INCORPORATING SILICA FILLER INTO POLYSILOXANE RUBBER

INCORPORATION D'UNE MATIERE DE CHARGE A BASE DE SILICE A DU CAOUTCHOUC AU POLYSILOXANE

English Abstract

There is disclosed a method for
incorporating silica filler into polysiloxane gum.
This method includes the steps of mixing curable,
non-condensable, polysiloxane gum, silica filler, and
condensable diorganopolysiloxane; and heating said
mixture to a temperature of at most about 210°C for a
sufficient time to complete the condensation reaction
between said silica filler and said condensable
diorganopolysiloxane. The method permits silica
filler to be surface treated in situ following
addition to the curable polysiloxane gum.

Claims

- 20 -
The embodiments of the invention in which an
exclusive property or privilege is claimed are defined
as follows:
1. A process for incorporating silica
filler into gum comprising:
(a) mixing components consisting essentially
of: curable polysiloxane gum, said gum being
substantially non-condensable with heating below about
210°C; from about 10 to about 400 parts by weight
silica filler having Si-bonded hydroxy or alkoxy
functional groups for each 100 parts by weight gum and
from about 5 to about 50 parts by weight condensable
diorganopolysiloxane for each 100 parts by weight
filler, said condensable diorganopolysiloxane
comprising the hydrolyzate of diorganodihalogensilanes
of the formulas R1RSiX2 and R?SiX2, wherein R1 is
3,3,3-trifluoropropyl, R is methyl or ethyl, R2 is
methyl or ethyl, and X is a halogen, said hydrolyzate
comprising a mixture of fluoroalkyl-functional cyclic
diorganopolysiloxanes having 3 to 10 siloxy units and
silanol end-stopped low molecular weight linear
diorganopolysiloxanes having hydroxy functionality
that is readily reactive with the surface of said
silica filler at temperatures less than about 210°C;
and
(b) heating said mixture to a temperature of
at most about 210°C for a sufficient time to complete
the condensation reaction between said silica filler
and said condensable diorganopolysiloxane.
2. The process of claim 1 wherein said
heating step is followed by the step of curing said
polysiloxane gum.
3. The process of claim 1 wherein said
heating step is followed by the step of adding a
polysiloxane gum cure catalyst.

- 21 -
4. The process of claim 1 wherein said
mixing and heating steps are performed simultaneously.
5. The process of claim 1 wherein said
temperature of heating ranges from about 110°C to
about 210°C.
6. The process of claim 5 wherein said
temperature of heating ranges from about 130°C to
about 180°C.
7. The process of claim 6 wherein said
temperature of heating ranges from about 140°C to
about 160°C.
8. The process of claim 1 wherein said
polysiloxane gum has a viscosity of from about 500,000
to about 300,000,000 centipoise at 23°C.
9. The process of claim 1 wherein said
polysiloxane gum has the general formula
Ra SiO4-a/2
where R is selected from alkyl radicals of 1 to 8
carbon atoms, vinyl radicals, phenyl radicals,
haloalkyl radicals of 3 to 10 carbon atoms, halophenyl
radicals, hydroxy radicals, alkoxy radicals, aryloxy
radicals, cyanoalkyl radicals, and mixtures thereof
and a varies from about 1.98 to about 2.01.
10. The process of claim 1 wherein said
polysiloxane gum has the general formula
<IMG>
where R1 may be vinyl, methyl, hydroxy, or alkoxy; R2
may be vinyl, phenyl, alkyl of 1 to 8 carbon atoms,
fluoroalkyl of 3 to 10 carbon atoms, or mixtures
thereof; and Y varies from 2,500 to 11,000.

