Note: Descriptions are shown in the official language in which they were submitted.
60SI- 78
i,
~ Back~round of the Invention
.' i
The present invention ~elates to a silicone foam composition and
more particularly the present invention rela.tes to SiH-oleIin
, platinum catalyzed silicone foam co~nposition in which the novel
~ l foaming ingredient i6 water
I Accordingly, in the construction of many plants arld buildings there
j are many steps taken to insulate electrical systems a~d more
¦ specifically sensitive electrical systems, 6uch that in the case of
fire that they will not burn easily and that if they do burn they will
~ .not propagate a fire very easily.
Accordingly, siliconer with their high temperature properS~es are
highly desirable as ~nsulative materials for such elec~rical sy~tem~.
For instance, silicones may tend to char and leave a protective a~h
~ on the system that they are insulating and still protect the electri-
¦l cal system and maintain its electrical integrity. Accordingly, such
1 burn res;stant properties of silicones have made them highly
~ desirable as insulative materials for electrical systems ancl more
i specifically for cables. Thus, one use of heat vulcanizable silicone
rubber compositions comprising a diorganopolysiloxane gum, silica
I filler, flame retardant additives such as platinum or carbon black
,1 and with or w*hout a peroxide catalyst has been to fill the ~oids in
electrical cables thus protecting the cable in case of fire.
Accordingly, in such use6 it has been found that such heat vulcaniz-
' able silicone rubber compositions either in the cured or in the
1~ uncured state with a base composition disclosed above alone or with
¦ the add~tion of other flame retardant additives have pr~tected the
'.
I
~ , - 1 - .
i'
4S~ 60SI- 78
~1 electrical integrity of the cables up to temperatures of 2000F for an
¦' appreciable period of time.
Accordingly, it was highly desirable to utilize such burn resistant
~. silicone compositions as insulative materials for electrical system.s
I and specifically electrical systems in nuclear plants. Concrete can
I be used to enclose and protect such electrical system.s. However,
¦ the cost of applying the concrete to irregular openings in walls and
j ceilings becomes quite expensive.
¦ Accordingly, it becam.e desirable to utilize for the insulat;ve pro-
i0 ¦ tection of such electrical systems silicone foams. A~s a ma~ter of
¦ fact, name retardant silicone foams are highly desirable not only
for the enclosure and protection o:E electrical systems but also :Eor
~ the protection of other types of components from. burning to sorne
1 ~ extent .
I An example of such a flame retardant silicone foam is that, for
¦ instance, to be found in Modic, U. S. patent 3, 4Z5, 967. This
' patent discloses a silicone oam composition which is produced by
¦I mixing ar~.interreacting a vinyl chain-stopped polysiloxane, an
1 organopolysiloxane copolymer which was a resin composed o mono-
¦ functional units and tetrafunctional units and optionally difunctional
, siloxy units and inorganic fibrous material selected from the class
j~ consisting of a~bestos and fibrous pc>tassium titanate, optionally a
!i finely divided inorganic filler, a platinum. catalyst and an organo
¦I hydrogen polysiloxane and finally a blo-wing agent.
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,
¦i 60SI-78
I'
The examples that are given of such blowing agents are, for
example, azo-isobutyronitrile, dinitrospentemethylene tetramine,
~, benzenesulfonhydrazide N, N'-dinitroso-N, li~'-dimethylterephtha
¦ amide, p, p~-oxy-bis(benzenesulfonhydra~idle), terephthalazide,
1 azodicarbonamide, etc. Such a system whiLe adequate for many
aspects had two main disadvantages. It required the use of a
complex blowing agent which increased the cost of the system and
also was foa~ed at elevated temperatures; that is, in order to
~ activate the blowing agent elevated temperatures were needed and
accordingly a foam could not be formed insitu in an electrical system
already in place at room temperature since external heating had to
be applied,
I ~ more recent attempt to produce an acceptabl~ silicone foam or
~ the insulation of electrical systems from fire is to be found in the
j, disclosure of Smith, U.S. patent 3, 923, 705. This patent reviews
1' some of the prior art with respect to silicone foams. The dis-
¦¦ advantages with such a system was that it required the reaction of
a silanol containing polysiloxane with hydrogen-containing poly-
~ siloxane. There was found that with such a system good foams were
I not always produced unless an extremely active platinum complex
J catalyst was utilized. The reason for this is that if an extremely
¦l active platinum complex catalyst was not utilized then the hydrogen
1~ polysiloxane reacted with hydroxy-containing polysiloxane at a slow
¦, rate, releasing hydrogen at a slow rate and as a result a foam with a
2,~ Il, proper density was not always obtained. Accordingly, the type of
foam and the amount of foam would vary from reaction to reaction
3 -
j ` 6 0SI - 7 8
and from. batch to batch of the composition.
, Accordingly, it was highly desirable to find a silicone foam which
i was not expensive and which would produce a reproducable foarn ~rom.
¦~ batch to batch that could be produced with most types of platinum
~ catalysts.
I In addition, in the construction of many buildings and partitions in
¦ buildings where concrete or m~sonry products were not utilized to
produce the partition, it has been common to leave such partitions
hollow or not containina any material in them.
Accordingly, it has been common especially in office buildings to
leave such ceilings and more particularly partitions hollow. It was
early suggested that silicone compositions could be utilized both as
mate rial s
heat insulative/and more particularly ~nd rnore importa:ntly as burn
resistmt materia~s in such partitions and ceilings.
I Accordingly, it is highly desirable to have a silicone foam.which is
¦ inexpensive and can be foamed at room temperature to a good qual*y
foam from batch to batch with most types of platinum catalysts. Such
silicone foam. can also be used as a burn resistant material in
I partitions in the construction of partitions in buildings and as an
¦ insulative material in the ceilings of buildings.
