesives,
and caulks that are paintable over an extended period of time and
which maintain the excellent elastomeric and other properties
inherent in silicone.
SUMMARY OF THE INVENTION
[0006] The organopolysiloxane compositions of the present invention
comprise an organic polymer, an organic oligomer, or combinations
of an organic polymer and an organic oligomer; an
organopolysiloxane polymer; and a crosslinker. The compositions may
further comprise other additives to modify the properties of the
organopolysiloxanes. The organic polymer can be a homopolymer, a
copolymer and mixtures thereof having reactive or non-reactive
terminal groups. It has been discovered that such compositions,
when cured, produce a silicone sealant that exhibits excellent
paintability and superior weathering properties.
[0007] The silicone compositions of the present invention, once
cured, can be painted without the formation of "fish eyes" on the
painted surface, and has an elongation of at least 150%. The
elongation of the cured silicone composition may be 200% or
greater, 800% or greater, or even 1000% or greater.
[0008] The curable silicone compositions of the present invention
generally contain from about 50% to about 95% (by weight, based on
total polymer) organopolysiloxane polymer; from about 1% to about
10% (by weight, based on organopolysiloxane) silicone functional
crosslinker; and from about 5% to about 50% (by weight, based on
total polymer) dispersed organic polymer. Preferably, the curable
silicone compositions comprise from 55% to 93% by weight
organopolysiloxane polymer. More preferably, the curable silicone
compositions comprise from 57% to 91% by weight organopolysiloxane
polymer.
[0009] Preferably, the curable silicone compositions of the present
invention comprise from 7% to 45% by weight organic polymer. More
preferably, the curable silicone compositions comprise from 9% to
43% by weight organic polymer.
[0010] The organopolysiloxane polymers preferably have at least two
reactive functional groups on the polymer chain. The reactive
functional groups may be from hydroxyl, alkoxy, silicone alkoxy,
acyloxy, ketoximo, amino, amido, aminoxy, alkenoxy, alkenyl, enoxy
and mixtures thereof. The reactive functional groups are end
groups, pendant groups, or a combination thereof.
[0011] The organic polymer used in the curable silicone
compositions of the present invention may be selected silylated and
non-silylated polyurethanes, silylated allylic terminated
polyethers, polyethers containing one or more silicone functional
groups, silylated and non-silylated acrylic functional polymers,
silylated and non-silylated butyl functional polymers, and
copolymers and mixtures thereof.
[0012] The amount of organic polymer used in preparing the
paintable, curable silicone compositions of the present invention
depends on the organic polymer used. The organic polymer is added
by weight, based on total polymer, and ranges from about 15% to
about 50% for silylated and non-silylated polyurethane; from about
15% to about 50% for silylated allylic terminated polyether; from
about 15% to about 50% silylated allylic terminated acrylic
polyether; from about 15% to about 50% for polyether having a
silicone functional group; from about 10% to about 50% for
silylated and non-silylated acrylic multipolymer; and from about 5%
to about 50% for silylated and non-silylated butyl functional
polymer.
[0013] The organopolysiloxane used in the present invention
preferably has a molecular weight in the range from 20,000 to
100,000 grams/mole. The organopolysiloxane has at least two
reactive groups and an organic polymer selected from the group
consisting of silylated polyurethane, non-silylated polyurethane,
silylated allylic terminated polyether, a polyether that contains a
silicone functional group, a silylated acrylic functional polymer,
a non-silylated acrylic functional polymer, a silylated butyl
functional polymer, a non-silylated butyl functional polymer, and
mixtures thereof. The reactive groups may be selected from end
groups, pendant groups, and combinations thereof.
[0014] The silicone crosslinker used in the paintable, curable
silicone compositions of the present invention may be selected from
such crosslinkers as oximes, alkoxysilanes,
epoxyalkylalkoxysilanes, amido silanes, aminosilanes, enoxysilanes,
tetraethoxysilanes, methyltrimethoxysilane, vinyltrimethoxysilane,
glycidoxypropyltrimethoxsi- lane, vinyltris-isopropenoxysilane,
methyltris-isopropenoxysilane, methyltris-cyclohexylaminosilane,
methyltris-secondarybutylaminosilane, condensation cure catalysts,
and combinations thereof. Preferred oxime crosslinkers include
vinyltrismethylethylketoximosilane,
methyltrismethylethylketoximosilane, and combinations thereof.