- 22 -
11. The process of claim 10 wherein said
polysiloxane gum is M-stopped.
12. The process of claim 10 wherein said
polysiloxane gum contains vinyl functional groups.
13. The process of claim 10 wherein said
polysiloxane gum contains hydroxy functional groups.
14. The process of claim 10 wherein said
polysiloxane gum contains alkoxy functional groups.
15. The process of claim 1 wherein said
heating step is followed by the step of adding a
crosslinking agent.
16. A mixture consisting essentially of:
(a) curable polysiloxane gum, said gum being
substantially non-condensable with heating below about
210°C;
(b) from about 10 to about 400 parts by
weight silica filler having Si-bonded hydroxy or
alkoxy functional groups for each 100 parts by weight
gum; and
(c) from about 5 to about 50 parts by weight
condensable diorganopolysiloxane for each 100 parts by
weight filler, said condensable diorganopolysiloxane
comprising the hydrolyzate of diorganodihalogensilanes
of the formula R1RSiX2 and R?SiX2, wherein R1 is
3,3,3-trifluoropropyl, R is methyl or ethyl, R2 is
methyl or ethyl, and X is a halogen, said hydrolyzate
comprising a mixture of fluoroalkyl-functional cyclic
diorganopolysiloxanes having 3 to 10 siloxy units and
silanol end-stopped low molecular weight linear
diorganopolysiloxanes having hydroxy functionality
that is readily reactive with the surface of said
silica filler at temperatures less than about 210°C.
17. The mixture of claim 16 wherein said
polysiloxane gum has the general formula

- 23 -
Ra SiO4-a/2
where R is selected from alkyl radicals of 1 to 8
carbon atoms, vinyl radicals, phenyl radicals,
haloalkyl radicals of 3 to 10 carbon atoms, halophenyl
radicals, hydroxy radicals, alkoxy radicals, aryloxy
radicals, cyanoalkyl radicals, and mixtures thereof
and a varies from about 1.98 to about 2.01.
18. A process for incorporating silica
filler into gum comprising:
(a) mixing components consisting essentially
of curable polysiloxane gum, said gum being
substantially non-condensable with heating below about
210°C; from about 10 to about 400 parts by weight
silica filler having Si-bonded hydroxy or alkoxy
functional groups for each 100 parts by weight gum; an
effective amount of crosslinking agent; and from about
5 to about 50 parts by weight condensable
diorganopolysiloxane for each 100 parts by weight
filler, said condensable diorganopolysiloxane
comprising the hydrolyzate of diorganodihalogensilanes
of the formulas R1RSiX2 and R?SiX2, wherein R1 is
3,3,3-trifluoropropyl, R is methyl or ethyl, R2 is
methyl or ethyl, and X is a halogen, said hydrolyzate
comprising a mixture of fluoroalkyl-functional cyclic
diorganopolysiloxanes having 3 to 10 siloxy units and
silanol end-stopped low molecular weight linear
diorganopolysiloxanes having hydroxy functionality
that is readily reactive with the surface of said
silica filler at temperatures less than about 210°C;
and
(b) heating said mixture to a temperature of
at most about 210°C for a sufficient time to complete
the condensation reaction between said silica filler
and said condensable diorganopolysiloxane.

- 24 -
19. A mixture consisting essentially of:
(a) curable polysiloxane gum, said gum being
substantially non-condensable with heating below about
210°C;
(b) from about 10 to about 400 parts by
weight silica filler having Si-bonded hydroxy or
alkoxy functional groups for each 100 parts by weight
gum;
(c) from about 5 to about 50 parts by weight
condensable diorganopolysiloxane for each 100 parts by
weight filler, said condensable diorganopolysiloxane
comprising the hydrolyzate of diorganodihalogensilanes
of the formulas R1RSiX2 and R?SiX2, wherein R1 is
3,3,3-trifluoropropyl, R is methyl or ethyl, R2 is
methyl or ethyl, and X is a halogen, said hydrolyzate
comprising a mixture of fluoroalkyl-functional cyclic
diorganopolysiloxanes having 3 to 10 siloxy units and
silanol end-stopped low molecular weight linear
diorganopolysiloxanes having hydroxy functionality
that is readily reactive with the surface of said
silica filler at temperatures less than about 210°C;
and
(d) an effective amount of crosslinking
agent.

