Note: Descriptions are shown in the official language in which they were submitted.
60SI 1033
3~9~32
ORGANOPOLYSILOXANE LIQVID
INJECTION MOLDI2~G COMPOSITION
-
The present inventiDn relates to translucent, high
strength, organopolysiloxane, liquid injection molding
compositions. More particularly, the present invention relates
to such compositions which are cured through SiH addition
reactions with a controlled mixture of olefin containing
organopolysiloxanes.
Background of the Invention
Li~uid injection moldable (LIM) organopolysiloxane
compositions are known and used. A problem with all such
compositions is that the hardness, tensile strength, elongation
and tear are so interdependent with;n themselves and with the
viscosity of the uncured liquid~ that it is difficult to
improve one property without suffering loss in another.
Particularly, it is desirable to improve hardness and tear
strength without reduction of other properties.
U.S. Pat. Nos. 3,884,866 and 3,957,713, Jeram, describe
high strength addition cured compositions suitable for low
pressure liquid injection molding. These compositions comprise
a first component containing a high viscosity vinyl end-stopped
organopolysiloxane, a low viscosity vinyl containing
organopolysiloxane, filler, and platinum catalyst which is
cured by mixing with a second component containing a hydrogen
silicone composition. This composition has a low durometer
(20 - 35 Shore A) and, moreover, it is difficult to raise the
durometer or hardness without adversely effecting other
properties.
.
1 ~ n n ~ 3 ~ PATENTS
1 ~ U ~ ~ 60SI-1033/~WH:mz/0285p
U.S. Pat. No. 4,162,243, Lee, et al., disclose compositiDns
similar to Jeram which contain, as the most important distinc-
tion, fumed silica treated with hexamethyldisila2ane and
tetramethyldivinyldisilazane. The Lee, et al., compositions
cure to elastomers having high hardness with good retentjon of
other properties including strength, e10ngation, and tear in
addition to having low YiSCosity in the uncured sta~e.
U.S. Pat. No. 4,427,801, Sweet, extends Lee, et al., by
incorporating a MMViQ resin in addition to the vinyl
containing treated fumed silica. This produces elastGmers
having even higher hardness and tear strengths but has the
disadvantage of higher compression set and lower Bashore
resilience.
It is an object of the present invention to produce a
liquid injection molding organopolysiloxane composition having
high hardness and high tear strengths without resultant adverse
effects on other physical properties.
It is another object of the present invention to produce
such liquid injection molding organopolysiloxane compositions
which additionally have good shelf stability and good mold
release.
These and other objects will become apparent to those
skilled in the art upon consideration of the instant
specification, examples and claims.
PATENTS
~ 1 3 0 9 ~ 3 2 60SI-1033/JWH:mz/028sp
Detailed Description of the Invention
There is provided by the present invention a LIM
organopolysiloxane compDsition combining low viscosity, high
strength and good elongation with exceptionally good hardness
and tear strength comprising:
(A) 100 parts by weight of a vinyl-containing
polyorganosiloxane component comprising:
(1) 70 to 98 parts by weight of a linear high
viscosity vinyl end-stopped organopolysiloxane
having no more than 25 mole percent of phenyl
radicals and having a viscosity of from about
2,000 to about 1,000,000 centipoise at 25C,
(2) 1 to 15 parts by weight of a linear low
viscosity organopolysiloxane having at least one
terminal vinyl group per molecule, having a
vinyl content that may vary from 0.01 mole
percent vinyl to 60 mole percent vinyl, having a
viscosity that varies from about 50 to about
5,000 centipoise at 25~C and having no more than
2~ mole percent phenyl radicals, and
(3) 1 to 15 parts by weight of a vinyl on chain
organopolysiloxane having from about 0.1 to
about 25 mole percent vinyl, having a viscosity
that varies from about 50 to about 100,000
2~ centipoise at 25C and having no more than about
25 mole percent phenyl radicals;
(B) from about 5 to about 70 parts by weight of a filler
or combination of fillers;
PATENTS
13 ~ 9 ~ 3 2 60SI-1033/JWH:mz/0285p
--4--
(C) from about 0.1 to 50 parts per million of the total
organopolysiloxane composition of a platinum catalyst;
~D) from about 0.1 to 10 parts by weight a SiH composition
selected from the class consisting of hydrogen
containing silanes and hydrogen containing
organopolysiloxanes; and
(E) optionally, from about 0.1 to 6.0 parts by weight a
hydroxy containing organopolysiloxane fluid having a
viscosity ranging from about 5 to about 100 centipoise
at 25C.
