Note: Descriptions are shown in the official language in which they were submitted.
60SI~338
SELF-BONDING ADDITION CURED SILICONE SYSTEMS
Background Of The Invention
The present invention relates to an SiH
Olefin platinum catalyzed addition silicone composition
and more parkicularly the present invention relates to
self-bonding Si~l Olefin platinum catalyzed compositions.
Si Olefin platinum catalyzed compositions are
well known. Such compositions are also referred to as
addition curing systems or compositions. Such compositions
generally comprise a base vinyl containing polysiloxane
polymer, a hydride cross-linking agent which can be either
a hydride resin composed of monofunctional units and
tetrafunctional units or a hydride resin composed of
monofunctional units and tetrafunctiona] units and
difunctional units or a hydride containing linear
polysiloxane fluid. The adclition of the hydrogen in
the hydride cxoss-linking agent to the vinyl of the
polysiloxane so as to cure the system is carried out
under the influence of a platinum catalyst. Many
platinum catalysts have been developed for such a purpose
particularly platinum complexes of aldehydes and
alcohols or a platinum complex catalyst formed by
reacting chloroplatinic acid with a vinyl containing
polysiloxane~
There is also disclosed by the prior art
that there may also be incorporated in such compositions
resins containing vinyl substitution such as disclosed
?4~ .
60SI-338
~ 2 --
in the patent of Frank J. Modic, U.S. Patent No.
3,436,366 - issued April 1,, 1969. It is disclosed in
, ~ the foregoing patent that/may be incorporated in such
SiH Olefin platinum catalyzed compositions or addition
systems, fillers, such as fumed silica or precipitated
silica or extending fillers. Such compositions are
prepared by placing the ~inyl polysiloxane filler in
one package and by mixing the hydride cross~linking
agent by itself with or without filler and having the
platinum catalyst with the vinyl siloxane which is
present in a separate package. The composition is
packaged or prepared into two components or two
packages. When it is desired to cure the composition,
the vinyl siloxane and the platinum catalyst is hrought
together with the hydride and can be cured at room
temperature to a silicone elastomer.
It has been found :that inhibitor compounds may
be incorporated in such compositions so that they remain
uncured at room temperature or can be cured in a
relatively rapid pace at elevated temperatures such as
temperatures above 100 and 150C. Examples of such
inhibitors are for instance, triallylisocyanurate and
hydroperoxy compounds as disclosed in the patent of
William J. Bobear, U.S. Patent No. 4,061,~,09 - issued
December 6r 1977. The inhibitor compounds of the
Bobear patent allow the composit.ion to be packaged in
a single package which without the curing of the composition
for a period of 6 months to a year or more, and then by
heating the composltion at elevated temperatures, the
composition cures to a silicone elastomer. It should be
noted that in the Bobear patent the hydroperoxide
compounds are disclosed solely as inhibitor compounds.
The compositions which cure to a silicone elastomer
result in good potting and encapsulation compositions,
for the dieIectric properties of the addition cure silicone
60SI-338
-- 3 --
are aptly suited for these uses. However, the lack of
adhesion of such compositions which are normally not
adhesive results at times in the causing of the
delamination of the encapsulated electronic components.
This results in subjecting the electrical components to
moisture, vibration, and damage. There may result
such heavy damage or destruction that electrical discharges
can occur across coating voids resulting from the
delamination of the encapsulant. The lack o
adhesiveness o such addition cure silicone composition
makes them admirably suited as molding compounds but
is decidedly a disadvanta~e when such compositions are
utilized to encapsulate or pot electrical components.
It should be noted that such addition cure silicone
systems or silicone elastomers have outstanding properties
such as optical clarityl tensile strength, elongation
and tear properties, resistance to reversions, and
high temperature.
The lack of adhesion of such addition cure
silicone compositions is a decided disadvantage when
such compositions are, for instance, to be applied
for gasketing applications, glass cloth impregnation
and silk screening applications. Primers may be
utilized to improve the adhesion or resul-t in the
desirable adhesion of the silicone cured elastomer to
a substrate. However, such primers represent an
additional step in the application of the system
increasing the cost of the application of addition
cure systems. Also such primers are hard to apply to
complex shapes and in complex printing system~ such
as the silk screening printing system. An example of
a primer for condensation RTV compositions is to be
found in Smith U.S. Patent No. 4,177,301 - issued
December 4, 1979.
Recently in condensation curing RTV and in
60SI-338
~ 4
heat curable vulcanizable silicone rubber composition
there has been developed self-bonding additives. For
example, see the Canadian Patent application of Smith,
DeZuba and Mitchell - Serial No. 359,263, disclosing
the use of silyl maleates and fumerates and succinates
to produce self-bonding condensation cured one-component
room temperature vulcanizable silicone rubber compositions.
However, such self~bonding additives are useless in
an addition cure system. One example of an attempt
~o to produce a viable self-bonding addition cure system
is to be found in the patent of Ballard, U.S. Patent No~
3,527,655 - issued September 8, 1970. However, it did
not produce enough self-bonding or adhesive properties
in the composi~ion. ~nother more successful at-tempt
is to be found in the Canadian Application Serial No.
325,063 - filed April ~, 1979, of Dujack and Hardman,
entitled "Self-Bonding Silicone Rubber Compositions".