Description

- 1334706
` - 60SI 1048
-- 1 --
INCORPORATING SILICA FILLER INTO
5POLYSILOXANE RUBBER
This invention relates to a method for incorporating silica
filler into polysiloxane rubber. More particularly, this
invention relates to a method for incorporating silica filler
into such rubber and surface treating in situ.
Background of the Invention
Curable silicone gums are normally compounded with
reinforcing fillers, such as finely divided silica, to impart
maximum physical - properties when cured into rubber. To
preclude or control crepe hardening during shelf aging, i.e.
preventing polymer-filler interactions, the filler is surface
treated with an agent octamethylcyclotetrasiloxane or a
fluorosilicone hydrolyzate to reduce the number of free silanol
groups on the surface of the finely divided silica.
One method for surface treating the silica filler, U.S.
Pat. No. 4,529,774, exposes the same to a fluorosilicone
hydrolyzate in the vapor phase. The hydrolyzate is a mixture
of silanol terminated linear siloxane oligomers with mixed
cyclic siloxane compounds. The ratio of linears to cyclics
varies with the linears being l4 - 36% by weight while the
cyclics may vary over the range of 64 - 86% by weight. The
hydroxy end-group content for such a hydrolyzate may vary over
the range of 1.0 - 2.5X by weight.
. .

7 0 6
- 2 - 60SI-1048
The vapor phase filler treatment involves an
initial heating of the silica in a fluidized reactor
at temperatures in excess of 110C to effect removal
of adsorbed moisture. The hydrolyzate is then pumped
in, under pressure, while the temperature is raised to
280 - 300C to effect the desired grafting to surface
silanols. This procedure usually provides good
reinforcing filler, however, depending upon the
acidity level and the presence of contaminants such as
iron, polymeric gum balls can be formed in the filler.
The conditions of treatment can also lead to
particulate contamination due to vessel corrosion. As
a consequence of the above, reproducibility of the
treatment is poor. Further, the treatment of filler
by this manner and incorporation of the same into
polysiloxane rubbers is a cumbersome process which
requires both treatment and blending facilities.
Accordingly, it is an object of the present
invention to simplify the treatment of silica filler
and the incorporation of the same in to polysiloxane
rubbers.
It is a further object of the present
invention to produce silica filled polysiloxane rubber
having the desired levels of physical properties at
reduced levels of silica filler content.
It is a further object of the present
invention to combine the surface treatment process for
silica filler and the incorporation of silica filler
into polysiloxane rubber into a single step.
It is still a further object of the present
invention to produce a heat age stable halogenated
alkyl or aryl substituted polysiloxane rubber wherein
silica filler is surface treated in situ.

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Detailed Description of the Invention
Briefly, according to the present invention there is
provided a method for incorporating silica filler into
polysiloxane gum. This method includes the steps of:
(a) mixing curable, non-condensable, polysiloxane gum,
silica filler, and condensable diorganopolysiloxane;
and
(b) heating said mixture to a temperature of at most about
210C for a sufficient time to complete the
condensation reaction between said silica filler and
said condensable diorganopolysiloxane.
The curable polysiloxane gum may be immediately shaped and
cured or it may be stored and cured at some later time.
Curable polysiloxane gum for use herein must be
non-condensable and non-reactive upon simple heating below
about 210C, i.e. in the absence of a catalyst or other curing
agent, it must not react in substantial amounts so as to
interfere with the surface treatment under heat or prevent a
subsequent cure. Curable polysiloxane gums which are preferred
herein are diorganopolysiloxane gums with silanol, vinyl,
alkoxy, or methyl functional groups.
Broadly, suitable diorganopolysiloxane gums have the
general formula:
Ra SiO4 a/2 (1)