[0015] In accordance with the present invention, the paintable,
curable silicone compositions may be 1-part curable compositions or
2-part curable compositions. The paintable, curable silicone
composition may be either thermally curing systems and room
temperature curing systems. The paintable, curable silicone may be
an extrusion or in situ cured systems.
[0016] The paintable, curable silicone compositions of the present
invention may further comprise from about 0.01% to about 2% (by
total weight) catalyst. Suitable catalysts include metal salts of
carboxylic acids, organotitanates, platinum complexes, peroxides,
and combinations thereof. Preferred catalysts comprising metal
salts of carboxylic acids include dibutyltindilaurate,
dibutyltindiacetate, dimethyltindi-2-ethylhe- xanoate, and
combinations thereof. Preferred organotitanates include
tetrabutyltitanate, tetra-n-propyltitanate,
diisopropoxydi(ethoxyacetoace- tyl)titanate,
bis(acetylacetonyl)diisopropyl titanate and combinations
thereof.
[0017] The paintable, curable silicone composition may further
include from about 3% to about 60% (by total weight) reinforcement
agents, semi-reinforcing agents, or combinations thereof. Some
preferred reinforcement agents include hydrophobic treated fumed
silicas, untreated fumed silicas, hydrophobic precipitated calcium
carbonates, ground calcium carbonates, talc, zinc oxides, polyvinyl
chloride powders, soft acrylic polymers and combinations thereof.
The paintable, curable silicone compostions may further comprise
from about 0.5% to about 2% (by total weight) adhesion
promoter.
[0018] A preferred organic polymer used in the paintable, curable
silicone compositions is a silylated polyurethane polymer. This
silylated polyurethane polymer may be derived by the steps of a)
reacting a diisocyanate compound with a polyol to form an
intermediate, wherein the intermediate is selected from
isocyantates or hydroxyl terminated polyurethane prepolymers; and
b) silylating the intermediate. Preferably, the intermediate is
silylated with an organo functional silane having one or more
hydrolyzable groups. Some preferred hydrolyzable groups include
1
[0019] (OCH.sub.3).sub.3, (OCH.sub.2CH.sub.3).sub.3, oximo, enoxy,
isopropenoxy,
[0020] and combinations thereof.
[0021] Preferably, the organo functional silane is of the
formula:
R"--X--Si--R'
[0022] wherein R' is selected from the group consisting of
(OCH.sub.3).sub.3, (OCH.sub.2CH.sub.3).sub.3,
CH.sub.3(OCH.sub.3).sub.2, or CH.sub.3(OCH.sub.2CH.sub.3).sub.2,
other hydrolyzable groups such as oximo substituents, enoxy, and
isopropenoxy; R" is selected from the group consisting of amino,
ureido, mercapto, isocyanato, and epoxy; and X is C.sub.1 to
C.sub.8. The molecular weight of the polyurethane prepolymer
intermediate ranges from 5,000 to 50,000 g/mol. The polyurethane
prepolymer intermediate has a NCO:OH ratio in the range from 1.4:1
to 3:1 or an OH:NCO ratio in the range from 1.4:1 to 3:1.
[0023] The organic polymer may also be silylated allylic terminated
polyether; wherein the silylated allylic terminated polyether is
derived from the reaction of a vinyl alkyl terminated polyol with a
hydride functional silane. Preferably, the hydride functional
silane is selected from the group consisting of triethoxysilane,
trimethoxysilane, methyldiethoxysilane, methyldimethylsilane and
combinations thereof.
[0024] The organic polymer may also be a polyether having a
silicone functional group. Preferably, when the organic polymer is
a polyether having a silicone functional group, the silicone
functional group is a hydrolyzable silane group. Preferable
polyethers having a silicone functional group are those having a
molecular weight in the range from about 2,000 to about 50,000
g/mole.
[0025] The present invention also relates to the methods of making
such curable silicone sealant compositions.