The Ballard patent discloses a vinyl alkoxy silane
that is a self bonding addition system with such an
additive which did not function satisfactorily in
all cases. A more suitable self-bonding addition
system was produced in the Hardman and DuJack
application by utilizing a partial hydrolyzate of a
vinyl triethoxy silane. However, such a system was
not satisfactory as would be desired in that the self-
bonding properties or adh~sion was not as good as
would be desired, but nevertheless, was superior to
that of the Ballard system.
Accordingly, there has been made a constant
effort and a constant attempt to produce a self-bonding
addit~on cure system and specifically for the
production of a self-bonding addition cure RTV that
could be utilized to produce gaskets on metal substrates
and on plastic substrates and which could be u-tilized
in various printing techniques. It should be noted that
60SI-338
-- 5 --
the silk screen printing methods are u-tilized to
produce gaskets from various materials on various types
of metal and plastic substrates. The purpose of the
silk screening method is to print out a complex
configuration. Machinery can be utilized to print a
relatively simple configuration, but silk screening
printing methods are utilized to produce gaskets of
a complex configuration. As previously stated, the
silk screening printing method comprises wherein a
silk screen of a certain thickness is taken and
everything but the shape of the gasket is varnished.
Then the composition that is desired to be printed is
applied over the figure that is to be printed. Wiper
blades force the composition through the silk screen
in the exact thickness of the silk screen so that it
comes through the silk screen and fall on the substrate
in the exact figuration which it is desired that the
composition be printed. This method results in the
printing of complex configurations and shapes on
various types of substrates. In order for the method
to work, the composition has to have adhesion or self-
bonding to the substrate. Accordingly, prior to the
present invention, addition cure compositions could
not be utilized in the silk screening method to
produce a complex gasket on substrate such as a
metallic, plastic and ceramic substrate.
Accordingly, it is one object of the present
invention to provide for an addition cured silicone
system which is self-bonding to metal, plastics and
ceramic substrates.
It is another object of -the present inven~ion
to provide for a process for producing addition cured
silicone elastomers and systems which are self-
bonding to metallic, plastic and ceramic substrates.
It is an additional object of the present
60SI-338
-- 6
invention to provide for an addition cured silicone
system which can be utilized to print -with the silk
screening method for printing of gaskets on a metallic,
plastic or ceramic substrate.
It is still yet an additional object of -~he
preserlt invention to provide for an article or laminate
which is produced from a self-bonding addition cured
silicone system.
It is still another additional object of
the present invention to provide for a method for
producing laminates and articles from a self-bonding
silicone addition cured system utilizing a silk screen
printing method.
These and other objects of the present
invention are accomplished means of the disclosure
set forth here and below.
Summary of the_Invention
In accordance with the above objects, there
is provided by the present invention a self-bonding
addition curing silicone composition comprising a
self-bonding addition curing silicone composition
comprising (A) 100 parts by weight of a base vinyl
containing dioryanopolysiloxane o a viscosity varying
from 100 to 500,000 centipoise at 25C where the vinyl
content varies from 0.04 to 1.5 percent by weight, the
organo group is a monovalent hydrocarbon radical;
(B) from 1 to 500 ppm of platinum catalyst; (C) from
.1 to 25 parts by weight of a hydride resin selected
from the class consisting of resins having HR2SiO units
and SiO2 units where the ratio of H+R to Si varies
from 1.0 to 2.7 and resins having HR2Sioo 5units,
SiO2 units and R2 -~iO units where the ratio oE H-~R+R
to Si varies from 1.2 to 2.7 where R is a monvalent
hydrocarbon radical and Rl is selected from hydrogen
and a monovalent hydrocarbon radical and (D) from 0.5
~ ~ ~(3 ~
60SI-338
-- 7
to 8 parts by weight of a self-bonding additive
selected from the C~rm consisting of silanes of the
formula,
72 1 5
(1) 2 C - o R - Si (O R )3-a
where R2, R , R5 are monovalent hydrocarbon radicals,
R is a divalent hydrocarbon radical and a is a whole
number 0 to 2, and siloxanes of the formula,
(2)~ C - O ~ Rb Si4-a1b
_ a'
where R2, R3 as defined where, R" is a monovalent
hydrocarbon radical, al varies from 0.005 to 2.0, b
varies from 1.0 to 2.5 and the sum of a+b varies from
1.005 to 3.0~ To increase the self-bonding properties
of the composition, there may be added at least 400 parts
per million of self-bonding promoter containing at least
one hydroperoxy radical and rom 2 to 25 parts by
weight based on 100 parts of the base polymer of a
fumed silica iller treated with silazanes. It should
be noted that in the process for forming such compositions
the hydride resin must be mixed with the acryloxy
compound first before the other compounds are mixed
into the hydride resin or the acryloxy compounds. The
preferred acryloxy compound is ~ -
me~hacryloxypropyltrimethoxysilane. Other details
of the respective present invention will be given
below.
