Note: Descriptions are shown in the official language in which they were submitted.
10783~5
This invention relates t~ a method o~ curing
silicone elastomer with ultraviolet light and electron beam.
Compositions containing ~ercaptoorgano
functional siloxanes and aliphatically unsaturated
organosiloxanes have been described in the prior art.
For example, Yiventi in U.S. Patent No. 3,816,282 teaches
silicone rubber compositions which cure at room
temperature in the presence o~ electromagnetic and
particulate radiation. The compositions exposed to
the radiation for curing comprise an organopolysiloxane
having a viscosity of 100 to 100,000 centipoise at 25~C.,
0.1 to 2.0 mole percent of the organic groups as
silicon-bonded vinyl radicals and from 1.98 to 2.05
organic groups per silicon atom, an organopolysiloxane
fluid having the general unit formula
R3a[HS(CH2)c]bsio4-a-b
where R3 is an al~yl or aryl radical of up to 18 carbon atoms,
c is 1 to 25, a is from 0.0~8 to 2.o8, b i3 from
0.009 to 0.97 and a + b is from 2.019 to 2.16 and the
number of mercapto siloxane units equal or exceed the
number of non-mercapto siloxane units, and from 0.025%
to 1% by weight of the composition of a free radical
source which includes certain organic peroxides.
Bazant et al. in German Patent Publication (OLS)
Number 2, oo8, 426 discloses five different possibilities
to make three dimensionally crosslinked silicone polymers.
These reactions ~ere found to proceed in the presence
of radical reaction initiators at a te~perature of
30-110C or by UV light initiation. The five possibilities
are defined as follows: One possibility is a reaction
. ~ .
--1--
10783ZS
between alkenylsiloxanes of the general formula
r R4 1 r R
I - SiO- ___ - Si-0
_ R4 _ m (CH2)XCH=CH~
where m + 1 is greater than 30, l:m is from 1:10 to 1:60,
x ls 0 to 4 and R4 ls alkyl groups of l to 6 carbon atoms,
cycloalkyl groups of 5 to 8 carbon atoms, aryl groups
or siloxy groups, and dithiols of the general formula
r ~ R~ : ~
II Hs(cH2)xsio- SiO - - Si(CH2)xSH
R5 R~ p R'
where ~ is 0 to 30,.x is 1 to 4 and R~ is alkyl
groups of 1 to 6 carbon atoms, cycloalkyl groups of
5 to 8 carbon atoms or aryl groups.
The second possibility is reactions between
alkenylsiloxanes of the general formula I and high
molecular thioalkylpolysiloxanes of the general formula
III { siolt sio
R~ p R~S q
where p + q is greater than 30, q:p is 1:10 to 1:60,
R~ is defined above and Rs is an alkylene group of 1 to 6
carbon atoms, a cycloalkylene group of 5 to 8 carbon
atoms or an arylene group.
~783Z5
. :.
The third possibility is reactions between
the thioalkylpolysiloxanes of the general formula III
and low molecular alkenylsiloxanes of the general formula
R' _ _ R'
IV CH2=CH(CH2)XSiO - SiO- Si(CH2)xCH=CH2
R' _ R~ _ r R~
where r is 0 to 30, x is 0 to 4 and R~ is defined above.
The fourth ~ossibllity is reactions of high
molecular thioalkyl and alkenyl substituted siloxanes
of the general formula
[ 'F
~SH m ' 1 CH=CH p r
where m ~ 1 + ~ is greater than 30, m:p is 1 to 1:60, and
R' and R6 are as defined above.
The fifth possibility is reactions between
thioalkylpolysiloxanes and organic diisocyanates.
