U.S. patent application number 10/823969 was filed with the patent office on 2005-10-20 for fast curing polydiorganosiloxanes.
Invention is credited to Bachon, Thomas, Ferencz, Andreas, Koch, Matthias, Lim, Thomas F..
Application Number | 20050234208 10/823969 |
Document ID | / |
Family ID | 34963786 |
Filed Date | 2005-10-20 |
United States Patent
Application |
20050234208 |
Kind Code |
A1 |
Koch, Matthias ; et
al. |
October 20, 2005 |
Fast curing polydiorganosiloxanes
Abstract
The present invention concerns .alpha.-silyl terminated
polydiorganosiloxanes, a method of making the .alpha.-silyl
terminated polydiorganosiloxanes, and sealant compositions
containing said compounds and a method of using such sealant
compositions.
Inventors: |
Koch, Matthias;
(Duesseldorf, DE) ; Bachon, Thomas; (Duesseldorf,
DE) ; Ferencz, Andreas; (Duesseldorf, DE) ;
Lim, Thomas F.; (Killingworth, CT) |
Correspondence
Address: |
HENKEL CORPORATION
THE TRIAD, SUITE 200
2200 RENAISSANCE BLVD.
GULPH MILLS
PA
19406
US
|
Family ID: |
34963786 |
Appl. No.: |
10/823969 |
Filed: |
April 14, 2004 |
Current U.S.
Class: |
528/34 |
Current CPC
Class: |
C08G 77/14 20130101;
C08G 77/24 20130101; C08G 77/30 20130101; C08G 77/28 20130101 |
Class at
Publication: |
528/034 |
International
Class: |
C08G 077/04; C08L
083/04 |
Claims
What is claimed is:
1. An .alpha.-silyl terminated polydiorganosiloxane having the
following general formula (I): 6wherein the radicals R.sup.1 are
selected from the group consisting of straight-chain aliphatic
radicals, branched aliphatic radicals, cycloaliphatic radicals,
aryl radicals, and aralkyl radicals, each radical R.sup.1
containing 1 to 12 carbon atoms and optionally one or more
heteroatoms and optionally being substituted with halogen, the
radicals R.sup.1 being identical or different within the
polydiorganosiloxane; the radicals R.sup.2 and R.sup.3, which are
identical or different, are selected from the group consisting of
straight-chain aliphatic radicals and branched aliphatic radicals;
the radicals R.sup.4 and R.sup.5, which are identical or different,
are selected from the group consisting of straight-chain aliphatic
radicals, branched aliphatic radicals, OR.sup.2 and OR.sup.3,
wherein R.sup.2 and R.sup.3 are defined as above; the radicals X
and Y, which are identical or different, are selected from the
group consisting of O, S, N, PR.sup.8 and NR.sup.8, wherein R.sup.8
is selected from the group consisting of H, --(C.dbd.O)NH--R.sup.9,
--(C.dbd.O)--R.sup.9 and --(SO.sub.2)--R.sup.9, wherein R.sup.9 is
selected from the group consisting of aliphatic radicals,
cycloaliphatic radicals, and aryl radicals, each radical R.sup.9
containing 1 to 12 carbon atoms and optionally containing one or
more heteroatoms; the radicals R.sup.6 and R.sup.7, which are
identical or different, are selected from the group consisting of
straight-chain aliphatic radicals with 1 to 12 carbon atoms,
branched aliphatic radicals with 1 to 12 carbon atoms,
cycloaliphatic radicals, cycloaliphatic radicals containing one or
more heteroatoms, aryl radicals, aryl radicals containing one or
more heteroatoms, .dbd.C.dbd.O, and --(C.dbd.O)R.sup.10, wherein
R.sup.10 is selected from the group consisting of straight-chain
aliphatic radicals with 1 to 12 carbon atoms, branched aliphatic
radicals with 1 to 12 carbon atoms, and Z-R.sup.11, wherein Z is
selected from the group consisting of S, O, PR.sup.8 and NH and
R.sup.11 is selected from the group consisting of straight-chain
aliphatic radicals with 1 to 12 carbon atoms and branched aliphatic
radicals with 1 to 12 carbon atoms; n is from 10 to 10000; and
salts of organic acids, inorganic acids or quaternization products
thereof.
2. The .alpha.-silyl terminated polydiorganosiloxane of claim 1,
wherein the radicals R.sup.1 are selected from the group consisting
of straight-chain alkyl radicals with 1 to 8 carbon atoms wherein
optionally one or more halogen atoms are substituted for hydrogen
atoms, branched alkyl radicals with 1 to 8 carbon atoms wherein
optionally one or more halogen atoms are substituted for hydrogen
atoms, 5-membered and 6-membered aryl radicals optionally
containing one or more heteroatoms and wherein optionally one or
more halogen atoms are substituted for hydrogen atoms, the radicals
R.sup.1 being identical or different within the
polydiorganosiloxane.
3. The .alpha.-silyl terminated polydiorganosiloxane of claim 1,
wherein the radicals R.sup.2 and R.sup.3, which are identical or
different, are selected from the group consisting of straight-chain
and branched alkyl radicals with 1 to 8 carbon atoms.
4. The .alpha.-silyl terminated polydiorganosiloxane of claim 1,
wherein the radicals R.sup.4 and R.sup.5, which are identical or
different, are selected from the group consisting of straight-chain
and branched alkyl radicals with 1 to 8 carbon atoms, OR.sup.2 and
OR.sup.3, wherein R.sup.2 and R.sup.3 are identical or different
and are selected from the group consisting of straight-chain and
branched alkyl radicals with 1 to 8 carbon atoms.
5. The .alpha.-silyl terminated polydiorganosiloxane of claim 1,
wherein the radicals X and Y, which are identical or different, are
selected from the group consisting of O, S, N, PR.sup.8 and
NR.sup.8, wherein R.sup.8 is selected from the group consisting of
H, --(C.dbd.O)NH--R.sup.9, --(C.dbd.O)--R.sup.9 and
--(SO.sub.2)--R.sup.9, wherein R.sup.9 is selected from the group
consisting of alkyl and cycloalkyl radicals with 1 to 8 carbon
atoms and 5-membered or and 6-membered aryl radicals optionally
containing one or more heteroatoms.