Descri.ption of The Preerred Embodiment
The base vinyl containing diorganopolysiloxane
polymer may be any vinyl containing diorganopolysiloxane
polymer that is utilized in SiH Olefin platinum
catalyzed compositions. The vinyl may be vinyl
- 8 - 60SI-338
in the chain or the vinyl may be on the siloxy terminal
units or it may be both in t:he chain and on the siloxy
terminal unitsO Preferably the base vinyl containing
diorganopolysiloxane polymer has a viscosity varying from
100 to 500,000 centipoi.se at 25C and more preferably a
viscosity varying from 100 to 200,000 centipoise at 25C
where the vinyl content generally varies from 0.0~ to
1.5 percent by weight and more preferably varies from 0.04
to 1.0 percent by weight. The organo groups other than
vinyl of such a polymer may be any monovalent hydrocarbon
radical such as alkyl radical of 1 to 8 carbon atoms such
as methyl ethyl, etc.; alkenyl radicals such as vinyl,
allyl, etc.; mononuclear aryl radicals such as phenyl,
menthylphenyl, etc.; cyclo alkyl radicals such as
cyclohexyl, cyclo heptyl, etc.; and f].uoroalkyl radicals
sllch as 3,3,3-trifluoropropyl. Preferably the organo
groups are selected from vinyl phenyl and methyl and most
preferably being selected from vinyl and methyl, generally
such a polymer may have the formula,
I 10 t I 10 ~ S o r vi
where Vi is vinyl and R10 is a monovalent hydrocarbon
radicalO The radical R10 may be any of the radicals
noted for the organo groups in the definition of the
diorganopolysiloxane vinyl containing polymer. However,
preEerably, the vinyl containing vinyl polysilo~ane
polymer has the Formula (3) above such that vinyl unit
only on the terminal position of the chain and R10 is
a monovalent hydrocarbon radical other than an
aliphatically unsaturated hydrocarbon radical. Most
60SI-338
preferably RlO is selected from the class consisting
of me-thyl phenyl and fluoro alkyl radicals and x and
y in the formula vary such that the viscosity of the
polymer varies rom lO0 to 500,000 centipoise at 25C
and more preferably varies from lO0 to 200,000
centipoise at 25C.
Another basic ingredient in the composition
is from O.l to 25 parts by weight of a hydride resin
defined above. Preferably the hydride resin contains
a hydride content broadly at .05 to 5 percent weight
and more preferably .l to l percent by weight. It
should be noted that the hydride resin must be present
in the SiH Olefin platinum catalyzed composition of the
instant case for solubility purposes. Accordingly, per
~5 lO0 parts of the base vinyl containing diorganopolysiloxane
polymer, there must be present from .l to 25 parts by
weight of a hydride resin as defined above. As pointed
our previously, R is selected from monovalent
hydrocarbon radicals and R' is selec~ed from hydrogen
and monovalent hydrocarbon radicals. The monovalent
hydrocarbon radicals can be any radical other than the
aliphatically unsaturated hydrocarbon radicals.
Accordingly/ R and R' insofar are monovalent hydrocarbon
radicals that can be selected from alkyl radicals of
l to 8 carbon atoms, cyclo alkyl radicals, and
mononuclear aryl radicals and fluoro alkyl radicals,
all up to 8 carbon atoms. Most preferably R is selected
from hydroyen, methyl, phenyl, and 3,3,3-fluoropropryl.
It should be noted t:hat the hydride resin might have
some vinyl unsatura1:ion but if it does have such vinyl
unsaturation it is important the platinum catalyst not
be mixed with it, otherwise the resin will cross-link
with itself.
The hydride resin is produced by methods well
known in ~he art. Such methods generally comprise the
60SI-33~
-- 10 ~
the hydrolysis of the appropriate hydride chlorosilanes,
preferably in a water hydrocarbon solvent mixture with
the extraction and purification of the resin product.
The other necessary ingredien-t in the composition is
from 1 to 500 parts per million of platinum catalyst
and more preferably from 1 to 200 parts per million
of platinum catalyst. It should be noted that the
platinum catalyst may be present as~ solid platinum
deposited on charcoal or on gamma ~m~ or it may be
solubilized platinum complex. Most preferably it i~
a solubilized platinum comple~
Generally, there must be ~tV~7~ at least
0.1 parts per million of a platinum catalyst in terms
of parts of platinum metal. This platinum catalys-t
may be in any form. It may be a solid platinum metal
deposited on a solid carrier or it may be a solubilized
platinum complex. Any type of platinum cataly~t will
work in the ins-tant invention. More preferably, the
platinum complex is a solubilized platinum complex.
Many types of platinum compounds for this SiH Olefin
addition reaction are knowrl and such platinum catalysts
may be used for the reaction of the present case.
The preferred platinum catalysts especially when optlcal
clarity is re~uired are those platinum compound catalysts
which are soluble in the present reaction mixture. The
platinum compound can be selected from those having
the formula (PtC12Olefin)2 and H(PtC12Olefin) as
described in U.S. Patent No. 3,159,601, Ashby. The
Olefin sho~n in the previous two formulas can be almost
any type of Olefin but is preferably an alkenylene
having from 2 to 8 carbon atoms, a cycloalkenylene
having from 5 to 7 carbon atoms or styrene. Specific
Olefins utilizable in the above formulas are ethylene,
propylene, the various isomers of butylene, octylene,
cyclopentene/ cyclohexene, cyclGheptene, etc.
60SI-338
A Further platinum containing material
usable in the composition of the present invention is
the platinum chloride cyclopropane complex
(PtCl~C3H~)2 described in U.S. Patent No. 3,159,662,
Ashby - issued December 1, 196~.
Still further, the pla-tinum containing
material can be a complex formed from chIoroplatinic
acid with up to 2 moles per gram of platinum of a
member selected from the class consisting of alcohols,
ethers, aldehydes and mixtures of the above as
described in U.S. Patent No. 3,220,972, Lamoreaux -
issued November 30, 1965.
The preferred platinum compound to be used
not only as a platinum catalyst but also as a flame
retardant a~ditive is that disclosed in Karstedt
U.S. Patent No. 3,8~,730 - issued June ~, 1974.