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where R is selected from alkyl radicals of 1 to 8 carbon atoms,
vinyl radicals, phenyl radicals, haloalkyl radicals of 3 to 10
carbon atoms, halophenyl radicals, hydroxy radicals, alkoxy
radicals, aryloxy radicals, cyano-alkyl and mixtures thereof
and a varies from about 1.98 to about 2.01. It should be
mentioned that the invention does not reside in the exact type
of gum employed nor the process and functional groups by which
it is cured. As stated above, it is only necessary that the
gum be non-condensable and non-reactive as defined above.
Preferably, the diorganopolysiloxane gum has the formula:
2 2 2
R R R
Rl _ SiO _ SiO - Si Rl (2)
R2 R2 y R2
and has a viscosity that varies from about 500,000 to about
300,000,000 and more preferably from about 1,000,000 to about
200,000,000 centipoise at 25C. In formula 2, Rl may be
vinyl, methyl, hydroxy, or alkoxy; R2 may be vinyl, phenyl,
alkyl of 1 to 8 carbon atoms, fluoroalkyl of 3 to 10 carbon
atoms, or mixtures thereof; and Y varies from 2,500 to 11,000.
Persons skilled in the art are familiar with gums fitting
the description of formulas 1 or 2 above and with the methods
of cure or vulcanization thereof. Generally a catalyst is
necessary to obtain reasonable reaction rates and cure times.
Common catalysts employed in free radical cure, i.e. that cure
involving crosslinking between free radical methyl or vinyl

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groups, are organic peroxide catalysts, such as dialkyl
peroxides, diaralkyl peroxides, alkyl aralkyl peroxides, and
the like; metallic catalysts, such as platinum;
organometallic catalysts such as organoplatinum complexes; and
organosilicon catalysts.
Crosslinking agents may be employed in the cure of the
rubber, such as low molecular weight M-stopped polysiloxanes
and vinyl polysiloxanes, however, hydride crosslinking agents
are not recommended due to their reactivity at temperatures and
conditions of surface treatment. Thus, it is desirable that
hydride crosslinking agents be added just subsequent to the
heating and treatment of the silica or formulated into a two
component system.
The diorganopolysiloxane gums are manufactured and cured
into rubber by methods well known in the art. Reference is
made to Chemistry and Technology of Silicones, Noll, Walter,
Academic Press, N.Y., N.Y., 1968
Silica fillers suitable for use herein are finely divided
reinforcing fillers which may have free hydroxyl groups in the
form of either Si-bonded functional groups or adsorbed
moisture, depending on their method of preparation. The
Si-bonded hydroxyl groups may also have been converted to other
functional groups, such as alkoxy, in their manufacture.
These silica fillers are reinforcing fillers in contrast to
other fillers of non-reinforcing, non-structure-forming type,
such as titanium dioxide or calcium carbonate. Examples of
,

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such silica fillers may be found described in U.S. Pat. Nos.
2,541,137; 2,610,167 and 2,657,149, as well as French Pat. Nos.
1,025,837 (issued 1953) and 1,OgO,566 (issued 1955). Such
structure-causing fillers may be slightly acidic or alkaline
(i.e., have pH's slightly below or above 7) depending upon the
method of manufacture, and may be obtained through the
aerosol-aerogel process, by fuming processes such as by the
vapor phase burning of silicon tetrachloride or ethyl silicate,
by precipitation means, etc. Commercially available fumed
silicas include CAB-O-SIL (~) (Cabot Corp.) and AEROSIL (~)
(Degussa, Inc.) Fumed silica is preferred.
Condensable diorganopolysiloxanes for use herein must at
some temperature less than 210 be liquids and have hydroxy or
alkoxy functionality which will readily react with the silica
surface. Insufficiently condensable diorgnopolysiloxanes can
be made readily reactive with the silica surface by the
addition of condensation promoters such as tin soaps, stannous
salts, and Lewis acids. These condensation promoters can be
added so long as they do not promote unwanted side reactions
such as polymerization evidenced by formation of gum balls.
Although hydroxy or alkoxy functionality may occur any where on
the polymer, the diorganopolysiloxanes are preferably hydroxy
terminated with no condensable substitution on chain to prevent
the formation of crosslinked gum balls. Preferred condensable
diorganopolysiloxanes have the general formula:
R 3
HO SiO H
X
R 3