DETAILED DESCRIPTION OF THE INVENTION
[0026] The organopolysiloxane compositions of the present invention
are comprised of a reactive organopolysiloxane polymer, a polymer
phase comprising an organic polymer/oligomer having limited
compatibility with the reactive organopolysiloxane polymer and a
silicone functional cross-linking system. The organic
polymer/oligomer phase may contain reactive organosilyl terminal
groups which can enter into a vulcanization reaction with the
silicone functional crosslinking system attached to the reactive
organopolysiloxane polymer. To maintain the superior weathering
resistance of typical elastomeric silicones and excellent
paintability unlike normal silicone elastomers, the concentration
of the organic polymer/oligomer must be maintained within precise
ranges. Both elevated and depressed levels of the organic
polymer/oligomer phase will cause a loss of good paintability. The
outstanding weathering resistance of these compositions has been
demonstrated by the lack of surface degradation after more than
20,000 hours exposure in a Xenon Arc Weatherometer as discussed
below. The compositions of the present invention may be painted by
a variety of paints, even after curing for several weeks while
maintaining the excellent elastomeric properties inherent in
silicone.
[0027] As used herein, the phrase "semi-compatible organic
polymer/oligomer" encompasses organic polymers and oligomers that
are not fully compatible with the organopolysiloxanes used in the
present invention, i.e., the semi-compatible organic
polymers/oligomers are not fully miscible with the
organopolysiloxanes of the present invention.
[0028] The paintable silicone composition of the present invention
is generally made by blending a semi-compatible organic
polymer/oligomer, a cross-linker, and other additives generally
used in silicone sealants and extrusions in the presence of a
reactive polysiloxane fluid.
[0029] The curable organopolysiloxane composition of the present
invention comprises a reactive organopolysiloxane polymer, a
semi-compatible organic polymer/oligomer, a crosslinker, and
optionally may include an adhesion promoter, a reinforcement agent,
a rheology modifier, a chain extender, and so forth. Once the
composition is reacted, the resulting silicone sealant is paintable
even after having been cured for a prolonged period.
[0030] The curable organopolysiloxane composition comprises by
weight from about 5% to about 50%, preferably from about 7% to
about 45%, and even more preferably from about 9% to about 43%
organic polymer/oligomer, from about 50% to about 95%, preferably
from about 55% to about 93%, even more preferably from about 57% to
about 91% organopolysiloxane polymer. When cured, the paintable
silicone composition has an elongation of at least 150%, and up to
200%, 400%, and even greater than 800%. The paintable silicone
compositions described herein have been shown to have elongations
of greater than 1000%.
[0031] The polyorganosiloxane generally contains at least two
reactive functional groups on the polymer chain, preferably at the
terminal portion thereof, i.e., preferably the reactive functional
groups are end-groups. The polyorgansiloxanes useful in this
invention are those which contain a condensable functional group
which can be an hydroxyl group, or hydrolyzable group such as a
silicon-bonded alkoxy group, acyloxy group, ketoximo group, amino
group, amido group, aminoxy group, an alkenoxy group, and so
forth.
[0032] The organopolysiloxane polymer is of the formula: 2
[0033] where R.sup.1 and R.sup.2, independently, are an alkyl
having from 1 to 8 carbon atoms, desirably from 1 to 4 carbon atoms
with methyl being preferred, or is an aromatic group or substituted
aromatic group having from 6 to 10 carbon atoms with phenyl being
preferred, and "n" is such that the weight average molecular weight
of the organopolysiloxane is from about 10,000 to about 200,000 and
desirably from about 20,000 to about 100,000 grams/mole. It is to
be understood that the above polymers also contain, as noted above,
two or more reactive functional groups (X) therein. The functional
groups, independently, can be OH, or OR.sup.3, or N(R.sup.4).sub.2,
enoxy, acyloxy, oximo, or aminoxy, wherein these functional groups
may have substituents at any substitutable location. For example,
3
[0034] wherein R.sup.3 through R.sup.14 are, independently, an
alkyl or cycloalkyl having from about 1 to about 8 carbon
atoms.
[0035] The organopolysiloxane of the present invention may be
depicted as 4
[0036] The one or more R groups, independently, is an alkyl having
from 1 to 8 carbon atoms or an aromatic or an alkyl-aromatic having
from 6 to 20 carbon atoms and optionally containing one or more
functional groups thereon, such as amine, hydroxyl, alkene, alkoxy,
and so forth. The amount of the functional groups, i.e., m, is 1, 2
or 3.