This composition may either be cured to an elastomer at room
temperature for 16 hours or may be cured at elevated
temperatures, such as, for example, 200C for 10 seconds. In a
preferred embodiment, the above composition is a two-component
composition where the first component contains at least all of
ingredient (C), and the second component contains at least all
of ingredient (D).
.
The linear high viscosity vinyl end-stopped organopoly-
siloxane, A (1), of the present invention has no more than 25
mole percent of phenyl radicals and a viscosity of from about
2,000 to about 1,000,000 centipoise at 25C, preferably from
about 10,000 to about 500,000 centipoise at 25C. These high
viscosity organopolysiloxanes may be represented by the general
formula:
PATENTS
i 3 ~ 9 ~ 3 2 6osl-lo~3/~H:mz/o28sp
--5--
R ~R ~ R
' \
(1) Yi - si._ - osi __osivi
R ~ R J x R
where Vi stands for vinyl, R is selected from the group
consisting of monovalent hydrocarbon radicals and halogenated
monovalent hydrocarbon radicals having up to about 20 carbon
atoms, and x may vary from about 100 to about 10,000,
preferably from 500 to 2,000. Suitable high viscosity
organopolysiloxanes are disclosed in United States
Patent Number 3,884,8~6.
The linear low viscosity organopolysiloxane, A (2), of the
instant invention has at least one terminal vinyl group per
molecule, a vinyl content that may vary from about 0.01 mole
percent vinyl to about 60 mole percent vinyl, preferably .05 to
10 mole percent vinyl; a viscosity that varies from about 50 to
about S,000 centipoise at 25C, preferably from about 50 to
about 1,000 centipoise at 25UC; and no more than about 25 mole
percent phenyl radicals. These low viscosity organopolysilox-
anes may be represented by the general formula:
R / R \ R
' \
(2) R - Si - OSi ~ OSi - Rl
' /
R ~ R / y R
wherein R is defined above, wherein Rl is the same as- R
except that at least one Rl must be vinyt, and y may vary
B
09532 PATENTS
1 ~) 60SI-1033/JW~.mz/0285p
from about l to about 750. Suitable low viscosity organopoly-
siloxanes are disclosed in United States Patent
Number 3,884,866.
The vinyl on chain organopolysiloxane, A (3), of the
present invention is critical to obtaining the desired
properties. Suitable vinyl on chain organopolysiloxanes have
from about O.l to about 25 mole percent vinyl and preferably
from about 0.2 to about 5 mole percent vinyl, a viscosity that
varies from about 50 to about lO0,900 centipoise at 25C,
perferably from about lO0 to about lO,000 centipoise at 25C,
and no more than about 25 mole percent phenyl radicals. These
organo- polysiloxanes may be characterized as copolymers of (I)
siloxane units having the formula:
~ (3) Ra Rb Si(4-a-b)/2
where R is defined above, R2 is an olefinic hydrocarbon
radical attached to silicon by a C-Si linkage, and generally
contains from l to 20 aliphatic carbons, straight or branched
chain, and preferably from l to 12 carbon atoms linked by
multiple bonds, a has a value of from 0 to 2, inclusive, and
the sum of a and b is equal to from 0.8 to 3.0, inclusive; and
(II) organosiloxane units having the structural formula:
(4) Rc Si (4-c)/2
where R is defined above and c has a value of from 0.8 to 2.5,
inclusive. R may be, for example, allyl, methallyl,
butenyl, pentenyl, ethenyl, and the like, but i5 preferably
vinyl. The copolymer generally contains from 0.5 to 99.5 mole
percent of the units of formula 3 and from 0.5 to 99.5 mole
~ 3 ~ 9 ~ 3 2 605l-1033/JWH mz/028~p
percent of the units of formula 4. The preparation of these
copolymers is well known in the art. They are disclosed jn
U.S. Pat. No. 3,344,111 ~o Chalk, and U.S. Pat. NQ. 3,436,366
to Modic .
Preferred vinyl on chain organopolysiloxanes are linear and
have the general formula;
R ~ R ~ ~ R ~ R
(5) Vi - Si ~ OS ~ 05 ~ OSi Vi
R R d R R
wherein R and R2 are defined above and d and e are positive
integers so that the polymer contains up to approximately 20
mole percent R2. Preferably, R2 jS vinyl, the polymer
contains from about 0.05 to 10 mole percent R2, and the
viscosity ranges from about 300 to approximately 1000
centipoise at 25C.
