Note: Descriptions are shown in the official language in which they were submitted.
60S~ 9~g
--
ROOM TEMPERATURE VULCANIZABLE SILICONE
COMPOSITIONS HAVING IMPROVED A3HESIOM
Background of the Intention
The present invention relates to room temperature vulcaniz-
able silicone rubber compositions which exhibit improved adhe-
sion upon curing. More particularly, the present invention
relates to room temperature vulcanizable silicone rubber compo-
sitions comprising a polydiorganosiloxane wherein the silicon
atom at each polymer chain end is ~erminated with at least two
hydrolyzable groups, a non-chelate condensation catalyst, and a
metal chelate adhesion promoter.
Prior to the present invention it was well known in the art
that various metal salts of carboxylic acids, metal chelates,
organic acids and organic bases could be used as condensation
catalysts for room temperature vulcanizable silicone rubber
compositions.
Evans~ U.S. Pat. No. 3,622,529, discloses a composition
stable under substantially anhydrous conditions and curable to
the solid, elastic state in the presence of moisture which
comprises a silanol chainstopped polydiorganosiloxane, an imid-
atosilane of the formula
60SI-99g/02~0p/GLL:mz
R3
(ROC = N ~ ~
Si - (R )d
(R20)b
where R and R are each organic radicals of not more than 18
carbon atoms selected from hydrocarbyl, halohydrocarbyl, nitro-
hydrocarbyl and alkoxyhydrocarbyl; R1 is hydrogen or a
radical selected from hydrocarbyl~ halohydrocarbyl, and cyano-
alkyl; R3 is hydrogen or an organic radical of not more than
18 carbon atoms selected from hydrocarbyl, halohydrocarbyl,
nitrohydrocarbyl, alkoxyhydrocarbyl, dialkylamino, and
R O C - CH2 -
wherein R4 is an organic radical selected from aliphatic
hydrocarbyl, aliphatic halohydrocarbyl, aliphatic nitrohydro-
carbyl and
R5
N
R6 ~
60SI-999/0200p/GLL:mz
where R5 and R6 are each aliphatic hydrocarbyl, a is an
integer from 2 to 4, inclusive, b is an integer from 0 to 2,
inclusive, d is 0 or 1, and the sum of a, b and d is 4, and,
optionally, a minor amount of carboxylic acid salt and/or
chelate of a metal ranging from lead to manganese, inclusive,
in the electromotive series of metals.
5mith et al., U.S. Pat. No. 3,708,467, discloses a composi-
tion stable under substantially anhydrous conditions and
curable to the solid, elastic state which comprises a silanol
chainstopped polydiorganosiloxane, a silane represented by the
formula RmSi(ORl)4 m where R and Rl are radicals having
not more than about 8 carbon atoms selected from the group
consisting or hydrocarbyl, halohydrocarbyl and cyano lower
alkyl, and a catalyst system containing a first catalyst which
is a salt, alkoxide, hydroxide or oxide of a metal ranging from
lead to manganese in the electromotive series of metals and 2
second catalyst which is a titanium chelate.
The present invention is based on the surprising discovery
that improved adhesion is obtained if a polydiorganosiloxane
having the silicon atom at each polymer chain end terminated
with at least two hydrolyzable groups is employed in combina-
tion with a non-chelate condensation catalyst and a metal
chelate adhesion promoter.
Summary of the_l_ver,tion
~t is an object of the present invention to provide room
temperature vulcanizable silicone rubber compositions which
exhibit improved adhesion to various substrates upon curing.
60SI-g99/0200p/GLL:mz
It is another object of the present invention to provide
methods for making room temperature vulcanizable silicone
rubber compositions which exhibit improved adhesion to various
substrates upon curing.
In accordance with one aspect of the present invention
there is provided a room temperature vulcanizable silicone
rubber composition having improved adhesion upon curing,
c~mprising:
(a) a polydiorganosiloxane wherein the silicon atom at
each polymer chain end is terminated with at least two
hydrolyzable radicals,
(b) an effective amount of non-chelate condensation
catalyst, and
(c) an effective amount of metal chelate adhesion promoter.