¦ Accordingly, it is one object of the present invention to provide for
¦ an SiH-olefin platinum catalyzed silicone foam.
Ij It is another object of the present invention to provide for an SiH-
¦, olefin platinum catalyzed silicone foam ~rhich can be catalyzed with mcst
lj types of platinum. catalysts to produce good quality foam. which is
li reproducable from batch to batch
It is yet an additional object of the present invention to provide for a
process for producing an SiH-olefin platinum catalyzed silicone foam
I
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60SI-78
11 ~
of good quality which is resistant to burning.
It is yet an additional object o~ the present invention to provide for
i a process for insulating electrical system.s by utilizing an ;~iH-
olefin platinum catalyzed silicone foar~ composition. ~hese and
5 I other objects of the present invention are accomplished by means of
'~ the disclosure set forth hereinbelow.
. .
Summary of the Invention
In accordance with the above objects there is provided by the present
¦ invention a silicone foam com.position useful as a burn resistant
10 ¦ material comprising (a) 100 parts by weight of a base vinyl-containing
polyrner of the formula;
R 1 I R
~I Rl t R ~ R
where R and Rl are selected :Erom the class consisting of alkyl
¦ radicals of I to 8 carbon atom.s, aryl radicals, vinyl radicals anl
¦ fluoroalkyl radicals of 3 to 8 carbon atoms, such that the polymer
' contains from. 0. 0002 to 3% by weight vinyl, and x varies such that
the viscosity of the polymer varies from 100 to 1, 000, 000 centipoise
at 25~C; (b) from. 0 to 200 parts by weight of a filler; ~c) from 100
I parts per million to 1. 5 parts by weight of wa~er; (d) fr~m 1 .to.50 partsl.
~ by weight of a hydride polymer of the formula;
ll
i ,
~ _ 5 _ .
Ii . .
60SI- 78
. .
(Z) R t si o ~ si o ~ si RZ
1 R3 z H y lR3
~! .
where R2 is selected from the class consisting of hydrogen, a~lcyl
radicals of 1 to 8 carbon atoms and aryl radicals, and fluoroalkyl
i radicals of 3 to 8 carbon atoms, and R3 is selected f~o~n alkyl and
aryl radicals of up to 8 carbon atoms where the hydride polymer has
a hydrogen content varying from 0. 3 to 1. 6yO by weight and z and y
vary such that the polymer has a viscosity varying from 5 to 100 centi-
poise at 25C, where there is at least 0. 2 moles of SiH per mole of
I water; and (e) from 1 to 250 parts per million of a platinum catal~rst,
I It should be noted that most type~ of platinum catalyst can be used in
the instant process and more specifically one of the platinum complexes
I such as the platinum olefin complex. The most preferred catalyst is
¦¦ a platinum complex of platinum and a vinyl-containing polysiloxane.
¦¦ Most preferably such a pl~tinum complex is substantially free of
'~ chlorine content. Such a catalyst is desired since it is extremely
¦ efficient and causes the vinyl-containing base polysiloxane polymer to
react with the hydxide-containing polysiloxane at a very fast rate to
I release hydrogen and form a good foam in the instant process.
1, However, as stated previously, the other platinum complexes will
Z0 ~ provide and produce suitable foams within the scope of the instant
invention. As such, the instant invention is not limited to the most
¦, preferred platinum complex catalyst.
It is preferred that the base vinyl-containing polymer only contain
vinyl terminal units, however, it can contain some vinyl on chain
, .
r
1 ~ 6 ~
~ 60SI-78
. ' 1
units also. Also, there can be utilized as the vinyl containing base
polymer, a polymer in which there is only virlyl on chain. Ho~ever,
j such a polymer is a less preferred polymer in the composition in
the process of the instant case. A filler may also be utilized in the
! instant process. It does improve the 1~me reta~dance of the
¦ composition. In addition, other 1ame retardant additives such as
carbon black can be utilized in the composition to increase ,and er~hance
the burn resistant properties of the compositions of the instant case.
With respect to the hydride polymer, such hydride polymer must have
a hydrogen atom on the polymer chain to produce a suitable foam,
I However, it may also have hydride on the terminal silico-re atoms,
¦ that is, the polymer may have hydrogen terminal units. Howe~rer, a
hydride polymer cannot be used as a cross-linking agent with only
I hydrogen terminal units and no hydrogen on the polymer chain.
Next, it is necessary in the compos*ions and processes of the instant
case that there be at least 0. 2 moles of hydrogen in the hydride-con-
taining poly6iloxane cross-linlcing agent, for every mole of water to
release sufficient hydrogen to produce a suitable foam,
I Finally, the composition is utilized to produce a oam by simply
¦ mixing the ingredients and allowing them to react to form a oam.
I Upon mixture of the ingredients, the ingredients wil1 immediately
.' I .
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i
I
!l
60SI-78
j' react with each other to liberate hydrogen and form the appropriate
silicone foam which cures to a silicone elastomeric foaIl~. However,
Il the instant process can be carried out a~ room temperature without
1~ the need of heating. If heat is applied, of course, the reaction will
i proceed at a very fast rate. Accordingly, the silicone foam.s of the
¦ instant invention may be formed insitu in buildings at room ternpera-
¦ ture where the ingredients are simply mixed together and poured
j into the partition container or crevice which is desired to be filled
¦ with a silicone foam and the resulting mixture will foam and cure to
¦ a silicone elastomeric foam within the period of tim.e of initial cure
¦ varying from 10 seconds to final cure which can take place in a period
¦ of time varying anywhere fron~ minutes to hours.