6. The .alpha.-silyl terminated polydiorganosiloxane of claim 1,
wherein the radicals R.sup.6 and R.sup.7, which are the same or
different, are selected from the group consisting of straight-chain
and branched alkyl radicals with 1 to 8 carbon atoms, 5-membered
and 6-membered cycloalkyl radicals, optionally containing one or
more heteroatoms and optionally containing one or more double
bonds, 5-membered and 6-membered aryl radicals, optionally
containing one or more heteroatoms, .dbd.C.dbd.O, and
--(C.dbd.O)R.sup.10, wherein R.sup.10 is selected from the group
consisting of straight-chain and branched alkyl radicals with 1 to
8 carbon atoms, straight-chain and branched alkylene radicals with
1 to 8 carbon atoms, Z-R.sup.11 radicals, wherein Z is selected
from the group consisting of S, O, PR.sup.8 and NH and R.sup.11 is
selected from the group consisting of straight-chain and branched
alkyl radicals with 1 to 8 carbon atoms.
7. The .alpha.-silyl terminated polydiorganosiloxane of claim 1,
wherein n is between 10 and 10000 and selected to provide the
.alpha.-silyl terminated polydiorganosiloxane with a viscosity of
1,000 to 900,000 mPa.multidot.s (according to Brookfield:
Brookfield RVT, 23.degree. C., Spindle No. 7, 2.5 rpm).
8. The .alpha.-silyl terminated polydiorganosiloxane of claim 1,
wherein the radical X is NH and wherein said NH radical is further
reacted with one or more CL quaternization reagents selected from
the group consisting of alkyl halides or wherein said NH radical is
further reacted with one or more inorganic acids or organic acids
selected from the group consisting of sulfuric acid, hydrochloric
acid, benzoic acid, terephthalic acid, phthalic acid, caproic acid,
stearic acid, ascorbic acid and tartaric acid.
9. A method for making an .alpha.-silyl terminated
polydiorganosiloxane, the method (I) comprising: (A) a first step
of adding one or more .alpha.-silanes of general formula (II):
7wherein R.sup.2 is selected from the group consisting of
straight-chain and branched aliphatic radicals; R.sup.4 is selected
from the group consisting of straight-chain or branched aliphatic
radicals, OR.sup.2 and OR.sup.8, X is selected from the group
consisting of O, S, PR.sup.8, NR.sup.8 and N, wherein R.sup.8 is
selected from the group consisting of H, --(C.dbd.O)NH--R.sup.9,
--(C.dbd.O)--R.sup.9 and --(SO.sub.2)--R.sup.9; wherein R.sup.9 is
selected from the group consisting of aliphatic and cycloaliphatic
radicals and aryl radicals, each radical R.sup.9 containing 1 to 12
carbon atoms and each radical R.sup.9 optionally containing one or
more heteroatoms; and R.sup.6 is selected from the group consisting
of straight-chain and branched aliphatic radicals with 1 to 12
carbon atoms, cycloaliphatic radicals, optionally containing one or
more heteroatoms, aryl radicals, optionally containing one or more
heteroatoms, .dbd.C.dbd.O, and --(C.dbd.O)R.sup.10, wherein
R.sup.10 is selected from the group consisting of straight-chain
and branched aliphatic radicals with 1 to 12 carbon atoms and
Z-R.sup.11 radicals, wherein Z is selected from the group
consisting of S, O, PR.sup.8 and NH and R.sup.11 is selected from
the group consisting of straight-chain and branched aliphatic
radicals with 1 to 12 carbon atoms; to one or more silanol
terminated polydiorganosiloxanes of general formula (III): 8wherein
R.sup.1 is selected from the group consisting of straight-chain and
branched aliphatic radicals, cycloaliphatic radicals, aryl
radicals, and aralkyl radicals, each radical R.sup.1 containing 1
to 12 carbon atoms and optionally containing one or more
heteroatoms and optionally being substituted with halogen, the
radicals R.sup.1 being identical or different within the
polydiorganosiloxane; to react both silanol groups; and optionally,
if X=NH (B) a second step, wherein one or more compounds selected
from the group consisting of R.sup.9NCO, R.sup.9(CO)Cl,
R.sup.9COOH, R.sup.9SO.sub.2Cl, (R.sup.9CO).sub.2O and alkylating
agents, wherein R.sup.9 is selected from the group consisting of
aliphatic radicals and aryl radicals, each radical R.sup.9
containing 1 to 12 carbon atoms and optionally containing one or
more heteroatoms; are added to achieve a complete or partial
reaction between the X radical of the product obtained in step (A)
and the selected compound or compounds.
10. The method according to claim 9, wherein step (A) is carried
out in the presence of a catalyst selected from the group
consisting of butyl lithium, lithium alkoxides, lithium hydroxide,
butyl potassium, potassium alkoxides, potassium hydroxide, butyl
sodium, sodium alkoxides, sodium hydroxides and Lewis bases.
11. The method of claim 9, wherein the .alpha.-silane according to
formula (II) is selected from the group consisting of
(N-cyclohexylaminomethyl)me- thyl-diethoxysilane,
(N-cyclohexylaminomethyl)triethoxysilane,
(N-phenylaminomethyl)methyldimethoxysilane,
(N-phenylaminomethyl)trimetho- xysilane,
(methacryloxymethyl)methyldimethoxysilane,
(methacryloxymethyl)trimethoxysilane,
(methacryloxymethyl)methyldiethoxys- ilane,
(methacryloxymethyl)triethoxysilane,
(isocyanatomethyl)methyldimeth- oxysilane,
(isocyanatomethyl)trimethoxysilane, and N-(trimethoxysilylmethy-
l)-O-methylcarbamate.
12. A sealant composition comprising an .alpha.-silyl terminated
polydiorganosiloxane according to claim 1.
13. The sealant composition according to claim 12, further
comprising one or more compounds selected from the group consisting
of water scavengers, fillers plasticizers, adhesion promoters,
photosensitizers and pigments.
14. The sealant composition according to claim 12, wherein the
.alpha.-silyl terminated polydiorganosiloxane comprises about 10%
by weight to about 95% by weight of the sealant composition.
15. The sealant composition according to claim 12, further
comprising a cross-linking catalyst selected from the group
consisting of Lewis bases, amines, amidines, and photolatent
bases.
