Note: Descriptions are shown in the official language in which they were submitted.
'79 60 SI l78
Background of the Invention
The present invention reldtes to a room temperature vulcanizable
silicone rubber composition and more particularly the present in- `-
velltion relates to a low modulus room tempesature vulcanizable
silicone rubber composition with a good shelf life which results
from the use of certain specific catalyst systems.
Sealants are well_known. A sealant and specifically a sealant that
is utilized in high rise constructîon must adhere to the substracte
to which it is applied and preferably has elastomeric properties.
The use of such sealants in high rise construction is well~known
in that such sealants are applied where the window pane meets the
building so as to seal the glass to the metal frame providing a
weathertight seal. In addition and especially in high rise construc-
tion there are ma~y areas in which the sealant is desirable for
seLling the materials a.~ainst the elements of weathering so as to
prevent moisture and dirt from entering the building once the sealant
is used to seal the window pane to the metal frame Many sealants
are used for such an application and speci~ically polysulfides.
Further, it is especially desirable that the sealant be an elastomer
in its cured form, that is, it can be compresssed and expanded,
that is,it has elasticity and an elastic mernory. It is desirable that
the sealant be in the form of a true elastomer since it then will
expand a~d contract in the joint in which it is located and, thus, will
:~
~ ~'
I - 1 ~
60 SI-178
'7~
continue to seal aga~nst the elements of weathering.
It sould be noted that in some such sealant
applications there is a preferred a sealant of high tensile
strength and good adhesion to the substrate. This is the
application where toughness of the sealant is of primary
importance and the lack of elasticity of the sealant is not
that important. Such sealant applications which are small
necessarily apply to the sealing of joints in which there
is a small joint moyement. Where the sealant is to
accommodate fairly large relatiye expansion and contraction
of a joint opening, then it is preferable to utilize a low
modulus sealant. ~ low modulus sealant means a sealant
which has a moderate tensile stxength, but a hi~h per cent
elongation. Such sealants may be made tougher by the
incorporation in them of a treated filler. Howeyer, the
important property in the sealant is its per cent eIongation
and, thus, it is desirable that the sealant will be able to
compress or expand at least 25~ pf the distance of the
thickness of the joint or more preferably be able to
expand and compress by 50C6 of the thickness of the joint.
The ~ore the sealant can expand and compress in terms of
the thickness of the joint, or of its own thickness, the
more desi`rable it i~s~, as long as the sealant has some
adhesi~on to the substrate, that is, it does not ~ithdraw or
release from the substrate when it expands or contracts.
One class of such sealants use~ul in h~gh rise construction
are one component room termperature
vulcanizable si~licone rubber sealants~. An example of such a
60 SI-178
sealant is ~or instance to be found disclosed in U.S. Patent
No. 3,2~6,161 - dated January 3, 1~67 - Kulpa. This patent
discloses the use of a dialkoxydiacyloxysilane additive to
improve the bond strengths OI a one component room
temperature vulcanizable silicone rubber acyloxy system.
Another patent which discloses such a sealant is for instance
that of U,S. Patent No. 3,382,205 - dated May 7, 1968 -
Beer~ which discloses a room temperature ~ulcani7.able silicone
rubber composition comprising as an additive for improying
the adhesion and/or lowering the modulus of a composition,
a fluid which is composed of R2SiO units R SiO3/2 units and
R3SiQ1~2 units where R is a monoyalent hydrocarbon radical.
It should be noted that the above are additives to
one component room temperature vulcanizable silicone rubber
compositions. Such a one part RTV composition (RTV shall be
used hereinafter to refer to room temperature vulcanizable
silicone rubber compositions) comprise a silanol terminated
diorganopolysiloxane polymer where the organo groups are
monoyalent hydroca:rbon radi.cals, a filler which is selected
from reinforcing or extending fillers (which fillers can be
treated and untreated - an example of a reinforcing filler
being fumed silica) and a cross-linking agent which is
preferably methyltriacetoxy silane although it can be any
alkyl triacyloxy silane. There is preferably utilized a
catalyst with such systems to expedit the cure and such a
catalyst is preferably the metal salt of a monocarboxylic
acid where the metal varies from lead to manganese in the
Periodic Table.
11;~1'79 60 sI-178
The basic ingredients of the silanol polymer, the filler, the acyloxy
crosslinking agent and the metal salt of carboxylic acid are simply .-
mixed under anhydrous conditions. When it is desired to cure the
system, the mixture is simply applied and exposed to atmospheric
~noisture whereupon it cures to a silicone elastomer with a release
of acetic acid. In the case where the cross-linking agent is methyl-
triacetoxy silane, there are many additives that can be added to such
a composition to change its properties. The foregoing patents that
were disclosed above of Beers '205 Patent and the Kulpa '161 Patent
disclosed two additives which may be added to such a system to
improve its properties in the case of Kulpa being the adhesion promo-
ter and in the case of the additive of Beers, it being an enhancement
of adhesion promotion, as well as lowering the modulus of the
sy stem.
In the case of such sealant compositions without major modification
of the ingredients, there results a silicone sealant which has plus or
minus 257~o extension and compression in the joint in which it is placed,
of a joint 1/16 to 1 inches wide. Accordingly, it is highly desirable
to modify such a traditional sealant of the composition disclosed
pre~riously and specifically silicone sealant of the composition disclosed
pre~riously, such that it has a plus or minus 50% compression and
extension in joints whose w;dth varies from 1/ 16 to 1 inch.
There are many ways for lowering the modulus of an acyloxy functional
silicone sealant, or other silicone sealants for that matter.
11;39~t~7~ 6051-178
One modification that may be made to the silicone sealant i8 to --
increase the viscosity or molecular weight or polymer chain length
of the base silanol terminated diorganopolysiloxane polymer. It
should be noted that the increasing of the viscosity, increasing the
molecular weight and increasing the polymer chain length all mean
the same thing; that is, by increasing the viscosity, the molecular
weight of the polymer is increased which makes the final silicone -
elastomer more elastic and thus it has a lower modulus. The longer
polymer chains will not be as highly cross-linlced as shorter polymer
chains and as such the silicone elastomer that is formed from the
longer polymer chains will be more elastic or have a lower modulus.