Description of the Invention
The present invention provides room temperature vulcaniz-
able silicone rubber compositions which cure to the solid,
elastic state upon exposure to moisture and exhibit improved
adhesion to various substrates, comprising:
(a) a polydiorganosiloxane wherein the silicon atom at
each polymer ehain end is terminated with at least two
hydrolyzàble radicals,
60SI-999/0200p/GLL:mz
(b) an effective amount of non-chelate condensation
catalyst, and
(c) an effective amount of metal chelate adhesion promoter.
Polydiorganosiloxanes wherein the silicon atom at each
polymer chain end is tenminated with at least two hydrolyzable
radicals are known in the art. Such polydiorganosiloxanes can
be represented by the general formula
( p,2 ) a ~ R ~ ( R2 )
(R )3-~a~b) ! ~siot si (OR )3-(a~b)
Xb R ~n Xb
where R is a C(l 13) mpnoYalent substituted or unsubstituted
hydrocarbon radical, which is preferably methyl, or a mixture
of a major amount of methyl and a minor amount of phenyl,
cyanoethyl, trifluoropropylO vinyl or mixture thereof; Rl is
a C(l 8) aliphatic organic radical selected from the group
consisting of alkyl, alkylether, alkylester, alkylketone and
alkylcyano radicals or a C(7 13) aralkyl radical; R2 ls a
C(l 13) monovalent substituted or unsubstituted hydrocarbon
radical; X is a hydrolyzable group selected from the group
consisting of amido, amino, carbamato, enoxy, imidato,
60SI-999/0200p/GLL:mz
isocyanato, oximato, thioisocyanato and ureido radicals, a
equals 0 or 1, b equals 0 to 2, inclusive~ the sum of a ~ b
equals 0 to 3, and n is an integer up to about 2500.
Preferably Rl and R2 are methyl.
Polydiorganositoxanes within the scope of the above formula
I. are known in the art, for example, those described in
United State~ Patent Number 4,395,526 to
White~et al, which ~atent is a~signed to the sam~ assignee
as the present invention.
It is especially preferable that polydiorganosiloxane (a)
have at least two alkoxy groups bonded to the silicon atom at
each polymer chain end. These polyalkoxy terminated polydi-
organosiloxanes can be made, for example, by following
the teaching of-Chung, in U~ited Stat~s Patent
~umber 4,515,~3~.- - -
The condensation catalyst (b) used in the practice of the
invention can be any of those known in the art except for metal
chelates. The reason that metal chelates are excluded is that
in the present invention metal chelates commonly employed as
condensation catalysts are utilized as adhesion promoters.
Thus, those skilled in the art will appreciate that although
the metal chelates will inherently function as condensation
catalysts, in the present invention they are utilized primarily
as a means for improving the adhesion of the cured silicone
composition to various substrates.
Accordingly, for purposes of the present lnventlon, the
condensation catalyst can be selected from, for example, metal
salts of monocarboxylic acids and dicarboxylic acids, metal
alkoxides, organic bases, organic acids, and the like. Prefer-
6051-999/0~09p/GLL:mz
red condensation catalysts are metal salts of carboxylic ~cids
and especially pre~erred are tin compounds such ~s dibutyltin-
ditaurate, dibutyltindiacetate, dibutyltindimethoxide~ carbo-
methoxyphenyl tin tris-uberate, tin octoate, dimethyl tin
dibutyrate, triethyl tin tartrate, tin oleate and tin naphthen-
ate. Dibutyl tin diacetate is particularly preferred.
Examples of other metal condensation catalysts are ~ircon-
ium octoate, lead 2-ethyloctoate, iron 2-ethylhexoate, cobalt
2-ethylhexoate, manganese 2-ethylhexoate, zinc 2-ethylhexoate,
antimony octoate, bismuth naphthenate~ zinc naphthenate and
zinc stearate.
Examples of nonmetal condensation catalysts are hexylam-
monium acetate and benzyltrimethylammonium acetate.
