Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
53~3~
ORGANOPOLYSILOXANE COMPOSITION CURABLE TO AN
ELASTOMER AND USE THEREOF
This invention relates to organopolysiloxane
compositions which are curable to elastomers and also re-
lates to the use of such elastomers as sealants.
Background Information
Organopolysiloxane compositions which cure to
elastomeric solids on exposure to water are well-known.
Such compositions have found wide application as sealing
materials for a variety of structures to which they may
be applied and allowed to form elastomers merely by
exposure to atmospheric moisture. Typically, such com-
positions comprise a polydiorganosiloxane and a cross-
linking agent for the polydiorganosiloxane, for example,
an alkoxy silane, an acetoxy silane, or an amino silane.
In addition, the compositions may also contain one or
more catalysts, fillers, pigments, adhesion promoters,
and other ingredients. Examples of such curable composi-
tions are those described in British Patents 862,576;
905,364; 920,020; 962,061; 975,603; 1,035,492; and
1,071,311.
One important application of the above-
described curable compositions is their use as sealants
in the building industry. For such applications, for
example, in the fabrication and installation of glazed
units, the cured elastomer should adhere strongly to both
glass and the structure in which the glass is mounted.
The elastomer should also have a relatively low modulus
of elasticity which would permit it to adapt to the
relative movement between the glazing and the structure
due to the effects of temperature variation, wind, and
other stresses. These requirements of adhesion and low
modulus are sufficiently important that certain countries
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~Z~39~
have established national standards relating to the use
of sealants in glazing and building joint applications.
For example, there exist in West Germany standards iden-
tified as DIN 18540 for building joints and DIN 18545 for
glazing, which specify certain requirements as to adhesion
and modulus of elasticity.
One type of curable composition which can be
employed as a glass-bonding material is that based on a
silanol-terminated polydiorganosiloxane and an oxime
silane crosslinking agent, see for example Bri~ish Patent
No. 1,468,467, Example 3. Such compositions have good
curing characteristics in that they cure at an acceptable
rate and do not produce corrosive substances during the
curing process. However, they provide elastomers of re-
latively high modulus and having generally poor adhesion
to glass and other substrates found in the building
industry. We have not discovered that the modulus of
such elastomers can be reduced and the adhesion thereof
to, e.g. glass improved if there is incorporated into the
elastomer-forming compositions certain complexes of
titanium.
British Patent No. 1,255,587 discloses com-
positions which are curable to elastomers on exposure to
water and which comprise a diorganopolysiloxane possessing
a silicon-bonded hydroxyl group in each of the terminal
units and an organosiloxane haviny three monovalent
hydrocarbon radicals, optionally-substituted, attached to
one silicon atom and three groups Y attached to the other,
Y being for example acyloxy, amino, aminoxy, aminoalkoxy,
or oxime. The compositions may contain, as an optional
ingredient, condensation catalysts for instance dibutyltin
dilaurate and organosiloxy titanium compounds.
1;~45394
British Patent Application No. 2,002,405, pub-
lished February 21, 1979, discloses compositions curable
to elastomers at room temperature and which contain inter
alia, an organopolysiloxane having terminal silicon-
bonded hydroxyl or hydrolyzable groups and a silicone-
containing crosslinker having at least three hydrolyzable
groups, e.g. alkoxy groups, acetoxy groups, amino groups,
and ketoxime groups. The compositions optionally contain
a curing catalyst examples of which are the metal salts
of carboxylic acids, certain titanium compounds, amines,
and amine salts. It is stated in the said application
that the catalyst varies according to the hydrolyzable
groups present. Example 1 discloses the use of a metal
(tin) carboxylate as catalyst in compositions containing
an alkoxy silane crosslinker. In Example 3, a composition
crosslinked by way of an alkoxy silane contains a titanium
chelate, as catalyst. There is no disclosure of a com-
position comprising a silanol-terminated polydiorgano-
siloxane, an oxime silane crosslinking a~ent and a
titanium chelate. Example 2 of British Patent Application
~o. 2,002,405 relates to a composition containing an oxime
silane but no catalyst is employed therein.
