Note: Descriptions are shown in the official language in which they were submitted.
- 1 60SI 00785
SELF-BONDING PRECIOUS METAL CATALYZED
SILICONE RUBBER COMPOSITIONS
Background of the Invention
The present invention relates to self-bonding
silicone rubber compositions. More particularly, the
present invention relates to SiH-olefin precious metal
catalyzed self-bonding silicone rubber compositions
wherein the self-bonding additive is selected from silyl
maleates, silyl fumarates, maleate-functional polysiloxanes
and fumarate-functional polysiloxanes.
SiH-olefin precious metal catalyzed compositions
are well known in the artO Such compositions generally
comprise a vinyl-containing polydiorganosiloxane, an
oxganohydrogenpolysiloxane crosslinking agent and a
precious metal or precious metal-containing catalyst.
In a particularly preferred embodiment there is also
included in the composition a filler, which may be a
reinforcing filler such as fumed silica or an extending
filler such as ground quartz, and an inhibitor such as
that described in U.S. Patent No. 4,061,509, issued
December 6, 1977 to Bobear.
~0 The aforesaid compositions are generally sold
in two packages but they can be sold in three or more
packages as described in U.S. Patent No. 4,322,320,
issued ~arch 30, 1982 to Caprino~ Those skilled in
the art recognize that these types of compositions can
be cured at room temperature, in the absence of an
inhibitor, over a period of time, for example, from
~7a~'73
- 2 - 60SI 00785
several minutes to 10 hours after the components have been
mixed together. If an inhibitor is present in the
composition or if it is desired to increase the rate of
curing, the mixed components can be cured in a
s relatively short time by exposing the composition to
elevated temperatures.
Such Si~-olefin precious metal catalyzed com-
positions are particularly useful in preparing silicone
molds, encapsulants and heat curable molded, extruded,
and calendered rubber articles. However, one dis-
advantage of these compositions is that they typically
form a poor bond between the silicone rubber and a
substrate, for example, glass, aluminum, copper, steel
or the like. To solve this problem primers were
developed which allowed the cured silicone rubber to
stronyly adhere to the substrate. Inasmuch as the
application of a primer to the substrate increases both
labor and material costs, it is desirable to have
available self-bonding silicone rubber compositions.
~0 Various attempts have been made to provide
self-bonding SiH-olefin precious metal catalyzed
silicone rubber compositions, but most such attempts
failed for one reason or another~ The most common
reason that prospective self-bonding additives failed
~5 to accomplish their intended purpose has been that the
additive would poison the precious metal catalyst.
Moreover, it has often been found that additives known
to promote adhesion in other types of systems, for
example, condensation curing room temperature vulcanizable
compositions, simply did not work in SiH-olefin precious
metal catalyzed systems.
One successful self-bonding SiH-olefin precious
metal catalyzed silicone rubber composition is described
in U.S. Patent No. 3,527,655, issued September 8, 1970 to
~5 Ballard, which patent is assigned to -the same assiynee
as the present invention. Briefly, the self-bonding
.. . ..
,, :.
.. , ., . :, .
. , ~ :. . .
: : . .
7~3
- 3 - 60SI 00785
additive of Barrard ls a fluid vinyl siloxane hydrolyzate
of the formula
( ~HO)z (RO)y (CH2 = CH) SiO~y~ ) x
~here R is a lower alkyl radical, ~ is a number greater
than 3, y has a value from 0.01 to 0.4 and z has a value
of from 0.1 to 0.4.
Another successful self-bonding SiH-olefin
precious metal catalyzed silicone rubber composition is
described in U.S. Patent No. 4,329,273, issued May 11,
1~2 to Hardman et al, which patent is assigned to the
same assignee as the present invention. Briefly, the
self-bonding additive of Hardman et al is the partial
hydrolysis product of a compound of the formula
(R)a Si (OR )4-a
~here R is an unsaturated aliphatic radical having from
~ to S carbon atoms, Rl is an alkyl radical having from
1 to 8 carbon atoms, and a is 1, and wherein the partial
hydrolysis product is such that on the average 16 to 49
mole percent of the hydrocarbonoxy groups of said silane
0 are hydrolyzed.
`'Summ'ar'y'o'f-the-'I'nve'ntion
It is an object of the present invention to
provide self-bonding Si~I-olefin precious metal catalyzed
silicone rubber compositions.
~5 It is another object of the present invention to
provide a process for producing such self-bondin~ SiH-
olefin precious metal catalyzed silicone rubber compositions.