[0037] The reactive functional group (X), can be OH, or OR', or
N(R'), or enoxy, or acyloxy, or oximo, or aminoxy, or amido,
wherein the reactive functional group may have substitutions, R',
at any substitutable C or N, and which is selected from the group
consisting of an alkyl having from about 1 to about 8 carbon atoms,
an aromatic, an alkyl-aromatic having from 6 to 20 carbon atoms,
and wherein R' may optionally contain one or more functional groups
thereon such as amine, hydroxyl, and so forth. An
organopolysiloxane fluid can furthermore contain a blend of two or
more different polysiloxanes and/or organopolysiloxanes having
different molecular weights. The polysiloxanes are generally a
viscous liquid and are commercially available from several silicone
manufacturers such as Wacker Corporation, General Electric, Dow
Corning and Rhone-Poulenc.
[0038] The paintable sealant compositions of the present invention
are cured by generally subjecting them to moisture or a curative.
Either a conventional one-component or two-component cure system
can be utilized. In a conventional one-component cure, the
organopolysiloxane is converted to a compound having an alkoxy, an
oxime, an enoxy, an amido, an amino, or an acetoxy blocking group
in a manner well known to the art and to the literature.
Conventional condensation catalysts may be utilized, such as an
organotin, for example, dibutyltindilaurate, dibutyltindiacetate,
dimethyltindi-2-ethylhexanoate, or dimethylhydroxytinoleate, or an
organotitanate.
[0039] The semi-compatible organic polymers/oligomers used in
accordance with the present invention are generally organic
polymers included in any of a variety of well known polymers having
non-reactive or reactive functional groups, or polymers with no
functional groups, and which can be intermixed with reactive
organopolysiloxane polymer. The organic polymer can be a
homopolymer, a copolymer or mixtures thereof and the polymer can be
a crosslinking or a non-crosslinking polymer. Organic polymers
include aromatic and aliphatic polyurethanes, polyurea, polyether,
polyester, acrylic, polystyrene, styrene butadiene, polybutadiene,
butyl rubber, with or without other organo functional groups
attached to then, and mixtures thereof. Aromatic and aliphatic
polyurethanes may have different backbones such as polyester,
polyether, polyacrylate, polybutadiene, polycarbonate, and so
forth, or a combination thereof. Futhermore, they could also have
other functional groups, such as acrylates, amides, maleic
anhydride, and so forth.
[0040] Another suitable organic polymer is a reactive silylated
aromatic or aliphatic polyurethane polymer from the above general
polyurethane category. Polyurethane prepolymers whose terminal ends
are partially, or fully, end-capped with either silane groups or
with a combination of silane groups and end capping groups that
have been derived from one or more aromatic alcohols, or one or
more aliphatic alcohols, or a combination of one or more aromatic
alcohols and one or more aliphatic alcohols.
[0041] Examples of suitable silanes corresponding to the
above-mentioned system include N-phenylaminopropyltrimethoxysilane,
N-ethylaminoisobutyltrimethoxysilane,
.gamma.-aminopropyltrimethoxysilane- ,
.gamma.-aminopropyltriethoxysilane, and the reaction product of an
aminosilane (such as .gamma.-aminopropyltrimethoxysilane,
.gamma.-aminopropyltriexthoxysilane,
.gamma.-aminopropylmethyldimethoxysi- lane) with an acrylic monomer
(such as ethyl acrylate, 2-ethylhexyl acrylate, methyl acrylate,
methyl methacrylate, and glycidal acrylate), mercaptosilane, the
reaction product of a mercaptosilane with a monoepoxide, the
reaction product of an epoxysilane with a secondary amine,
isocyanato propyl triethoxy silane, and ureido propyl trimethoxy
silane.
[0042] In another embodiment of the invention the organic polymer
is a silylated allylic terminated linear or branched polyether. The
polyether backbone may have other functional groups, such as
acrylates, amides, maleic anhydride, and so forth. The polymers'
terminal ends could be partially or fully end-capped either with
silane groups or with a combination of silane groups and other
end-capping groups.
[0043] Another suitable class of organic polymer/oligomer are
reactive silylated polyols. These polyols may be selected from
polyester, polyether, polyacrylate, polybutadiene, polycarbonate,
and so forth. The silylation may be done as discussed above.