16. The sealant composition according to claim 15 wherein the
cross-linking catalyst is a photolatent base, the photolatent base
being selected from the group consisting of
5-benzyl-1,5-diazabicyclo[4.3.0]non- ane and
8-benzyl-1,8-diazabicyclo[5.4.0.]undecane, wherein the benzyl
residue in each can further be substituted by halide, alkyl,
nitril, nitro, alkoxy or aromatic residues condensed to the benzyl
residue.
17. A method of using the sealant composition of claim 12,
comprising a first step of applying the sealant composition to a
substrate to be sealed; a second step of exposing the sealant
composition to moisture; and an optional third step of activating a
photolatent base contained in the sealant composition by
irradiation.
Description
FIELD OF THE INVENTION
[0001] This invention relates to polydiorganosiloxanes, a method of
producing the same, sealant compositions containing the
polydiorganosiloxanes of the invention and a method of using such
sealant compositions.
BRIEF DESCRIPTION OF THE RELATED ART
[0002] In the synthesis of room-temperature-vulcanizing sealants
(RTV sealants) based on silicones, so-called silanol terminated
polydiorganosiloxanes, are widely used as initial compounds.
[0003] Generally, RTV sealants based on silicone are created in two
steps. First the silanol terminated polydiorganosiloxanes are
reacted with a multifunctional silane, whereby the silanol end
group is substantially displaced by the multifunctional silane. In
a second step the resultant silane terminated polyorganosiloxane is
exposed to moisture to be hydrolyzed and condensed to form
cross-linked sealants.
[0004] Most commonly used systems rely on the presence of acetoxy,
enoxy, oxime, methoxy and amine functionalized silanes for coupling
with the silanol terminated polydiorganosiloxane in the above
mentioned first step. Those systems release acetic acid, acetone,
oximes, methanol and amines, respectively, upon hydrolysis in the
above mentioned second step. Besides the toxic character of some of
the released compounds, like methanol, various oximes and amines,
some compounds like amines and acetic acid possess an offensive
smell.
[0005] Acetoxy systems in general rely on tin catalysts. The tin
level of those systems is at least 50 ppm, typically even up to ten
times higher. Since the use of organometallic compounds conflicts
with recent environmental efforts, such compounds should
essentially be avoided where possible.
[0006] Moreover, prior art methoxy .gamma.-silane based RTV systems
are to be catalyzed by titanates, tin compounds and/or other
organometallic compounds, which are highly questionable for
environmental reasons. Even taking into account the use of
organometallic compounds, using ethoxy .gamma.-silanes instead of
methoxy silanes to release ethanol instead of methanol during
moisture catalyzed hydrolysis is not practicable either. This is
because ethoxy .gamma.-silane based RTV systems lack reactivity and
are therefore disadvantageous regarding skin-over-time,
tack-free-time and vulcanization rate.
[0007] Reactivity of alkoxy silanes is not only limited to methoxy
derivatives but to the trimethoxy derivatives, which is due to the
reduced reactivity of the dialkoxy analogues. Therefore prior art
alkoxy silane coupled silicones are obtained by the reaction of
silanol terminated polydiorganosiloxanes with trimethoxy
.gamma.-silanes. Since dialkoxy derivatives are not suitable, only
cross-linking between such alkoxysilane terminated
polydiorganosiloxanes can occur and a regulatory mere
chain-extension by use of dialkoxy derivatives instead of trialkoxy
derivatives is not possible.
[0008] U.S. Pat. No. 5,457,148 (Lucas et al.) describes an RTV
vulcanizable silicone rubber composition and process for the
manufacture thereof having a good application rate and good
thixotropy, which comprises a polyalkoxy terminated
polydimethylsiloxane and a low viscosity silanol stopped
polydimethylsiloxane, whereby the composition contains significant
amounts of an organo tin catalyst, which are to be avoided in the
present invention.
[0009] Published international Pat. Appl. No. WO 03/008485
(Schindler et al.) describes compositions usable as joint compounds
on silicone basis, eliminating alcohols while cross-linking to
elastomers takes place. Those compounds are synthesized from
silanol terminated polydiorganosiloxanes, isocyanato silanes and
silazanes, whereby the employed silanes are limited to isocyanato
silanes due to the coupling mechanism--urea bond formation by
reaction with silazanes--to the silanol groups. The compositions
used in the examples contain significant amounts of tin compounds
and skin-over-times are 15 min or more.
[0010] Accordingly, besides overcoming the drawbacks of the above
mentioned prior art sealants, the objects and advantages of the
present invention are:
[0011] (a) to reduce the use of RTV silicone sealant systems
containing or releasing toxic and/or environmentally questionable
compounds;
[0012] (b) to provide RTV silicone sealants possessing fast curing
speeds, thus minimizing curing time and enabling soonest possible
use of the facilities sealed; and
[0013] (c) to provide RTV silicone sealants which are customizable
to comply with different curing conditions, like moisture, curing
time and the like, to provide sealants with adjustable
skin-over-times; tack-free-times and vulcanization rates.
[0014] Still further objects and advantages will become apparent
from a consideration of the ensuing description.