Other suitable condensation catalysts will be obvious to
those skilled in the art or can be easily ascertained without
undue experimentation.
Generally, an effec$ive amount of condensation catalyst is
from about 0,001 to about 2 parts by weight per 100 parts by
weight of polydiorganosiloxane (a). More preferably, the
condensation catalyst is used in an amount ranging from about
0.1 to about 1 part by weight per 100 parts by weight of polydi-
organosiloxane (a).
The metal chelates employed as adhesion promoters in the
practice of the present invention can be based on lead, tin,
zirconium, antimony, zinc, chromium, cobalt, nickel, aluminum,
gallium, germanium or titanium. Most preferably, however~ the
metal chelate is a titanium chelate.
- 8 - 60SI-999
Illustrative titanium chelate compounds useful
for practiciny the present invention are described in
U.S. Pat. Mo. 3,334,067 to Weyenberg, U.S. Pat. No.
3,689,454 to Smith et al., and U.S. Pat. No. 4,438,039
to Beers et al.
Among the more preferred titanium chelates are,
for example:
/CH3 (C2H20)9CH3
CH ~ 0 = C / H2 \ 0 - C
C ~ Ti CH C~ Ti D -C-CH3
CH2 - 0 - C 2 0 - C
CH3 2 CH3 ~ 2
C2H5 / (C2H5)2
/CH2 0 \ 0 = C \ CH 0 0 = C
C ~ Ti/ f H C~ Ti/ CH
CH2 0 CH3 CH2 0 0- -C 2
~69L~
- 9 -60SI-999
/ 9 19 (CH2) 2N
\ / C CH
CH3 2 2 ~ 2
C~ Z
:
- 10 - 60SI-999
/C2H5 /C15 32
C~3 ~ C \ 0=C
fH --o \ fHo ~
T CH T D H
CH2 0 \ ~ H2 \
O C O C
CH3 2 CH3 2
. CH3 CH3
CH ~O C CH --O ~O C
HO--C~ T CH C~ T J ~
2 --C CH2 O \O C// 2
6051 -~99/()200p/GLL :mz
~LI tlO lDcludeJ ~r~:
d~lJo~t~Aroyl~thyl~De t~t~D~tæ
~isaD~u~ dl~Pth~cryl,-te o~ysc~tatP
l~taniu~ d~Dcryl~te t~y~c~-tP
~It~DiUll' dl(cu~ylph~Dol~te)~y~cetate
T3tJoiu~ dl~diDctylpho6ph~te)c~y4c~t~t~
d~(dlo~tylphc)~p~l~t2)ethy~D2 t~t~te
~t~DiU~ di (d~octy~p~rophDBph~te)o~y~c~tate
dl(dioctylpyropbo6phat~)etby~eDc t~t-l~ate
The following titanates are particularly preferred.
~ CH3(or ~C2H5
\ /~ \
CH2 Ti ~ ~ CH C H ~ ~ ~ ~ o
CH2 0 O C 2 ~ CH
l CH3 2
60SI-999/0200p/GlL:mz
It has been found that an effective ~mount of metal chelate
adhesion promoter generally ranges from about 0.05 to about 2
percent by weight of polydiorganosiloxane (a). Of course, more
can be used~but no particular advantage is obtained thereby.
If less than about 0.05 percent by weight of metal chelate is
utilized, the adhesive bond between the silicone elastomer and
the substrate is not sufficiently strong for most purposes. In
more preferred embodiments the metal chelate is present in an
amount of from about 0.1 to about 1.5 percent by weight of
I0 polydiorganosiloxane (a). Of course, mixtures of metal che-
lates are also contemplated by the present invention.
,
Conventional additives such as fillers, plasticizers,
crosslinking agents, scavengers for hydroxy functional groups,
and the like may also be included in the compositions of the
I5 present invention.
In the practice of the present invention, the room tempera-
ture vulcanizable compositions can be made by agitating, for
example stirring, the respective ingredients of the curable
composition in the substantial absence of moisture. The
temperature can vary from about 0C to about 180C depending
upon the degree of blending, the type and amount of filler, etc.