[0044] Optionally, the blocked one-component cure system can
contain crosslinking agents as set forth herein. In a two-component
cure system, crosslinking agents, such as a multi-functional alkoxy
silane or oligomers thereof and catalysts are kept separate from
the organopolysiloxane until reaction. The amount of catalyst for
the two-component system is generally higher than in the
one-component system. Such cure systems are well known to the art,
see, e.g., Maurice Morton, et al., Rubber Technology, 3.sup.rd Ed.,
pp. 406-407, (1987), which is hereby fully incorporated by
reference. When a two part cure is used, the two-part cure may
either be a room-temperature curable or a thermally curing
material.
[0045] While a variety of conventional crosslinkers are suitable,
oxime and alkoxy crosslinkers are preferred, such as, for example,
vinyltris-methylethylketoximosilane, and
methyltris-methylethylketoximosi- lane, and alkoxysilanes such as
methyltrimethoxysilane and vinyltrimethoxysilane.
Methyltrimethoxysilane is available, for example, under the trade
name A-1630 and vinyltrimethoxysilane is available, for example,
under the trade name A-171 from General Electric-OSI Specialties.
Methyltris-methylethylketoximosilane (MOS) is available under the
trade name OS-1000, for example, and vinyl
tris-methylketoximosilane under the trade name of OS-2000 by
Honeywell Corporation, for example. Other crosslinkers are also
suitable, such as alkoxysilanes, epoxyalkylalkoxysilanes,
amidosilanes, aminosilanes, enoxysilanes and the like, as well as
tetraethoxysilanes, glycidoxypropyltrimethoxsilane,
vinyltris-isopropenoxysilane, methyltris-isopropenoxysilane,
methyltris-cyclohexylaminosilane, and
methyltris-secondarybutylaminosilane. Mixtures of crosslinkers may
also be employed. The amount of the crosslinking agent is generally
from about 0.2 to about 20 parts by weight, desirably from about 1
to about 10 parts by weight, and preferably from about 1.5 to about
6.5 parts by weight for every 100 parts by weight of said
copolymer-organopolysiloxane. Addition cure crosslinkers may also
be used in conjunction with alkenyl functional organopolysiloxane
polymers. These crosslinkers may be pre-reacted to the
polyorganosilane polymers.
[0046] The crosslinker is used in amounts which are conventionally
used for making curable silicone elastomeric compositions. Those
skilled in the art may determine the proper amounts for
room-temperature curable and thermally curable crosslinkers. The
amounts used will vary depending upon the particular crosslinker
chosen and the properties of the cured elastomer desired, and may
readily be determined by those of ordinary skill in the art.
[0047] A mixture of polyorganosiloxane and crosslinker will usually
cure at room temperature when exposed to moisture, however,
sometimes it is desirable to accelerate the cure rate, i.e., reduce
the time to cure composition. In these situations a catalyst may be
used. Preferred catalysts include metal salts of carboxylic acids
such as dibutyltindilaurate, dibutyltindiacetate, and
dimethyltindi-2-ethylhexano- ate; organotitanates such as
tetrabutyltitanate, tetra-n-propyltitanate,
diisopropoxydi(ethoxyacetoacetyl)titanate, and
bis(acetylacetonyl)diisopr- opyltitanate. Alternatively, thermally
curable materials may be used in addition to or in place of the
room-temperature curable systems.
[0048] The paintable sealant compositions described herein become
tack free in generally about 0.05 to about 12 hours, desirably from
about 0.1 to about 2 hours once the cure is initiated. The sealants
become substantially cured, i.e., chemically crosslinked, in about
7 days, although this may vary depending upon the curing system,
depth of cure, and particularly the catalyst employed. The sealants
are typically completely cured at about 21 days at 25.degree. C.
and 50% relative humidity. However, in the case of extruded
materials, they would be vulcanized as they come out from the
extruder.
[0049] The curable silicone compositions described herein may be
made to pass a "paint adhesion tape test." In accordance with this
specification, the "paint adhesion tape test" is set forth as ASTM
test method D3359 and is performed as follows. The sealant
composition is adhered to a surface and painted. A crisscross,
i.e., cross-hatches, are cut through the paint and sealant layers
using a razor blade. A 0.5-inch wide by 4-inch long strip of clear
Scotch.RTM. brand adhesive tape (3M Corp.) is firmly applied across
the pre-cut crisscross area. The tape, which is tenaciously adhered
to the painted surface, is then pulled away at a 90.degree. angle.