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wherein X has a value of from about 1 to 20 and R3 is a
monovalent substituted or unsubstituted hydrocarbon radical.
Preferably, the condensable diorganopolysiloxanes are all
hydroxy terminated diorganopolysiloxanes of the above formula.
The balance of the condensable diorganopolysiloxanes may be,
for example, side chain hydroxy substituted siloxanes and the
like. It is preferred that X in the above formula be between
about 2 and 10 and most preferably about 2 or 3 and the R3 of
the above formula is generally at least about 50X by number
methyl with the balance selected from alkyl, such as methyl,
ethyl, propyl, butyl, hexyl, and the like; alkenyl, such as
vinyl and the- like; aryl, such as phenyl and the like;
cycloalkyl, such as cyclopentyl, cyclohexyl, cycloheptyl, and
the like;~ halogenated alkyl, such as 3-chloropropyl,
4-chlorobutyl, 3,3-difluoroallyl, 3,3,3-trifluoropropyl and the
like; halogenated aryl, such as 3-fluorophenyl and the like;
halogenated cycloalkyl; and the like. Where R3 is
halogenated, the preferred R3 is -CH2CH2R4 wherein R4
is perfluoroalkyl such as perfluoromethyl, perfluoroethyl,
perfluorohexyl, and the like. R3 should have no more than
about 10 carbon atoms.
The above hydroxy terminated diorganopolysiloxanes may be
produced by methods well known to the art. In one method,
diorganodihalogensilanes are partially hydrolyzed to form a
mixture of cyclic and linear diorganopolysiloxanes. Further
details of this method may be found in U.S. Pat. Nos. 2,737,506
(Hurd, et al.), 3,937,684 (Razzano) 4,341,888 (Razzano) and
4,529,774 (Evans, et al.).

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In another method, cyclic diorganopolysiloxanes are heated
in an organic solvent in the presence of a H treated clay
catalyst to open the ring and produce a hydroxyl terminated
diorganopolysiloxane. In this method, composition of the
diorganopolysiloxane product can be controlled by controlling
the purity and ring size of the cyclic diorganopolysiloxane
feedstock. This second method is preferred due to the purity
and variety of the cyclic polydiorganosiloxanes available.
Other additives may be present in the uncured mixture,
including, pigments, stabilizers, plasticizers, additional
fillers and the like. Persons skilled in the art will realize
what additives are necessary and suitable to accomplish a given
purpose.
According to the process of the present invention the
curable, non-condensable polysiloxane gum, silica filler, and
condensable diorganopolysiloxane are mixed in a vessel under
mild heating if necessary to reduce viscosity. Where the gum
is very viscous, the silica must be added in stepwise or
incremental portions in order to allow the batch to mass with
mixing.
The amount of silica filler added to the batch varies
within very wide limitations. It may be desirable to master
batch the curable polysiloxane gum for later cutting with
unfilled gum. Thus, from about 10 to about 400 parts by weight
silica filler may be added for each lOO parts by weight curable
polysiloxane gum. Normally, from about lO to about lOO parts
by weight of silica filler is employed. The amount of
condensable diorganopolysiloxane added to the batch of course