In a preferred method for making the compositions of the
present invention the polydiorganosiloxane having at least two
hydrolyzable groups at each polymer chain end is admixed with
reinforcing filler and plasticizing fluid to form an RTV base.
Thereafter, a s;lane crosslink;ng agent, a scavenger for
hydroxy functional groups, condensation catalyst, and metal
chelate adhesion promoter are mixed with the RTV base,
605I-999/0200p/GLL:mz
In order to better enable the artisan to practice the
present invention, the following examples are provided by way
of illustration and not by way of limitation. All parts are by
weight unless otherwise noted.
EXAMPLES
Exam
A vinyldimethoxy endstopped polydimethylsiloxane W3S
prepared by charging a one gallon Ross ~ mixer equipped with
a vacuum line and nitrogen purge with 100 parts by weight
I0 silanol endstopped polydimethylsiloxane having a viscosity of
22,000 centipoise at 25C, 1.5 parts by weight vinyltrimethoxy-
silane, 0.2 parts by weight dibutylamine and 0.05 parts by
weight acetic acid. This mixture was agitated for 15 minutes
at 100C under a nitrogen atmosphere. An additional 45 minutes
I5 mix at 100C under a 5 mm Hg vacuum yielded a shelf stable
vinyldimethoxy endstopped polydimethylsiloxane having a
viscosity of 26,900 centipoise at 25~C.
Example 2
A one gallon Baker-Perkins mixer equipped with a vacuum
line and nitrogen purge was charged with 100 parts by weight of
the vinylmethoxy endstopped polydimethylsiloxane prepared in
Example 1, 40 parts by weight of fumed silica filler treated
with octamethy kyclotetrasilo%ane and hexamethyldisilazane, 40
parts by weight of a 3000 centipoise t-buytl-silanol endstopped
polydimethylsiloxane, and 15 parts by weight of a 50 centipoise
silanol endstopped polydimethylsiloxane. This mixture was
agitated under 20 mm Hg vacuum for 60 minutes to provide an RTV
base.
,
60S~-999/0200p/GLL:mz
-14-
~o 100 parts by weight of the RTV base was added 7 parts by
weight vinyltrimethoxysilane crosslinking agent, 2 parts by
weight hexamethyldisilazane scav2nger for hydroxy functional
groups, 1.0 part by weight dipropoxytitanium-bis-(ethylaceto-
acetate) and 0.1 part by weight dibutyltindiacetate, using a
Semco ~ catalyzer/mixer. Foll~wing mixing, a profile o~ the
physical properties of the composition was obtained. The
results are set forth in Table 1.
- T~ble l. E_a~ple 2 E~p~r~eDtal ~u~t~
Prope rty
Exp~ 2 Results
Sp. CrAv1ty ~.08S
AppllcatloD R~t~, g/~1D. 240
l~ck Free Tl~ in. 30
~ov, lDch 0 05 .
Duro~reter, Shore A ~ 33
T~DSI1~, p61 ~ 5~9
E~C~D8atloD, ~ * 49~
Peel Adheslo~ ppi *R
Al ulD. 2024 80
Cold rolled atee~ 55
G~a66 83
48 hr/lOO~C Accel. Age *~
Duro~eter, Shore A 35
~en~lle, p~l 409
ElODgatl~lD, % 461
7 d~y cure flt 5~ R .H . aDd 25 ~C
14 day cure ~t 502 R.H. ~nd 25-C
60SI-999/0200p/GLL:mz
-15
Example 3
Exa~ple 1 was repeated, using 1.5 parts by weight methyltri~
methoxysilane to provide a methyldimethoxy endstopped polydi-
methylsiloxane having a viscosity of 26,500 centipoise at 25JC.
Example 4
-
An RTY base was prepared as in Example 2 using the methyl-
dimethoxy endstopped polymer of Example 3 and vinyltrimethoxy-
silane crosslinking agent was replaced with 1 part by weight
methyltrimethoxysilane crosslinking ayent. The physical
properties of this composition were also obtained and are set
forth in ~able 2.
