Canadian Patents Database / Patent 1096529 Summary

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(12) Patent: (11) CA 1096529
(21) Application Number: 273301
(54) English Title: LOW OILING SILICONE GEL FILLED FLEXIBLE ARTICLES AND GELS THEREFOR
(54) French Title: ARTICLES EN SILICONE SOUPLE CONTENANT UN GEL ET GELS A CET EFFET
(52) Canadian Patent Classification (CPC):
  • 3/113
  • 400/5307
(51) International Patent Classification (IPC):
  • A47C 27/08 (2006.01)
  • A61F 2/12 (2006.01)
  • A61F 2/52 (2006.01)
  • A61L 27/18 (2006.01)
  • C08L 83/04 (2006.01)
(72) Inventors :
  • BRILL, ALFRED P., III (United States of America)
(73) Owners :
  • DOW CORNING CORPORATION (United States of America)
(71) Applicants :
(74) Agent: GOWLING LAFLEUR HENDERSON LLP
(74) Associate agent: GOWLING LAFLEUR HENDERSON LLP
(45) Issued: 1981-02-24
(22) Filed Date: 1977-03-07
(30) Availability of licence: N/A
(30) Language of filing: English

(30) Application Priority Data:
Application No. Country/Territory Date
755,322 United States of America 1976-12-29
690,706 United States of America 1976-05-27

English Abstract





Abstract of the Disclosure

A gel filled flexible article which is a
container having silicone rubber walls of less than 0.001
metre thick filled with a silicone gel such that the
silicone gel contacts the silicone rubber wall, provides
a low oiling article where the silicone rubber is based
on an essentially polydimethylsiloxane gum and the gel is
a crosslinked polydimethylsiloxane and has a penetration of
10 to 60 millimetres and produces a linear swell of the
silicone rubber when said silicone rubber is encapsulated
in the gel for 21 days at room temperature of less than
5 percent. The gel filled flexible articles are useful
as external breast prostheses.


Note: Claims are shown in the official language in which they were submitted.


The embodiments of the invention in which an exclusive property or privilege
is claimed as defined as follows:

1. In a gel filled flexible article comprising a flexible
container having at least a portion of the container wall composed of silicone
rubber which is less than about 0.0015 meter thick and said container contain-
ing silicone gel which contacts at least a portion of the container wall,
the improvement which comprises the silicone rubber and the
silicone gel being selected in combination such that the silicone rubber is
essentially a polydimethylsiloxane gum and the silicone gel comprises cross-
linked essentially polydimethylsiloxane having a penetration of 10 to 60
millimeters and producing a linear swell of the silicone rubber when the
rubber is encapsulated in the gel for 21 days at room temperature of less
than 5 percent.



21

Note: Descriptions are shown in the official language in which they were submitted.

~0965Z9


This invention relates to gel filled flexible
articles and the gels therefor.
The combination of a silicone rubber container
~illed with a silicone gel is well known in the art. Such
articles are known for use as surgically implantable human
breast prostheses and external breast ?rostheses.
.. ,.. :,
Cronin in U.S. Patent No. 3,2!~3,663 af Dec.l!66 describes a silicone
rubber container filled wi~h a soft silicone gel as an
implantable breast prosthesis. Cronin describes a suitable
gel as belng one disclosed by Nelson in U.S. Pa~ent No.
3,020~260 of Feb.J62. ~he organosiloxaie gel disclos~d by Nelson