Summary of the Invention
According to the present invention, there is
provided a composition curable to an elastomer in the
presence of moisture and comprising the product obtained
by mixing (A) 100 parts by weight of a polydiorgano-
siloxane having terminal silicon-bonded hydroxyl groups
and wherein at least 50 percent of the total organic
substituents are methyl, (B) from 2 to 20 parts by weight
of a complex of titanium represented by the general formula
~L245394
" ,,o = CX
(QO)2Ti- CY
~ `O - CZ 2
wherein each Q is a group having from 2 to 6 carbon atoms
per group which is selected from hydrocarbon groups and
groups composed of carbon, hydrogen, and oxygen in the form
of ether linkages, each X and Z is an alkyl group having
from 1 to 4 inclusive carbon atoms per group, and each Y is
a hydrogen atom or an alkyl group having from 1 to 4
inclusive carbon atoms per group, and (C) from 3.3 to 33.3
parts by weight of one or more oxime silanes of the general
formula
R4_nSi(ON=cR 2)n
wherein each R is a monovalent group selected from alkyl
groups having less than 6 carbon atoms, vinyl, allyl, and
phenyl, each R' is a monovalent group selected from alkyl
groups having from 1 to 6 inclusive carbon atoms and phenyl,
and n has an average value of from 2.1 to 3.
Also included within the scope of this invention
is the cured elastomeric product of the said compositions
:~2~3g4
and the use of such compositions for sealing joints,
cavities, and other spaces.
Detailed Description of the Invention
In the polydiorganosiloxanes (A) the organic
substituents are selected from lower aliphatic hydrocarbon
groups, e.g. methyl, ethyl, propyl, or vinyl; phenyl, and
fluorinated hydrocarbon groups, e.g. 3.3.3-trifluoropropyl.
At least 50 percent of the total organic substituents
should be methyl, the preferred polydiorganosiloxanes being
those wherein substantially all of the organic substituents
are methyl. The viscosity of the polydiorganosiloxane
employed is not critical but preferably lies within the
range from 500 to 200,000 mPa s at 25C. Most preferred
are the polydimethylsiloxanes having a viscosity within the
range from 1,000 to 75,000 mPa s at 25C. Polydiorgano-
siloxanes (A) are well-known substances. They are widely
employed in the production of moisture-curable silicone
compositions and can be represented by the general formula
HO-SiR''2(OSiR''2)XOH
wherein each R" represents an organic substituent, e.g.
methyl, and x is an integer, preferably having an average
value of from about 150 to about 1500.
,.. . .. . .
,.
539~
The titanium complexes employed as component IB)
of the compositions of this invention are titanium chelates
represented by the general formula
, ,O=CX
(Qo)2Ti CY
\ ~o - CZ 2
wherein each Q represents a group having from 2 to 6 carbon
atoms and selected from hydrocarbon groups and groups com-
posed of carbon, hydrogen, and oxygen in the form of ether
linkages, X and Z each represent an alkyl group having from
1 to 4 inclusive carbon atoms and Y represents a hydrogen
atom or an alkyl group having from 1 to 4 carbon atoms. In
the general formula, Q may be, for example, ethyl, isopropyl,
n-butyl, pentyl, methoxyethyl, methoxypropyl, or
CH30C2H40C2H4-. Preferably Q is butyl or pentyl, X and Z
are each methyl and Y is hydrogen. The most preferred com-
plex for use in the compositions is di-butoxytitanium-
bis(acetylacetonate).
The titanium complexes (B) are, in general, known
substances and a number of them are commercially available.
They may be prepared, for example, by reacting an alcoholate
of titanium, derived from, e.g. ethanol, butanol, diethylene
. ~
-
~L2~539~
glycol monomethyl ether, or phenol, with a diketone, e.g.
acetylacetone.
At least 2 and up to 20 parts by weight of the
complex (B) can be employed. When less than 2 parts (B)
are employed, reduced adhesion of the cured elastomer to
certain substrates can occur. More than 20 parts by weight
of (B) can result in an undesirably soft elastomer and ex-
tended curing time. In general, it is preferred to employ
from about 5 to about 12 parts by weight of the titanium
complex.