Generally speaking, this type of platinum complex is
formed by reacting chloroplatinic acid containing
4 moles of water of hydration with
tet.ravinylcyclotetrasiloxane in the presence of
sodium bicarbonate in an ethanol solution.
It should be noted that the preparation of
such hydride resi.ns and also the solubilized platinum
catalyst are well known to a worker skilled in the art.
Preparation of a base vinyl containin~ polymer is also
well k:nown -to a worker skilled in the art and generally
comprises taking cyclotetrasiloxanes o~ the appropriate
organo substitution or of the desired organo
substitution, and equilibrating them at elevated
temperatures in the presence o~ an alkali metal
hydroxide with the appropriate amount of chain
stoppers. The chain stoppers are preferably low
molecular weight vinyl terminated diorganopolysiloxane
polymers; for instance, divinyltetramethyldisiloxane.
From the resulting equilibration, there results the
~ ~ ~ V~ 60SI-338
- 12 -
desired polymer and when the equilibration is completethat is when about 8~ percent of cyclotetrasiloxane
has been converted to linear polymer, the reaction
temperature is lowered, the alkali metal hydroxide
catalyst is neutralized, preferably with acidic a~ent
such as a chlorosilane or a silyl phosphate or a
phospheric acid, and the excess cyclics that are
unreacted are vented off to give the desired polymer.
When it is desired to produce a low molecular weight
diorganopolysiloxane polymer in the viscosity range
of 50 to 10,000 centipoise at 25C, then there may be
utilized an acidic catalyst in such equilibration
reaction such as toluene sulfonic acid or acid treated
clay such as Filtrol, manufactured and sold by the
Filtrol Corporation of Los Angeles, California.
~nother necessary ingredient in the composition is
generally f-rom .5 to 8 parts by weic~ht and more
preferably from 1 to 5 parts by weight of the
acryloxy silane. In formula 1 above, R , R and R
are monovalent hydrocarbon radicals. Such monovalent
hydrocarbon radicals can be any of the monovalent
hydrocarbon radicals defined previously for the vinyl
containin~ base polymer. Accordin~ly, such monovalent
hydrocarbon radicals can be alkyl radicals of 1 to 8
carbon atoms, mononuclear aryl radicals such as phenyl,
alkenyl radicals such as vinyl, cyclo alkyl radicals
such as cyclo hexyl, fluoro alkyl radicals such as
3,3,3-trifluoropropyl. Most preferably R , R , and
R are selected from alkyl radicals of 1 to 8 carbon
atoms such as methyl, and R3 is a divalent hydrocarbon
radical and is preferably selected from alkylene and
arylene radicals of up to 8 carbon atoms. Preferably
R3 has at least 3 carbon atoms. It has been found
that the compound is not hydrolytically stable if it
has less than 3 carbon atoms. Most preferably, R3
~ 3~ 60SI-338
~ 13 -
is propyl since the propyl group is hydrolyti.cally
stable and is most readily available for producing
the compounds of Formula 1, A can be as a is a whole
number that varies from 0 to 2 and is most preferably 0
Preferably, the compound of Formula 1 is formed by the
following reaction,
R2 o
C~I2 ~- C -- C O R13 +
R
la
H - li (OR )3-a
where R13 is an aliphatically unsaturated monovalent
hydrocarbon radical of at least 3 carbon atoms,
generally of 3 to 8 carbons where R , R and R are
as previously defined. The above reaction is carried
out in the presence of a platinum catalyst and is
well known in the silicone chemical art. The hydrogen
group adds on ~o the olefinically ~msaturated group
R13 in the presence of the platinum catalyst to form
-the compound of Formula 1, the acryloxy intermediate for
forming the compound of Formula 1 is readily available
ln the industry and is sold by chemical companies such
as Union Carbide Corporation and Dynamit Nobel Chemical Co.
In place of the acryloxy silane self-bonding
additive that may be utilized at the same concentrations
and the acryloxy polysiloxane self-bonding additiVe of
Formula 2. Such acryloxy polysiloxane compounds are
formed from the following reaction,
R O
12 11 13
CH2 -- C C O ~ +
- H ~bl 4 - a - b
~ 60SI-338
Again, this is a well-known reaction in
silicone chemistry which is cured out presence of
platinum catalyst and can be any of the platinum
catalysts identified previously for the compositions
of the present invention. In the above formulas o~
the hydride polysiloxane a varies from 0.05 to 2.0~
b varies from 1.0 ~o 2.5 and the sum of a plus b varies
from ln 005 to 3Ø
In the Formula 1, and as well as in the
hydride formula polysiloxane above, Rll is a monovalent
hydrocarbon radical that can be any of the monovalent
hydrocarbon radicals identified previously for the
base vinyl containing polymer. Accordin~ly, R can
be the alkyl radical of l to 8 carbon atoms, a mononuclear
aryl radical, an alkenyl radical, a cycloalkyl radical
or a fluoroalkyl radical. Most preferably Rll is
selected from methyl vinyl and phenyl and
3,3,3-trilfuoropropyl. The acryloxy olefinic
unsaturated compounds which are utilized in this reaction
to produce the acryloxy polysiloxanes and the acryloxy
silanes can be ob-tained ~rom the above manufacturers
of chemical compounds as identified previously.
In preparing the composition, the acryloxy
s:ilane or siloxane is first mixed with a hydride
resin and has to be mixed with resin first, irrespective
of whether additional ingredients are then added as will
be described below. The platinum catalyst is mixed
with a vinyl containing polysiloxane base polymer.