If it is desirable in such a composition, there optionally rnay be
! included a mild inhibitor such as a vinyl-containing cyclicpoly-
15 I siloxane. Such an inhibitor will give the mixture sufficient pot life
to be applied to the enclosure in which it is desired that the silicone
. I foam be produced and then the system will then cure at room
1I temperature at a slower rate than if the inhibitor was not present.
I If heat is applied, it can be appreciated that the system. will form a
I silicone foam much faster. This is especia.lly true if the inhibitor
! is present in the mixture. It can also be appreciated that the compo-
sitions of the instant case can be placed in enclosures or molds and
~' allow the foam to form a shape block of silicone elastomeric foam.
', The use of the process of forming the silicone foam.s of the instant
I case can be varied as suits the worker skilled in the art,
I!
Il
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60SI-78
1~ .
jl Description of the Preferred Embodiment
The basic vinyl-containing polymer has Formula (1) shown previously.
i In such formula, R and R' may be selected from the hydrocarbon and
! halogenated hydrocarbon radical with a proviso that there is present
from 0. 0002 to 3% by weight of vinyl substitution in the polymer,
I which vinyl substitution must be present such that the viscosity of the
j polyrner varies from 100 to 1, 000, 000 centipoise at 25C.
Accordingly, such hydrocarbon groups and halogenated hydrocarbon
groups may be selected from alkyl radicals, methyl, ethyl, propyl,
etc.; cycloalkyl radicals such as, cyclohexyl, cycloheptyl, cyclo
octyl, etc.; mononuclear aryl radicals such as, phenyl, methyl-
phenyl, ethylphenyl, etc.; allcenyl radicals such as, vinyl, allyl,
~ etc. and more preferably, vinyl and other well known substituent
¦ groups for diorganopolysiloxane polymers. Preferably, the R and R~
I! radicals are selected from the class consisting of alkyl radicals of
I 1 to 8 carbon atoms, aryl radicals such as, phenyl~ vinyl radicals
I and halogenated hydrocarbon radicals such as, fluoroalkyl radicals
¦ of 3 to 8 carbon atoms, suchas, for instance, 3, 3, 3-trifluoropropyl.
are
Most preferably, the R and R' radicals/selected from methyl radicals,
I phenyl radicals, vinyl radicals and 3, 3, 3-trinuoropropyl radicals
¦ where the polymer has the foregoing vinyl substitution.
The preferred YiSCoSity range of the polymer is, of course, a little
, more limited in that the preferred viscosity ranges from 2500 to
1 250, 000 centipoise at 25C, with a preferred vinyl concentration
; being from 0. 0002 to 0.1% by weight of vinyl concentration of the
i
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',
60SI-78
.
I .
, polymer. Although a polymer having the broad range of vinyl con-
j, centration will operate in the present invention, the more limited
vinyl concentration would allow for a reaction in which the reaction
~ proceeds at the appropriate rate that is not too slow and yet
. sufficiently in accordance ~,vith the description of the invention and
allows the proper cross-linking in the polymer to produce the cured
silicone elastom.eric foam. With respect to the-preferred range of the
viscosity, as can be appreciated, it is preferred that the viscosity of
the vinyl mixed cornposition prior to forming the silicone foam. be not
too high otherwise the composition is difficult to handle and to pour,
Accordingly, the lower viscosities are preferred for the vinyl-
containing polymer in preparing the composition of the instant case.
l~ccordingly, in accordance with the above description it is preferred
I that the viscosity of the base vinyl containing polymer vary anywhere
I from 1000 to 250, 000 centipoise or more preferably 2500 to 100, 000
centipoise at 25C. If the viscosity of the base vinyl-containing
. I polymer is kept low then the viscosity of the total composition will
also be lower than would be the case with a higher viscosity base vinyl-
1 containing polymer and as such the composition will have a total
¦ mixture viscosity that is lower and thus the composition will be easier
~ to handle and pour into the opsnings in which it is desired to have a
,~ silicone foam formed; The preferred formula for the base vinyl-
!i containingpolymeris asfollows;
1~ R~ ¦ R' ¦ R
1 (3) Vi - Si ~ t sio t si vi
R' R' x R'
1,i,
.. 1~
I . - 1 0
~, .
' ' ' '. ' i', ~ ' , . .. . . .
OSI 78
., .
,~ where R' is selected from the class consisting of methyl, phenyl and
~; 3, 3, 3-trihloropropyl and mixtures thereof. In the most preferred
form of the base vinyl-containing polymer of the instant case, it is
1 preferred that there be only vinyl groups in the siloxy terminal units
¦', as disclosed in Formula (3) above. However, it is possible to use a
polymer in which there is only vinyl units in the siloxy units in the
polymer chain. Thus, there can be produced a silicone foam in which
the vinyl units appear only on the siloxane chain and.in which there are
I no vinyl terminating units in the polymer. However, such a base
¦ vinyl-cont~ining polymer does not result in a foam with as good
¦ physical properties as does the silicone ~oam produced with a vinyl-
containing polymer containing vinyl terminal siloxy units.
. In a,nother and more prcferred ernbodiment of the instant case, there
I can be utilized as the base vinyl-containing polymer, a polymer
! wherein the vinyl units are both on the terminal positions of the
I polymer chain as well as on the siloxy units in the polymer chain.
¦~ While such a polymer will produce an appropriate silicone elasto-
1~ meric foam such a foam is not as desirable and does not have as good
¦I physical properties as when the vinyl terminated base polymer of
¦~ Formula t3) is utilized abcv e, which is tl~c most preferred polymer
Ij for utilization in the process of the instant case. Such vinyl-containing
¦, polymers are well known in the art and can be produced by methods
¦~ well known in the art.