~ble 2: E~p~e 4 E~perlDental R~ultc
Property E3p. 4 Re6l~1t6
.
Sp . Gr~vl t y ~ . 086
App~ic~tiDD R~te~ ~lD. 224
ck Free ~ ;e, mlD, 30
~1 ~v, ~ nch 0, 05
I>uro~eter, Shore A *~ 35
leD~lle, pol ~ 49B
E~OD,~,~t~ , 2 ~ .~50
P~el AdhPSioD ppl ~
Al u~ . 2024 74
Col d rol~ ~d steel 68
Gl ~ sc 82
48 hr/~00c Accel. ~,ge nll
~uro~ter, 5~,or~ A 3]
TeD6l1~, p61 3B2
El onga t I DD, 2 4 91
7 day c~re ~t 502 R.H. Dnd 25-C
4 d~y cure at 502 R.H. Dd 25-C
,~.
60Sl-999/0200p/GLL:~z
Example 5
In this example, Example 4 was repeated without the
addition of titanium chelate. The results are set forth in
~able 3.
Table 3: Ex~p~e 5 E~pPri eDtal Recult6
E~p. 5 RP~U1t6
Property
1 .083
Sp. Gravi ty 201
Appllcatl OD Rate, g/~lD.
Tack Free Ti~e, ~io. O.OS
Fl ow, i Dch 31
Duros;eter, Shore A t
Te n~ i 1 e , p~ i 50 2
EIC~DgatiOD~ 2
Pee~ Adhe~loD pp~
Al u~ . 2024
Cold roll ed ~teel
GIA~ .
48 hr/lOO~C Acc~ e
Duro~eter, SP~ore A
TeD6il e, pti
El onga t i o~, 2
7 ~day cure at 5G~ R.H. and 25DC
14 day cure at 50~ R~H. and 25 C
60SI-99g/0200p/GLL:mz
Example 6
Example 4 was again r~peated, h~wever, this time 1.0 part
by weight aminoethylaminopropyltrimethoxysilane was used as an
adhesion promoter in place of the titanium chelate. The
results are reported in Table 4.
~bl ~ 4: ~a~pl e 6 E ~P~r1~DeDta1 Rr~ul
P ro pe r t y Esp . S Re 6u 1 t
Sp GrB~lty 1.080
,~ppllcatioD Rate, ~/~Dln. 281
~ck Free Tl~e, ~1D. 20
~10W, 1DC~
Duro~eter, Shore A ~ 4~
Sen~11e, p61 ~' 472
EloDgatioD~ Z h 41D
Pee~ Adhe~loD ppi **
1~ u~. 2024 12
Cold rolled 6teel 4
Gla6~ 14
48 hr/~00C Accel. A~e l~
D-lro~eter, Shore A 38
Ie r~ p6 i L02
E~O~atlOD, a 45~
7 day cure ~t 507. R.H. and 25C
~* 14 day cure at 50~ R.H. and 25C
60SI-999/0200p/GLL:mz
-18-
Example 7
~ xample 4 was repeated, however, this time 1.0 parts by
weight of 1,3-dioxypropanetitanium-bis(acetylacetonate) was
used as the adhesion promoter. The test results are pr~Yided
in ~able 5.
Table ~: E~J~ple 7 E~p~rl~ta~ R~ulta
Property E3p. 7 Re~ul t6
-
Sp Gra~ity gl 1 089
TPck Free ll~e, 010.
~ow, inch
Duro~eter, Shore ~ * 42
TeD61le, p61 64l
E~oD~stl~n, S
Peel Adhesio~ ppl ~
A]u~. 2024 71
Cold rol~ed 6teel 5~
Glass 86
48 hrll~ooc Accel~ A~e e*
Duro~Pter, Shore A 34
TeDl;ile, p6i 441
El OD&a t i OD, ~ 519
7 d~y cure at 50~ R.H. aDd 25CC
~* 14 day cure at 50~ R.H. aDd 25C