is a reaction product of an intimate mixture of a
triorganosiloxy endblocked polydiorganosiloxane having a
viscosity of 100 to 10,000 cs~ ~approximately 0.1 to 10
pascal-seconds) at 25C. and at least 0.174 molar pTecent of
the units are RViSiO where Vi is vinyl and R is methyl
or phenyl, and a liquid hydrogensilo~ane of the formula
HRCH3siO~R2si)nsiCH3RH
~"here R is methyl or phenyl and n has a value to provide
a ~iscosity of no more than 10,000 cs (approximately
10 pascal-se onds) at 25C. and a platinum catalyst. These
gels have at least one RViSiO unit for each silicon-bonded
hydrogen atom. Cronin uses a gel where the ratio of atoms
of silicon-bonded hydrogen per gram molecular weight
of triorganosiloxy endblocked polydiorganosiloxane is
adjusted ~o about 1.3 and where this gel preferably has a
pene~ration from 30.0 to 20.0 mm. Cronin also suggests that
~he gel should be one which is inert toward the container.
Other references to implantable prostheses include U.S.
3a Patent ~os.3,559,214 to Pan ~an of l~eb./71; 3,600,718 to Bootle ~f ~ug./71;
3,665,520 to Perras et al; 3,681,787 to Perras of A~g./72;
-B

~0965Z~

3,852,832 to M~:Ghan et al of Dec,i~74; and 3,934,274 to Hartley of 3an/76.
- External breast prostheses using silrQone rubber containers and filled with
silicone gel are described ~ Hankin et al in U.S. Patent 3,896,506 of July/75
and Hankin in U.S. Patent No. 3,911,503 of Qct/75. I~ese va ~ous
patents describe methods of manufacture, designs and
construction of both implantable and external breast
prostheses. They also show the desirability of using
silicone rubber containers with a silicone gel filling
because of the low reactivity of the body toward the silicone
materials and because the silicone materials may be easily
cleaned and sterilized by steam or boiling water. Although
- these reerences show the desirability of the silicone
materials, they do not discuss the problem encountered in
using a silicone rubber as the container material and a
silicone gel as the filling material. When a silicone gel
is in contact with a ~ilicone rubber, there is a tendency
for components of the gel to exude through the silicone
- rubber. If the gel filled silicone rubber container is
an ex~ernal breast prosthesis~ the exudate will stain the
wearer's clothing and be embarrassing. It is, therefore,
desirable ~o reduce or eliminate the exudation, oiling or
bleed of the gel components through the silicone rubber
container. The prior art silicone gel filled silicone rubber
containers have an undesirable amount of oiling or bleed
because in order to obtain the desired penetration values
for the gel with the appropriate natural simulated
characteristics, large amounts of unreacted fluid
were included in the gel network. This fluid would bleed
through the silicone rubber containar walls and thus be
a problem as described above. A oombination of materlals

~2-


5 ~

has no~ been discovered which will provide an article with
reduced oiling without departing from the desirable silicone
materials.
An object of this invention is to provide a low
oiling silicone gel filled silicone rubber container.
A silicone rubber comprising a gum of an
essentially polydimethylsiloxane is used for container
walls which are in contact with a silicone gel which is a
crosslinked polydimethylsiloxane. Such articles have low
oiling characteristics where the linear swell of the
silicone rubber is less than 5 percent ~hen the silicone
rubber is encapsulated in the gel for 21 days at room
temperature. These articles are useful as breast prostheses
such as the external type, as well as, for other prostheses,
pillows and pads.
One preerred silicone gel is prepared from
dimethylvinylsiloxy endblocked polydimethylsiloxane which
has an effecti~e viscosity of 4.5 to 30 pascal-seconds
(Pa s) at 25C,
This invention relates to a gel filled flexible
article comprising a flexible container having at least a
portion of the container wall composed o-f silicone rubber
which is less than 0.0015 metres thick and said silicone
rubber comprising a gum which is essentially polydimethyl-
siloxane, said container containing silicone gel which at
least contacts the container wall composed of silicone
rubber, said gel has a penetration of ~rom 10 to 60 milli-
metres and produces a linear swell of the silicone rubber
when said silicone rubber is encapsulated in the gel
for 21 days at room temperature of less than 5 percent, and