When it is desired to cure the composition, the two
components are mixed and applied to whatever substrate
it is desired to adhere thereto and the composition
will at room temperature cure to a silicone elastomer
or cure at elevated temperatures to silicone elastomers,
that is above 80C and 150C. The cure at above 100 C
is extremely rapid, in a matter of minutes or even seconds.
60SI-33
- 15 -
~lowever, to improve the self~bonding properties
of the compositions, there may be added to the
composition at least 400 parts per million of a
self-bonding promoter having at least one hydroperoxy
radical. Accordingly, generally there may be utilized
~00 to 10,000 pzrts per million of a hydroperoxy
compound as a self-bonding promoter, or preferably
fxom 400 to 2,000 parts per million of a self-bonding
promoter, which compound contains a hydroperoxy
radical. Most preferably, the self-bonding promoter
is methyl ethyl ketone hydroperoxide. Other
hydroperoxide self-bondiny promoters that may be
utilized are 1,1,3,3-tetramethylbutyl hydroperoxide,
2,5-dimethyl-2,5-dihydroperoxy hexane, cumene hydroperoxide,
1,1,3,3-tetramethylbutylhydroperoxide,
2,5 dimethyl-2,5, dihydroperoxy hexane, decalin
hydroperoxide, l,1,2,2-tetramethylpropyl, p-methane
hydroperoxide and pinane hydroperoxide. These
compounds are manufactured and sold by Pennwalt Corp.,
Hercules, Inc., and Lucidol Chemical Company.
It should be noted that these compounds are
taken out o U.S. Patent No. 4,061,609 - W.S. Bobear,
issued December 6, 1977. It should be noted these
hydroperoxy compounds are disclosed in the foregoiny
~5 patent as inhibitors and as very effective inhibitors
in SiH Olefin platinum catalyzed compositions. They are
not disclosed in the patent as self-bonding promoters.
It is only in the present application that they are
disclosed as self-bonding promoters.
It also should be noted that the most
effective acryloxy silane self-bonding additive that
is desirably utilized in the present invention, is
~ - methyl a~ryloxy propyl trimethoxy silane. To urther
increase the self-bonding properties of the composition
there may also be incorporated per 100 parts of the
~ ~ ~ 60SI-338
- 16 -
base polymer from 2 to 25 parts by weight of a fumed
silica which is treated with silazanes. This is
another self-bonding promoter which by the use of
siloxane treated fumed silica the self-bonding
properties of the composition are improved over
compositions not having such silazane treated ~umed
silica. The fumed silica may also be treated with
cyclotetxasiloxanes in addition to the silazanes.
However, this is not necessary. An example of such
treatment of such fillers is for instance to be found
in the Beers U.S~ Patent Mo. 3,837,878 - issued
September 24, 1974. Preferably, there is utilized
only from 2 to 15 parts by weight oE fumed silica
treated with silazanes. However, it is not desired
to utilize more than 25 parts of fumed silica in any
case hecause the viscosity of the composition becomes
too high for the composition to be used in silk
screen printing applications. ~owever, the composition
with a high viscosity may be utilized in other applications
such as encapsulation and potting of electrical
components. The treatment of fumed silica with
cyclotetra siloxane and silazanes is well known in
the art.
In addition to such treatment and utilization
of fumed silica there may be utilized an extending
filler. Generally, there may be utilized anywhere
from 5 to 100 parts of an extending filler and more
preferably from 5 to 50 parts of an extendiny filler
based on 100 parts by weight of the base vinyl
containing polymer where the extending filler is
selected from a class consisting of titaninum oxide
lithopone, zinc oxide, zirconium silicate, silica
aerogel, iron oxide, diatomaceous earth, calcium
carbonate, glass fibers, magnesium oxide, chromic
oxide, zirconium oxide, magnesium oxide, alpha quartz,
60SI-338
- 17 -
calcined clay, carbon graphite, cork, cotton and
synthetic fibers. These fillers are disclosed in
William Bobear, U.S. Patent No. 4,061,609. A patent
on the use oE the silazanes to treat fumed silica i5
U.S. Patent No. 3,635,743 - issued January 18, 1972.
Accordingly, with these additional ingredients
of the hydroperoxy compound along with a silazane
treated fumed silica there is disclosed a very
desirable and advantageous self-bonding SiH Olefin
platinum catalyzed composition. Accordingly, with
the hydroperoxy self-bonding promoter and the silazane
treated fumed silica which can be added with advantayes
to the acryloxy silane or siloxane composition, there
is obtained a very advantageous self-bonding addition
cure system. It may be utilized in silk screening
applications as it has the desired adhesion to various
types of substrates. The substrates to which good
adhesion is obtained from by the above composition
with the foregoing self-bonding promoters are copper,
aluminum, polyvinylchloride, glass, polyethylene
terephthalate, epoxy fiberglass, phenolic-linen,
Lexan, trade name for polycarbonates~ styrene,
n~lon, polyphenylene oxides. It should be noted that
most preferably the ex-tending filler is alpha quartz,
since alpha quartz increases the tensile strength
of the composition without increasing to too great an
extent the viscosity of the uncured compositions.