SUMMARY OF THE INVENTION
[0015] In a first embodiment, the present invention is directed to
an .alpha.-silyl terminated polydiorganosiloxane having the
following general formula (I): 1
[0016] wherein
[0017] the radicals R.sup.1 correspond to a straight-chain or
branched aliphatic radical; a cycloaliphatic radical; an aryl
radical; an aralkyl radical; each radical R.sup.1 containing 1 to
12 carbon atoms; each radical R.sup.1 optionally containing one or
more heteroatoms and optionally being substituted with halogen; the
radicals R.sup.1 being identical or different within the
polydiorganosiloxane;
[0018] the radicals R.sup.2 and R.sup.3, which are identical or
different, correspond to a straight-chain or branched aliphatic
radical;
[0019] the radicals R.sup.4 and R.sup.5, which are identical or
different, correspond to a straight-chain or branched aliphatic
radical; or correspond to OR.sup.2 and OR.sup.3,
[0020] wherein R.sup.2 and R.sup.3 are defined as above;
[0021] the radicals X and Y, which are identical or different,
correspond to O, S, N, PR.sup.8 or NR.sup.8,
[0022] wherein R.sup.8 corresponds to H, R.sup.9, a radical
--(C.dbd.O)NH--R.sup.9, --(C.dbd.O)--R.sup.9 or
--(SO.sub.2)--R.sup.9,
[0023] wherein R.sup.9 corresponds to an aliphatic or
cycloaliphatic radical; an aryl radical; each radical R.sup.9
containing 1 to 12 carbon atoms; and each radical R.sup.9
optionally containing one or more heteroatoms;
[0024] the radicals R.sup.6 and R.sup.7, which are identical or
different, correspond to a straight-chain or branched aliphatic
radical with 1 to 12 carbon atoms; a cycloaliphatic radical,
optionally containing one or more heteroatoms; an aryl radical,
optionally containing one or more heteroatoms; the .dbd.C.dbd.O
radical; or
[0025] --(C.dbd.O)R.sup.10, wherein
[0026] R.sup.10 corresponds to a straight-chain or branched
aliphatic radical with 1 to 12 carbon atoms; an Z-R.sup.11 radical,
wherein
[0027] Z corresponds to S, O, PR.sup.8 or NH and
[0028] R.sup.11 corresponds to a straight-chain or branched
aliphatic radical with 1 to 12 carbon atoms;
[0029] n being from 10 to 10000 or
[0030] salts of organic acids, inorganic acids or quaternization
products thereof.
[0031] In a second embodiment, the present invention provides a
method of making an .alpha.-silyl terminated polydiorganosiloxane
or mixtures thereof, comprising:
[0032] (A) a first step of adding one or more .alpha.-silanes of
general formula (II): 2
[0033] wherein R.sup.2, R.sup.4, and R.sup.6 are defined as above
and X=O, S, PR.sup.8, N, NH or NR.sup.8, R.sup.8 being defined as
above;
[0034] to one or more silanol terminated polydiorganosiloxanes of
general formula (III): 3
[0035] wherein R.sup.1 is defined as above,
[0036] to react both silanol groups; and optionally,
[0037] if X=NH
[0038] (B) a second step, wherein one or more compounds selected
from the group consisting of R.sup.9NCO, R.sup.9(CO)C.sup.1,
R.sup.9COOH, (R.sup.9CO).sub.2O, R.sup.9SO.sub.2Cl and alkylating
agents such as alkyl iodide are added to achieve a complete or
partial reaction between the X radical of the product obtained in
step (A) and the selected compound or compounds.
[0039] In an alternative method, if X=the NH radical, a partial or
complete reaction of the compound according to general formula (II)
with one or more of the compounds listed under step (B) can be
carried out prior to the reaction with the compound according to
general formula (III). In some cases using this alternative method
it is desired to add an additional basic catalyst, like butyl
lithium or lithium alkoxides, lithium hydroxide, potassium or
sodium compounds (whereas lithium is replaced with potassium or
sodium in the above mentioned compounds) or Lewis bases.
[0040] In a fourth embodiment, the present invention is directed to
a sealant composition, comprising the .alpha.-silyl terminated
polydiorganosiloxane of the invention.
[0041] A fifth embodiment of the invention is directed to a method
of applying the sealant composition of the invention, comprising a
first step of applying the sealant toga substrate to be sealed, a
second step of exposing the sealant to moisture and an optional
third step of activating a photolatent base contained in the
sealant composition by irradiation.
DETAILED DESCRIPTION
[0042] In a preferred embodiment of the .alpha.-silyl terminated
polydiorganosiloxane of the invention the radicals R.sup.1
correspond to a straight-chain or branched alkyl radical with 1 to
8 carbon atoms, like methyl, ethyl, n-propyl, iso-propyl, n-butyl,
iso-butyl, tert.-butyl and the like. A widely used alkyl radical in
silicones is e.g. methyl. Optionally such radicals can contain
heteroatoms like oxygen, sulfur or nitrogen, such as an
alkoxyalkylene radical, for example. The radicals R.sup.1 can
optionally further contain halogen, like chlorine or fluorine
instead of hydrogen atoms, e.g. in radicals like the
perfluoropropylene radical.
[0043] Other possible radicals R.sup.1 are aryl radicals, whereby
5-membered and 6-membered aryl radicals, like phenyl, are
preferred. Optionally those residues may contain heteroatoms, like
oxygen, sulfur or nitrogen. Optionally halogen atoms are
substituted for hydrogen atoms.
[0044] In a further embodiment of the invention the radicals
R.sup.1 along the n Si(R.sup.1).sub.2--O-unit containing
polydiorganosiloxane chain can be identical, like e.g. in a
polydimethylsiloxane chain; or different, like e.g. in a
polytrifluoropropylmethylsiloxane chain, wherein some of the methyl
groups of a polydimethylsiloxane chain are substituted by
--CH.sub.2--CH.sub.2--CF.sub.3 radicals or in a
poly(diphenylsiloxane/dim- ethylsiloxane) copolymer chain, wherein
some of the Si(CH.sub.3).sub.2--O-units are replaced by
Si(phenyl).sub.2--O-units.
[0045] In general all radicals R.sup.1 are independent from each
other in structure or number along the polydiorganosiloxane
chain.
[0046] The most common radical R.sup.1 in view of commercial
availability of silanol terminated polyorganosiloxanes is
methyl.
[0047] The radicals R.sup.2 and R.sup.3, which are identical or
different, preferably correspond to a straight-chain or branched
alkyl radical with 1 to 8 carbon atoms. In view of the above
environmental statements and toxicity reasons the ethyl radical is
preferred over the methyl radical. Nevertheless where reactivity of
such groups in cross-linking is the crucial factor, the employment
of methyl groups might be considered, since reactivity slows down
as the chain length of the alkyl group increases.
[0048] The radicals R.sup.4 and R.sup.5, which are identical or
different, preferably correspond to a straight-chain or branched
alkyl radical with 1 to 8 carbon atoms or the OR.sup.2 and OR.sup.3
radicals, wherein R.sup.2 and R.sup.3 have the above meaning.