~ 5 ~

said gel comprising a crosslinked essentially polydimethyl-
siloxane.
The articles of this invention can be of any
construction and can be made by any method inasmuch as the
design, construction or method of manufacture constitutes
no part of the present invention except that at least part
of the wall portion which is made of silicone rubber be
in contact with silicone gel. This combination is part
of the invention because it is this relationship which will
result in oiling or bleed.
Containers which have walls made of silicone
rubber which is less than 0.001~ metre thick and which have
silicone gel in contact with the silicone rubber wall will
oil excessively unless the silicone rubber wall material
has a linear swell of less than 5 percent ~hen encapsulated
in the silicone gel for 21 days at room temperature. Suitable
combinations of wall material and gel can readily be
determined by a simple swell test~
The container need not ha~e all the walls made
of silicone rubber as long as some portion of a silicone - -
rubber wall is in contact with silicone gel. The silicone
rubber is based on an essentially polydimethylsiloxane gum
which has been cured. By essentially polydimethylsiloxane
it is to be understood that the gum is composed primarily of
dimethylsiloxane Wlits but that other diorganosiloxane units
can be present such as methylvinylsiloxane units, methyl-
phenylsiloxane units; diphenylsiloxane units and
3,3,3-t-rifluoropropylsiloxane units, there being no more
than 2 mol percent methylvinylsiloxane units and less than
~5 mol percent of other diorganosiloxane units where the mol
percentages are based on the total number of diorganosiloxane

-4-


~ 9 ~

units in the gum. The gum can also contain minor amounts
of monoorganosiloxane units and SiO2 units which provide
branching. The gums can be endblocked by conventional
endblocking units such as triorganosiloxy units, such as
dimethylvinylsiloxy units, trimethylsiloxy units or
methylphenylvinylsiloxy units or hydroxyl groups. These
gums are well known in the art and need not be discussed
further.
The silicone rubber is well known and can contain
fillers, such as reinforcing silica filler, processing
aids, additives, pigments and can be vulcanized by conventional
means, such as with organic peroxides, electromagnetic
radiation, or by using a polysiloxane crosslinker containing
silicon-bonded hydrogen atoms with a vinyl containing gum
and a platinum catalyst. The proportions of these ingredients
are well known in the art and those skilled in the silicone
rubber art can readily adjust the ingredients and
proportions to provide a silicone rubber which will suit
their particular desires in physical properties.
The silicone gel suitable for this invention
has a penetration of 10 to 6~ millimetres and is a
crosslinked polydimethylsiloxanec The gel must provide a
linear swell of less than S percent to the silicone rubber
when the silicone rubber is encapsulated in the gel for
21 days at room temperature. Preferably, the gel provides a
linear swell of less than 5 percent to the silicone rubber
when the silicone rubber is encapsulated in the gel for
60 days. The linear swell test is defined in more detail
herein. The silicone gel is a crosslinked essentially
polydimethylsiloxane. As stated above for the gum, other




diorganosiloxane unlts, monoorganosiloxane units and SiO2
units can be present in the gel in amounts similar to - ;
those stated for the gum.
One particular type of silicone gel suitable to
provide less than 5 percent linear swell is based on a
methylphenylvinylsiloxy endblocked polydimethylsiloxane which
has an effective viscosity of 4.5 to 30 Pa's at 25C. By
the phrase "an effective viscosity of 4.5 to 30 Pa's at 25C."
is meant that the base polymer has a viscos;.ty of 4.5 to 30
Pa s at 25C. or the base polymer in combination with
suitable "in si*u" chain extenders provides a gel which
for all practical purposes is equivalent to a gel prepared
from a base polymer having a viscosity of 4.5 to 30 Pa s
at 25C. It has been found that this type of crosslinked
polydimethylsiloxane gel in combination with the silicone
rubbel provides the desired linear swell.
The gel is to have a penetration of from 10 to 60
-millimetres as determined by the method described in
U.S. Patent No. 3,293~663. Preferably, the penetration
is from 25 to 45 millimetres, particularly for the breast
prosthesis articles. Although the penetration values
are not different from most gels used in these types
of articles, it is pertinent to provide a range of
penetration values for this invention in that the penetration
values provide a means ~o determine a suitable degree of
crosslinXing wherein the base polymers have the viscosity
range of 4.5 to 30 Pa s at 25C. The penetration values
were obtained in prior art gels by using large amounts of
unreacted fluid in the gel preparation such as trimethyl-
siloxy endbloc~ed polydimethylsiloxane fluid. These