' With respect to the non-fluorinated polymers, such vinyl-containing
~5 1l polymers can be produced by hydrolyzing the appropriate diorgano-
dichlorosilanes in water, then cracking the hydrolyzate with an alkali
, ' ~, ' .
-- 1 1 --
60Si-78
l'
', metal hydroxide, preferably KOH, at elevated temperatures to
preferentially distill overhead cyclictetrasiloxanes or cyclictri-
, siloxanes in case of the fluorinated polymers and then taking the
i cyclictetrasiloxanes and equilibrating them at elevated temperatures,
~ that is, temperatures above 150C, in the presence of srx~all
quantities of potassium hydroxide and also in the presence of the
~, appropriate chain-stopperæ. For instance, to produce the polymer
Jl of Formula (3) there would be needed to be utilized divinyltetraorgano-
j disiloxane chain-stoppers such as, for instance, divinyltetramethyldi-
I siloxane chain-stopper in the appropriate amounts.
il The resulting mixture is heated at ternperatures above 150C and
allowed to equilibrate until approxirnately 85% by weight of the cyclic-
totra~iloxanes have been converted to the linear polyrner of the
~ desired viscosity. At that point the mixture is cooled, the alkali
metal hydroxide is neutralized with an appropriate mild acid such as,
,
phosphoric acid, and unreacted cyclics are vented off to leave behind
, the desired vinyl-containing polymer. The appropriate vinyl-con-
i taining polymers can be obtained not only for :I?ormula (3), but also
¦ with vinyl in the polymer chain by equilibrating the appropriate vinyl-
I containing cyclictetrasiloxanes. More details are to be found in the
¦ production of such vinyl-containing polyrners in the foregoing Modic,
~ United States Patent Num~er 3,425,967 dated
¦. February 4, 1969.
¦I The second preferred but not really necessary ingredient in the compo-
I sitions of the instant case is from 0 to 200 parts by weight of a filler,
, which may be either an extending or reinforcing filler. It should be
'.. .,
I~ - 12 -
~ 60SI-78
noted the extending fillers are preEerred since reinforcing
fillers such as fumed silica and precipitated silica when
incorporated into the composition in any concentration
unduly increase the viscosity of the composition, thus,
making it difficult to handle and to pour. However,
fumed silica and precipitated silica have t]he advantages
of increasing the physical properties, that is, the
Tensile Strength, as well as the Tear of the silicone
elastomeric foam that is formed from the composition.
Accordingly, in the more preferred embodiment of the
instant case there is utilized from 10 to 100 parts of
filler based on 100 parts of the vinyl-containing base
polymer.
It should be no-ted that all the concentration oE
in~redients set forth in the instant case are based per
100 parts Oe the base vinyl containing polymer.
Accordingly, there may be utilized in the preferred
embodiment anywhere from 10 to 100 parts of a filler
selected from the class consisting of reinforcing fillers
and extending fillers and, more preferably, just extending
fillers. A preferred extending filler that may be utilized
in the instant composition which does not unduly increase
the viscosity oE the uncured composition is ground quartz.
Ground quartz has the additional advanta~e that to some
extent it increases the burn resistance properties of the
cured silicone foam that is produced from the composition.
Other extending fillers that may be utilized in the instant
compositions are, for instance, titanium dioxide, lithopone,
zinc oxide, zirconium silicate, silica aerogel, iron oxide,
diatomaceous earth, calcium carbonate, glass flbers, mag-
nesium oxide, chromic oxide, zirconium oxide, aluminum
oxide, alpha quartz, calcined clay, carbon, graphite, etc.
` 60SI-78
It should be noted if reinforcing fillers are used such
as, fumed silica and precipitated silica, that in order to
keep the viscosity increase in the composition as low as
possible, such filler even the extending fillers may be
treated, for instance, with cyclicpolysiloxanes or sila-
zanes. The disclosure in which silica fillers may be treated,
for instance, with cyclicpolysiloxanes is set forth in
U.S. patent No. 2,938,009 - Lucas dated May 24, 1960.
However, such is only one method of treating reinforcing
fillers and other methods with other agents are also
available in the art.
Another method of treating reinforcing fillers is,
for instance, to be found in Brown, U.S. patent No.
3,02~,126 dated March 6, 1962, Smith, U.S. patent No.
3,635,635 dated ~anuary 18, 1972 and Beers, U.S. patent
No. 3,837,878 dated September 2~, 197~. Such ingredients
such as, cyclicpolysiloxanes, may also be utilized to
treat extending fillers such as, ground quartz, with some
advantage since such treatment does also alleviate the
viscosity increase caused by extending fillers. ~owever,
as stated previously, the most preferred filler for
utilization to produce silicone foam oE the instant case,
is ground quartz. Quartz enhances the burn resistant
properties of the composition as well as imparting some
enhanced physical properties to the final cured silicone
foam. Based on the 100 parts of vinyl-containing polymer,
there is then preferably utilized as a third ingredients
in the composition of the instant case from 100 parts
per million to 1.5 parts by weight of water. If less than
100 parts per million of water is utilized, then there
will not be produced sufficient hydrogen to properly
foam the composition. It can be appreciated in the compo-
-- 1~ --
60SI-78
sition of the instant case, water is the blowing agent.
The advantages of the utilization of water is that it is
non-toxic, and participates with the actual cure of the
silicone foam that is formed from the basic SiH-olefin
platinum catalyzed composition and the only vapors that
are given off are hydrogen and works with a variety of
plarinum complexes. In the more preferred embodiment
of the instant case there is used from 500 to 15,000
parts per million of the total composition of water.