Another way of decreasing the modulus is to use an extending oil in
+he composition that is a diorganopolysiloxane polymer which is
unreactive to the system and which simply acts as a plasticizer.
This again will make the composition more elastic and lower the
modulus of the cured system. Another way of lowering the modulus
of the system is to add the fluid of the Beers USP 3, 382, 205, such a
fluid acts as a chainstopping fluid, thus, lowering the amount of
cross-linking that is carried out by the acyloxy functional silane
crosslinking agent. The lower crosslinking makes the cured compo-
sition more elastic and thus allows it to have a lower modulus.
Finally, fumed silica or precipitated silica that is a reinforcing filler
may be added to the composition and preferably such reinforcing filler
is treated so as to increase the tensile product of the composition,
i. e., the toughness of the composition. Accordingly, all of the above
modifications may be made to one component acyloxy functional RTV
60 SI~17~
systen~ such that it has the plus or minus 50% desired compression
and expansion in the joints.
.
Accordingly, it is highly desirable to formulate an acyloxy functional
silicone sealant which has the foregoing low modulus so as to meet
the specific compression and expansion requirement set forth above.
HoweYer, it has been found that when such is done or ca~ried out that
the shelf life of the compositions suffer, that is, the composition
will have a shelf life of anywhere from 6 months to 9 months, and
after that time may c~re very slowly or not cure at all. It is also
noted that when the sixth or ninth month period i8 passed, the compo-
sition will have a tack-free time that is e~ceedingly long which is
unde sirable .
. :
Accordingly, it is one object of the present invention to provide for
a low modulus, one package RTV acyloxy functional sealant, which has
a good shelf life, that is a shelf life of one year or more.
.
It is another object of the present invention to provide for a low
m odulu s a cyloxy ~ ln ct i on a 1 one c o mp o n e nt R T V s e ala nt whi ch ha s a
shelf life of 18 to 27 months.
It i9 an additional object of the present invention to provide for a
composition of a one component acyloxy functional RTV composition
which when applied to a joint width of a specified size will ha~e plus
or minue 50% compression and expansion, that is, it is a low modulus
silicone sealant which has a short tack-free time and a lon~ shelf life.
~l;l't~'7~ 6051-178
It is stil~ an additional object of the present invention to provide for the
process of producing a low modulus one component acyloxy functional
RTV sealant which will have a short takc-free time and a long shelf
life. These and other objects of the present invention are accomplishe
. 5 by means of the disclosure set forth hereinbelow.
In accordance with the above object, there is provided by the
present invention a low modulus room temperature vulcanizable
silicone rubber composition with a good shelf life comprising (A) a
first mixture of (l) lOO parts by weight of a silanol terminated
diorganopolysiloxane polymer with a viscosity varying from 50, 000 -
350, 000 centipoise at Z5 C where the organo groups are monovalent
hydrocarbon radicals; (2) from 5 to lOO parts by weight of a fiLler;
and (B) a second mixture where there is utilized from 1 to 20 parts
by weight of the second rmixture per lOO parts of the first mixture of
t3) from 60 to lOO parts by weight of an acyloxy functional silane of the
f o rmul a,
R Si (OCOR')3
where R and R' are monovalent hydrocarbon radicals and (4) from
O. l to 5 parts by weight of a catalyst selected from the class consistin
of zinc salts of carboxylic acid, zirconium salts of carboxylic acid and
mi~tures thereof~
Such compositions while having a good cure and a good shelf life.
for extended periods of time such as 18 months to 27 months after
they are prepared, nevertheless have an extended tack-free time, such
11;~9~79 60 SI-178
as 40 to 60 minutes. If it is desired to have a low modulus compo-
sition with a good shelf life and a good cure after a period of time of
18 months to 27 months, there is utilized in the mixture (B) in the
composition above in addition to the acyloxy functional silane a co_
catalyst system. Such a co-catalyst system contains from . 5 to 5
parts by weight of a tin salt of ~ carboxylic acid and from . 001 to . 4 -
parts by weight of a co-catalyst selected from the class consisting
of a z;nc salt of a carboxylic acid and zirconium salt of a carboxylic
acid. As pointed out previously, such a co-catalyst system unlike the
first catalyst system has a good shelf life, that is the composition will
cure after 18 - Z7 months after it has been prepared and will have a
short tack~-free time of 20 minutes or less; unlike the extended tack-
free time of the composition of the first catalyst system. One type of
tin salt that can be utilized in the co-catalyst system is dibutyltin-
dilaurate. A much more preferred tin salt which give the advantageous
tack~free time in the instant compositions is dimethyl tin neo-decanoate
The preferred zirconium salt is ~irconium octoate while the preferred
zinc salt is zinc octoate. Other zinc salts and zirconium salts would
operate just as effectively in the instant invention. The above compo- -
sitions may contain any of a number of well-known additives as will
be described below.
Descriptioll of the Preferred Embodiment
The base polymer of the one component room temperature vulcanizable
silicone rubber composition of the instant case comprises a silanol
terminated diorganopolysiloxane polymer having the viscosity varying
from 50, 000 to 350, 000 centipoise at 25 C and more preferably has a
94';r9 6051_~78
viscosity tkat varies lO0, 000 to Z50, 000 centipoise at 25 C.
It should be r~oted of course that the higher the viscosity of the base
polymer, the lower the modulus of the resulting composition. The
organo groups of said diorganopolysiloxane polymer can be selected
from any monovalent hydrocarbon radical and halogenated monovalent
hydrocarbon radical. Examples of substituent groups whic~ the
or"ano radical can stand for, for instance a~cyl radicals, such as
methyl, ethyl, propyl of 1 to 8 carbon atoms; cycloallcyl radicals
such as cyclohexyl, cycloheptyL etc. of 4 to 8 carbon atoms; mono_
nuclear aryl radicals such as phenyl, rnethylphenyl, ethylphenyl, etc.;
and alkenyl radicals such as vinyi allyl, etc.