It should be noted that any of the extending fillers
may be utilized with advantage to increase the tensile
strength of the composition without necessarily
increasing the viscosity of the uncured composi-tion
by a great extent. In the present case, there may
also be incorporated additional hydride for curing
purposes, to increase the rate of cure when it is
desired, that is by the heating of the composition by
60SI-338
- :L8 -
elevated t.emperatures. There may be present from
1 to 50 parts by weight of a resin hydride polysiloxane
of the formula,
(4) H - - t sio ~ slo si H
where R6 is selected from the class consisting of a
monovalent hydrocarbon radical and a mixture of
hydrogen and a monovalent hydrocarbon radical s is 0 or
a positive number and t is a 0 or a positive number such
that the polymer was a viscosity varying from 10 to 1,000
centipoise at 25C or more preferably has a viscosity
varyiny ~rom 10 to 100 centipoise at 25 C. The R6
:L5 radical is preferably selected from alkyl radicals of
1 to 8 carbon atoms, cycloalkyl radicals, mononuclear
aryl radicals, fluoroalkyl radicals, and other
monovalent hydrocarbon radicals. It should be noted
that R6 can be alkenyl radicals such as vinyl as long
~0 as the platinum catal.yst is not packaged with it in
the formation oE the 2 component composition system.
The xadical ~6 is preferably selected from emthyl,
phenyl, and 3,3,3-tri-~luoropropyl radi.cals. Normally
the hydride polysiloxane generally as a hydride content
varying anywhere from 0.15 to 2.0 percent by weight
and more preferably has a hydride content varying
from 0.25 to 1.7 percent by weight. Preferably there
is utilized as an additional hydride polysiloxane
1 to 20 parts by weight of the hydride polysiloxane
based on 100 parts of the base vinyl containing polymer
of Formula 3.
It should be noted that there must be
present in the composition of the instant case in
order for it to be soluble, the hydride resin. Such
,~,
~ a hydride resin should be present in the composition
~ OSI-338
- 19 -
and must be first mixed with the acryloxy silane -to
be soluble. ~s an additional hydride additive or
in place oE the hydride resin in order to increase
the cure rate of the system, there may be present a
linear hydride polysiloxane of the formula shown
above. The hydride of polysiloxane of the formula
shown above is a well known chemical in the art and
may be obtained by the hydrolysis of the appropriate
chlorosilanes to produce the desired hydride polysiloxane.
Preferably, there should be a hydride resin in the
composition and such hydride resin must be first
mixed with the acryloxy silane and acryloxy polysiloxane
initially in order for the composition to have the
desired solubility properties of the instant case.
After the hydride resin has been mixed with the acryloxy
silane and polysiloxane, there may be added to it the
linear hydride polysiloxane polymer disclosed above.
There may also be added to the composition reinforcing
resins. Such resins take the place of silica fillers
and increase the ~ensile strength of the cured
composition as well as the tear strength of the cured
composition wi.thout unduly increasing the uncured
viscosity o~ the composition so that there may be
incorporated into the composition per 100 parts of
the base polymer from l to 70 parts by weight of a
resin composed of R3 SiOo 5 Si 2 where R7 is a radical
selected from the class consisting of vinyl radicals,
alkyl radicals and aryl radicals and fluoroalkyl
radicals of l to 8 carbon atoms with a ratio of
monofunctional units to tetrafunctional units and is
from 0.5 to l.l and where from about 2.5 to mole
percent of the silicone atoms contain silica bonded
vinyl groups.
In place of such a resin there may be
incorpora-ted in the composition of a resin composed of
8~
60SI-338
- 20 -
monofunctional units, -tetrafunctional units, difunctional
units. Accordingly, per 100 parts of a base vinyl
containing polymer, there may be incorporated in the
composition from 1 to 70 parts by weight of a resin
comprising R3 SiOo 5, R SiO units and SiO2 units where
R is a radical selected from the class consisting of
vinyl radicals, alkyl radicals, aryl radicals and
fluoro alkyl radicals where the ratio of monofunc-tional
units to the tetrafunctional units is from .5 to 1 and
1:1 and the difunctional units are present in an amount
equal to about 1 to 10 mole percent based on the total
number of moles of siloxane units in the copolymer and
wherein from about 2.5 to 10 mole percent of the
sili.cone atoms containing silicone bonded vinyl
groups. Such resins are known for such Olefin platinum
catalyst compositions as disclosed in Modic U.S. Patent
No. ~ - issued ~ , 1969.
The composition may also contain other
additives and ingredients such as heat aging additives,
additional flame retardant additives and swell
resistant additives, if the composition is not
fluorosilicone, etc. It should be noted that the
hydroperoxy compound in the composition will act as
an inhibitor. However, if used in the present invention
it is being utilized first of all as a self-bonding
addi-tive and then as an inhibitor. Accordingly, per
100 parts of the total composition there may be
utilized from 100 to 10,000 parts per million of an
additional inhibitor compound in tne composition such
as trialkenylisocyanurate. Suitable inhibitor
compounds may be uti~ized as long as they do not
conflict with the self-bonding properties or self-
bonding activity in the system of the ac~yloxy silane
and siloxane.
60SI-338
- 21 -
It has been found -that trialkyenylisocyanurate
does not interfere with the self-bondinc~ properties of
acryloxy silane and acryloxy polysiloxane. The
inhibited composition has a desirable work life at
room temperature but when heated at elevated temperatures
would cure in the matter of minutes or seconds to a
silicone elastomer. With an inhibitor such as
trialkenylisocyanurate in the composition, the
composition may have hours or even days of shelf life
without curing at room temperature. The hydroperoxy
compound may be utilized also as an inhibitor but
should be preferably utilized in the concentrations
disclosed used above it if lt is to act as a self-bonding
promoter in the instant composition and secondly as an
inhibitor. If it is utilized at more than the
concentrations indicated above, then the self-bonding
promoter properties of the hydroperoxide are not
changed but the composition is considerably more
inhibited.