This is the appropriate amount of water as a blowing agent
to properly foam the composition without liberating too much
hydrogen or without liberating too little hydrogen to
produce an appropriate foam. Accordingly, there should
be utilized Erom 0.2:1 to 50:1 moles oE SiH per mole of
water. The preferred range o:E moles o:E Si~l to water is
from 1 mole of SiH to 1 mole of water to 5 moles of
SiH to 1 mole of water. Within the preferred range, the
preferred amount of hydrogen is liberated to produce the
desired silicone foam without liberating too much
hydrogen and yet liberating enough hydrogen to produce
the desired low density silicone foam. It should be
noted that the lower the density of the silicone foam
the more desirable this is since less silicone material
is utilized to produce the foam and accordingly, the
less expensive the foam becomes. The only caveat to be
observed in such production of low density foam is that
it is undesirable to have large cavities in the foam where
insufficient silicone material is present in the foam,
such that the foam does not have sufficient physical
strength. It also can be appreciated that the other
hydride polymers in excess of that necessary to react with
the water will add on the vinyl groups of the base vinyl-
- 15 -
~ P~ ~ 60SI-78
containing polymer to cross-link the vinyl-containing
polymer and form the silicone foam in the presence of
a platinum catalyst. The advantages of water as a
blowing agent is that it costs nothing and releases no
noxious fumes. The fourth ingredient that is necessary
in the composition of the instant case is that there
must be present from 1 to 50 parts by weight of the
hydride polysiloxane of Formula (2~ above, where R is
selected from the class consisting of hydrogen, alkyl
radicals of l to 8 carbon atoms, aryl radicals and
fluoroalkyl radicals of 3 to 8 carbon atoms, and R3 is
selected from alkyl radicals, aryl radicals of up -to
8 carbon atoms, where the hydride polymer has the
hydrogen content varying from 0.3 to 1.6~ by weight and
z and y varies such that the polymer has a viscosity
varying from 5 to lO0 centipoise at 25 C. The concentration
of moles of water to hydride pol~mer has been discussed
above, which concentration limits must be met in order to
produce a foam that is desirable. It should be noted that
the other limitation above is that the hydrogen con-tent
of the hydride polysiloxane polymer varies from 0.3 to
1.6~ by weight. Of necessity, this limitation must be
met, otherwise, the hydride polymer will not have enough
hydrogen molecules to react with water to liberate the
hydrogen and also react and cross-lin]c with the vinyl
molecules of the vinyl-containing polysiloxane to form
the cured silicone foam. If there is not enough hydride
in the polymer, that is, the 0.3% lower limitation by
weight, -then there will not be sufficient hydrogen in
the polymer to crosslink with the vinyl-containing polymer.
Accordingly, the hydrogen content of such polymer must be
observed strictly as the amount of moles of water per
mole of hydrogen polysiloxane cross-linking agent. It
- 16 -
~ 60SI-78
should be noted also that the viscosity is quite important
and that y varies such that the viscosity of the polymer
varies from 5 to 100 centipoise and more preferably
from 5 to 40 centipoise. It should be noted that
hydride containing polysiloxanes of a higher viscosity
and molecular weight may be utilized, however, such
polymers are difficult to obtain and difficult to
utilize with the appropriate hydride content for use in
the instant invention. The reason for the above is that
for the reaction of the instant invention to proceed in
accordance with the disclosure, it is necessary that the
hydride polymer of Formula (3) contain hydrogen on the
siloxane chain. Although it may contain hydrogen atoms
on a terminal siloxy atom, it must contain hydride atoms
on the polymer chain in order for the reaction oE the
:Lnstan~ case to operate. ~f there are no hydrogen atoms
in the polymer chain of the hydride polymer,then a
proper silicone foam is not obtained. Accordingly, a
hydride polymer of the instant case with only hydrogen
atoms on the terminal siloxy atoms will not work to form
a silicone foam in the composition of the instant case.
In accordance with the above and as limited above,
R may be selected from the class cons:isting oE hydrogen
and any hydrocarbon radical and halo~enated hydrocarbon
radical normally associated with polysiloxane polymers,
preferably, other than aliphatic unsaturated radicals.
Accordingly, the R2 radical may preferably be selected
from any alkyl radicals such as, methyl, ethyl, propyl;
cycloalkyl radicals such as, cyclohexyl, cycloheptyl,
eic.; mononuclear aryl radicals such as, phenyl,
methylphenyl, ethylphenyl, etc.; halogenated hydrocarbon
radicals such as, fluoroalkyl radicals, 3,3,3-trifluoro-
~ 60SI-78
propyl, etc. Most preferably, the R radical is selected
from the class consisting of hydrogen, al~yl radicals of
1 to 8 carbon atoms, aryl radicals of 6 to 8 carbon atoms
and fluoroalkyl radicals of 3 to 8 carbon atoms, and most
preferably R2 is selcted from methyl, phenyl and 3,3,3- -
trifuoropropyl radicals. The R radical is selected from
alkyl and aryl radicals of up to 8 carbon atoms. It is
desirable that the vinyl-containing polymer not contain
any hydrogen substituent groups and in the hydrogen
polysiloxane polymer of Formula (2) there be no vinyl or
aliphatic unsaturated substituent groups. Ir should be
noted there is preferably used from 1 to 50 parts by
weight of hydride polysiloxane cross-linking agent of
Formula (2), per 100 parts oE base vinyl-containing
polymer o~ Formula (1) above. I'he production of the
hydrogen substituted polysiloxane polymer which is non-
fluorinated is must simpler than the foregoing production
of ~he vinyl-containing polymer. Such low viscosity
hydride substituted polysiloxane polymers are basically
obtained by hydrolyzing the appropriate hydride sub-
stituted dichlorosilanes with diorganodichlorosilanes
with the appropriate amount oE chainstoppers, whether
they be hydride substituted or not.