Another object of the present invention is to '
provide articles of manufacture having the self-bonding
SiH-olefin precious metal catalyzed silicone rubber
compositions bonded thereto.
Still another object of the present invention
is to provide a process for making articles of
` ~
. . .-, . -... ,. , :, .~ . :, ,, :
.. : :......... : :
~2 ~ 3
- 4 - 60SI 00785
manufacture which utilize the self-bonding SiH-olefin
precious metal catalyzed silieone rubber compositions
of the present invention.
In accordance with one aspect of the present
5 invention there is provided a curable composition,
eomprising:
(a) an olefin-containing polydiorganosiloxane
having a viscosity of at least about 250,000 centipoise at
~5C;
(b) an organohydrogenpolysiloxane crosslinking
agent;
(e) a preeious metal or precious metal
eontaining eatalyst; and
(d) an effeetive amount of adhesion promoter or
self-bonding additive seleeted from the group consisting
of silyl maleates, silyl fumarates, maleate-funetional
polysiloxanes and fumarate-functional polysiloxanes.
Description o-f 'the' Inve'ntion
There is provided in aceordance with one aspect
?~ of the present invention there is provided a curable
eomposition, eomprising:
(a) an olefin-eontaining polydiorganosiloxane
having a viseosity of at least about 250,000 eentipoise
at 25C;
~5 (b) an organohydrogenpolysiloxane erosslinking
agent;
(e) a preeious metal or preeious metal containing
eatalyst; and
(d) an effective amount of adhesion promoter or
self-bonding additive selected from the group consisting
of silyl maleates, silyl fumarates, maleate-functional
polysiloxanes and fumarate-functional polysiloxanes.
Olefin-eontaining polydiorganosiloxane (a) is
well known in the art and id described, for example in
the aforessaid U.S. Patent Nos. 4,061,609 and 4,329,273.
Basieally, polydiorganosiloxane (a) contains at least
0.005 mole pereent olefinie radieals and more preferably
-, :, :-
: ~ : ,. ~ , .
. .: : ~ : : ~ ..
- 5 - 60SI 00785
contains from about 0.01 to about 1 mole percent olefinic
radicals. It is especially preferable that the polymer
be substantially linear and that the olefinic radicals be
vinyl radicals. The olefinic radicals can be only on the
interior of the polymer chain or there can be a mixture of
terminal and on-chain olefinic radicals.
The artisan will appreciate that polydiorgano-
siloxane (a) can be a single polymeric specie or it can
be a blend of olefin-containing polymers. The viscosity
of polydiorganosiloxane ~a) can be anywhere from about
~50,000 centipoise at 25C to about 300,000,000 centipoise
at ~5~C. More preferably, the viscosity is from about
500,000 centipoise at 25C to about 200,000,000 centipoise
at ~5C, and most preferably is from about 1,000,000
centipoise at 25C to about 100,000,000 centipoise at
~5C.
The organo substituents of polydiorganosiloxane
~a), in addition to the olefinic radicals, can be any
monovalent hydrocarbon radical or substituted monovalent
2~ hydrocarbon radical. Preferred organo radicals include
methyl, phenyl r trifluoropropyl and mixtures thereof.
The second essential component of the present
invention is organohydrogenpolysiloxane (b), which is
also well known in the art and described in the
~5 aforementioned U.S. Patent Nos. 3,527,65~, 4,061,609 and
~,3~9,~73. Organohydrogenpolysiloxane (b) can be any
~olydiorganosiloxane having silicon-bonded hydrogen
atoms which is normally utilized by the artisan as a
crosslinking ag0nt. Such organohydrogenpolysiloxanes can
3a be linear polymers or resinous materials.
Processes for producing olefin-containing
polydiorganosiloxane (a) and organohydrogenpolysiloxane
(b) are well known in the art. Fluoro-containing
organohydrogenpolysiloxane crosslinking agents which
are intended to be within the scope of the present
invention are described in U.S. Patent No. 4,041,010,
3~2~73
- 6 - 60SI 00785
issued Au~ust 9, 1977 to Jeram, assigned to -the same
assignee as the present invention.
Precious metal or precious metal-containing
catalyst (c) includes all of the well known platinum
and rhodium based catalysts which are effective for
promoting the reaction between silicon-bonded olefinic
radicals of polydiorganosiloxane (a) and silicon-bonded
hydrogen atoms of organohydrogenpolysiloxane (b). These
materials especially include ~he platinum hydrocarbon
1~ complexes described in U.S. Patent Nos. 3,159,601 and
3,159,662, both issued December 1, 1964 to Ashby and
the platinum alcoholate complexes described in U.S.