To prepare the cured composition the vinyl
polymer optionally, the vinyl resin, the filler are
all mixed together along with the platinum catalyst
to form one component. Then the hydride resin is
mixed with the acryloxy silane or acryloxy polysiloxane,
and then there is added to them preferably a linear
hydride polysiloxane. A hydroperoxy self-bonding
promoter additive and optionally the filler is added
to the vinyl polymer. Accordingly, when it is desired
to cure the composition the two components are mixed
together to form a uniform mixture preferably in a 10
to 1 mixing weight ratio, then the composition is
applied to whatever form it is desired. In one
embodiment the composition can be applied to a silk
screen and then pressed through the silk screen by the
wiper bars into the substrate below which may be of
~ 60SI-338
- 22 -
ceramic, plastic or glass and the composition is then
heated at e]eva-ted temperatures to cure the composition
to the desired shape so as to Eorm, ~or instance, a
gasket on a metal, plastic or ceramic substrate by -the
silk screen printing method. It should be noted that
the silk screen is varnished in all the areas except
the areas it is desired that the composition pass
through it to form the desired shape for the printed
matter that is going to be placed on the substrate.
All parts in the examples below are by
weight. The examples below are given for the purpose
of illustrating the present invention and they are
not given for the purpose of setting limits and boundaries
of the present invention. In the examples below, there
was utilized a composition A. Such composition may
comprise oE 100 parts of vinyl terminated
dimethylpolysiloxane polymer having 0.14 percent vinyl
and a viscosity of 3~00 centipoise at 25C. Wi~h this
polymer there is mixed 33 parts of a resin composed of
trimethylsiloxane units of SiO2 and methyl vinyl SiO
units with a ratio o~ mono unit to the tetra and the
difunctional units in an amount sufEicient to provide
0.8 trimethylsiloxane units per SiO2 -unit and with the
methylvinylsiloxane units heing present in an amount
such that 7.0 mole percent of the methylvinylsiloxane
atoms are present as methylvinylsiloxane units and
the remaining silicone atoms are present as a por-tion
of a trimethyl siloxane unit or an SiO2 unit. In
the example~ there was utilized a linear hydride
composed of hydride dimethylsiloxy terminal units and
methyl hydrogen siloxane units in the internal portion
of the polymer chain where the viscosity of the
polymer was lO centipoise at 25C and the hydride
concentration of the polymer was 1.7 percent by
weight
60SI-338
- 23 -
Example 1
Composition A above was taken and there was
mixed into 100 parts of Composition A, 10 parts of
Composition B made by mixing 28 parts o~ gamma
methacryloxypropyltrimethoxysilane with 64 parts of
a resin composed o hydrogen dlmethylsiloxy units
and SiO2 units, containing an average of two of the
dimethyl hydrogen units per SiO2 unit and 7 parts of
the linear hydride disclosed above. This was the
weight ratio of one component to the other in component
B. From the cured composition ASTM sheets were made
and cured at 100C for 1 hour in a heated press. The
adhesion was measured via a lap joint adhesion using
Alclad aluminum panels and 1 square inch, 25 mil thick
bond. The samples were pulled at .5 inches per minute.
The test on the physical properties yield the following
result. Durometer, Shore: 41; Tensile psi: 575;
Elongation gO 110; Tear lb./in.: 15; lap shear psi: 500;
% Cohesion: 100%.
xample 2
To 100 parts of Composition A there was
added 10 parts of component B comprising 50 parts of
the resin hydride oE Example 1 and 50 parts of a
vinyl terminated dimethylpolysiloxane polymer
having 0.14 percent vinyl and a viscosity of 3800
centipoise at 25C. The resulting cured sheets had
the following properties: Shore A durometer: 35;
tensile psi: 750; Elongation %: 120; Tear lbs./in.: 10;
~ap Shear psi: less than 1; % Cohesion: 0.
Example 3
The composition of Example 1 was used as a
potting compound for 1" x 4" strips of a substrate
shown in Table I. The silicone was cured at 80C for
1 hour. The silicone was examined for adhesion to
the substrate by scrapping and pulling the silicone
off with a razor blade. Composition A was cured with
60SI-338
- 2~ -
Composition B of Example 2 at a 10 to 1 ratio and used
to po~ the substrates for the sake of comparison.
Characteristic of dimeth~lvinyl chain-stopped
organopolysiloxanes, the cured silicone elastomer
delaminated and readily released free of the substrates.
Example 4
Then to Composition A above there was added
610 parts per million of methylethylketone
hydroperoxide. With the hydroperoxide the shelf life
exceeded 6 months for the catalyzed composition. Pot
li~e exceedin~ 6 months are obtained when the hydro
hydroperoxide is added to the mi~ture of Example 1.
Further, the number of plastics to which the composition
adheres to ls increased as shown in Table 1 below.
With the addition of the hydroperoxide the catalyst
composition must be subjected to a post bake of 125C
for 10 minutes to complete the cureO In all other
respec~s the composition was processed the same as in
the Example 1. The results are set forth in Table 1
below.