If the paint remains intact on the surface of the sealant it is
considered to have passed the test.
[0050] Optionally, an adhesion promoter may be added to the
paintable sealant. The amount of adhesion promoter may readily be
determined by those of ordinary skill in the art. The amount of the
adhesion promoter in the paintable sealant is generally from 0 to
about 10, desirably from about 1 to about 8, preferably from about
2 to about 6, and more preferably from about 1.5 to about 3 parts
by weight per 100 parts of organosilicone polymer.
[0051] The adhesion promoter, although optional, is highly
preferred; the adhesion promoter provides the sealant with
long-term adhesion to the substrate. Suitable classes of adhesion
promoters are aminoalkyl, mercaptoalkyl, ureidoalkyl, carboxy,
acrylate and isocyanurate functional silanes. Examples of suitable
adhesion promoters are mercaptopropyltrimethoxysilane,
glycidoxypropyltrimemethoxysilane, aminopropyltriethoxysilane,
aminopropyltrimethoxysilane, aminoethylaminopropyltrimethoxysilane,
ureidopropyltrimethyloxysilane,
bis-.gamma.-trimethoxysilylpropylurea,
1,3,5-tris-.gamma.-trimethyloxysil- ylproplisocyanurate,
bis-.gamma.-trimethoxysilylpropylmaleate and fumarate and
.gamma.-methacryloxypropyltrimethoxysilane.
[0052] Optionally, reinforcing agents may be added to the paintable
sealant compositions of the present invention. The amount of the
reinforcing agent is generally from 0 to about 250, desirably from
about 30 to about 200, preferably from about 20 to about 150, and
more preferably from about 10 to about 100 parts by weight of
polymer.
[0053] The reinforcing agents are optional, although highly
preferred, particularly when the sealant is used as a caulk.
Reinforcing agents increase tensile strength in the cured sealant
and reduce sag of the uncured sealant. The reinforcing agent also
functions as a thixotrope. Such reinforcing agents are finely
divided particulates and include both the conventionally known
reinforcing agents and semi-reinforcing agents, typically having a
particle size less than about 10 microns, preferably about 5
microns or less, more preferably about 0.1 microns or less.
Suitable reinforcing agents include hydrophobic treated fumed
silicas, such as TS 720 from Cabot Corporation, or R-972 from
Degussa Corporation, hydrophobic precipitated calcium carbonates,
talc, zinc oxides, polyvinyl chloride powders, and soft acrylates
such as those of U.S. Pat. No. 6,403,711B1, incorporated herein by
reference. Other ingredients can also be utilized in the sealant
formulation in amounts up to about 20 parts by weight and desirably
from about 0.01 to about 15 parts by weight per 100 parts by weight
of the copolymer and the organopolysiloxane. Such ingredients
include fungicides. Moreover, extender fillers such as ground
calcium carbonates and diatomaceous earth are optionally employed.
Such extenders have minimal or no reinforcing effect and/or minimal
or no thixotropic effect.
[0054] UV stabilizers may also optionally be added. Pigments or
colorants such as titanium dioxide, iron oxide, carbon black are
optionally employed to impart color to the sealant and/or to act as
ultraviolet stabilizer. LTV inhibitors, anitozonates are also
optionally added.
[0055] The sealant in its uncured state may optionally contain
solvents such as organic solvents to reduce the viscosity.
EXAMPLES
Example 1
[0056] In this example, about 43% organic polymer (based on the
total weight of organic and inorganic polymer) was used to prepare
a medium modulus sealant with a shore-A of 15. The organic polymer
comprised a silyl terminated polyurethane. The amounts are listed
in Table 1 below.
1TABLE 1 Weight Composition Percent 2400 cps. silanol terminated
dimethylpolysiloxane 10.44 50,000 cps. silanol terminated
dimethylpolysiloxane polymer 23.43 Soft acrylic filler (thixotrope)
19.38 Hydrophobic treated precipitated calcium carbonate 5.86
Hexamethyldisilazane 0.35 Hydrophobic treated ground calcium
carbonate 2.34 Acrylic functional plasticizer 7.14
Dimethylbis-secondary butylaminosilane 0.64
Methyltris-methylethylketoximosilane 3.99 A trimethoxysilylalkyl
terminated polyurethane 25.56 Aminoethylaminopropyltrimethoxysilane
0.86 Dibutyltindilaurate 0.01 TOTAL 100.00
[0057] The above composition was painted after curing, yielding a
smooth painted surface having no "fish eyes." The above composition
passed the paint adhesion test, as described in the specification.