George A. Gant in British Patent No. 1,409,223,
issued February 4, 1976, discloses a composition which
ls curable with ultraviolet light consisting essentially
of a siloxane havlng 0.1 to lOO mole percent mercapto
functional siloxane units of the formula
~HSR7)yR a xSiO X y :
and any other siloxane unit being of the formula
V RazSiO z
1~783ZS
where x is 0 to 2, ~ is 1 to 2, x + y is 1 to 3,
z is 0 to 3, R7 is an alkylene radical and R3 is a
monovalent hydrocarbon radical or a monovalent halogenated
hydrocarbon radical, a siloxane having 0.1 to 100 mole
percent of vinyl siloxane units of the formula
( CHz=CH)RalSiO
where 1 is 0 to 2 and R3 is defined above and any other
non-vinyl containing siloxane units are defined by
~ormula V, and a photosensitizing amount of a photo-
sensitizer, where the ratio of vinyl to mercapto isfrom 1:100 to 100~
~ Michael et al. in U.S. Patent No. 3,873,499
teach that resin compositions containing a copolymer of
10 to 30 mol percent
HSR'SiO 3/ 2
10 to 75 mol percent monopropylsiloxane, 5 to 35 mol
percent dimethylsiloxane and 5 to 43 mol percent monomethyl-
siloxane where R' is ethylene or propylene, a methylvinyl-
polysiloxane and a gelation inhibitor can be cured to
resins by exposure to ultraviolet light or electron
radiation. The ratio of vinyl per SH is from 0.8 to 1.2.
Although the prior art describes that
compositions containing mercapto functional siloxanes and
vinyl containing siloxanes can be cured and that some
compositions cure to elastomeric products, it is not
obvious that certain compositions containing fillers can
be cured in thic~ section by ultraviol~t light or electron
beam radiation. ~or example, Viventi requires specific
mercapto containing siloxanes, a free radical source
and radiation for curing his composition, Bazant et al.
--4--
iO78325
place strict limitations on the type of alkenyl siloxanes
and mercapto siloxanes which can be combined to provlde
a three dimensional crosslinked siloxane and describes
no fillers, Gant requires the presence of a photosensitizer
and ultraviolet light to cure his compositions and
finally Michael et al. teach only resins with high
mercapto content which require a gelation inhibitor
to get useful products. Thus, it was unexpected that
polydiorganosiloxanes having aliphatically unsaturated
radicals, mercaptoorganopolysiloxanes and a filler
could be cured to an elastomer with ultraviolet light .
or electron beam radiation.
This invention relates to a method of forming
thick section elastomer by mixing an aliphatically
unsaturated polydiorganosiloxane, a mercaptoorganopolysiloxane
and a filler, forming the composition into a thickness of at
least .25 mm and then exposing the shaped composition to
ultraviolet light or electron beam radiation.
This method results in elastomeric articles
which are cured rapidly and without the need for other
ingredients to activate the composition even though filler
is present.
This invention relates to a method of forming
thick section elastomer comprising (I) mixing to form a
composition (A) an aliphatically unsaturated polydiorgano-
siloxane having at least three diorganosiloxane units per
molecule wherein each unit of a combination forming the
molecule is selected from the group consisting of
dimethylsiloxane units, methylvinylsiloxane units and
units of the formula
--5--
.. . ,, . . . . , .. .. ~
10783;~5
CH-CH 2
11 = sio,
CH-CH2
and endblocking siloxane units present being selected from :
the group consisting of trimethylsiloxane units, methyl-
phenylvinylsiloxane units, dimethylvinylsiloxane units *
and units of the formula :~
R
CH-CH2
11 --siOo.~ ' '
CH-CH2 ~ -
wherein R is a monovalent radical selected from the group :
consisting of alkyl radicals of from 1 to 3 carbon atoms
and phenyl radicals, there being at least two aliphatically
unsaturated siloxane units per molecule, (B) a mercapto-
organopolysiloxane consisting essentially of a combination
selected from dimethylsiloxane units, trimethylsiloxane
units, unlts of the formula
CnH nSH
RSiO
units of the formula
OR'
HSCnH nSiO
OR'
units of the formula
OR'
HSCH -CH2
~SiOo 7
CH2-CH2
--6--
~783Z5
units of the formula
HSCH -CH2
t SiOo-
~
CH 2 ~CH2 ~units of the formula
HSCH -CHz
sio
CH2-CH2 ~
and units of the formula
R ~ .