As stated above, R is selected from the group consisting of
monovalent hydrocarbon radicals and halogenated monovalent
hydrocarbon radicals having up to about 20 carbon atoms, that
is, radicals normally associated as substituent groups for
organopolysiloxanes. Thus, the radical R may be selected from
the class consisting of mononuclear and binuclear aryl radicals
such as, phenyl, tolyl, xylyl, naphthyl and etc.; halogenated
mononuclear and binuclear aryl radicals such as, chlorophenyl,
chloronaphthyl, and etc.; mononuclear aryl lower alkyl radicals
having from 1 tn 8 carbon atoms per alkyl groups such as,
~309532
- 8 - 60SI-1033
benzyl, phenyl and etc.; lower alkyl radical having from
1 to 8 carbon atoms such as, methyl, ethyl, propyl,
butyl, pentyl, hexyl, octyl and etc.; lower alkenyl
radicals having from 2 to 8 carbon atoms such as, vinyl,
allyl and l-propenyl; halo lower alkyl radicals having
from 1 to 8 carbon atoms such as, chloropropyl,
trifluoropropyl; and cycloalkyl radicals such as,
cyclobutyl, cyclopentyl and cyclohexyl. Though R may be
any of the above, persons skilled in the art will readily
recognize that not every R can be a high molecular weight
radical and that R should not be chosen so as to
adversely affect the vinyl group reactions. Preferably R
is a lower alkyl radical of 1 to 8 carbon atoms, such as,
methyl, ethyl, phenyl or trifluoropropyl. More
particularly, R is at least about 70 percent by number
methyl.
The essence of the present invention, and
particularly the way the present invention distinguishes
from the SiH olefin addition silicone rubber compositions
of the prior art, is the presence in the composition of
three vinyl containing organopolysiloxanes. As above,
these vinyl containing organopolysiloxanes are the high
viscosity organopolysiloxane, A (l); the low viscosity
organopolysiloxane, A (2); and the vinyl on chain
organopolysiloxane, A (3). For each 100 parts by weight
vinyl containing organopolysiloxane there should be from
about 70 to 98 parts by weight A (1), from about 1 to 15
parts by weight A (2), and from about 1 to 15 parts by
weight A (3). More preferably, there should be from
30 about 80 to 98 parts by weight A (1), from about 3 to 10
parts by weight A (2), and from about 3 to 10 parts by
weight A (3). Such a mixture of vinyl containing
organopolysiloxanes results in a cured composition having
exceptionally good hardness and tear along with high
strength and good elongation. The cured composition
"~
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605I-1033/JWH:mz/0285p
will have a tensile strength of approximately 1000 psi or more,
an elongation of 600% or more, a tear strength of 200 lbs./in.
or more, and a Shore A hardness of 35 to 40 or ~ore.
The SiH composition, (D), of the present invention serves
as a crosslinking agent and may be selected from the class
consisting of hydrogen containing silanes and hydrogen contain-
ing organopolysiloxanes. It is preferably a hydrogen contain-
ing organopolysiloxane~ Thus hydrogen containing organopoly-
siloxanes of the present invention can be characterized as
copolymers containing at least one unit per molecule having the
formula:
(6) f 9 (4-f-h)/2
where the remaining siloxane units in the organopolysiloxane
are within the scope of formula 4 above~ with the notable
exception the R of formula 4 as well as the R herein should be
saturated; f has a value of from 0 to 2, inclusive; and the sum
of f and g is equal to from 0.8 to 3Ø The viscosity of the
hydrogen containing organopolysiloxane should range from about
5 to about 1000 and preferably from about 5 to about 100
centipoise at 25C.
Included with the hydrogen containing organopolysiloxane
described above are MQ resins having units of, for example,
H(R)2 SiOl/2 and SiO2~ Also included therein are MDQ,
MTQ, MDT, etc. resins with hydrogen substitution. This
2~ copolymer generally contains from 0.5 to 9g.5 mole percent of
the units of formula 6 and from 0.5 to 99.5 mole percent of the
units of formula 4.