~9~5;~
.




types of fluids, because they remain unreacted, readily
bleed through the silicone rubber container walls. Prior
art gels which were examined and which did not contain
the unreacted fluids were either too low in penetration values
and rubber-like and/or would still bleed in undesirable
amounts. It was found that only by providing a gel which
provided less than 5 percent linear swell in the silicone
rubber as stated above could the bleeding be reduced. One
way of reducing the linear swell below 5 percent and likewise
1~ reducing the bleed through the silicone rubber container
walls was by making a gel from a methylphenylvinylsiloxy
endblocked polydimethylsiloxane which had a viscosity from 4.5
to 30 Pa-s at 25C., and preferably from 6 to 12 Pa-s at Z5C.
Although polymers of higher viscosity may also provide less
than 5 percent linear swell, these polymers are difficult to
work with, have a delicate stoichiometry and low penetration
values.
The gels may be best prepared by mixing a
methylphenylvinylsiloxy endblocked polydimethylsiloxane having a
visc~sity of 0.1 to 6 Pa's at 25C~, preferably from 1.5 to
3 Pa's at 25C., a dimethylhydrogensiloxy endblocked
polydimethylsiloxane having a viscosity of less than 0.5
Pa s at 25C. present in an amount sufficient to provide
an effective viscosity for the methylphenylvinylsiloxy
endblocked polydimethylsiloxane of 4.5 to 30 Pa-s at 25C., a
polymethylsiloxane having an average of at least three
silicon-bonded hydrogen atoms per molecule where the
polymethylsiloxane is present in an amount to provide a ratio
of total silicon-bonded hydrogen atoms to vinyl radicals in the
composition of from 0.2 to 0.8, preferably from 0.3 to 0.74
and a catalytic amount of a compatible platinum catalyst.



The methylphenylvinylsiloxy endblocked polydimethyl-
siloxanes are known in the art, as are the o~her ingredients.
The general concept of chain extension for systems containing
vinyl endblocked base polymers, silicon-bonded hydrogen
polymers, silicon-bonded hydrogen endblocked chain extenders,
polymethylsiloxanes containing at least three silicon-bonded
hydrogen atoms and platinum catalysts are known for the
preparation of silicone elastomers. These ingredients are
further defined by Polmanteer et al. in U.S. Patent No.
1~ 3,697,473. Although Polmanteer et al. describe the
various ingredients, they do not describe the preparation
of gels as used herein.
The dimethylhydrogensiloxy endblocked
polydimethylsiloxane is present in the composition to make
the gel in amounts sufficient to provide the base polymer
with a viscosity of 4.~ to 30 Pa-s at 25C. Inasmuch as
the silicon-bonded hydrogen atom content of this chain
extender can vary considerably~ as well as, the viscosity of the
base polymer, any numerical value or the amount of chain
extender is less precise than the above statement. To
determine the amount of chain extender ~or a given base
polymer viscosity and chain extender, silicon-bonded hydrogen
atom content, one can mix the two in varying ratios with
a small amount of platinum catalyst and then measure the
viscosity after the material has reacted which takes only a
few minutes. The desired combination can then be selected
and used in the preparation of the gel. Preerably, the
dimethylhydrogensiloxy endbloc~ed polydimethylsilo~ane has
a silicon-bonded hydrogen atom content of 0.1 to 0.~
waight percent based on the weight of the chain extender and