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depends on the amount of silica added. This amount should
range from about 5 to about 50 parts by weight, more preferably
from about 17 to about 30 parts by weight and most preferably
from about 19 to about 25 parts by weight condensable
diorganopolysiloxane for each 100 parts by weight silica.
When the batch is fully massed, treatment of the filler may
be accomplished by simply raising the temperature of the batch
under mixing to at most about 210C. Temperatures in excess of
210C will begin to degrade and prematurely cure the
polysiloxane gum. Of course, to this point no cure catalyst
for the gum has been added, and generally gums below about
210C will not cure without a catalyst. The temperature of
treatment may range down to about 110C while maintaining
acceptable treatment times. Reasonable treatment or reaction
times vary from about 1 to about 4 hours with about 2 hours
being common practice. Preferred reaction temperatures vary
from about 130C to about 180C with optimum reaction
temperatures ranging from about 140C to about 160C.
During heating and treatment, volatiles may be removed by
purge or vacuum. Water is produced by condensation and also
non-condensable or non-curable volatiles may have been added to
the batch which it is desirable to remove. For example, where
the condensable diorganopolysiloxanes are added as a
hydrolyzate, the cyclopolysiloxanes may be removed at this
point by vacuum or nitrogen purge.
Following the treatment or heating step, catalysts
stabilizers and even additional gums or crosslinking agents may
be added to provide cure and long term storage capability in

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-10-
the curable polysiloxane gum. As explained above, the gum may
be a heat curable gum, a room temperature curable gum, or even
a low temperature cured gum. Judicious selection of materials
and simple experimentation is contemplated to achieve optimal
performance for a given situation.
In order that persons skilled in the art may better
understand how to practice the present invention, the following
examples are offered by way of illustration and not by way of
limitation.
EXAMPLES
Examples 1 and 2
To a clean 1420 ml rdough mixer was charged 20 grams of a
condensable diorganopolysiloxane treating agent being a silanol
terminated methyl-3,3,3-trifluoropropylpolysiloxane fluid
having a hydroxy end-group content of 6.8% by weight and 401.5
grams of a non-condensable polysiloxane gum and additives
consisting of 380 grams vinyl terminated
methyl-3,3,3-trifluoropropylsiloxane gum with a Williams
Plasticity (3' value at 25C) of 200 + 20 and vinyl end-group
content of 0.01-0.20% by weight, 20 grams vinyl terminated
methyl-3,3,3-trifluoropropylsiloxane gum having a vinyl on
chain content of 1.6% by weight (as CH2 = CH-) and a ~illiams
Plasticity (3' value at 25C) of 190+ 20, 0.5 grams M-stopped
polydimethyl siloxane gum with 4.2X by weight vinyl on chain
and 1.0 gram of a vinyl terminated polydimethylsilox- ane
plasticizer. This mixture was mixed at a shear rate of 20-45
rpm for 30 minutes then heated to 50C while under a blanket of
nitrogen. Finely divided untreated fumed silica having a

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surface area of 200 + 20 m2/gram was added incrementally with
time given between each addition for the batch to mass. The
total weight amounts of fumed silica added is shown in Table I.
When the filler addition was completed and the batch was fully
massed, the temperature was increased to 120-160C and held for
1 to 3 hours under a nitrogen purge rate of 1-6 ft3/hr. The
nitrogen purge rate was then increased to 10-15 ft3/hr for
2-6 hours. The batch temperature was finally reduced to less
than 80C prior to the addition of 0.7 grams of a stabilizer,
cerium hydroxide having a purity of 90.5X and a si~rvfin size of
+250 mesh. The gums are cured by adding Lupersol 101 curing
~'#`"-- agent, 2,5-dimethyl-2,5-di(t-butylperoxy) hexane, in the
proportion of 0.75 grams/100 grams of silica plus diluent gum
and subsequently press curing for 15 min. at 177C followed by
a post bake at 204C for 4 hours.
Control
To a clean 1420 ml dough mixer was charged 412.5 grams of
non-condensable polysiloxane gum and additives consisting of
380 grams vinyl terminated methyl-3,3,3-trifluoropropylsiloxane
2û gum with a Williams Plasticity (3' value at 25C) of 200 + 20
and a vinyl end-group content of 0.01 - 0.20X by weight, 20
grams vinyl terminated methyl-3,3,3-trifluoropropylsiloxane gum
having a vinyl on chain content of 1.6% by weight (as CH2 =
CH-) and a Williams Plasticity (3' value at 25C) of 190 + 20,
0.5 grams M-stopped polydimethylsiloxane gum with 4.2X by
weight vinyl on chain and 12 grams process aid, a silanol
terminated polydimethylsiloxane telomer where the average chain
contains 5 siloxane units. This mixture was mixed at a shear
rate of 20-45 rpm for 30 minutes then heated to 50C. While