This composition also maintained excellent weatherability as
demonstrated with no surface cracks and no change in shore-A, even
after more than 20,000 hours of UV exposure in the Xenon
weatherometer.
Example 2
[0058] In this example, about 29% (by weight, based on total
polymer) organic polymer was used to prepare a medium modulus
sealant with a shore-A of 15. The organic polymer comprised a silyl
terminated polyether polymer as shown in Table 2. This composition
was designed to give a paintable fast curing silicone sealant
having medium modulus properties combined with excellent adhesion
properties on plastics, glass and anodized aluminum.
2TABLE 2 Weight Composition Percent 50,000 cps. silanol terminated
dimethylpolysiloxane polymer 25.46 20,000 cps. silanol terminated
dimethylpolysiloxane polymer 16.97 Hydrophobic treated precipitated
calcium carbonate 33.94 Hexamethyldisilazane 0.85
Dimethylbis-secondary butylaminosilane 2.25
Vinyitris-methylethylketoximosilane 1.70 Alkoxy silyl terminated
polyether 16.97 Aminoethylaminopropyltr- imethoxysilane 1.80
Dibutyltindiacetate 0.06 TOTAL 100.00
[0059] The unpainted composition upon curing had a tack free of
time of 15 minutes accompanied by tooling time of 9 minutes. It
underwent more than 20,000 hours of weathering tests in the Xenon
Arc Weatherometer without any observable surface changes taking
place. The sealant had excellent paintability. Laboratory studies
indicated that the sealant retained its paintability
characteristics indefinitely as shown by periodic paintability
tests carried over a period of 79 days. The painted composition was
smooth and had no "fish eyes."
Example 3
[0060] In this example, about 24% (by weight, based on total
polymer) organic polymer was used to prepare a medium modulus
sealant. The organic polymer comprised a silyl terminated polyether
polymer as shown in Table 3, below.
3TABLE 3 Weight Composition Percent 50,000 cps. silanol terminated
dimethylpolysiloxane polymer 3.83 20,000 cps. silanol terminated
dimethylpolysiloxane polymer 34.51 2400 cps. silanol terminated
dimethylpolysiloxane polymer 4.02
Vinyltris-methylethylketoximosilane 1.53
Dimethylbis-secondarybutylaminosilane 2.037 Hexamethyldisilazane
0.84 Hydrophobic treated precipitated calcium carbonate 30.68 Soft
acrylic filler 7.48 Alkoxy silyl terminated polyether polymer 13.42
Aminopropyltriethoxysilane 1.63 Dibutyltindiacetate 0.023 TOTAL
100.00
[0061] The above composition was painted after curing, yielding a
smooth painted surface having no "fish eyes." The above composition
also passed the paint adhesion test while maintaining excellent
weatherability as demonstrated with no surface cracks and no change
in shore-A, even after more than 20,000 hours of UV exposure in the
Xenon weatherometer.
Example 4
[0062] In this example, about 26% (by weight, based on total
polymer) organic polymer was used to prepare a medium modulus
sealant. The organic polymer comprised an MDI terminated
polyurethane polymer as shown in Table 4, below.
4TABLE 4 Weight Composition Percent 50,000 cps. silanol terminated
dimethylpolysiloxane polymer 26.12 20,000 cps. silanol terminated
dimethylpolysiloxane polymer 17.41
Vinyltris-methylethylketoximosilane 2.394
Dimethylbis-secondarybutylaminosilane 1.22 Hexamethyldisilazane
0.871 Hydrophobic treated precipitated calcium carbonate 34.83 MDI
terminated polyurethane prepolymer 15.24 Aminopropyltriethoxysilane
1.85 Dibutyltindiacetate 0.065 TOTAL 100.00
[0063] The above composition was painted after curing, yielding a
smooth painted surface having no "fish eyes." The above composition
also passed the paint adhesion test while maintaining excellent
weatherability as demonstrated with no surface cracks after UV
exposure of more than 20,000 hours in the Xenon Weatherometer.