Patent No. 3,220,972, issued November 30, 1965
to Lamoreaux, as well as the platinum complex catalysts
of U.S. Patent No. 3,184,730, issued June 4, 1974 to
~arstedt. Additionally, the platinum chloride-olefin
comple~es described in U.S. Patent No. 3,516,946 issued
~une 23, 1970 to Modic are also useful herein.
Other metal or metal complex catalysts which
~0 can be used to practice the present invention include
those which are based on ruthenium, palladium, osmium
and irridium.
The precious metal or precious metal containing
catalyst is employed in an amount effective for promoting
~5 crosslinking of the aforesaid polydiorganosiloxane (a)
and organohydrogenpolysiloxane ~b). Generally, an
effective amount of hydrosilation catalyst ranges from
about 1 to about 500 parts per million, as platinum
metal, based on the weight of polydiorganosiloxane (a)
and or~anohydrogenpolysiloxane (b). Of course more or
less catalyst may be utilized without departing from
the spirit or intended scope of the invention.
The final essential ingredient of the curable
composition of the present invention is adhesion promoter
(d). For purposes of the present invention, the terms
`'adhesion promoter" and "self-bonding additive`' are
: , : -, . . :: -: . , ~ :
- . ,.. - ~ . . : - :
.:
. . ...
, ~: : ~ : , . . , . :
:, .
. . .
73
- 7 - 60SI 00785
intended to be synonymous and, therefore, are u~ed
interchangeably. Adhesion promoter (d) can generally
be described as a silyl maleate, silyl fumarate, a
maleate-functional polysiloxane, fumarate-functional
polysiloxane, or mixture thereof. These compounds and
their methods of preparation are described in U.S.
Patent No. 3,759,968, issued September 18, 1973 to
Berger et al, which patent is assigned to the same
assignee as the present invention.
1~ Generally, adhesion promoters within the
intended scope of the present invention are within the
scope of the following formulas:
(1) R2 C - Z - R - Si (R )n (M)3-n
R - C - Z - G
(2) R - C - Z - R - Si (R )n (M)3-n
G - Z - C - R2
f 2
15 (3) ( R - C - Z - R ~ ~2 ~
R - C - Z - GJ a ~ J SiO 4-a-b and
~ 2
(4) ~ R - C - Z - R 2
~G _ n _ C - R2 a R b 4-a-b
O O
where Z is selected from C - O, C, phenylene, CONH, and
CONRl, G is selected from hydrogen, R3 and R4HC(Rl)dSio3 c d~
where R is selected from monovalent hydrocarbon 2
radicals and monovalent halogenated hydrocarbon radicals,
where R and R4 are divalent hydrocarbon radicals, R is
selected from monovalent hydrocarbon radicals and
monovalent halogenated hydrocarbon radicals, a varies
from 0.005 to 2.0, b varies from 1.0 to 2.5, the sum of
,: ;, . ,. . ; .::,.: : : .: .:
~7~ 73
- 8 - 60SI 00785
a and b varies from 1.005 to 3.0, c varies from 0 to 1.0,
d varies from l.0 to 2.5, the sum of c and d varies from
l.o to 3.0, M is selected from R3O and o radicals,
R3Co
R~ is selected from hydrogen and alkyl radicals having
from 1 to about 15 carbon atoms, and n is a whole number
from l to 3, inclusive.
Especially preferable adhesion promoters for
practicing the present invention are:
bis-(trimethoxysilylpropyl) maleate,
l~ bis-~trimethoxysilylpropyl) fumarate,
bis-(dimethoxymethylsilylpropyl) maleate,
bis-(dimethoxymethylsilylpropyl) fumarate,
trimethoxysilylpropyl allyl maleate, and
trimethoxysilylpropyl allyl fumarate.
The most preferred adhesion promoters for practicing the
present invention are bis-(trimethoxysilylpropyl) maleate
and bis-(trimethoxysilylpropyl) fumarate, or a mixture
thereof.
The artisan can readily determine which compounds
~0 within the foregoing general formulas (1) to (4) are most
effective for a particular purpose without undue
experimentation.
In practicing the present invention it has been
found that an effective amount of adhesion promoter
~5 ~an~es from about 0.1 to about 5 parts by weight per 100
parts by weight of olefin-containing polydiorganosiloxane (a).
Methods for preparing such silyl maleates, silyl
fumarates, maleate-functional polysiloxanes and fumarate-
functional polysiloxanes are described in the aforesaid
~.S. Patent No. 3,759,968.