In additioD, the organo groups in such diorganopolysiloxane polymer ca
stand for halogenated monovalent hydrocarbon radicals such fluoro-
alkyl radicals are for instance 3, 3, 3 trifluoropropyl. Such diorgano-
polysiloxane polyrner is preferably lOO(~o a linear diorganopolysiloxane
polymer. However, up to 0. 1 by weight of combined monofunctional
siloxy units and trifunctional siloxy units can be tolerated in the
polymer. This is, the combined monofunctionality and trifunctionality
of siloxy units cannot exceed 0.1% by weight. Preferably the linear
diorganopolysiloxane polyrner has the formula,
where R is selected from mono~alent hydrocarbon radicals and
4~9 60 SI-178
halogenated rnonovalent hydroca.rbon radicals, which are the same as -
the radicals given as examples for the organo radicals above and .
where t varies such that the polymer has a ~riscosity varying from
50, 000 to 350l 000 centipoise at 25 C and more preferably has a , -
viscosity varying from lO0, 000 to 250, 000 centipoise at 25~C.
The production of such silanol terminated diorganopolysiloxane polyme s --
is well-known in the art. Briefly, there istaken diorganodichloro_
silanes with up to lO~lo by weight of monofunctionality or trifunctionality -
and the chlorosilanes are hydrolyæed in water. The resulting hydrolyz te ---
is then taken and the water separated from it and there is added to it,
anywhere from 1 to ~% by weight of potassium hydroxide The
hydrolyzate is heated at temperatures of over 100 and preferably
150C for a period of time varying any~rhere from l to 8 hours so as
to preferentially form cyclopolysiloxanes.
lt should ~e noted that the hydxolyzate mixture as obtained from the
water hydrolysîs contains in it low molecular weight cyclopolysiloxane
as well as low molecular weight silanol terminated diorganopolysiloxan
polymers. By cracking such a hydrolyzate with potassium hydroxide
at elevated temperatures most of the contents of the silicone hydrolyza e
is predominately converted to the cyclotetrasiloxanes. The foregoing
cyclotetrasiloxanes are then taken and they are mixed together and -
there is added to such cyclotetrasiloxanes anywhere from 50 to 500
parts per million of potassium hydroxide and the desired amount of
water as a chainstopper. The resulting mixture is then heated at
elevated temperatures so as to preferentially form at above 100 and
4'79 ~ ~
60 SI-178
more preferably above 150C in an equilibration reaction that desired -
silanol terminated diorganopolysiloxane polymer. The final viscosity -
of the polymer that is formed -~,vill depend on the amount of water that
is added as a chainstopper. The more water that i~ present as a
S chainstopper then the lower the moleculare weight of tne silanol
terminated diorganopolysiloxane polymer that will be formed. The
less water that is added, the higher the molecular weight of the silanol
terminated diorganopolysiloxane polymer that will be formed.
In addition to the water there n~ay be utilized as a chainstopper, low
molecular weight silanol terminated diorganopolysiloxane polymers,
that is the polymers that are obtained when the diorganodichlorosilanes
are hydrolyzed in water, may also be used as chainstoppers. When
the desired amount of silanol terminated diorganopolysiloxane polymer
ha3 been formed in the equilibration reaction, then the alkali metal
hydroxide catalyst, that is the potassium hydro~cide is neutralized,
and the unrea¢ted cyclics are stripped off to yield the desired base -
polymer. ,
.
It should be noted that the process for forming the silanol terminated
diorganopolysiloxane polymer having fluoroalkyl substituted groups
Z0 differs from the process or producing the diorganopolysiloxane
polyrners having non-halogenated substituent groups in that the fluoro-
alkyl substituted polyn~er can be produced both from cyclotrisiloxanes
as well as from cyclotetrasilo~sanes. The process of the production
of the polymer from the cyclotrisiloxanes is preferred since that
results in a maximum conversion of the cyclic trisiloxanes to the
desired polymex. S
i4~79 6051-178 ~ ~
In accordance with the present invention there is utiliæed per l00
parts by weight of the base silanol terrninated polymer of from 5 to -
l00 parts by weight of a filler and more preferably from 10 to 30 parts -
by weight of a filler. Such a filler can be selected from reinforcing
fillers or from extending fillers. The reinforcing fillers as is tivell .-
knowD, are furlled silica and precipitated silica. The reinforcing ~
the
fillers are preferred in/composition, if it is desired to increase the
tensile strength of the cured silicone elastomer. The disadvantage of t'~: e
reinforcing fillers, however, is that they unduly increase the v;scosity
of the uncured composition and decrease its elongation properties.
Such effects can be alleviated by treating the filler as will be --
e~plained hereinbelow.
If it is desired to increase the tensile strength of the composition to .-
some extent, without unduly increasing the viscosity of the uncured
composition and without unduly decreasing the elongation,there may be
incorporated an extending filler into the composition in the above con- -
centrations. Examples of extending filler s are for instancè titanium
dioxide, zirconium silicate, silica aerogel, iron oxide, diatomaceous
earth, glass fibers, polyvinyl chloride, ground quartz. Other
examples of extending fillers that can be utilized are lithopone, zinc :~
oxide, calcium carbonate, magnesium oxide, chromic oxide,
zirconium oxide! aluminum oxide, alpha quartz, calcined clay,
carbon, graphite, quartz, cotton s~ thetic fibers, etc.
In accordance with the instant case, it is preferred that the filler that
ZS l ~ bt oti zed be of a reinforcing type and ;pecifica11y of fumed ;ilica,
-12-
~13947~ 60 SI-178
' since even a small quantity of such fumed silLca ~ill
; increase the tensile strength.and toughness of the final
elastomer sealant.
Further if such fumed silica is utilized i:n
small enough quantities, it will not duly decrease the per
cent elongation of the cured elastomer to prevent the fi~ller
from decreasin~ the per cent elongation of the cured
composition and als.o to preyent the fi~ller from increa$~ing
the viSCQSity of the uncured compos~tion to undesirable
lQ levels~ the filler is preferably treated. Thus, the silica
filler may be treated as for example as disclosed in U.S.