~0 ~ ~ 2~

is present in amou~ts to provide an effective viscosity
for the methylphenylvinylsiloxy endblocked polydimethylsiloxane
of 6 to 12 Pa-s at 25C.
After the amount of chain extender has been
determined, the amount of crosslinker, the polymethylsiloxane,
can then be found by using an amount sufficient to provide
a ratio of total silicon-bonded hydrogen atoms to vinyl
', ~
radicals of the base polymer in the~ composition of from 0.2
to 0.8, preferably from 0.3 to 0.74. The polyme~hylsiloxane can
be any of a broad spectrum o~ siloxanes having silicon-bonded
methyl radicals, where the units can be various combinations
selected from dimethylsiloxane units, methylhydrogensiloxane
units, trimethylsiloxy units, dimethylhydrogensiloxy units,
monomethylsiloxane units, SiO2 units and hydrogensiloxane units.
The polymethylsiloxan~ has an average of at least three
silicon-bonded hydrogen atoms per molecule and can contain
10 or more per molecule, preferably the polymethylsiloxane
has an average of 4 to 8 silicon-bonded hydrogen atoms per
molecule. The preferred polymethylsiloxanes are those
which contain trimethylsiloxy units, dimethylsiloxane units
and methylhydrogensiloxane units with a silicon-bonded
hydrogen atom content of from 0.5 to 1.0 weight percent
based on the weight of the polym~thylsiloxane and a viscosity
of less than 0.5 Pa s at 25C.
The platinum catalysts can be those which are
described in Polmanteer et al. and which are compatible
in the siloxane composition. The platinum catalysts are
preferably the complexed platinum catalysts, such as
the silicone platinum catalyst described by Willing in
U.S. Pacent No. 3~419~;930f Dec./68. The platinum catalyst is


~,. ".,, ~

5 Z~

used in catalytic amounts such as greater than about
0.1 part by wei~ht platinum per one million parts by
weight of composition.
Tlle gel can also contain pigments if it is
desirable to provide a colored gel with a clear silicone
rubber container or the silicone rubber can be pigmented
to provide a colored article or both can be pigmented to
provide a colored article. Color can also be produced by
dyes.
The gel can be cured by allowing it to set at room
temperature or it can be cured by heating it at a temperature
of from 100 to 200C. for from 10 to 60 minutes. Certainly
other curing conditions may be found suitable and can be
used so long as the desired gel ch~racteristics are not
destroyed. Inasmuch as, a combination of vi~yl containing
polymer, silicon-bonded hydrogen containing components and
platinum catalyst will react at room temperature, they
should not be stored in combination unless cure is desired.
Preferably, it is desirable to mix the ingredients, except
for the platinum catalyst and add the platinum catalyst just
prior to the filling of the container which has a wall
which is at least part silicone rubber of less than
0.0015 metre thick and then the gel composition is cured to a
gel by heating.
The silicone gels which are suitable for this
inven*ion are those which provide less than a 5 percent linear
swell for the silicone rubber when the silicone rubber is
encapsulated in the gel or 21 days at room temperature,
preferably less than 5 percent linear swell for the silicone
rubber ~rhen the silicone rubber is encapsulated in the gel

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~ 5 ~9

for 60 days at room temperature. The linear swell as used
herein was determined by cutting a piece of silicone rubber
of the appropriate thickness and about 2.8 by 5.0 centimetres.
The sample length is measured to the nearest 0.01 centimetre.
The sample is carefully-cleaned by using isopropanol and
allowed to dry before further testing. The test sample is
then completely immersed in the gel to be tested and the
resulting assembly is co~ered and allowed to stand for
a designated time at room temperature. After the predetermined
time, the silicone rubber test piece is removed from the gel
and the length is measured to the nearest 0.01 centimetre.
The percent linear swell is determined by subtracting the
original length from the final length and multiplying by 100.
If several time periods of immersion are desired, one can
replace the test piece in the gel and continue the test for
additional time.
The gel filled flexible articles of this invention
were found to have reduced bleed or oiling and thus are more
useful as an external breast prosthesis. This reduced
bleeding characteristic was observed where the silicone
rubber was based on an essentially polydimethylsiloxane
gum and the gel in contact with this silicone rubber
provided linear swell of less than 5 percent.
The bleed as shown in the examples was determined
by lining a crystallization dish with aluminum foil, washing
the aluminum foil with isopropanol and then drying for about
10 minutes in an oven at 100C., cooling the dish to room
temperature, weighing the dish, washing a gel filled flexible
article with isopropanol, and then placing the article in the
dish and storing it in a clean, dry place which is free of any