[0049] In case one or more of R.sup.4 or R.sup.5 denote alkyl
radicals, cross-linking is reduced compared to the case where one
or both of R.sup.4 and R.sup.5 correspond to OR.sup.2 and OR.sup.3
radicals. The number of OR.sup.2 and/or OR.sup.3 radicals within
one .alpha.-silyl terminated polydiorganosiloxane is determined by
the .alpha.-silane used as reaction partner with the silanol
terminated polyorganosiloxane. In case the only .alpha.-silanes are
trialkoxy .alpha.-silanes the resulting .alpha.-silyl terminated
polydiorganosiloxane will carry a maximum of 4 OR.sup.2 and/or
OR.sup.3 radicals. In case the only .alpha.-silanes are dialkoxy
.alpha.-silanes the resulting .alpha.-silyl terminated
polydiorganosiloxane will carry a maximum of 2 OR.sup.2 and/or
OR.sup.3 radicals. Nevertheless, if a mixture of dialkoxyl
.alpha.-silanes and trialkoxy .alpha.-silanes is employed any
number of OR.sup.2 and/or OR.sup.3 radicals between 2 and 4 can be
adjusted depending on the ratio between dialkoxyl .alpha.-silanes
and trialkoxy .alpha.-silanes and their reactivity. Generally
trialkoxy .alpha.-silanes are more reactive compared to dialkoxy
.alpha.-silanes. Nevertheless their reactivity is also influenced
by the XR.sup.6 or YR.sup.7 groups, which will be discussed below
and the nature of the R.sup.2 and R.sup.3 groups which was
discussed above.
[0050] The radicals X and Y, which are identical or different,
correspond to O, S, N or NR.sup.8, wherein R.sup.8 corresponds to
H, R.sup.9, a radical --(C.dbd.O)NH--R.sup.9, --(C.dbd.O)--R.sup.9
or --(SO.sub.2)--R.sup.9, wherein R.sup.9 preferably corresponds to
an alkyl or cycloalkyl radical with 1 to 8 carbon atoms, a
5-membered or a 6-membered aryl radical optionally containing
heteroatoms. In view of a high cross-linking activity, resulting in
low skin-over-times and tack-free-times as well as high
vulcanization rates, it is preferred that X and/or Y are NH, which
is a radical suitable to auto-catalyze the cross-linking between
the .alpha.-silyl terminated polydiorganosiloxanes, due to the
basic character of the NH radical.
[0051] Moreover, the NH radical-containing .alpha.-silanes are also
advantageous in view of the reaction with silanol terminated
polydiorganosiloxanes, since the basic character of this group
typically makes the employment of catalysts unnecessary.
[0052] Further, the .alpha.-silyl terminated polydiorganosiloxanes
carrying the NH radical as radical X and/or Y can not only be used
for sealant purposes as such, but can serve as precursors in a
further reaction with isocyanates of the general formula
R.sup.9--NCO, or acid halides of the general formula
R.sup.9--COHal, anhydrides ((R.sup.9CO).sub.2O), or
R.sup.9--SO.sub.2Hal, wherein R.sup.9 corresponds to an aliphatic
radical, an aryl radical, each radical R.sup.9 containing 1 to 12
carbon atoms and each radical R.sup.9 optionally containing one or
more heteroatoms, whereby R.sup.9 preferably corresponds to an
alkyl radical with 1 to 8 carbon atoms, a 5-membered or a
6-membered aryl radical optionally containing one or more
heteroatoms; and Hal corresponds to an halogen atom, like
chlorine.
[0053] The .alpha.-silyl terminated polydiorganosiloxanes carrying
the NH radical as radical X and/or Y can partially or completely be
reacted with the isocyanate of the general formula R.sup.9--NCO,
e.g. phenylisocyanate, cyclohexylisocyanate, isopropylisocyanate,
or with an acid halide of the general formula R.sup.9--COHal, e.g.
benzoylchloride. This reaction leads to the products wherein X
and/or Y are NR.sup.8, R.sup.8 being defined as above. Due to the
complete or partial loss of NH radicals caused by the reaction with
the isocyanate or acid halide, the basic character is partially
lost and reactivity is decreased. This optional reaction is
therefore suitable to customize the .alpha.-silyl terminated
polydiorganosiloxanes of the invention with respect to curing times
(skin-over-time, tack-free-time) and vulcanization rates expected
by the skilled sealant user.
[0054] Instead of the above mentioned reactions, salts of inorganic
acids, like sulfuric acid, hydrochloric acid or organic acids, like
benzoic acid, which additionally serves as preservative,
terephthalic acid, phthalic acid, caproic acid, fatty acids (like
stearic acid), ascorbic acid, or tartaric acid can be formed, to
modulate the basic character of the NH-containing silyl radicals as
desired.
[0055] A further possibility to modulate the basicity of the
NH-containing silyl radicals is to carry out a quaternization
reaction of the NH radical, e.g. with a reactive alkyl halide, like
methyl iodide.
[0056] The radicals R.sup.6 and R.sup.7, which can be same or
different, preferably correspond to a straight-chain or branched
alkyl radical with 1 to 8 carbon atoms, like methyl, ethyl,
n-propyl, iso-propyl, n-butyl, iso-butyl or tert.-butyl radicals; a
5-membered or 6-membered cycloalkyl radical, like cyclopentyl or
cyclohexyl, which optionally may contain one or more heteroatoms,
like in the morpholino radical and which optionally may contain
double bonds a 5-membered or 6-membered aryl radical, like the
phenyl radical, which optionally may contain one or more
heteroatoms; or the .dbd.C.dbd.O radical. The radicals R.sup.6
and/or R.sup.7 can also denote the radical --(C.dbd.O)R.sup.10,
wherein R.sup.10 corresponds to a straight-chain or branched alkyl
radical with 1 to 8 carbon atoms; a straight-chain or branched
alkylene radical with 1 to 8 carbon atoms, like the
--C(CH.sub.3).dbd.CH.sub.2 radical; a Z-R.sup.11 radical, wherein Z
corresponds to S, O or NH and R.sup.11 corresponds to a
straight-chain or branched alkyl radical with 1 to 8 carbon atoms,
like methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl or
tert.-butyl radicals.
[0057] The number of n in general formula (I) typically influences
the viscosity of the resultant sealant. The general range for n is
10 to 10000. Suitable viscosities of the .alpha.-silyl terminated
polydiorganosiloxanes of the invention can e.g. range from about
1,000 to about 900,000 mPa.multidot.s (according to Brookfield:
Brookfield RVT, 23.degree. C., Spindle No. 7, 2.5 rpm).