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under a blanket of nitrogen 120 grams finely divided, treated,
fumed silica which had a surface area prior to treatment of 200
+ 20 m /gram was added incrementally with time given between
each addition for the batch to mass. Treatment of the fumed
silica had been carried out according to U.S. Pat. No.
4,529,774. Specifically, the fumed silica had been dried, and
contracted at 280 - 300C for 8 hours with fluorosilicone
hydrolyzate being a mixture of fluorosilicone telomeric silanol
and fluorosilicone cyclics, in the vapor phase. Subse~uently,
the residual fluorosilicone hydrolyzate had been blown off and
the treated fumed silica devolatilized for 10 hours at 300
under nitrogen purge. When the filler addition was completed
and the batch was fully massed, the temperature was increased
to 120 - 160C and held for 1 to 3 hours under a nitrogen purge
rate of 1 - 6 ft3/hr. The batch temperature was finally
reduced to 80C prior to the addition of 0.7 grams of a
stabilizer, cerium hydroxide having a purity of 90.5X and a
sieve size of +250 mesh. The gum and fumed silica mixture was
~ and 2.
~ ~

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Table I
1 2 C
Treating 20 20
agent, grams
Non-condensable gum 401.5 401.5 412.5
additives, grams
Fumed silica, grams 100 80 120
Shore A 42 38 40
Tensile, psi 1665 1615 1500
Elongation % 465 510 450
Die B Tear, pi 165 150 170
Spec. grav. 1.42 1.426 1.42
Comp. Set.,
Method B,
22 hours/177C, % 14.0 -- 18.0
Processability Very Good Very Good Very Good

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-~4-
As seen in Table 1, fumed silica incorporated into gum
atcording to the present invention produces a polydiorgano-
siloxane rubber having at least as good a property profile as
pretreated fumed silica of the prior art.
Examples 3 and 4
To a clean 1420 ml dough mixer was charged hydrolyzate
fluid, prepared according to U.S. Pat. No. 4,529,774 from
dichloromethyl-3,3,3-trifluoropropyl silane, containing
non-condensable cyclopolysiloxanes in addition to condensable
telomeric silanol as shown in Table 2 and 401.5 grams of a
non-condensable polydiorganosiloxane gum and additives
consisting of 380 grams vinyl terminated
methyl-3,3,3-trifluoropropylsiloxane gum with a Williams
Plasticity of (3' value at 25C) of 200 + 20 and vinyl
end-group content of 0.01 - 0.20X by weight, 20 grams vinyl
terminated methyl-3,3,3-trifluoropropylsiloxane gum having a
vinyl on chain content of 1.6% by weight (as CH2 = CH-) and a
Williams Plasticity (3' value at 25C) of 190+ 20, 0.5 grams
M-stopped polydimethylsioxane gum with 4.2X by weight vinyl on
chain and 1.0 gram of a vinyl terminated polydimethylsiloxane
plasticizer. This mixture was mixed at a shear rate of 20-45
rpm for 30 minutes then heated to 50C. While under a blanket
of nitrogen 112 grams of finely divided untreated fumed silica
having a surface area of 200 + 20 m2/gram was added
incrementally with time given between each addition for the
batch to mass. When the filler addition was completed and the
batch was fully massed the temperature was increased to 120 -
160C and held for 1 to 3 hours under a nitrogen purge rate of
1 - 6 ft3/hr. The nitrogen purge rate was then increased to