~09~

possible dust contaimination or other possible causes ~or
weight increases. After a predetermined time period, the
dish containing the article is filled with isopropanol, the
article is then moved in the isopropanol for two or three
minutes and then the article is lifted from the dish allowing
all the solvent to drip into the dish. The removed article
is then washed thoroughly by spraying a stream of
isopropanol over the article surface while allowing the
wash to drip into the dish. The rinsing is repeated three
times. After all the isopropanol has dripped into the
dish, the article is allowed to air dry and the dish
containing the isopropanol solution is placed on a hot
plate and heated gently to slowly evaporate some of the
isopropanol. When a small amount of solution remains the
dish is placed in a 100C. oven for about 10 minutes to
e~aporate the remaining isopropanol. The dish is removed from
the oven, allowed to cool to room temperature and then
weighed. The amount of bleed is determined by subtracting
the original weight from the final weight and the result
is the amount of material which exuded from the article
and is the amount of bleed.
The following examples are illustrative only
and should not be construed as limiting the present
invention which is properly delineated in the claims. All
parts are parts by weight unless otherwise stated and all
viscosities are at 25C. unless otherwise stated.

A. A silicone ~el was prepared by mixing 97.5
parts of methylphenylvinylsiloxy endblocked polydimethyl-
siloxane having a viscosity o~ 0.00216 square metres per

-12-


&5Z~

second ~m2/s~ (hereinafter identified as Polymer A), 2.40
parts of dimethylhydrogensiloxy endblocked polydimethylsiloxane
having a silicon-bonded hydrogen atom content of 0.159 percent
by weight and sufficient to provide Polymer A with an
effective viscosity of 0.0101 m2/s (about 10.1 Pa-s), 0.21
part of trimethylsiloxy endblocked polymethylsiloxane having
20 mol percent trimethylsiloxy units, 30 mol percent
dimethylsiloxane units and 50 mol percent methylhydrogensiloxane
units and having a silicon-bonded hydrogen atom content
of 0.779 percent by weight and 0.1 part of a chloroplatinic
acid catalyst complex with symmetrical divinyltetramethyldi-
siloxane containing about 0.65 weight percent platinum and
prepared in accordance with the method de~ined in U.S. Patent
No. 3,419,593. The resulting mixture was heated for 20 minutes
at 160C. to cure the composition~ The molecular weight of
the methylphenylvinylsiloxy endblocked polydimethylsiloxane
can be approximated by the formula in U.S. Patent No. 3,020,260.
B. A silicone gel was prepared by mixing 98.2
parts of Polymer A, 1.70 part of dimethylhydrogensiloxy
endblocked polydimethylsiloxane having a silicon-bonded
hydrogen atom content of 0.159 percent by weight and
sufficient to provide Polymer A with an effective viscosity
of 0.0049 m2/s ~about 4.9 Pa s), 0.27 part of the
polymethylsiloxane described in A. above with a silicon-bonded
hydrogen atom content of 0.779 percent by weight and 0.1
part of the platinum catalyst as defined in A. above. The
resulting mixture was cured by heating at 160C. for 20 minutes.
C. A silicone gel was prepared by mixing 97.62
parts of methylphenylvinylsiloxy endblocked polydimethyl-
siloxane having a viscosiky of 0.00184 m2/s ~about 1.84