n 2n, ~ ~
R ~ :
wherein R is a monovalent radical selected from the group
consisting of alkyl radicals of from 1 to 3 carbon atoms
inclusive and phenyl radicals, R' is methyl or ethyl and :
n has a value of from 1 to 4 inclusive, there being in
said mercaptoorganopolysiloxane an average of at least
two sulfur containing siloxane units per molecule and no
more than 10 mol percent -SH containing siloxane units `~
based on the total number of siloxane units in the
mercaptoorganopolysiloxane, (A) and (B) being combined
in a weight ratio sufficient enough to provide a molar
ratio of moles of -SH group in (B) per mole of vinyl
radical in (A) of 0.2:1 to 10:1, at least one of (A) and (B)
havlng at least 100 siloxane units per molecule and (C) a
filler in an amount sufficient to alter the physical
characteristics o~ the final cured elastomer compared
to a cured elastomer without filler (II) forming the
composition from (I) into a shape having a thickness .
--7--
~7~3ZS
of at least 0.25 mm, and thereafter (III) exposing the
shaped composition of (II) to ultraviolet radiation or
electron beam until the composition is cured into an
elastomer.
Before the present method was discovered films
or webs or sheets which were pigmented or contained filler,
could only be cured practically i-n thicknesses up to
about 0.25 mm with electron beam radiation and much
less for ultraviolet radiation. The present method
which involves using filler or pigmented compositions
can cure compositions in thicknesses of at least 0.25 mm
and even up to 5 mm or higher. ~ven high radiation
absorblng fillers, such as carbon black, can be used
and cured by the present method to elastomers.
The present method of forming the thick section
elastomers comprises mixing an aliphatic unsaturated
polydiorganosiloxane, a mercaptoorganopolysiloxane and a
filler, forming the resulting composition into a thickness
of greater than 0.25 mm and thereafter exposing the formed
composition to ultraviolet radiation or electron beam
radiation to form the cured elastomer.
The composition can be prepared by mixing (A),
(B) and (C) in any order. Preferably, the ingredlents
are not heated to achieve mixing in that some undesirable
reaction can occur prematurely and the working time
can be reduced. Although (A), (B) and (C) can be mixed
and stored for sufficiently long times, it is preferred
to mix the components within a period of less than six months
before use and preferably within a month of the time of the
curing operation. Conventionally available mixing equipment
1~7~3325
can be used to prepare the composition, such as blade mixers,
2 or 3 roll rubber mills, static mixers or extruder mixers.
The composition can be mixed immediately before the forming
and exposure steps or it can be mixed in advance of these
steps.
After the composition is formulated, it is then
formed into a shape which has a thickness of at least
0.25 mm. For purposes of this invention, a thickness of
0.25 mm or greater is considered a thick section. Thick
section ls to be understood as the thickness of the
composltion or cured elastomer in the direction which is
- parallel to the direction of the radiation directed at the
composition. The shape of the composition can be a film,
sheet, web, coating, or any other form which has a thickness
greater than 0.25 mm. It is not necessary that the shape
be flat or plate-like. It can be curYed or irregular.
Also it is not necessary for the composition to cure all
the way through if only a thick cured surface is desired.
After the shape has been formed, the composition
is exposed to ultraviolet radiation or electron beam
radiation. 30urces for these radiations are known
ln the art. The distance from the source can be varied
according to the users preference or equipment. The
duration of exposure will depend upon the specific
composition and the energy of the radiation. However, for
most commercial radiation sources the time can be short
such as a fraction of a second to a few seconds.
The polydiorganosiloxanes of (A) are
aliphatically unsaturated siloxane polymers which have
at least three diorganosiloxane units per molecule ~nd
_9_
``` 1(~783ZS
an average of at least two aliphatically unsaturated
diorganosiloxane units per molecule. The polydiorgano- -
siloxanes can be cyclic, linear, low viscosity fluids,
gums and mixtur`es of these polymeric species. The
diorganosiloxane units can be dimethylsiloxane units,
methylvinylsiloxane units or units of the formula
CH-CH2
Il --sio.