Patent No. 2,9,38,009 - dated MaY 24, 1~60 - Lucas with
cylicpolysiloxanes. Another method for treating fillers that
can be utilized in the invention of the Lnstant case ,is that
disclosed in U.S. Patent No. 3,024,126' ~ dated March 6, 1962
Brown.
In add~tion silazane treated fillexs i,n accordance
with the disclosure of S~ith`U.S. Patent 3,3,65,743 - dated
January 18, 1972 and V.S. Patent No. 3,837,878 - dated
September 24, 1974 - Beers are preferred as treated fillers in
the inStant inyention However, the most preferred treated
filler in the instant i`nyention i.s fumed s-~licR txeated with
cyclopoly~siloxanes and more specifically~ with cyclotetrapoly-
siloxanes: such as octamethylcyclotetrasiloxane.
The above mixture of filler and silanol terminated
diorganopolysiloxane polymer forms the base mixture of the
instant composit~on. To anywhere of 100 parts of the base
mixture there is added in accordance with the instant
inYenti:on from 1 to 20 parts by weight of a cataly~st
3Q mixtuxe wherein the catalys:t mixture is generally
composed of a crosslinking
~ 13 -
l ~
60 SI~17~
agent, the adhesion promoter and the true catalyst that accelerates
the reaction. There is used from l to 20 parts by weight of the
catalyst mixture per 100 parts of the base mixture. The mixture of
the s;lanol terminated diorganopolysiloxane polymer and filler can -
be cousidered to be the first mixture or base rnixture, and preferably
there is utilized 1 to 10 parts by weight of the catalyst mixh~re or
second mixture per hundred parts by weight of the first mixture and
in such catalyst mixture there will be anywhere from 60 to lOO parts
by weight of an acyloxy functional silane of the formula,
R Si (OCOR')3
Where R and R' are monovalent hydrocarbon radicals and are preferabl
alkyl radicals of 1 to 8 carbon atoms, phenyl radicals and most
preferably methyl radicals. The above acyloxy functional silane
is the crosslinking agent in the instant composition. The most
preferred and most common of such crosslinking agents is, of
course, methyltriacetoxy silane. There is no need to explain the
workings of such ;~ crosslinking agent or how it is obtained since
such is well-know~ to a worker skilled in the art. The catalyst that
may be utilized with such acyloxy functional silane crosslinking agent
is a tin salt of carboxylic acid such as for instance dibutyl tin dilaurate
or tin neodecanoate. However, as stated previously when the compo-
sition is desired to be low modulus and there is utili2ed the above tin
catalyst, the composition had an imperrnissible shelf life, that is a
shelf life of 6 - 9 months and after that time the composition will not
cure .
11~ 79 60 SI-178
Accordingly, it was highly unexpected to find a composition that
would have an acceptable shelf life by combining in said second mixture
with the acyloxy functional silane instead of the tin salt from .1 to
5 parts by weight of a catalyst selected from a class consistirg of .-
zinc salts of carboxylic acid and zirconium salts of carboxylic acid
and mixtures thereof. Preferably there is used from . 5 to 3 parts
by weight of such salts. The preferred catalysts are of course zinc
octoates or zirconium octoate.
The only disadvantage with such a composition was that while it had
a good shelf life that is, it had a shelf life that would vary any~here
from 18 months _ 27 months, nevertheless it had a tack-free time
that was long. Thus, the composition could have a tack-free time of
anywhere from 30 minutes to 60 minute~ with the foregoing use of the
zirconium salt or the zinc salt in place of the tin salt in the composition.
If this i9 acceptable, then the zirconium salt and the zinc salt or
mixtures thereof can be utilized as catalysts in the instant composition
in place of the traditional tin salts the composition will have a good
shelf life although longer than normal tack-free time.
It should be pointed out that the compositions of the prior art, that is
the low modul~ls compositions o:f the prior art containing a tin salt
therein had a lengthening of tack-free time after the 6 - 9 months of
storage to the point where permanent residual surface tack was present
after several days cure, that i9 the composition would not become
tack-free except after a very long period of time. This is not the case
Z 5 ~ With th ns t8nt c ~mpo siti on ~i~ing zir conium s alt s or zinc salts .
11;~9'~'751 6 o Sl- 1 713
After 30 minutes, 60 minutes or at the rnost 2 hours, the cornpositions
do becor~e tack-free and the compositions do cure and do have a --
shel~ stability in the range of 18 months - 27 months.
It should also be noted that the prior art composition using the low
modulus composition, that is the low modulus prior art composition
utilizing tin salts as a catalyst would after storage beyond the 9 month --
period would have a decrease of total cure so that the material e~ren
after a 24 hour cure had a putty like consistency and pressure applied
to the material caused permanent deformation. Initially, this e~ect
was the notice of loss Shore A Hardness. In the latter stages of aging,
the putty-like consistency would remain even after a one month time --
at ambient conditions, that is the composit;on was curing 30 slowly
that it appeared it wou ld never cure. -
The low rnodulus compositiolls of the instant case with zirconium and
zinc salts in them in the above concentrations will cure within 24 hours
even after a 9 month period in spite of the fact that the tack-free
tirne may be as long as 1 hour.
',''.'.-
It should be noted that in the second mixture of the catalyst there is
preferably used anywhere rom 60 to 100 parts by weight of the cross-
linking agent and more preferably from 80 to 100 parts by weight of the ~
crosslinking agent with from generally .1 to 5 parts and more prefer-
ably . 5 to 3 parts by weight of the catalyst which is selected frorn zinc
salts and the zirconium salts of carboxylic acid.