[0058] In another embodiment the present invention provides a
method of making .alpha.-silyl terminated polydiorganosiloxanes or
mixtures thereof, comprising
[0059] (A) a first step of adding one or more .alpha.-silanes of
general formula (II): 4
[0060] wherein R.sup.2, R.sup.4 and R.sup.6 are defined as above
and X=O, S, PR.sup.8, N, NH or NR.sup.8
[0061] to one or more silanol terminated polydiorganosiloxanes of
general formula (III): 5
[0062] wherein R.sup.1 is defined as above,
[0063] to react both silanol groups; and optionally
[0064] if X=NH.
[0065] (B) a second step, wherein a compound selected from the
group consisting of R.sup.9NCO, R.sup.9(CO)Cl, R.sup.9COOH,
R.sup.9SO.sub.2Cl, (R.sup.9CO).sub.2O, and alkylating agents such
as alkyl iodide is added to completely or partially react with the
X radical of the product obtained in step (A).
[0066] Suitable .alpha.-silanes of formula (II) are e.g.
(N-cyclohexylaminomethyl)methyldiethoxysilane,
(N-cyclohexylaminomethyl)t- riethoxysilane
(N-phenylaminomethyl)methyldimethoxysilane,
(N-phenylaminomethyl)trimethoxysilane,
(methacryloxymethyl)methyldimethox- ysilane,
(methacryloxymethyl)trimethoxysilane, (methacryloxymethyl)methyld-
iethoxysilane, (methacryloxymethyl)triethoxysilane,
(isocyanatomethyl)methyldimethoxysilane,
(isocyanatomethyl)trimethoxysila- ne,
N-(morpholinomethyl)trimethoxysilane,
N-(morpholinomethyl)triethoxysil- an,
N-(dimethoxymethylsilylmethyl)-O-methylcarbamate, or
N-(trimethoxysilylmethyl)-O-methylcarbamate. Those products are
e.g. commercially available from Wacker, Burghausen, Germany under
the tradename series GENIOSIL.RTM. XL.
[0067] Stoichiometrically two .alpha.-silanes of formula (II) react
with one silanol terminated polydiorganosiloxane, which possesses
two --OH end groups. Preferably the .alpha.-silanes of formula (II)
are added in excess, whereby a stoichiometric excess of greater
than 1 up to 4 is more preferable and a stoichiometric excess of 2
to 3 is most preferable, to ensure complete reaction of the silanol
groups and to reduce cross-linking reactions.
[0068] If step (B) is not carried out, e.g. in case X=O or S; or
XR.sup.6=NCO, a catalyst is preferably added. A suitable catalyst
is according to EP 564253 butyl lithium.
[0069] If step (B) is not carried out because a product wherein
X=NH is desired, the catalyst is preferably omitted, nevertheless
the addition of a catalyst does not interfere with the reaction
either.
[0070] The reactions are usually carried out at temperatures from 0
to 120.degree. C., preferably 20 to 40.degree. C.
[0071] Any of the above .alpha.-silyl terminated
polydiorganosiloxanes according to formula (I) or mixtures thereof
or reaction products obtained by the methods of making,
.alpha.-silyl terminated polydiorganosiloxanes of the invention are
suitable as sealant components.
[0072] Therefore another embodiment of the present invention
provides sealant compositions, comprising one or more .alpha.-silyl
terminated polydiorganosiloxanes according to the invention.
[0073] The content of .alpha.-silyl terminated
polydiorganosiloxanes within the sealant compositions of the
invention typically varies between 10 and 95% by weight based on
the weight of the total composition. Preferably their content is in
the range of 40 to 80% by weight.
[0074] Typically such sealant compositions comprise further
additives, like water scavengers, fillers, plasticizers, adhesion
promoters, photosensitizers, pigments and other standard
supplementary agents. Since the .alpha.-silyl terminated
polydiorganosiloxanes of the invention are highly reactive and
moisture sensitive, those additives are preferably mixed with the
.alpha.-silyl terminated polydiorganosiloxanes of the invention in
a bone-dry (anhydrous) state to prevent interference with storage
stability and to prevent premature vulcanization.
[0075] Typical water scavengers are e.g. vinyltrimethoxysilane,
vinyltripropenoxysilane, carbamatomethylsilanes, tetraethoxysilane,
hexamethyldisilanzane, acetoxysilanes, or isocyanates.
[0076] Typical fillers in sealant compositions are e.g., silica,
carbon black, metal oxides, like titanium dioxide, ferric oxide,
aluminum oxide, zinc oxide, quartz, calcium carbonate clay,
zirconium silicate, gypsum, silicium nitride, boron nitride, barium
sulfate, zeolite, glass and plastic powder.
[0077] Plasticizers in sealant compositions in general comprise
compounds like trimethylsilyl terminated polydimethylsiloxanes or
organic esters or mineralic oils.
[0078] Typical adhesion promoters are e.g.
3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane,
3-aminopropylmethyldiethoxysilane,
3-aminopropylmethyldimethoxysilane,
methylaminopropyltrimethoxysilane,
1,3,5-tris(trimethylsilylpropyl)isocyanurate,
3-glycidoxypropyltrimethoxy- silane,
3-glycidoxypropylethyldimethoxysilane, 2-glycidoxyethyltrimethoxys-
ilane, 2-cyanoethyltrimethoxysilane, 3-cyanopropyltriethoxysilane,
isocyanatopropyltriethoxysilane; isocyanatopropyltrimethoxysilane,
or mixtures thereof.
[0079] Further the .alpha.-homologues of the herein before
mentioned .gamma.-silanes are suitable adhesion promoters. Moreover
titanium organic compounds, like tetraalkoxytitanates, or
organophosphorus compounds are suitable adhesion promoters and
known to the one skilled in the art of the field of invention.
[0080] Other supplementary agents e.g. comprise soluble dyes,
inorganic and organic pigments, anti-oxidants, flame-retardants,
UV-stabilziers, biocides, like fungicides, thermal stabilizing
agents, rheological additives, and tackifiers.
[0081] In case the .alpha.-silyl terminated polydiorganosiloxane
contained in the sealant composition does not already contain an
auto-catalyzing basic nitrogen radical, like NH or other basic
radicals, a cross-linking catalyst is preferably added to the
composition. Upon exposure to moisture, e.g. ambient humidity, the
auto-catalyzing sealant composition or the sealant composition to
which a catalyst was added, will in general start vulcanizing.