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~96~Z~

Pa~s), 2.10 part of dime~hylhydrogensiloxy endbloc~ed
polydimethylsiloxane having a silicon-bonded hydrogen atom
content of 0.159 percent by weight and sufficient to provide
methylphenylvinylsiloxy endblocked polydimethylsiloxane
an effective viscosity of 0.0046 m2/s (about 4.6 Pa-s),
0.28 part by weight of the polymethylsiloxane, 0.28 part of
the polymethylsiloxane defined in A. above having a
- silicon-bonded hydrogen atom content of 0.779 percent by
weight and 0.04 part of the platinum catalyst as defined
in A. above. The resulting mixture was cured by heating
at 160C. for 20 minutes.
D. A silicone gel was prepared by mixing 99.90 parts
of methylphenylvinylsiloxy endblocked polydimethylsiloxane
having a viscosity of 0.00912 m2/s (about 9.12 Pa s), 0.22
part of the polymethylsiloxane defined in A. above having
a silicon-bonded hydrogen atom content of 0.779 percent by
weight and 0.1 part of platinum catalyst as defined in A.
above. The resulting mixture was cured by heating for
20 minutes at 160C.
E. A silicone gel was prepared for comparative
purposes by mixing 99.53 parts of Polymer A, 0.37 part of
the polymethylsiloxane as deined in A. above having a
silicon-bonded hydrogen atom content of 0.779 percent by
weight and 0.1 part of platinum catalyst as defined in
A. above. The resulting mixture was cured by heating
30 minutes at 150C.
P. A silicone gel was prepared for comparative
purposes by mixing 99.97 parts of trimethylsiloxy endblocked
polydiorganosiloxane having dimethylsiloxane uni~s and
methylvinylsiloxane units having about 0.3 weight percent


~33 ~ S Z~

vinyl radical and having a viscosity of about 0.8 Pa s
(hereinafter identified as Polymer B) and 0.03 part of
the platinum catalyst as defined in A. above. To 100 parts
of the resulting mixture, 3.62 parts of polymethylsiloxane
defined in Ao above having a silicon-bonded hydrogen atom
content of 0.159 percent by weight was added. The resulting
mixtuTe was cured by heating fsr 30 minutes at 150C.
G. A silicone gel was prepared for comparative
purposes by mixing 91.22 parts of Polymer B9 8.75 parts of
a trimethylsiloxy endblocked polydimethylsiloxane having a
small amount of monomethylsiloxane units and having a viscosity
of 0.0001 m2/s (about 0.1 Pa s), and 0.03 part of platinum
catalyst as defined in A. above. To 100 parts of the
resulting mixture, 3.30 parts of the polymethylsiloxane
having a silicon-bonded hydrogen atom content of 0.159 percent
by weight was added. The resulting mixture was cured by
heating at 150C, for 30 minu~es.
~ l. A silicone gel was prepared -for comparative
purposes by mixing 91.22 parts of Polymer B, 8.75 parts
of trimethylsiloxy endblocked polydimethylsiloxane having
a viscosity of 0.001 m2/s (about 1.0 Pa's) and 0.03 part of
platinum catalyst as defined in A. above. To 100 parts of
the resulting mixture, 3.30 parts of the polymethylsiloxane
having a silicon-bonded hydrogen atom content of 0.159
percent by weight was added. The resulting mixture was
cured by heating at 150C. for 30 minutes.
I. A silicone gel was prepared by mixing 96.60
parts of Polymer A, 3.30 parts of dimethylhydrogensiloxy
endblocl~ed polydimethylsiloxane having a silicon-bonded
hydrogen atom content of 0.15~ percent by weight and

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~09~iZ'~

suficient to provide Polymer A with an-effective viscosity
of 0.023 m2/s (about 23 Pa's), 0.12 part of the polymethyl-
siloxane as defined in A. above having a silicon-bonded
hydrogen atom content of 0.779 percent by weight and 0.1
part of the platinum catalyst as defined in A. above.
The resulting mixture was cured by heating for 20 minutes
at 160C.
J. A silicone gel was prepared by mixing 97,46
parts of methylphenylvinylsiloxy endblocked polydimethyl-
siloxane having a viscosity of 0.001968 m2/s (about 1.968 Pa s),
~hereinafter identified as Polymer C), 2.50 parts of dimethyl-
hydrogensiloxy endblocked polydimethylsiloxane having a
silicon-bonded hydrogen atom content of 0.172 percent by
weight and sufficient to provide Polymer C with an
effective viscosity of 0.0064 m2/s (about 6.4 Pa-s) and
0.325 parts of the polymethylsiloxane defined in A. above
having a silicon-bonded hydrogen atom content of 0.782 percent
by weight. To 100 part~ of the resulting mixture~ 0.04 part
of platinum catalyst as defined in A. above was added.
The resulting mixture was cured by heating for 20 minutes
at 160C.
K. ~ silicone gel was prepared by mixing 97.49
parts of Polymer C, 2.51 parts of dimethylhydrogensiloxy
endblocked polydimethylsiloxane having a silicon-bonded
hydrogen atom content of 0.172 percent by weight and
sufficient to provide Polymer C with an e~fective viscosity
of 0.006~ m2/s (about 6.4 Pa-s) and 0.29 part o-f the
polymethylsiloxane defined in A. above having a
silicon-bonded hydrogen atom content o-f 0.782 percent by
weight. To 100 parts of the resulting mixture, 0.04 part