-16-
11;~ 79 60 SI-178
~urther, in a more preferred embodiment of the instant case, there .
i9 utilized a co-catalyst system with the cross-linking agent, where
in the co-catalyst system contains fro.m . 1 to 5 parts by weight
of an alkyl tin salt of a carboxylic acid and fro~n . 001 to . 4
pa~ts by weight of a co-catalyst selected from the class consisting
of a zinc salt of a carboxylic acid and a zirconium saIt of a
carboxylic acid. More preferably, there is utilized as a co-catalys
in the system from 0. 01 to 0. 2 parts by weight of the zirlc salt
or the zirconium salt of carboxylic acid with from 0.1 to l parts
by weight of a dialkyl tin salt of carboxylic acid with the al~cyl
group having 1 to 2 carbon atoms . The co- catalyst system of the
tim salt with the zirconium or zinc salt is preferred over single
catalyst system of the zirconium salt or the zinc salt since the
co-catalyst system results in a composition which has good cure
after storage varying from 18 months to 27 months with a tack-
free time of 15 to 20 minutes. The composition without the
combination or co- catalyst system of both the zinc or zirconium
salt in combination with a dialkyl tin salt re sults in a composition
with a good shelf lie that will produce a good cure after storage fo .
a period of time of 18 - 27 months, but will have a prolonged
tack-free time of 30 minutes to 60 minutes or more. The COlnpO-
sition with a co- catalyst system of the tin salt in combination with
the zirconium salt or zinc salt will have a good shelf life, that
is, it will have a good cure at periods of storage of as much as
18 months or as much as 27 months and will also have a short
~ -17_
11;3~1~'7g 60 51-178
,ack-free time of 15 minute~ to 30 minutes.
A less preferred tin salt that can be utilized in cornbination with
the zinc salt or zirconium salt is for instance dibutyltindialurate.
However, the tin salt that is preferred in the instant compositions
is one which has a diallcyl group which is a dial~yl tin soap of a
carboxylic acid in which the dailkyl group is selected from dimethyl
and the carboxylic acid portion contains anywhere from 2 to 22
carbon atoms and is most preferably neodecanoate.
Accordingly, the most preferred tin salt is dimethyl tin neodecanoat
l 0 as the tin salt in combination with the ~inc salt or the zirconium
salt in the co-catalyst system oi the instant invention.
Accordingly, to pxepare the compositions of the instant case, the
co-catalyst system or the catalyst system is mixed with the
acyloxy functional silane and the second mixture is then mixed at
a concentration of anywhere from 1 to 20 parts by weight per
lO0 parts by weight of the first mixture and the entire mixture is
then packed in a moisture-proo~ container. Such a composition
is maintained in the anhydrous state until it is desired to cure the
composition. Then the composition is appl ied as a sealant in
whatever rnanner it is desired and exposed to atmospheric moisture
to cure to form an elastomeric silicone sealant.
~ .
It should be noted that even though the composition is disclosed and -
claimed in the form of mixing two mixtures, the claims in the
disclosuxe of the instant case are directed to a one-componerlt RTV~
,~ -18-
1 ~ 9~7~3
60 SI~178
system. All of the ingredients are mixed together into a single
mixture and stored as such. When it is desired to utilize the --:
composition or convert it to a silicone elastomer, it is simply
taken and exposed to atmospheric moisture either by squeezing frorr~
a tube or being pushed put of a caulking tube, such that it is
exposed to atmospheric ~noistur~ whereupon the acyloxy functional -
silane wil~ hydrolyze and crosslink to a silicone elastomer. -
It should be noted that the clain~ language in the specification dis-
cioses the formation of two mixtures which are mixed together to
form the single component of the instant composition, since this
is how the composition is prepared in practice and also to acilitate
the description and recitation of the concentrations thereof of the -
ingredients. There are additional ingredierts to the instant
composition ancl specifically in the instant composition there are
additional ingredients which are pre sent to make the composition a
low modulus composition.
As pointed out previously, there is desirably utilized a high viscosit
silanol terminated diorganopolysiloxane base polymer in the instant
composition so as to lower the modulus of the composition or
increase the per cent elongation. In the above cornposition and
specifically to decxease the modulus of the composition, there is
present int he first mixture of the one component composition of
the instant case per 100 parts of the silanol terminated diorgano-
polysiloxane polymer of from 0 to 50 parts by weight of a plasticize -
which is a diorganopolysiloxane polyrner of a viscosity varying from
1~ 4~79 60 SI-178
10 to 5, 000 centipoise at 25'C where the organo groups are
monovalent hydrocarborL radicals.
It should also be noted that the organo groups of such diorgano-
polysiloxane polymer are the same as the organo groups of the
silanol base polymer.
It should al~o be noted that such diorganopolysiloxane polymer i8
triorganosilylendstopped. It is preferred that the diorganopolysiloxa ~e
polymer be strictly linear. However, up to 1% of tri~unctionality
and monofunctionality combined is permitted. Generally, there
may be utilized f~om 1 to 50 parts by weight of the plasticizer
diorganopolysiloxane polymer and more preferably there is utilized
anywhere from 20 to 30 p~ rts by weight of diorganopolysilcxane
polymer per 100 parts of the silanol terminated diorganopolysiloxane
polymer. Further, although the viscos*y of the polymer can
vary from 10 to 5, 000 centipoise, it preferably varies anywhere
from 10 to 500 centipoise at 25C. The diorganopolysiloxane polym r
of which the most preferably type for use in the present invention
is a dimethylpolysiloxane polymer of a viscosity varying from 10 to .
500 centipoise at 25 C which is trimethylsiloxy endstopped and whic~
is substantially a linear polymer can be produced by methods well
known in the art. Thus, the polymer can be produced by simply
hydrolyzing diorganodichlorosilanes with triorganochlorosilanes
and separating the resulting fluid that is formed. It can be appreci ted
that such a fluid will not be completely linear and may have up to
-20-
11;1~'17~ 60 51-178
l % of monofunctional siloxy units and trifunctional siloxy units.
However, such units will not detract from the plasticizing effect -
. of the diorganopolysiloxane polymer.
Accordingly, the use of the plasticizer, that is the diorganopolysilo~ ~ne-
fluid, having triorganosiloxy endstopped units will decrease the
modulus of the composition if utilized i~ the foregoing quantities.