T.~BLE I
c~l~L~ d~e~i~
ubstrate Example 3Example
Polyvinyl chloride Good Good
Copper Good Good
Glass Good Good
Polyethyl.ene terephthalate Good Good
Epoxy-fiberglass Good Good
Phenolic - linen Good Good
Lexan None Good
Styrene None Good
Nylon None Good
Noryl None Good
Polyvinyl acetate None None
Acrylic None None
8~
- 25 - 60SI-338
Examp e 5
Prepared a Composition C which had the same
composition as Composition A but the proportion of a
vinyl polymer to a vinyl resin was 60~ by weight of
polymer per ~0% by weight o~ resin while the composition
is 75% by weiyht of polymer to 25% by weight of vinyl
resin in Composition A~ The composition C was cured
with the component B o-f Example 1 at room temperature.
The silicone gelled within 2~ hours and cuxed to a
transparent compound with a Shbre llardness of 35. In
comparison, when the gamma methyl acryloxy propyl
trimethoxy sllane was added directly to composition A
a precipitate immediately developed. The precipitate
remained even after the addi-tion of the linear silicone
hydride. This mixture, cured either at room temperature
or up to 150C, resulted in an opa~ue compound exhibiting
intermittent cohesive bonding with less than 25% to
aluminum panels.
The acryloxy silane o~ Example 1 was added to
dimethylvinyl chain-stopped organopolysiloxane having
a viscosity of 80,000 centipoise at 25C and a dimethyl-
vinyl terminated polysiloxane polymer having a viscosity
of 3800 centipoise at 25C. ~ precipitate formed,
and after 24 hours yellow liquid was collected which
was identified as the acryloxysilane of Example 1.
These results were duplicated using the linear hydride
polysiloxane as well. The acryloxysilane was soluble
and stable for more than a year only when first rnixed
with the methyl hydride resin. The resin hydride may,
be made by reacting ethylsilicate with dimethylhydrogen
chlorosilane in water. When the acryloxy of Example 1
is first mixed wi~h the resin hydride, shel-f stable
solutions using other linear hydrogen polysiloxanes
and clear organo polysiloxane compounds can be made.
~, ~
,~,J '
60SI-338
- 26 -
In these examples, solutions of curing ayents
containing the acryloxysilane of Example 1 and silicon
hydrides were made and cured and used to cure C'omposition ~,
a resin reinforced vinyl chainstopped polymer. The solutions
were made by first mixing together the acryloxysilanes of
Example 1 and the hydride resin and then adding the
remaining component. Ten parts of curing agent were added
to 100 parts or polymer. Adhesion was tested to aluminum
by curing 30 grams of the mixed compound on an aluminum
weighing dish. The samples were cured for 1 hour. When
methylethylketone hydroperoxide was added to Composition A,
a cure temperature of 125C was used. The adhesion was
determined by the cuttiny of 1/2" strips of the cured
compound out of the aluminum dishes and peeling the aluminum
strip off using an Instron, Model TM. The strip was pulled
at 90C at a rate of 12" per minute. The values are reported
in lbs./in. and the strips were examined for cohesive failure
as set forth in Table II below.
TABLE II
Example 6 7 8 9 10 11 12 13 1~ 15
B Component
~ydride Resin 64.2 74.8 47.0 83.6 79.1 74.0 83.7 81.9 61.7 35
of Example
Acry]oxy 28.3 16.4 44.2 16.4 16.5 16.4 16.3 18.0 13.6 7
Silane of
Example 1
Linear 7.5 8.8 8.8 4.4 24.7 56
Hydride 1
Linear 8.6
Hydride 2
Methyl ethyl 606 606 606
ketone
hydroperoxide
(added to "A"
Parts) ppm
60SI-338
_ ~7 _
TABLE II (Cont'd)
Example 6 - 7 8 9 10 11 12 13 14 15
. . _ ~ _ _ _ _
Properties
Cure Temp.100 80 100 100 100 100 125125 125 10
C for
1 hour
% Cohesive100 100 100 100 100 100 100100 100 10
Bond Strength 3 2.5 3.2 2.8 2.72~9 2.6 2.6 2.6 2.0
lbs./in.
Shore A 32 32 30 33 32 31 33 31 29
Room Temp.24 5 24 24 24 24 72~720 720 5
Gel Time,
h-urs
% MEMOS in28.3 16.4 44.2 16.4 16.5 16.4 16.318 13.6 7.8
Part B
~ MEMOS in2.6 1.5 4.0 1.5 1.5 1.5 1.5 1.6 1.2 0.7
cured RTV
1. Linear hydride of Example 1.
2. Linear hydride comprising a polysiloxane having hydrogen
terminal units and methyl hydrogen on chain with a
viscosity of 55 centipoise at 25C and weight percent
hydrogen o 1.0%.
Example 16
The cornposition of Example 6 was mixed and
weighed into an aluminum dish. The compound was cured
at 100C for one hour and percent solids as weight was
determined. The loss was found to be .4 percent by
weight. The cured sample was heated further at 150C
for 720 hours without experiencing any further weight
loss. A sample of Composition A and Composition B of
Example 2 was tested under the same condition and had a
weight loss of .2 percent by weight.
Example 17
Solutions of the hydride resin containing 10,
20 and 50 percent weight of methyl methacrylate were
made and were used to cure Composition A using a ratio
of 100 parts of Composition A to one part of the curiny
- 28 - 60SI-338
agent. The cure was carried out at either 80C or
100C. The samp:Les did not evidence any adhesion
to aluminum and developed a cloudy 2 phase system.
No adhesion was obtained with addition to the
system of methyl ethyl ke~one hydroperoxide.
Substitution with triallylisocyranuate resulted in
no cure or adhesion.