Both in the production of vinyl-containing polymers
of Formula (1l, as well as in the production of the
hydride polymer, the appropriate substituted chain-stopper
may be any disiloxane, trisiloxane or low molecular weight
linear polymer. With respect to the hydrolysis reaction
in the production of the hydride polysiloxane polymer then
there is utilized as chain-stoppers a monofunctional silane
having the appropriate substituent groups such as, hydrogen
dimethylchlorosilane, trimethylchlorosilane, 3,3,3-tr:if-
- 18 -
. .
60SI-78
luoropropyldimethylchlorosilaneO Accordingly, such chain-
stoppers which are chlorosilanes having the appropriate
substituent groups may be utilized to form the low
viscosity and low molecular weight hydride polysiloxane
polymers cross-linking agent of Formula (2).
It is also possible to make such low molecular weight
polymers by equilibrating the appropriate cyclictet-
rasiloxanes with a very mild acid catalyst such as, acid
activated clay, such as the foregoing Filtrol with the
appropriate chain-stoppers.
It should also be noted that in such equilibration
procedures which are carried out at elevated temperatures
with an acid catalyst -they are preferably carr:ied out
at tcmperatures above 90C, ancl more preEerably above
100C to equilibrclte the cyclict etrasiloxanes and form
and convert about 85% of the cyclictetsiloxanes to the
linear polymer whereupon the acid catalyst is removed by
filtration and the cyclics are vented off to give the
desired linear polymer.
With fluorinated polymers a slightly difEerent
procedure is utilized -to produce such fluorinated polymers.
:Ln the case oE the vinyl-containincJ base polyrner of
Formula (1), the appropriate fluorinated cyclic-tetra-
siloxanes are equilibrated with chain-stoppers in -the
presence of cer-tain basic catalysts such as, cesium
hydroxide, potassium silanolate, at temperatures above
90 C, or slightly above to produce a-t anywhere from 50
to an 60% conversion of the linear polymer a-t viscosities
a-t least up to 1,000,000 centipoise at 25C, wherein the
catalyst is then neu-tralized with a mild acicl and the
cyclics are vented off -to give the fluorina-ted polymer.
~he fluorina-ted cyclicte-trasiloxanes are obtained by
19 -
~ 60SI-7~
hydrolyzing the appropriate fluorinated dichlorosilane and ;
then cracking the hydrolyzate with KOH and obtaining as
much of the pure tetrasilozanes as possible. However,
another preferred method of producing such fluorinated
polymers, that is, a vinyl-containing polysiloxane
polymer of Formula (1), which is fluorinate substituted
is to crack the hydrolyzate with KOH and preferentially
distill overhead the fluorinated cyclictrisiloxanes
which are produced in greater quantities than the
fluorinated cyclictetrasiloxanes by careful fractionation.
The fluorinated cyclictetrasiloxanes when equilibrated
with an alkali metal hydroxide catalyst are converted
to -the high viscosity or low viscosi-ty fluo:rinated sub-
st:itutecl polymer. Such cycl:ictris:iloxanes can be also
cqui.~ibrated in the presence of a mild ~asic catalyst
to form fluoro-substituted linear fluids, that is,
materials having viscosities in the area oE 1000 to
10,000 centipoise of viscosity at 25C or less. A
fuller disclosure as to the production of such fluorine
substituted polymers used in SiH-olefin addition reactions
is to be found in Jeram, U.S. Patent No. ~,0~1,010 dated
Au~ust 9, 1977. For the purpose o:E the instan-t case, if
is is desired to obtain a Eluorine-substituted hydride
polysiloxane polymer within the scope of Formula (2),
it can be obtained by direct hydrolysis of the appro-
priate fluoro-substituted chlorosilanes. Finally, in
the process of the instant case there is utilized generally
from 1 to 250 parts per million of a platinum ca-talyst
and more preferably 1 to 200 parts per million of a
platinum catalyst. It is more preferred to utilize a
stabilized platinum complex in the process of the .instant
case since it disperses in the ingredients much more
20 -
1~6~ 60SI-78
easily and as such results in faster reaction time.
Many types of platinum compounds for this SiH-olefin
addition reaction are known and such platinum catalysts
may be used also for the reaction of the present case.
The preferred platinum catalysts especially when optical
clarity is required are those platinum compound catalysts
which are soluble in the present reaction mixture. The
platinum compound can be selected from those having the
formula (PtC12.Olefin)2 and H(PtC13). Olefin) as described
in U.S. Pat. No. 3,159,601 dated December 1, 1964, Ashby.
The olefin shown in the previous two formulas can be
almost any type of ole~in but it prefexably an alkenylene
having from 2 to 8 carbon atoms, a cycloalkenylene having
from 5 to 7 carbon atoms ox styrene. Specific oleEins
utilizable in the above ~ormulas are ethylcne, propylene,
the various isomers of butylene, octylene, cyclopentene,
cyclohexene, cycloheptene, etc.
A further platinum containing material usuable in
the composition of the present invention is the platinum
chloride cyclopropane complex (PtC12.C3H6)2 described in
U.S. Pat. No. 3,159,662 dated December 1, 1964. Still,
further, the patent containing material can be a complex
formed from chloroplatinic 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. Pat. No. 3,220,972
dated November 30, 1965 - Lamoreaux.
The preferred platinum compound to be used not only
as a platinum catalyst but also as a flame retardant
additive is that disclosed in U.S. Pat. No.3,775,452,
Karstedt dated November 27, 1973. Generally speaking this
type of platinum complex is formed by reacting chloro
- 21 -
~ 60SI-78
platinic acid containing 4 moles of water of hydration with
tetramethyltetravinylcyclosiloxane in the presence of
sodium bicarbonate in an ethanol solution.