To further decrease the modulus of the composition there may
be utilized in the base or first mixt~re per 100 parts by weight of
the silanol terminated diorganopolysiloxane polyme r of anywhere
from l - 25 parts by weight more preferably 5 - 15 parts by
weight of a chainstopping fluid having in it monofunctional siloxy
units, difunctional siloxy units and trifunctional siloxy units. Thus,
preferably the 1uid is composed of R2 SiO units R33 SiOo 5 units
and R3 SiOl 5 units where the ratio of organosiloxy units and
diorganosiloxy units varies frorn 0. ll to l. 4, inclusive and the
ratio of the triorganosiloxy units and diorganosiloxy units varies
from 0. 02 to about l. 0, inclusive and R3 is a monovalent hydro_
carbon radical. It should be noted the term R3 being a Inonovalent
hydrocarbon radical intended to include both mono~ralent hydrocarbon
radicals and halogenated monovalent hydrocarbon radicals such as
3, 3, 3 trifluoropropyl. The groups for which R3 radical may
stand for is much the same as given before in the definition of the
organo groups and the R2 groups for the silanol termi~ated diorganc -
polysiloxane polymer which is the base polymer in the instant
~`1
~ 79? 6 0 SI- 17 8
compositions. Such a polymer cornposed of monofunctional,
difunctional and trifunctional siloxy lmits will contain anywhere
fxom .1 to 8% by weight of nydroxy radicals. Such silicone fluid
or chainstopped fluid has two advantages.
. . ,.-
}D another aspect, it acts as an adhesion promoter and allows the
cured composition to adhere to various types of substrates with
better adhesion than would be the case if it was not utilized.
The production of such fluid is also well-known ir~ the art and
generally comprises hydrolyzing the appropriate quantities of diorgar~ o-
dichlorosilanes with m~noorganotrichlorosilanes and triorganochloro_
silanes in water and then separating and purifying the resulting
fluid that is formed. An example of the foregoing f}uid composed o~
the rr,onofunctional siloxy units and difunctional siloxy units and
trifunctional siloxy units for use in one part RTV Compositions is
disclosed in Beers USP 3, 382, 205.
Use of such fluid to improve the
shelf life of one component acylo~y funcL.ional silane RTV compositio ns
is disclosed in this patent. However, the use of such lluid in ¦
combination with the other fluids and modifications of the instant
case to both lower the modulus of the composition and increase the
shelf life is not disclosed in the above Beers Patent.
However, this increase in tensile strength and decrease in modulus
is more than offset by the other ingredients and modifications
disclosed above to result in a low modulus one component RTV
2~ cornposition with the desired modulus and the desired shelf life.
1 l~i7~ 60 SI-178
, 1,'
Finally, there is utilized an adhesion prornoter or an ingredient ~:
which serves primarly as an adhesion promoter ilL the instant ~--
cornposition.
..,-,'.
Accordingly, in the seconal mixture or the catalyst mixture there
is present arlywhere from 5 to 40 parts by weight of an adhesion
promoter which is preferably a ditertiaryalkoxydiacyloxy functional :
silane. More preferably, there is utilized anywhere from 10 to
30 parts by weight of the ditertiaryalkoxydiacyloxy functional -
silane. More broadly, there may be utilized a dialkoxydiacyio,~
functional silane as the adhesion promoter. However, it has been
found that the ditertiaryalkoxydiacyloxy functional silane s are more
effective as adhesion promoters in the instant compositions than
is the case with the plain dialkoxysilane ingredients or additive s.
.
Preferably, there is utili~ed ditertiarybutoxydiacytoxysilane as the
adhesion promoter in the instant composition which is utilized in the
concentration of anywhere from 10 to 30 parts by weight based on
60 - 100 parts by weight of the acyloxy functional silane cross-
linking agent whose formula was given previously. This adhesion
promoter is disclosed in Kulpa USP 3, 296, 161~ - dated
January 3, 1967.
The instant disclosure particularly exemplifies and illustrates the
use of such an adhesion promoter in one component acyloxy function Ll
RT~J Composition and the instant case is not limited to sush adhesic
39~'7
60 SI-178
promoter~. There cas~ be u~ od other adhesion p~osnoters in the ~ I
instant composition. It can be appreciated also there can be -
utilized other plasticizers other than the triorganosilylendstopped -
diorganopolysiloxane polymers which are utilized as plasticizers ---
in the instant case. In additio4 there can ~e util~7.ed other
chainstopping fluids other than the fluid composed of monofunctional
siloxy units and difunctional siloxy units and trifunctional siloxy
unit~, as disclosed in the above specification. The above ingredienl s
and additives have been specified since that resul ts in a composi- ~::
tion with competitive low modulus properties, which has a good
shelf life that has a good cure after periods of time of storage
of as long as 18 months or as long as Z7 months and in which l,
the foregoing catalyst, that is zinc salt or zirconium salt catalyts f-
are utilized by themselves or more pre~erably the tin catalyst -
is used in combination with the zirconiurn salt and zinc salt in
the co-catalyst system which is the preferred system of the instant -
ca se .
It should be noted that while variations may be made in the above
compositiQn, it i9 the above composition with the ingredients define
above both in the broad sense and in the more limiting sense that
discloses a one component RTV low modulus composition with
acceptable sheLf life in pe2iods of time varying frorn 18 months -
Z7 months of storage.
-24-
60S~-178
Accordingly, even though a good many of the additives of the
instant case are disclosed for utilization in one component RTV
compositions by the prior art, it was not disclosed by the prior
art the optinaum combination of ingredients of the instant case for
producing a composition both of low modulus and good tensile
strength properties and a cornposition having good shelf Iife after
a period of storage of l 8 months - 27 months ater manufacture
and ha~ing a ~ood cure after that time.