In the general formula of the oxime silanes tC),
the substituents R may be, for example, methyl, ethyl,
propyl, vinyl, allyl, or phenyl and R' may be an alkyl
group as exemplified for R or phenyl. The preferred oxime
silanes are those wherein R represents methyl, ethyl, or
vinyl, each R' represents methyl or ethyl and n is 3.
Examples of the operative silanes (C) are methyl tris(methyl-
ethylketoxime)silane, vinyl tris(methylethylketoxime)silane,
methyl tris(diethylketoxime)silane, and phenyl tris(methyl-
ethylketoxime)silane. ~rom 3.3 to 33.3 parts by weight of
the oxime silane are employed, the preferred level of
addition for general application being from about 5 to
about 18 parts by weight.
The compositions of this invention can be pre
pared by mixing (A)~ (B), and (C) in any order and employing
539~
any suitable mixing equipment. However, where reduced
modulus is the prime consideration, it is desirable that at
least a portion of the complex (B) be mixed with the polydi-
organosilo~ane (A) prior to the addition of the oxime silane
(C). Such a method of operation is particularly preferred
if an active condensation catalyst, e.gO a tin carboxylate
is present in the mixture.
The compositions of this invention may contain as
optional constituents other ingredients which are conven-
tional to the formulation of silicone rubber sealants and
the like. For example, the compositions will normally con-
tain one or more reinforcing and/or extending fillers such
as high surface area fume and precipitated silicas, crushed
quartz, diatomaceous earths, calcium carbonate, barium
sulphate, iron oxide, titanium dioxide, and carbon black.
The proportion of such fillers employed will depend on the
properties desired in the elastomer-forming composition and
the cured elastomer. Usually the filler content of the
compositions will reside within the range from about 5 to
about 150 parts by weight per 100 parts by weight of poly-
diorganosiloxane (A).
Other ingredients which may be included in the
compositions are catalysts for increasing the rate of cure
of the composition, pigments, agents (usually organosilicon
compounds) for treating fillers, and additional adhesion
,:.,.
, ~
539~
improving substances. Suitable curing catalysts are well-
known in the art and include the metal salts of carboxylic
acids, for example, lead octoate, dibutyltin dilaurate,
dibutyltin diacetate, stannous octoate, and dibutyltin
diversatate. The catalyst may be employed in conventional
amounts, i.e. from about 0.05 to 10 parts by weight per 100
parts of (A). Another conventional ingredient which can be
employed as a plasticizer and to reduce further the modulus
of the cured elastomer is a polydimethylsiloxane having
terminal triorganosiloxy grGups wherein the organic
substituents are, e.g. methyl, vinyl or phenyl or combina-
tions of these groups. Such polydimethylsiloxanes normally
have a viscosity of from about 100 to about 100,000 mPa s
at 25C and can be employed in amounts up to about ~0 parts
per 100 parts of (A).
Any optional additional ingredients may be incor~
porated at any stage of the mixing operation. As herein-
before indicated, however, it is generally preferred to add
the curing catalyst after mixing together the complex (B)
and the polydiorganosiloxane (A). After mixing, the com-
positions may be stored under substantially anhydrous con-
ditions, for example, in sealed containers until required
for use.
~; The compositions of this invention cure on
exposure to atmospheric moisture and may be employed in a
.
12~539~
variety of applications, for example, as coating, caulking
and encapsulating materials. They are, however, particularly
suitable for sealing joints, cavities and other spaces in
articles and structures which are subject to relative move-
ment. They are thus particularly suitable as glazing
sealants and for sealing building structures and the decks
of ships.
The following Examples in which the parts are ex-
pressed by weight illustrate the invention.
_a~æ~
A silanol-terminated polydimethylsiloxane having
a viscosity at 25C of 50 Pa-s (45 parts) was thoroughly
mixed with di(n-butoxy)titanium bis-acetylacetonate (com-
plex) (4 parts of a 75% by weight solution in butanol).