It can be appreciated that, as stated previously,
many types of platinum catalysts can be utilized in the
process of the instant case to produce a silicone foam
since the compositions of the instant case are not as
sensitive to a particular type of platinum catalyst as was
the case with the prior art compositions. However, a
preferred platinum catalyst within the scope of the
instant case is either the Lamoreaux catalyst disclosed
in the foregoing patent set forth above or the Karstedt
platinum catalyst set forth in the disclosure hereinabove.
The Karstedt platinum cataLyst which is the one
pre~erred catalyst within the scope of the instant case,
comprises reacting chloroplatinic acid with a vinyl-
containing cyclotetrasiloxane or a vinyl- containing low
molecular weight polysiloxane in the presence of an
alcohol and a mild base such as, sodium bicarbonate, such
that the platinum complex is substantially chlorine free.
Such a catalyst, because of its reactivity, can be used
with advantage in the compositions of the ins-tan-t case.
The advantage of the platinum catalyst, such as the
Karstedt platinum complex catalyst within the scope of
the instant case, is that it is so reactive that the foam
is formed at a good rate and hydrogen gases liberated
at a good rate so that the desired low density is formed
in a faster manner than is the case when other types of
platinum catalyst are used.
It should also be noted that platinum complexes formed
between chloroplatinic acid and a vinyl-containing si:Loxane
material can also be used as a catalyst in the process in
~ 4~ 60SI-78
compositions of the instant case, irrespective of whether
they are chlorine free. However, a platinum complex
catalyst which is obtained by reacting a vinyl-containing
siloxanes with a chloroplastinic acid and in which the
chlorine content is substantially reduced is a catalyst
with different properties and is more advantageously
utilized in the production of the silicone foams of
the instant case. Finally, the low density silicone foams
of the composition of the instant case are -to some extent
burn resistant. To enhance the burn resistance of the
silicone foams of the instant case, other burn resistant
additives may be added to the composi-tion to obtain such
property. For instance, per hundred parts of the base
vinyl containing polymer oE Formula (1), there may be
ac~cled anywhere from 0.1 to 10 parts of carbon black and
more preferably, a carbon black that is low in residual
sulfur. Such carbon blacks which are low in residual
sulfur produce the best flame resistant properties when
added to such composition. More preferably, there may be
utilized anywhere from 0.5 to 2 parts of a low residual
20 content carbon black per 100 parts of the base vinyl-
containing polymer. It is noted that the additional
amount of carbon black above 2 parts cloes add burn
resistant properties but not to such a great extent.
Accordingly, the preferred range of carbon black utilized
in the compositions of the instant case, so as to impact
advantageous burn resistant properties to the composition,
is from 0.5 to 2 parts or carbon black. Although 0.2
parts of low residual sulfur carbon black will impart
some burn resistant properties to the composition, it is
desirable that it be utilized at a concentration of 0.5
parts to obtain the more desirable burn resistan-t propert:ies.
It can also be appreciated that the burn resistant
- 23 -
60SI-78
properties of the silicone foam of the instant composition
may be further improved by adding to the composition other
well known burn resistant additives so long as they do
not interfere with the basic reactions of producing
silicone foams of the instant case and as long as they do
not inhibit or poison the platinum catalyst or the SiH-
olefin platinum catalyzed reaction to form the silicone
elastomer of the composition of the instant case.
Finally, the compositions of the instant case are
10 produced by incorporating carbon black and the filler,
if any, into the vinyl-containing polymer and then
mixing the platinum catalyst either with a vinyl-
containing polymer or with a hydride polysiloxane cross-
linking agent along with the platinum catalyst.
Th~ platinum is incorporated, preferably, in th~ vinyl-
containing polymer. The water may be added to the vinyl-
containing polymer or it may be incorporated in the hydride
polysiloxane. Again, however, preferably the water is
incorporated into the vinyl-containing polymer since
there is more of the vinyl containing base polymer and
as such can be more easily incorporated into the composition.
It can also be appreciated that water may be added to the
composition just prior to when the reaction is carried
out. ~Iowever, the hydride polymer without a platinum
catalyst is advantageously packed separately from the
vinyl-containing base polymer such ~hat there are two
components. When the party or purchaser desires to form
the silicone foam, the hydride polysiloxane is rapidly
mixed into the vinyl-containing polymer containing the
platinum catalyst and the water or the water may be added
at the time of mixing and the composition is poured into
the desired cavity and allowed to form a silicone foam.
- 24 -
6 0 S I - 7 8
The composition will then cure all liberate hydrogen and
the vinyl-containing base polymer will react with the
hydrogen polysiloxane in the presence of the platinum
catalysts to cure to form a silicone foam. Although
such a process is advantageous for many purposes, it is
sometimes desired to have a certain amount of work life
or pot life in the mixed composition prior to its cure.
Accordingly, for such purposes, it is normal to use an
inhibitor. It has been found that to the compositions
of the instant case there is desirably used a-t least
200 parts per million based on the total composition
of an inhibitor which is a vinyl-containing cyclictet-
rasiloxane such as, tetramethyltetravinylcyclopolysiLoxane.
When added to the co-mpositlon this compound ~:ives the
compositlon some work li~e or pot lLfe. More preferably,
such a vinyl-containing cyclictetrasiloxane is added to
the composition at a concentration of anywhere from 100
parts per million to 10,000 parts per million based on
the total composition so as to give to the composition
a work life varying anywhere from 5 20 minutes at room
temperature. Smaller amounts of such an inhibitor does
not give an appreciable increase of work life at room
temperature of the composition and larger amounts of
the inhibitor may be used than 10,000 parts per million,
per weight of the composition. However, such has not
been found to be necessary.