In a preferred embodiment of the present
invention there is also included a hydroperoxide inhibitor
as described in aforesaid U.S. Patent No. 4,061,609.
The artisan will appreciate that the inclusion of such
an inhibitor will extend the work iife of the heat curable
compositions of the present in~ention. For most
~ , . , i
",,~ ,
.:: ,i,;, ,,; , , "
-. . . ~ ., - . :-:
73
~ 9 ~ 60SI 007~5
applications there should be present from about 0.01 to
10 parts by weight inhibitor per 100 parts by weight
olefin-containing polydiorganosiloxane (a). Suitable
hydroperoxy inhibitors are described in the aforementioned
Bobear U.S. Patent 4,061,609 and the interested reader
is referred thereto for further information.
Another additive that can be employed to provide
a preferred embodiment of the present invention is a filler.
O course, the filler can be included in the composition
1~ whether or not the inhibitor is included. Generally,
the amount of filler can be as small as 5 parts by weight
per 100 parts by weight olefin-containing polydiorgano-
siloxane (a) to as much as 250 parts or more by weight
of filler per 100 parts by weight of olefin-containing
polydiorganosiloxane (a). The preferred fillers are
reinforcing fillers such as fumed silica and
precipitated silica, however, extending fillers can be
used in addition to or in place of such reinforclng
fillers. Examples of suitable extending fillers
include iron oxide, diatomaceous earth, calcium
carbonate, ground quartz, cork and the like.
Other additives known in the art may also be
included in the self-bonding curable compositions of the
present invention, for example, flame retardants, plast-
~5 icizers, pigments and the like.
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 indicated.
EXAMPLES
Ex-ampl`e ]
A precious metal catalyzed heat curable
silicone rubber composition was prepared by mixing the
following components:
vinyl chainstopped polydimethylsiloxane 40 parts
having a viscosity of 20,000,000 cps. at 25C
:~ . ,: ,., ~ ., . . , : , :
~27~97~
- 10 - 60SI 00785
vinyl chainstopped methylvinylpolysiloxane 40 parts
having 0.05 mole % vinyl on the polymer
chain and a viscosity of 20,000,000 cps. at 25C
vinyl chainstopped methylvinylpolysiloxane 20 parts
having 0.6 mole % vinyl on the polymer
chain and a viscosity of 20,000,000 cps. at 25C
silanol-containing polydimethylsiloxane2 parts
process aid having a viscosity of 20
centipoise at 25C
octanlethylcyclotetrasiloxane treated fumed silica 53 parts
linear methylhydrogenpolysiloxane 2 parts
crosslinking agent
platinum complex catalyst 1 parts
This composition, designated as Composition I,
is illustrative of prior art compositions.
Example 2
A composition, designated as Composition II,
was prepared as in Example I except that it also included
1 weight percent bis-(trimethoxysilylpropyl) maleate in
~0 accordance with the present invention.
Example 3
A composition, designated as Composition III, was
prepared as in Example 1 except that it also included 2
weight percent bis-(-trimethoxysilylpropyl) maleate in
~5 accordance with the present invention.
Example` 4
A 60 mil sheet of each of Composition I,
Composition II, and Composition III was pressed onto
each side of untreated fiberglass cloth and vulcanized
at 350F for 15 minutes. One inch by four inch sprips
of the resultant laminates were tested for peel strength
in a Monsanto Tensometer at a jaw speed of two inches
per minute. The results are set forth in Table I.
Table I
Composition I Composition II Composition III
peel strength 1 6 14*
tpounds/inch~
*Rubber tore before adhesive bond failed.
-- . ,: ~:: ,:: ~. : . :
.... . .. ,;. , .
., ." . ,., .. .. :: . , . ~ -
7~
- 11 ~ 60SI 00785
These results thus illustrate the improved
results obtained by incorporating an adhesion promoter
of the present invention into heat curable silicone rubber
compositions.
Example 5
In this example lap shear tests were conducted
on one inch by six inch strips of Composition III
vulcanized directly on galvanized steel and anodized
aluminum, respectively. Each metallic surface was
wiped with toluene prior to assembling the metal/rubber/metal
lap shear construction. The rubber thickness was
appro~imately 20 mils and the overlap distance was one
inch. After curing at 350F for 15 minutes, lap shear
values were obtained on a Tinius Olsen tensometer at
a jaw speed of 0.5 inch per minute as set forth in
Table II.
Table II
` Anodized Aluminum Galvanized Steel
Lap Shear Strength 538 689
~0 (psi)
. j