Nevertheless it is also possible to add one or more photolatent
bases, as e.g. o-nitrobenzyloxicarbonylamine, benzoincarbamate,
.alpha.,.alpha.-dimethylbenzoyloxycarbonylamine,
formanilid-derivatives, O-acyloxime, photolatent
diazabicyclo[4.3.0]non-5- -ene (PL-DBN) or PL-tertiary amines or
amidines as catalysts and to start vulcanization upon irradiation
of such photolatent base containing sealants subsequent to their
application. Due to irradiation the free base will be created
within the sealant composition from the photolatent base and
vulcanization will start.
[0082] Another embodiment of the invention is therefore directed to
a method of applying the sealant composition of the invention,
comprising a first step of applying the sealant to a substrate to
be sealed, a second step of exposing the sealant to moisture and an
optional third step of activating a photolatent base contained in
the sealant composition by irradiation.
[0083] Typical substrates for RTV silicone based sealants comprise
e.g. metals, e.g. aluminum, iron, magnesium, copper, chrome, alloys
thereof, and the like, polymers, e.g. polyacrylates,
polymethacrylates, polyvinylchlorides, polycarbonates and the like,
ceramics, tiles, glass, marble, concrete, granite, sandstone,
limestone and wood.
[0084] In general it is preferred that the ambient humidity is
above 30% of relative humidity to ensure a fast curing of the
sealants.
[0085] In case photolatent bases are used as crosslinking
catalysts, any photolatent bases possessing suitable basicity are
applicable. Besides the well-known photolatent bases as described
by Cameron et al. in J. Am. Chem. Soc. 118 (1996) 12925, J. Chem.
Soc. Perkin Trans. I (1997) 2429 and J. Org. Chem. 55 (1990) 5919,
by Nishikubo et al. in Polym. J. 29 (1997) 450 and Polym. J. 25
(1993) 365, as well as Ito et al. in J. Poly. Sci. Part A: Polym.
Chem. 32 (1994) 2177, a new generation of photolatent bases has
been described by CIBA, Basel, Switzerland (WO 03/033500).
Prominent species of those photolatent bases are e.g. photolatent
diazabicyclononanes, in particular
5-benzyl-1,5-diazabicyclo[4.3.0]nonane- , wherein the 5-benzyl
residue maybe substituted by one or more substituents. Suitable
substituents at the 5-benzyl residue are halide, like chlorine or
bromine, alkyl residues, like methyl, ethyl or propyl, nitril
residues, nitro groups, alkoxy groups like methoxy or ethoxy groups
or aromatic residues which are condensed to the residue, as e.g. a
5-(naphth-2-ylmethyl) residue or a 5-(anthracen-9-yl-methyl)
residue derived from a 5-(benzyl) residue. It is also possible to
introduce a 5-(anthrachinon-2-yl-methyl) residue instead of the
5-benzyl residue. Besides such substitutions at the 5-benzyl
residue it is also possible to further substitute the
diazacyclononane residue to get photolatent bases like
5-benzyl-2-methyl-1,5-diazabicyclo[4.3.0]nonane.
[0086] Besides the photolatent diazabicyclononanes it is also
possible to use photolatent diazabicycloundecanes, like for example
8-benzyl-1,8-diazabicyclo[5.4.0]undecanes and its derivatives. The
8-benzyl residue can be substituted in the same way as shown for
the 5-benzyl residue in 5-benzyl-1,5-diazabicyclo[4.3.0]nonane.
Further substitution at the diazabicyclononane residue is likewise
possible.
[0087] It is also possible to use photolatent bases comprising two
releasable bases within one molecule. An example for such compounds
is 1,4-bis(1,5-diazabicyclo[4.3.0]nonanylmethyl)benzene. In case
photolatent bases are used in the compositions of the present
invention it is preferable to add photosensitizers to the
composition. It is further preferable to use one or more
substituted or unsubstituted benzophenones, thioxanthones,
anthrachinones, 3-acylcoumarines or dyes like oxacines, acridines,
phenacines and rodamines as photosensitizers.
[0088] Compositions containing photolatent bases require
irradiation to liberate or release the free base. The irradiation
wavelength used to cause formation of the free base can be varied
over a wide range, ranging from the UV region through the visible
region into the infrared region, depending on the photolatent base.
Most preferably wave lengths ranging from about 200 to about 700 nm
will be used. Suitable radiation comprises, for example, sunlight
or light from artificial light sources. Both point sources and flat
radiators are suitable. Examples are carbon arc lamps, xenon arc
lamps, medium-pressure, high-pressure and low-pressure mercury
lamps, doped if desired with metal halides (metal halogen lamps),
microwave-stimulated metal vapour lamps, excimer lamps,
superactinic fluorescent tubes, fluorescent lamps, incandescent
argon lamps, electronic flashlights, xenon flashlights,
photographic flood lamps, electron beams and X-rays, produced by
means of synchrotrons or laser plasma. The distance between the
lamp and the substrate preferably range from about 1 cm to about 2
m, but depends on the light source and the sensitivity of the
photolatent bases as well as the presence or absence of further
photosensitizers.
EXAMPLES
PREPARATION EXAMPLES
Example 1
Preparation of a Fast Cure Silicone RTV Sealant
[0089] 80 g of silanol terminated polydimethylsiloxane (molecular
weight of approximately 32,000 g/mol; n--as defined above--is
approximately 430) is de-aerated for 10 min at room temperature
under vacuum. 0.01 g of n-butyl lithium (1.6M solution in hexane)
is added as catalyst. The resultant mixture is mixed under N.sub.2
for 2 min (mixer: model PLM 5, obtained from Premier Mill Corp.,
Reading, Pa., U.S.A.). A mixture of 2.03 g of
N-(trimethoxysilylmethyl)-O-methylcarbamate and 0.67 g of
N-(cyclohexylaminomethyl)-triethoxysilane is added, and the
resultant mixture is mixed under vacuum for 60 min at room
temperature. 10.81 g of trimethylsiloxy terminated
polydimethylsiloxane (Dow Corning 200.RTM., Fluid, 1000 CST.) is
added as a plasticizer. After mixing for 5 min, 6.30 g silica
(Aerosil.RTM. R 974, obtained from Degussa, Germany) is added.