1 3 0 9 5 3 2 60SI-1033/JRR~70285p
-10-
The preferred hydrogen containing organopolysiloxane is a
linear organopolysiloxane polymer of the formula
R ~ R ~ R ~ R
R R h R i R
wherein R is defined above, excluding unsaturated compounds,
R3 is the same as R excluding unsaturated compounds and with
the addition of hydrogen~ h varies from 1 to 1000, and i varies
from 5 to 200. More preferably, h Yaries from 10 to 500 and is
varies from 5 to 200.
The hydrogen containing organopolysiloxane, (D)~ is
utilized at a concentration of anywhere from about 0.5 to 25
parts by weight per 100 parts by weight (A), and preferably, at
a concentration of from about 0.5 to 10 parts by weight per 100
parts by weight (A). It is desirable that jn the SiH material
there is at least one hydrogen atom for every vinyl group in
~A) and preferably from about 1.5 to about 2.5 hydrogen atoms
for every vinyl group.
Many types of platinum catalysts 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 ratalysts 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 (PtC1201efin)2 and
H(PtC1301efin) as described in U.S. Pat. No. 3,159,601,
1~09~32
PATENTS
60S}-1033/JWH~mz/0285p
Ashby. The blefin shown jn the previous two formulas can be
almost any type of olefin but is preferably an alkenylene
having from 2 to 8 carbon atoms, a cycloalkenylene having from
5 to 7 carbon atoms or styrene. Specific olefins utilizable in
the above formulas are ethylene, pr~pylene, the various isomers
of butylene, Dctylene, cyclopentene, cyclohexene, cycloheptene,
etc.
A further platinum containing material usable in the
composition of the present invention is the platinum chloride
cyclopropane complex (PtC12C3H6)2 described in U.S.
Pat. No. 3,159,662, Ashby.
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, Lamoreaux.
The preferred platinum compound to be used not only
as a platinum catalyst but.also as a flame retardant.
additive is`that dis~losed.in French Pat. No. 1,548,775,
Karstedt. Generally speaking, this type of platinum
complex is formed by reacting chloroplatinic acid
containing 4 moles of water of hydration with
tetravinylcyclotetrasiloxane in the presence of
sodium bicarbonate in an ethanol solution.
13~9~32
PA~E~TS
60SI-1033/JWH:mz/02~5p
-12-
Persons skilled in the art can easily determine an
effective amount of platinum catalyst. 6enerally, an effective
amount ranges from about 0.1 to ~0 parts per millio~ of the
total organopolysiloxane composition.
In order to get high tensile strength in the compositions
of the instant case and particularly where compositions are
formed to thin coatings or films, it is desirab7e to
incorporate a filler, (B), into the composition. Illustrative
of the many fillers which can be employed are titanium dioxide,
lithopone, zinc oxide, zirconium silicate, silica aerogel, iron
oxide, diatomaceous earth, calcium carbonate, fumed silica,
silazane treated silica, precipitated silica, glass fibers,
magnesium oxide, chromic oxide, zirconium oxide, aluminum
oxide, alpha quartz, calcined clay, asbestos, carbon, graphite,
` cork, cotton, synthetic fibers and etc.
The preferred fillers that should be utilized in the
composition of the instant case are either a fumed silica or a
precipitated silica that has been surface treated. In one
method of surface treatment, the fumed silica or precipitated
silica is exposed to cyclic organopolysiloxanes under heat and
pressure. This method of surface treatment is disclosed in
United States Patent Number 2,938,009 to Lucas.
Another method for surface treating fillers is one
jn which silica is exposed to siloxanes or silanes in the
presence of an arnine compound. This method is disclosed in
U.S. Pat. No. 3,024.126.
1309~32
- 13 - 60SI-1033
The preferred method of surface treating
fillers employs methyl silane or silazane surface
treating agents. Methylsilane or silazane surface
treated fumed or precipitated silica fillers flow
easily and do not undesirably increase the low
viscosity of the uncured composition. At the same
time, however, the silazane treated silica fillers
increase the physical properties of the cured
elastomer, particularly, the tear strength of the
cured elastomer. Best properties are obtained where
the silazane treatment is applied to the filler in
situ, that is, where the filler has been combined with
composition (A). Silazane treated fumed silica or
precipitated silica are described in United States
15 Patent Number 3,635,743 to Smith and in United States
Patent Number 3,847,848 to Beers.
The filler, (B), is generally utilized in a
concentration of 5 to 70 parts, preferably 15 to 50
parts filler for each 100 parts by weight of (A). The
preferred filler is silazane treated fumed silica or
mixtures of silazane treated fumed silica with
silazane treated precipitated silica. This latter
mixture is particularly preferred. Such mixtures of
silica should contain a weight ratio of fumed silica
to precipitated silica of about 25/1 to about 1/] and
preferably from about 10/1 to about 5/1.