The Examples below are given for the purpose of illustrating the
present invention and are not given for any purpose or reason to
set limits or definitions as to the extent of the instant invention or
the extent of the instant claims. All parts in the examples are
by weight unless specified otherwise. ;.-
EXAMP LE I
There was prepared base compounds X, ZX and 3X comprising
¦ taking a dimethylpolysiloxane polymer which was silanol stopped
and which had the viscosity shown in the table below (Table I) and
there was mixed with it the stated quantities of fumed silica treated
with octamethylcyclotetrasiloxane, the dimethyl polysiloxane oil7
which is trimethylsiloxy endstopped of 100 centipoise viscosity at
25 C. There was added to the mixture the stated quantities of
such an oil and in addition there was added to the mixture thë
silicone oil composed of trimethylsiloxymonofunctional siloxy units,
difunctlonal siloxy units and methyltrifunctional silo y units
li;~9'~ Y 60 5~- 1 7~
which silicone fluid had a . 5 weight per cerlt hydroxy content as
indicated in Table I below. The foregoing type s of ingredients
were combined i~ the quantities set forth in Table I below. To
the base compou~d there was added the amount of the catalyst
S a~d the concent2ation of the catalyst in the second mixture of the
crosslinking agent, adhesion promoter a:nd catalyst ingredients as
set forth in Table I below. The compositions had the following
properties as set forth in Table I below,
TABLE
Achievement o Low Modulus Characteristics, and Improved Toughne s
Factor (Tensile Product). Parts by Wei ht ( bw)
~ P . _
A. Base ComPound
__
X 2X 3X
A dimethyl silanol stopped
15 polymer viscosity at 25 C 10, 000 100, 000 100, 000
pbw level 100. pbw 100, pbw 100. pbw
Fumed si7 i ca t. eated wit h octz--
methylcyclotetrzsiloxane 20,pbw 18. 5pbw 18. 5pbw
Dimethylpolysiloxane oil o 100
20 centipoise at 25c C - - - 25. pbw 25. pbw
Silicone oil co;~posed of (CH3)3
sioo 5 units 15, pbw 8. pbw 8. pbw
(CH3)2SiO units and CH3SiO1 5
units with 0. 2 wt. % hydroxy groups
2 5 B, Cataly st
Amount of catalyst mixture per 4. 2 3. 9 4. 2
100 pts of base - Level (pbw on base)
F o ;: mula
Methyltriacetoxysilane 80. pbw 80. pbw 80~ pbw
Ditertiarybutoxydiaceto~ysilane 20. pbw 20. pbw 20. pbw
Dibutyl tin dilaurate 0. 60pbw 0, 60pbw _ _ _
l)imethyl tin neodecanoate - - - - - - 0. 525pb
Zirconium octoate (12% Zr) - _ 0. 120pb; J
9'17~ ~
60 SI-178
TABLE I - continued -
X 2X 3X --
C . P ropertie s
App}ication Rate, gm,l min.270. 74. 100.
Taclc-free Time, minutes 15. 35. 20.
Cure Condition 24 hrs. / RTGood Good Good
ASTM Sheet Physicals . -
Shore A 34 17 20 -
Tensile, psi 350 300 360 -
Elongatio~, % 400 930 860 --
Tensile Product (x10-3) 144. 279. 310.
S e cant Modulu s, p si
0.25 in.tin. 232. - - ~ 136. -
1. 00 in.lin. 122. - - - 60. :-
3.00 in./in. _ _ _ _ _ _ 39
D. 180 Peel Adhesion - 10 day Room Temperature Cure
.. ...
Note: - All values - (lb./ in. )/ (% Cohesive Failure) -
Substrate X 2X 3X
Anodized Aluminum 17/ ~ 5% 45/ 15% 75! 85%
304 Stainless Steel 71/ 100% 70/ 60% 72/ 100% --
E. 180 Peel Ad~lesion - 10 day/ E~oom Temperature Cure plus
7 day/ l~oom Temperature/ H20 immersior
Note: - All values (lb. per inch) / (% Cohesive Failure)
Sub strate X 2X 3X
___ .
25Anodized Aluminum <2/ 0% 6/ 0% ~30/ 100%
304 Stainless Steel ~2/ 0% 60/ 60% ~30/ 100%
F. Accelerated A~in~ Data
Note - All Values: Tack-free Time/ Cure Condition at 24 hrs
100 C Accelerated Aging
30Time (hours) X 2X 3X
_
24 15 min/ g ood - - - - _ - -
32 _ _ _ ~60 min/poor 20'/good -~
48 - / g ood - - _ _ _ _
30 min/ good ~ _ _
27_
9':~'79 60 51-178
The ~alues in Table I above indicate the co~nposition with the ~owest
modulus and a good shelf life or a good rate of cure after accelerat d '-
aging only when the catalyst system of the instant case was utilized.
There wa3 obtained a system with low modulus, good tensile -
properties and good curing after aging only with the irgredients and
the catalyst system of the insta~t case was utilized in the compo-
sition. There was prepared a performance comparison of
Composition 3X with a prior art sealant. The results are as
follows:
l 0 TAB LE TT
Co arison with High Performance Competitive Material
rnp, , ~~ :
Property Prior Art Sealant 3 X
A. Application Properties
Application Rate, grn,/ min. 146 lOZ
l 5 Tack-free Time, min. 25 20
B Initial Physieals
.
Shore A ~ardness 25 20
Tensile, psi 190 360
Elongation, % 810 860
Tensile Product (x10-3) 154 310
C. Heat Aged Physicals (24 hr./480F)
Shore A Hardness 51 43
Tensile, psi 100 170
Elongation, % 50 93
Tensile Product (x10-3) 5 o 16. 0
Weight Loss, %, stability of 4. 1 4. 6
material addition of 2 did not
destabiliæe system -
D. Adhesion, l 80 Peel
F ailur e .Failur
Subst~ate Lb. / in. (% Cohesive) Lb. / in. ~% Coh s
..
Anodized Aluminum 66 lO0 75 85
'7~ 60 51-178
The results above indicate the Composition 3X, the composition of .
the instant case has superior low modulus and cured properties .",
with re spe ct to the prior art sealant.