Example 5
[0064] In this example, about 31% (by weight, based on total
polymer) organic oligomer was used to prepare a silicone sealant.
The organic oligomer comprised an oximo silane terminated polyether
polyol as shown in Table 5, below. The oximo silane terminated
polyether polyol was prepared by prereacting it with
vinyl-methylethylketoximosilane.
5TABLE 5 Weight Composition Percent 50,000 cps. silanol terminated
dimethylpolysiloxane polymer 24.90 20,000 cps. silanol terminated
dimethylpolysiloxane polymer 16.60
Vinyltris-methylethylketoximosilane 2.90 Oximo silane terminated
polyether polyol 17.43 Dimethylbis-secondarybutylaminosilane 2.20
Hexamethyldisilazane 0.95 Hydrophobic treated precipitated calcium
carbonate 33.20 Aminopropyltriethoxysilane 1.76 Dibutyltindiacetate
0.06 Total 100.00
[0065] The above composition was painted after curing, yielding a
smooth painted surface having no "fish eyes." The above composition
also passed the paint adhesion test while maintaining excellent
weatherability as demonstrated with no surface cracks and no change
in shore-A, even after more than 20,000 hours of UV exposure in the
Xenon weatherometer.
Example 6
[0066] In this example, about 15% (by weight, based on total
polymer) organic polymer was used to prepare a paintable sealant.
The sealant had a Shore-A Hardness of 40, accompanied by an
elongation of 760% and tensile strength of 220 psi. The organic
polymer comprised an acrylic terpolymer and polyether polyol as
shown in Table 6, below.
6TABLE 6 Weight Composition Percent 50,000 cps. silanol terminated
dimethylpolysiloxane polymer 24.42 20,000 cps. silanol terminated
dimethylpolysiloxane polymer 16.28 Hydrophobic precipitated calcium
carbonate 32.56 Ground calcium carbonate 7.79 Talc 0.90 Titanium
dioxide 0.26 Hexamethyldisilazane 0.81
Dimethylbis-secondarybutylam- inosilane 2.16
Vinyltris-methylethylketoximosilane 1.63 Ethyl acrylate
acrylonitrile acrylic acid terpolymer 6.81 Polyether polyol 0.20
Butyl benzyl phthalate 0.77 Solvent 2.77 Ceramic fiber 0.85
Aminoethylaminopropyltrimethoxysila- ne 1.73 Dibutyltindiacetate
0.06 Total 100.00
[0067] After curing, the above sealant was painted with acrylic
latex paint. The painted surface was smooth, and showed no fish
eyes. Three days after painting, the surface was subjected to the
paint adhesion test, described above without any paint removal
taking place.
Example 7
[0068] In this example, about 9% (by weight, based on total polymer
weight) organic polymer was used to prepare a paintable sealant. It
had a Shore-A Hardness of 43, accompanied by an elongation of 355%
and a tensile strength of 300 psi. The organic polymer comprised an
isobutylene-isoprene copolymer and polybutene and a hydrocarbon
resin tackifier as shown in Table 7, below.
7TABLE 7 Weight Composition Percent 50,000 cps. silanol terminated
polydimethylsiloxane polymer 24.42 20,000 cps. silanol terminated
polydimethylsiloxane polymer 16.28 Hydrophobic precipitated calcium
carbonate 32.56 Ground calcium carbonate 11.14 Titanium dioxide
0.27 Magnesium carbonate 0.22 Crystalline silica 0.09
Hexamethyldisilazane 0.81 Dimethylbis-secondarybutylaminosilane
2.16 Vinyltris-methylethylketoximosilane 1.63 Polybutene 2.81
Isobutylene isoprene copolymer 1.14 Hydrocarbon resin 0.24 Castor
oil 0.24 Solvent 2.89 Aminoethylaminopropyltrimethoxysilane 1.73
Dibutyltindiacetate 0.06 Total 100.00
[0069] The resulting sealant was painted and tested in the same
manner as described earlier. The painted surface was smooth and had
no fish eyes. The above composition also passed the paint adhesion
test while maintaining excellent weatherability as demonstrated
with no surface cracks and no change in shore-A.
[0070] The examples included herein are for illustration and are
not meant to limit the scope of the invention.
* * * * *