[0090] The resultant mixture is mixed at low blade-speed until the
silica is wetted in, and then the mixing continues at a higher
blade-speed for 15 min to disperse the silica further.
[0091] 0.18 g hexamethydisilazane is added and the resultant
mixture is mixed under vacuum for 15 min. The resultant mixture is
a ready-to-use sealant.
[0092] The resultant sealant was tested with respect to its
vulcanization rate and skin-over-time at 23.degree. C. and 50%
relative humidity. The results are shown in Table 1.
Example 2
Preparation of a Fast Cure Silicone RTV Sealant
[0093] 85.23 g. of silanol terminated polydimethylsiloxane
(molecular weight of approximately 32,000 g/mol) is de-aerated for
10 min at room temperature under vacuum. A mixture of 1.52 g of
N-(cyclohexylaminomethyl- )-methyldiethoxysilan and 1.70 g of
N-(cyclohexylaminomethyl)-triethoxysil- ane is added under
stirring. The resultant mixture is mixed under vacuum for 60 min at
room temperature. Afterwards 7.22 g silica (Aerosil.RTM. R 974,
obtained from Degussa, Germany) is added in small portions. The
mixture is mixed at high speed under nitrogen atmosphere for 15
min. 0.21 g hexamethydisilazane and 1.03 g of
.gamma.-aminopropyltriethoxysilane are mixed in. Subsequently 2.06
g of zinc oxide and 1.03 g of titanium dioxide are added. The
resultant mixture is stirred under vacuum for 15 min to become a
ready-to-use sealant.
[0094] The resultant sealant was tested with respect to its
vulcanization rate and skin-over-time at 23.degree. C. and 50%
relative humidity. The results are shown in Table 1.
Example 3
Preparation of a Fast Cure Silicone RTV Sealant
[0095] 88.63 g of silanol terminated polydimethylsiloxane
(molecular weight of approximately 32,000 g/mol) is de-aerated for
10 min. at room temperature under vacuum. 0.01 g of n-butyllithium
(1.6M solution in hexane) is added as catalyst. The resultant
mixture is mixed under N.sub.2 for 2 min. A mixture of 0.64 g of
N-(cyclohexylaminomethyl)-methy- ldiethoxysilan and 2.96 g of
N-(cyclohexylaminomethyl)-triethoxysilane is added, and the
resultant mixture is mixed under vacuum for 30 min at room
temperature in order to complete the end-capping. 0.56 g of
phenylisocyanate is added and the mixture is mixed for 15 min at
room temperature under vacuum. The progress of the reaction is
controlled by IR spectroscopy. After completion of the reaction
7.00 g of silica (Aerosil.RTM. R 974, obtained from Degussa,
Germany) is added whereby the mixture is mixed at low blade-speed.
Afterwards the formulation is mixed with high blade-speed under
nitrogen atmosphere for 15 min in order to disperse the silica
homogenously. 0.20 g hexamethydisilazane is added and the resultant
mixture is mixed under vacuum for 15 min. The resultant mixture is
a ready-to-use sealant.
[0096] The resultant sealant was tested with respect to its
vulcanization rate and skin-over-time at 23.degree. C. and 50%
relative humidity. The results are shown in Table 1.
Comparative Example
Commercial Available Sealant
[0097] Commercially available ready-to-use, fast curing silicone
sealant available from Rhodia, Leverkusen, Germany under the
tradename "ELCH" sealant. This sealant releases acetic acid while
cross-linking occurs.
[0098] The sealant was tested with respect to its vulcanization
rate and skin-over-time at 23.degree. C. and 50% relative humidity.
The results are shown in Table 1.
1 TABLE 1 Comparative Example 1 Example 2 Example 3 Example
skin-over-time 5 3 7.5 6 [min] vulcanization 0.84 0.83 0.73 0.25
rate [mm/2 h] vulcanization 4.8 4.6 4.5 3.7 rate [mm/d]
Examples 4 to 8
Preparation of Silicone RTV Sealants Customized in Skin-Over-Time
and Tack-Free-Time
[0099] 40 g of silanol terminated polydimethylsiloxane (molecular
weight of approximately 32,000 g/mol) is de-aerated for 10 min at
room temperature under vacuum and mixed with 1.65 g of
N-(cyclohexylaminomethy- l)-triethoxysilane. The resultant mixture
is mixed under nitrogen atmosphere for 15 min at room temperature.
Afterwards phenylisocyanate (PIC) is added (Example 4: 0.00 g PIC;
Example 5: 0.18 g PIC; Example 6: 0.36 g PIC; Example 7: 0.54 g
PIC; and Example 8: 0.72 g PIC). The resultant reaction mixture is
further mixed under nitrogen atmosphere at room temperature until
no isocyanate absorption was detectable in an infrared spectrum.
The different amounts of PIC added allowed different degrees of
conversion of the basic nitrogen atom in the terminal
N-cyclohexylaminomethyl radicals to urea groups. The conversion was
0% for Example 4, 25% for Example 5, 50% for Example 6, 75% for
Example 7 and 100% for Example 8 based on the total silane
content.
[0100] The resultant RTV silicone sealant mixtures were tested
regarding their skin-over-time and tack-free-time at 23.degree. C.
and 50% relative humidity. The respective results are given in
Table 2.
2 TABLE 2 Ex- ample 4 Example 5 Example 6 Example 7 Example 8
skin-over-time 3.5 5 10 12 >480 [min] tack-free-time 19 34 73
>480 >1440 [min]
[0101] The results shown in Table 2 clearly demonstrate that a
conversion of the secondary amino group in the terminal
N-cyclohexylaminomethyl radicals to urea groups significantly
decreases the reactivity of the sealants resulting in increased
skin-over-times and tack-free-times. Therefore in case a longer
processability of the sealants is preferred and high-speed curing
is not desired or of priority, the environmentally advantageous
sealants of the present invention can be customized to the need of
the skilled worker in the field of sealants.
[0102] Although the description and examples above contain many
specificities, these should not be construed as limiting the scope
of the invention but as merely providing illustrations of some of
the presently preferred embodiments of this invention. Thus the
scope of the invention should be determined by the appended claims
and their legal equivalents, rather than by the examples given.
* * * * *