EXAMP LE II
There was prepared the base Compositions 4X, 5X, 6X, 7X and 8X .,.
as indicated in Table III beIow, comprisirlg forming the ba se -.
compound by mixing 100 parts by weight of silanol terminated di-
methylpolysiloxane which was a blend of dimethylpolysiloxanes such ,.,
that the blend had an end viscosity of 80, 000 centipoise at 25C
and such that the Composition 8X was a blend of silanol terminated .,,
dimethylpolysiloxanes that had an end viscosity of 95, 000 centipoise .
at 25C. To such silanol polymers there was added 15. 5 parts .,
by weight of fDed silica treated with octamethylcyclotetrasiloxane
22, 0 parts by weight of a trimethylsiloxy endstopped dimethylpoly- .,.
siloxane oil of 100 centipoise viscosity at 25D5 and 6. 5 parts of a
silicone oil fluid composed of trimethylmonofunct ional siloxy units, -
dimethyldifunctional siloxy units and monomethyltrifunctional siloxy
units in which the polynaer contained . 5 weight per cent of hydroxy
groups. To the above base compounds there was added the amount .
of catalyst mixture as well as ingredients of the catalyst mixture -
shown in Table III below. The results of initial cure and .-
accelerated aging cure to determine shelf life of the compositi,ons
is indicated in Table III below.
~ 9 ~ 7~ 6 0 SI - 17 8
o~ 1.
a~l 3 O ~ \ ~ ~ o ' , u~ ~ ,
o~~ I C2~ O ~
~ . ,
~1 ~ 3 3O ' ' ' o o ~
~ o~,,, ` o ,
3 l 3 ;) ~
~1 u~ I o i , ~ , , , , u- ~ ,,'
_ h ~ O
3 o 1 3 ~ ) _ ~3 33 a~ .
~1 ~3 ~ ~ ~ ~ C ~ ~ O ~
v O ~ . U~ O U~ O O I ~ I ~D O :~ :'
rC ~ O U~ ~ ~O O O I I I O U~ ~ .'
3 O r~ ~ x (~ ~
r~ .~ ~ , O
a ~ o
L~ ~ ~
_30- .
11391'7~ 60 sl-17a
xl e
_ 31.- . '
~ :113~'}79
60 SI-178
The results of Table III indicate that Compositions which were
cataly~ed only with tin soaps had good initial cure and good initial
tack-free time, but had very poor cure upon accelerzted aging
while compositions cured solely with zirconiurn octoate, that is
7X or ~inc octoate, that is 8X had long initial tack-free time, but
good initial cures and had upon accelerated aging long tack-free -
time that is 40 minutes or so, but good cures after such
accelerated aging. The results of Table III substantiate the zinc
octoate and zirconium octoate, that is zinc salts and zirconiurn
salts or carboxylic acid were good catalyst for the low modulus
compositions of the instant case and provided good shelf life to
the composition.
EXAMP LE III
There was prepared a base compound comprlsing 100 parts by
weight of a silanol terminated dimethylpolysiloxane oil fluid o~ -
112, 000 centipoise viscosity at 25'C, 18 5 parts by weight of a -
fumed silica treal:ed with octamethylcyclotetrasiloxane, 25 parts by
weight of a trimethyl siloxy endstopped dimethylpolysiloxane oil r
of 100 centipoise viscosity at 25 C and 8 parts by weight of a
silicone oil composed of trimethylmonofunctional siloxy units,
dimethyldifunctional siloxy units and rnonomethyltrifunctional siloxy
units with . 5 weight percent of hydroxy groups. To the resulting
mi~cture there was added the amount of catalyst mixture and types
of ingredients and amounts of i~gredients in the catalyst mixture
shown in Table IV below. The compositions, one of which is the
X Composition of Exampl~ s compared with the s dghtly differen~
~ 3~4~7~
60 SI-178
composition, ga~re the following tack-free time and cure rates
and cures upon initially being cured and upon being cured after
accelerated aging as indicated in Table IV below.
TABLE IV
Ffect of Co~nbinations of Dimethyl Tin Neodecanoate and
Zinc or_Zirconium Soap - Parts by Weight_(pbw) __
1, Formulation
A. Base Compound (All Formulatiorls)
Silanol terminated dimethylpolysiloxane
112, 000 cps. viscosity at 25~C 100pbw
Fumed silica treated octamethylcyclotetra-
siloxane 18. 5pbw
Dimethylpolysiloxane oil of 100
centipoise viscosity at 25C 25. ~pbw
- 15 Silicone oil composed (CH3)3SiOo 5 units,
(CH3)2Si0 units and (CH3)Si01 5 units
O. 5 weight % of hydroxy groups 8. Opbw
B. Catalyst
1. Formula 9X 3X
Methyltriacetoxysilane 80. 80.
Ditertiarybutoxy~<diacetoxysilane 20. 20.
Zirconium Octoate (12% Zr) - - 0.120
Zinc Octoate 0. 075 _ _ _
Dimethyl tin neodecanoate 0, 525 0. 525
2. LeYel Wt. % of catalyst mixtures 5. 0 5. 0
per 100 pts of Base Compound
2. Properties - Accelerated Age
Initial
Tack-free time, minutes 15 Z0
Cure Condition good cure good cure
Accelerated Age, 32 hrs/ 100 C
_
Tack-free time, minutes 14 20
Cure Condition good cure good cure
l I li;~9~1'79 ~o 5~-178
The above re sults in Table I~l show that the low modulus compo-
sitions of the instant case which were cured with the combinatiou o
zinc octoate and dimethyl tin neodecanoate or zirconium octoate
or a combination of zirconium octoate and dimethyl tin neodecanoate
resulted in compositions with good tack-free times, that is tack-
free times in the neighborhood of 15 - 20 minutes and good cure s
both on being cured initia~ly upon being prepared or upon being
cured after accelexated aging indicating that both compositions
had good shelf life. The above results indicate that there is ~.
obtained good low modulus compositions having good tensile
properties as well as compositions having good acceptable tack-
free time s and long shelf life .