-16-

65~


of the platinum catalyst as defined in A. above was added.
The resulting mixture was cured by heating at 160C. for
20 minutes.
L. A silicone gel was prepared by mixing 97.50
parts of Polymer C, 2.51 parts of dimethylhydrogensiloxy
endblocked polydimethylsiloxane having a silicon-bonded
hydrogen atom content of 0.172 percent by weight and sufficient
to provide Polymer C with an effective viscosity of 0.0064
m2/s (ab,out 6.4 Pa s) and 0.28 part of the polymethyl-
siloxane having a silicon-bo~ded hydrogen atom content of
0.782 percent by weight. To 100 parts of the resulting
mixture, 0.04 part of the platinum catalyst defined in A.
above was added. The resulting mixture was cured by
heating at 160C. for 20 minutes.
M. A silicone gel was prepared by mixing 99.73
part of methylphenyl~inylsiloxy endblocked polydimethyl-
siloxane having a viscosity of 0.0092 m2/s (about 9.2 Pa s),
0.23 part of the polymethylsiloxane as defined in A. above
having a silicon-bonded hydroge~ atom content of 0.782
percent by weight and 0.04 part of the platinum catalyst
defined in ~. above. The resulting mixture was cured by
heating for 20 mi~utes at 160C.
The bleed was determined on the silicone gel filled
rubber article by the test defined above. The articles were
an external breast prosthesis, with a silicone gel as
identified in Table I. The silicone rubber was a rei~forced
silica filled polydimethylsiloxane gum which was vulcanized
with 2,4-dichlorobenzoyl peroxide. The silicone rubber
container has part of the wall of about 0.0006 metre thick
and the remaining part o the wall of about 0.0011 metre

2~

thick. The silicone rubber containers for each test were
the same size and were filled with approximately equal amounta
of gel composition. The containers were filled with gel
composition as defined and then the containers were sealed
and allowed to stand for about 20 minutes, any air pockets
were removed by a hypodermic syringe and the hole made by
the needle sealed after the air was removed. The deaired,
gel filled container was then cured in an oven at the cure
temperature and ~or the times indicated for each gel
composition.
The penetration was determined on cured gel
samples as defined herein and the linear swell was also
done as defined herein using the same cured silicone rubber
as used in making the containers. The results of the
bleed test9 the linear swell test and the penetration were
as shown in Table I,
Exam~le 2
- This example iâ presented to assist those in
determining the manner to use the chain extension technique.
In Table II compositions prepared by mixing 97.86 parts of
methylphenylvinylsiloxy endblocked polydimethylsiloxane having
a viscosity aa shown in Table II as the vinyl polymer, 2.10
parts of dimethylhydrogensiloxy endblocked polydimethyl-
siloxane having a silicon-bonded hydrogen atom ~SiH) content
as shown in Table II and 0.04 part of the platinum catalyst
as defined in Example 1, A. The resulting viscosity of the
reacted mix~ures were determined and were as shown in
Table II.







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-20-

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Admin Status

Title Date
Forecasted Issue Date 1981-02-24
(22) Filed 1977-03-07
(45) Issued 1981-02-24
Expired 1998-02-24

Abandonment History

There is no abandonment history.

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Filing $0.00 1977-03-07
Current owners on record shown in alphabetical order.
Current Owners on Record
DOW CORNING CORPORATION
Past owners on record shown in alphabetical order.
Past Owners on Record
None
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.

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