Hydroxy containing organopolysiloxane fluid,
(E), may be added to extend the shelf life of the LIM
organopolysiloxane composition. Where silazane treated
precipitated silica filler is present in the
composition, the hydroxy containing organopolysiloxane
fluid may be added in conjunction with the precipitated
silica filler to obtain extended shelf-life and
~',;, i
13~9~32 PATENTS
60SI-1033/JWH:mz/0285p
-14-
mold release, Suitable hydroxy containing organopolysiloxanefluid has a viscosity of from about 5 to about 100 centipo;se
at 25DC and preferably from about 20 to about ~0 centipoise.
These fluids ray be represented by the formula:
(8) Rj (OH)k Si (4-j-k)/2
where R is defined above, j may range from 0 to 3, preferably9
0.5 to 2.0, k has a value of 0.005 to about 2, and the sum of j
and k is equal to from 0.8 to 3. Preferably, the hydroxy
containing organopolysiloxane fluid i5 linear with terminal
hydroxy substitution.
To obtain mold release properties employing a combination
of silazane treated precipitated silica and composition (E), or
to obtain extended shelf-life upon the addition of (E) alone,
there should be present in composition (B) at least about 2
parts by weight silazane treated precipitated silica for each
100 parts by weight of (A) and there should be present as
composition (E) from about 1 to about 5 parts by weight for
each 100 parts by weight (A~.
The ingredients present in composition (C), component 1,
are packaged separately from the ingredients present in
composition (D), component 2, until the time of cure.
Compositions (A), (B), (E) and additives may be divided between
either component or wholly added to component. Premature
reactions are hindered in this manner during storage and
transport. When it is desired to form the cured silicone
rubber composition, the two components are mixed into each
other and the composition is allowed to cure either ~or 16
hours at room temperature or at increasingly elevated
temperatures for increasingly lower cure times.
~30~532 PATENTS
60SI-l033/~WH:mi/0285p
-15-
Mixed components l and 2 may be injection molded directly
or dissolved in solvents for application as a film or coating.
In injection molding, the mixing barrel and shut chamber must
be cool in order to prevent premature cure. The mold
temperature generally varies from about 150~F to about 500~F.
Solvents for coating films or coatings include the usual
organic solvents for the prior art SiH olefin addition
reactants. Such solvents are, for example, hexane, heptane,
pentane, octane, cyclohexane, toluene, xylene, acetone, and
others. Other ingredients may of course be added to achieve
various purposes. Pigments, thixotropic agents, thermal
stabilizers, and the like may be added according to the
teachings in the art. Particularly, it is desirable to add
inhibitors, such as the maleates, jn order to obtain a
reasonable work life in the catalyzed material. Suitable
inhibitors are taught in U.S. Pat. No. 4,256,870 .-
. _ .. . .. _ _
13~9532 PATENTS
60SI-1033/~WR:mz/0285p
-16-
. Examples
Materials
. .
(A) High Viscosity Vinyl End-stopped Organopolysiloxane
HVOl - dimethylvinyl terminated polydimethylsiloxane
polymer having a viscosity of 80,000 centipoise
at 25C.
~V02 - dimethylvinyl terminated polydimethylsiloxane
polymer having a viscosity of 43000 centipoise
at 25C.
(B) Low Yiscosity Vinyl Containing Orsanopolysiloxane
LVO - 1/~ trimethylsilyl/dimethylvinyl terminated
polydimethyl siloxane polymer having a viscosity
of 500 centipoise at 25C.
(C) Vinyl on Chain Organopolysiloxane
VCOl - dimethylvinyl terminated poly(dimethyl-methyl-
vinyl)siloxane polymer having a viscosity of 500
centipoise at 25C and approximately 1.65 wtX
vinyl.
VC02 - trimethylsilyl terminated poly(dimethyl-methyl-
vinyl) siloxane polymer having a viscosity of
2,000,000 centipoise at 25C and 13.5 mole
percent MeVi siloxy.
13~9532
PATENTS
60SI-1033/JWH:m2/0285p
(D) Silica filler
Fumed Silica - Methyl cyclic tetramer surface treated
Precipitated Silica - Hexamethyl disilazane treated
(E) Catalyst
Karstedt platinum catalyst is dissolved in methylvinyl
tetramer.