Into this mixture was then incorporated the oxime silane
CH3Si[ON=C(CH3)(C2H5)]3 (2.5 parts), dibutyltin dilaurate
(0.5 part), a trimethylsiloxy-terminated polydimethyl-
siloxane having a viscosity of 1000 mPa's at 25C (20
parts), calcium carbonate (18.5 parts) and fume silica (5.5
parts). The components were mixed in a Drais planetary
mixer fitted with a vacuum port. Three additional com-
positions were then prepared in identical mannex except
that the proportions of oxime silane employed were
respectively fi.5, 6.5, and 8.5 parts.
~L2~5394
The freshly prepared compositions were poured
into flat molds and exposed to the normal laboratory atmos-
phere (approximately 50~ relative humidity and 22C) for
one week. The physical properties of the cured samples
were then measured using dumbbell-shaped test pieces (DIN
Standard 2 x 4 x approximately 40 mm) cut from the sheets,
and a tensile test machine (FRANK Type 81560) and Shore A
hardness test equipment. The results were as shown in
Table I:
,
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o
.,~
M C~
_l ~r! U
r-J .IJ
~ U~ Z
O r~
C)
a) ~ co 0
S~ ~ ~ u~
O
~ m
H
~ dP
rl
~ ~ O O O O
o m u~
r~
~o
U~
a) ~
o
~O r~
~ tn ,~
.r~
X
o ,~ P~
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Example 2
A series of compositions was prepared employing
the method, ingredients and proportions described in
Example 1 except that the amount of oxime silane was
maintained constant at 4.5 parts and the proportion of
the solution of titanium complex varied from O to 12
parts. The freshly-prepared samples were allowed to cure
to elastomeric sheets as described in Example 1 and
physical property measurements performed on dumbbell test
pieces with the following results as shown in Table II:
.. ~ . .,
539~
U~
O ~ ~ co ~ r~
,~
UO N 1` ~ '\ ~ Cl~
~ U~ Z
O ~
O
O ~
U~ o
,~ K
~ Ll~
C~ O
S~ ~
O
H h
H
m
~ ~P
E~ o
U~
~o~ V
~Y o o o Ln O O U~
a) u~ O ~ O
tll h ~ D ~ 1-- co ~) ~r ~ ,1
O
~1
_
U~
O a) h
1: o Q
GO ~ r ~ ~ ~1 ~ o 1-
o
X ~--
O U~
~rl ~
O ~ O U~ O O O
0'-1
O--~ o ~ ~ ~ ~ ~ oo
U~
14
,.,
,
~2~5394
It can be seen from the table that in the
absence of the complex an elastomer is obtained having an
undesirably high modulus of elasticity for sealant applica-
tions. The composition having 12 parts of complex sol-
ution (9 parts of complex) cures to an elastomer having
little strength and which would thus be generally unsuit-
able for the majority of applications. Compositions con-
taining about 3 to 4 parts of the complex solution cure
to elastomers having a desirable combination of properties
for sealant purposes, namely relatively low hardness,
moderate modulus of elasticity, and large elongation at
break.
This example illustrates the effect of a
titanium complex on the adhesion of the elastomer to
glass, aluminium, and polyvinyl chloride substrates.
An elastomer-forming composition was prepared
according to the method and formulation of Example 1, the
amount of oxime silane employed being 4.5 parts. For
comparison, a second composition was similarly prepared
except that the titanium complex was omitted.
A bead of each composition 12 x 12 x 5~ mm was
formed between two surfaces of each of the substrates to
form sandwich-like H-pieces and the compositions allowed
to cure under normal atmospheric conditions for one month.
The parallel substrates in each H-piece were then pulled
aBart at a rate of 6 mm per second and the percentage
elongation at which breakage occurred was noted. The
results obtained are given in Table III and clearly show
the effect of the titanium complex.
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TABLE III
Without
Substrate With Complex _m~lex
Glass > 300 % 66%
Aluminum > 300 % 0% *
PVC ~ 300 % 0% *
* No adhesion to substrate
Example 4
An elastomer-forming composition was prepared as
in Example 1 employing 4.5 parts of the oxime silane and
the dibutyltin dilaurate being omitted. The composition
cured to a low modulus elastomer when exposed to the normal
laboratory atmosphere.
16
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