It has been found that the foregoing concentrations
of the vinyl-containing cyclictetrasiloxanes will impact
the desired amount of work life to the compositions of
the instant case for most applications. As stated
previously, the composition of the instant case may be
used without the presence of a weak inhibitor. Upon the
h4~ ~ 60SI-78
mixing of the two components, the composition will start
to cure immediately with the liberation of hydrogen to
produce a silicone foam.
As stated previously, the inhibitor may be present
in either component, it only being necessary with respect
to preparing the silicone foam to add the amount of water
that is appropriate if the water has not been added
already, to mix the two components thoroughly, and then
to apply the composition into the appropriate cavity or
mold and allow the composition to foam to a silicone
foam.
The only caution that has to be maintained in
preparing the two components or packayes is that the
hydrogen-containing polysiloxane cross-l:inking agent is
to be packaged :in a component separate Erom the platinum
catalyst base polymer component, and where the component
with which the other ingredients are packaged into will
be determined by the particular two component system
that is desired to be prepared.
It should be noted that x, y in Formulas (1), (2)
and (3~ above are whole numbers that vary such that the
polymers oE Formulas (1), (2) and 3 have the desired
general and specific viscosities disclosed previously,
that is, x of Formulas (1) and (3) will vary such that
the base vinyl-containing polymer has generally a viscosity
that varies from 100 to 1,000,000 centipoise at 25C, or
more preferably, varies from 2500 to 100,000 centipoise at
25C, and y in Formula (2) of the hydride polysiloxane
cross-linking agent disclosed above will vary such that
generally the polymer may have a viscosity varying any-
where from 5 to 100 centipoise at 25C, but more pre-
ferably varying from 5 to 40 centipoise at 25C.
- 26 -
~ 60SI-78
The examples below are given for the purpose of
illustrating the practice of the above invention. They
are not given for any purpose of setting limitations and
defining the scope of the invention as set forth in the
specification and claims. All parts are by weight.
EXAMPLE 1
To 20 parts of a vinyl-terminated dimethylpoly-
siloxane polymer of 3500 centipoise at 25C, and having
a 0.0014~ by weight vinyl content. There was added
two drops of water (0,05 parts) and two drops of tet-
ramethyltetravinylcyclictetrasiloxane. To this mixture
there was added 20 parts per million platinum in the
form of the Karstedt platinum complex set Eorth previously.
To this composi-tion there was added two parts of a black
masterbatch containing 1 par-t of carbon black with low
residual sulfur. To cure and Eoam this basic mixture
there was added to 100 parts of the above mixture, 10
parts of a hydrogen polysiloxane of 20 viscosity at 25C
having a 1.5% by weight of hydrogen content and having
the following formula;
IH3 IH3 1 3
HSi O - - Si - _ O Si CH3
CH3 H CH3
After mixing for approximately 30 seconds, the catalyzed
mixture began to foam and started to gel. The expansion
of the foam was complete within two minutes and cured
completely after one hour.
- 27 -
4?~)
6OSI-78
When the cured foam was exposed to a sunsen burner
flame, it would glow but would not sustain combustion
after the flame was removed. It should be noted that
with the composition and process of the instant case as
soon as the two components have been mixed and as soon
as the effect of any inhibitor that is present has
dissipated, the hydrogen polysiloxane reacts with the
vinyl-containing polysiloxane to cure the silicone foam
that is formed. After the initial reaction proceeds
to form the silicone elastomeric foam which in the case
if no inhibitor is present is immediate, the final cured
silicone elastomeric foam is obtained in the period of
time varying anywhere from 1 hour to 12 hours for final
cure.
EX~MPLE 2
There was formed a Composition A by taking a 3500
centipoise at 25C vinyl dimethyl end-stopped poly-
dimethylsiloxane to which was added 30 parts per million
of platinum in the form of the Karstedt catalyst. The
following ingredients were added to Composition A,
shown in the following table, in the amounts indicated
in the Table I where the amounts were par-ts by weight:
Composition B - water
Composition C - methylvinylcyclotetrasiloxane
Composition D - trimethyl end-stopped poly-
methyl hydrogen silicone having
1.5% silicon bonded hydrogen
60SI-78
Composition A B C D
1 30 0.03 0.04 0.5
2 30 0.03 0.04 1.0 -
3 60 0.03 0.04 1.0
4 90 0.03 0.04 1.0
120 0.03 0.04 1.0
All the compositions in the above table produced foams
within minutes.
EXAMPLE 3
To a 70,000 centipoise at 25C vinyl dimethyl end-stopped
polydimethylsiloxane was added 25 parts per million of
platinum or the Karstedt catalyst. To 100 parts of this
70,000 centipois~ vinyl polymer ~as added 0.05 parts of
water and 0.04 parts oE me-thyl vinyl cyclics. Then 5
parts o~ Composition D of E~ample 2 was added to above,
and immediately hydrogen gas was evolved. The mixture
began to foam and produced a very fine called foam. This
foam had a much finer cell size than the foams made
uwing the lower viscosity vinyl polymer of 3500 centi-
poise at 25C.
EXAMPLE 4
A mixture was prepared by blending 10.5 parts of 380
centipoise at 25C, vinyl dimethylpolysiloxane, 9.4
parts of 10 micro alpha quartz, 0.1 parts of carbon
black and a platinum catalyst as defined by the Lamoreaux
patent in an amount sufficient to give 30 parts per million
platinum. To this mixture there was added one drop (.028
parts) of water and 0.03 parts of methylvinyl cyclote-
trasiloxane. Then 1 part of Composition D of Example 2
was added and after mixing for forty-five seconds a foam
_ 29 _
60SI-78
began to form. The resulting foam has a specific gravity
of 0.4 and was fire retardant. It has a Limiting Oxyqen
Index of 33Ø
_ 30