Lamoreaux platinum cata1yst is dispersed is a carrier of
LYOl at a concentration of lOX by weight.
(F) SiH Crosslinking Agent
RHC - resin hydride crosslinker, represented by the
formula M2HQ, having a viscosity of 20
centipoise at 25C and approximately 0.9 percent
by weight H.
LHC - linear hydride crosslinker represented by the
formula MHDhDHMH, havjng a viscosity
of 55 centipoise at 25C~ and approximately 0.8
percent by weight H.
(G) Hydroxy Fluid
HF - silanol terminated polydimethyl siloxane fluid,
HO-D6 g-OH, 30 centistokes at 25C.
13~953~
PA~ENTS
605I-1033/JWH:mz/028~p
~18-
The following examples are presented for the purpose of
illustrating the present invention and are not meant in any way
or manner to limit the scope of the present specification ~r
claims.
Exam~le 1 - 7
Liquid injection molding compositions were prepared by
first mixing the vinyl organopolysiloxanes and the fumed silica
filler. The fumed silica, as shown above, had been treated
only with cyclic tetramer. The fumed silica filler was treated
jn situ by adding 6.0 parts by weight hexamethyldisilazane and
2.0 parts by weight water. This mixture was heated to 135C
under vacuum. The water and ammonia by-products were removed
during treatment. Subsequently, the remaining ingredients were
added and the resultant composition was injection molded as
shown in Table 1.
-
,
_
.
~309~32
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60SI-1033/JWH:mz/0285p
_19_
Table 1
Example 1 2 3 4 5 - -
HY01/HV02* 70 70 70 70 70 70 70
fumed silica 30 30 30 30 30 30 30
methyl tetramer 0.3 0.30.3 0.3 0.3 0.3 0.3
Lamoreaux catalyst, ppm 10 10 10 10 10 10 10
inhibitor, ppm 500 500500 500 500 500 500
RHC SiH/SiYi number ratio constant at 1.88
YC01 0 1 2 3 4 5 6
Cured Sheets, 12 min at 400F
Shore A 30 31 33 34 34 36 37
Tensile St, psi1258 1182 1226 1132 1138 1085 841
% Elongation 800 800 770 730 720 670 550
. Tear St, pi 102 112 176 166 160 200+ 182
Bashore 51 S0 50 Sl 55 54 50
Postbaked, 4 hours at 400F
Shore A 34 36 33 39 40 41 44
Tensile St, psi1367 1200 1277 1150 1058 1132 941
% 1Ongation 740 690 690 640 580 580 460
Tear St, pi 128 200 194 191 187 200+ 211
Bashore resilience51 50 50 54 54 56 53
* mixture blended to 40,000 centipoise at 25C
1309~32
PATENTS
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-20-
These examples clearly show that increasing polymer vinyl
on chain content while holding the SiH/SiVi ratio constant
yields a higher durometer and tear strength material without
substantial loss of tensile strength and elongation. Shelf
S stability and mold release of these compositions were poor.
Additionally, tear strengths were not at sufficient levels due
to the absence of LV0.
Example 8
The procedure of Examples 1-7 was repeated using the
1~ composition of Table 2. Shelf stability and mold release of
this composition were excellent.
Example 9
The procedure of Examples 1-7 was repeated using the
compositions of Table 3. Shelf stability and mold release of
this composition was poor.
` 1309532 PATENTS
60SI-1033/JWH:mz/0285p
Table 2
Example 8
HV01/HV02* 70
VC01 3.9
LV0 3 9
hydroxy fluid 1.2
fumed silica 25.0
precipitated silica 4.0
Lamoreaux catalyst, ppm Pt 10
diallylmaleate, ppm S00
RHC** 0.88
LHC** 0 30
cured sheets 12 min. at 400F
Shore A 40
Tensile St., psi 1150
X Elongation 700
Tear St., pi 230
Bashore resilience 52
* mixture blended to 40,000 centipoise at 25C
** SiH/SiYi number ratio approximately 1.7
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60SI-1033/JWH:mz/0285p
Table 3
Example 3
HY01 20.2
HY02 43.0
VC02 1.0
LV0 ~.7
fumed silica 31.1
Lamoreaux catalyst, ppm Pt 1.0
methyl tetramer 0:01
RHC
Cured sheets 12 min at 400~F
Shore A 50
Tensile St., psi 1074
X Elongation 480
Tear St., pi 230
Bashore resi~ience 52