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-15-
10 - 15 ft3/hr for 2-6 hours. The batch temperature was
finally reduced to less than 80C prior to the addition of 0.7
grams of a stabilize!, cerimum hydroxide having a purity of
90.5% and a sieve size of ~250 mesh. The non-condensable
~ cyclopolysiloxanes were substantially removed during nitrogen
purge. The gums are cured by adding LUPERSOL 101 curing agent,
2,5-dimethyl-2,5-di(t-butylperoxy) hexane, in the proportion of
0.75 grams/100 grams of silica plus diluent gum and
subsequently press curing for 15 min. at 177C followed by post
~ ~
\~
\

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Table 2
3 4
Hydrolyzate 28 44.8
fluid , grams
Non-condensable gum 401.5 401.5
& additives, grams
Fumed silica, grams 112 112
Hydrolyzate fluid, 70/30 45/55
silanol/cyclic,
wght ratio
Shore A 43 42
Tensile, psi 1545 1545
Elongation X 480 515
Die B Tear, pi 170 165
Spec. grav. 1.424 1.416
Processability Yery Good Very Good

1334~06
- 60SI-1048/0272p
JWH:mz
Table 2 shows that the hydrolyzate treating agent of the
prior art may be used with the incorporation method of the
present invention to produce treated silica with at least
equivalent properties.
Examples S -7
To a clean 1420 ml dough mixer was charged hydrolyzate
fluid, prepared according to U.S. Pat. No. 4,529,774 from
dichloromethyl-3,3,3-trifluoropropyl silane, containing non-
condensable cyclopolysiloxanes in addition to condensable
telomeric silanol as shown in Table 3 and 416 grams of a non-
condensable polydiorganosiloxane gum and additives consisting
of silanol terminated methyl-3,3,3-trifluoropropylsiloxane gum
having a Williams Plasticity (3' value at 25C) of 200 + 30 and
~ a vinyl on chain content of 0.06 - 0.07% by weight and 16 grams
of a trimethyl siloxy stopped polydimethylsiloxane gum having a
~illiams Plasticity of 90 + 20 and a vinyl on chain content of
4.2X by weight (as CH2 = CH-). The mixture is agitated at a
shear of 20-50 rpms while heating to 50C under a nitrogen
blanket. After 30 minutes of mixing, 9Z grams of finely
divided silica was added incrementally with time given between
each addition for the batch to mass. When filler addition was
completed and the batch was fully massed, the temperature was
increased to 140-160C for 1-3 hours with a nitrogen purge rate
of 1 - 6 ft3/hr. The nitrogen purge rate was then increased
to 10 - 15 ft3/hr for 2-6 hours. The batch temperature was
finally reduced to less than 80C and 1.0 gram titanium dioxide
was added along with 0.2 grams of iron octoate stabilizer,
iron-2-ethylhexanoate 6% by weight in mineral spirits. The
non-condensable cyclopolysiloxanes were substantially removed

~- 133~706
60SI-1048/0272p
JWH:mz
-18-
J~L during nitrogen purge. The gums are cured by adding CADOX
TS-50 curing agent, 2,4-dichlorobenzoylperoxide in the
proportion of 1.6 grams/100 grams of silica plus diluent gum
and subsequently press curing for 15 minutes at 124C and post
\

133470~
60SI-1048/0272p
JWH:mz
-19-
Table 3
6 ~ 7
Hydrolyzate 40 52 66
fluid , grams
Non-condensable gum 416 416 416
additives, grams
Fumed silica, 92 92 92
grams
Hydrolyzate fluid, 1.7 1.7 1.7
hydroxy end-group
content, wght %
Shore A 38 40 40
Tensile, psi 1285 1475 1290
Elongation % 450 448 460
Die B Tear, pi 96 98 100
Spec. grav. 1.394 1.395 1 393
Comp. Set.,
Method B,
22 hours/149C, X 20.6 16.5 18.0
Processability Good Yery Good Partitions
and sticks