CH-CH2 ~
These diorganosiloxane units are combined to provide at
least two aliphatlcally unsaturated diorganosiloxane units
per molecule, forming copolymers or they can be comblned
to provide polydiorganosiloxanes having all units with
aliphatic unsaturation, such as polymethylvinylcyclosiloxanes.
The linear polydiorganosiloxanes are endblocked w~th siloxane
units selected from trimethylsiloxane, methylphenylvinyl- ~ ;
slloxane, dimethylvinylsiloxane and units of the formula
R
CH-CH2
ll --SiOo .
CH-CH2 ~
wherein R is a methyl, ethyl, propyl or phenyl. These ~;
polydior~anosiloxanes are known in the art. The
silacyclopentenylsiloxy units defined by the above
formula includes two isomers as illustrated below, namely
R R
CH =CH ' CH-CH2
' ~ SiOo., and 1l SiOo .
CH2-CH2 ~ CH-C~2 ~
The preparation of the silacyclopentenyl usually results
-10-
.~.
1~7832S
in a mixture of isomers. Inasmuch as, there is no
problem in using the mixture, separation is not attempted.
The silacyclopentenyl containing copolymers are known
in the art from U.S. Patent No. 3~509,191.
~ he mercaptoorganopolysiloxanes of (B) contain
combinations of two or more of the following units:
dimethylsiloxane units, trimethylsiloxane units, and
units of the formulae
OR'
CnH nSH HSCH -CHz SiOo.~ ~ : :
RSiO , CX2-CH2 -
HSCH -CH2 ' HSCH -CH~
--SiOo.~ SiO~
CH2-CH2 ~ CH2-CH2 ~
OR' R
HSCnX nSi ' and HSCnH nSi
OR' R
where R is an alkyl of 1 to 3 carbon atoms including
methyl, ethyl and propyl, or phenyl, R' is methyl or
ethyl and n is 1 to 4 inclusive, preferably n is 3 and
R and R' are methyl. The mercaptoorganopolysiloxanes
for use in the present invention are those which have
at least two sulfur atoms per molecule and no more than
10 mol percent -SH containing siloxane units based on
the total number of siloxane units of the mercaptoorgano-
polysiloxane. Preferably, the mercaptoorganopolysiloxanes
have a molecular weight greater than 5000 and no more
than 3.5 weight percent -SH group and the most preferred
--11--
~0783ZS ,
- are those with no more than 2.2 weight percent -SH group.
The mercaptoorganopolysiloxanes are known in the art as
evidenced by the prior art cited herein. The silacyclo-
pentane mercapto siloxanes can be prepared by the method
defined in U.S. Patent No. 3,655,713. The mercapto-
organosiloxanes which contain endblocking units of
the formula
OR'
HSCnH2nSiOo
OR'
can be prepared by reacting a hydroxyl endblocked
polydimethylsiloxane and a mercaptoalkyl trialkoxysilane
of the formula
HSCnH nSi(OR') 3
in the presence of solid potassium hydroxide or potassium
silanolate catalysts. The potassium silanolate catalyst is
preferred for the higher viscosity polydimethylsiloxanes.
The mercaptoalkyltrialkoxysilane is preferably used in
excess of about 10 weight percent over stoichiometric
amounts. The resulting product is essentially a
polydimethylsiloxane endblocked with the units of the
formula
OR'
CnH2nSiOo
OR'
but there may be some small amounts of units wherein two
SiOH groups have reacted with one mercaptoalkyltrialkoxy-
silane molecule, but these amounts are small enough that
the character of the endblocked polydimethylsiloxane is
not noticeably altered.
-12-
1078325
Fillers are used in the compositions of this
invention. The fillers can be both treated and untreated
reinforcing fillers, such as fume silica and fume silica
having triorganosiloxy groups, such as trimethylsiloxy
groups on the surface, carbon black or precipitated silica,
and extending fillers such as crushed or ground quartz,
diatomaceous earth, and calcium carbonate. The amount
of filler ls enough to provlde a change in the physical
characteristlcs of the cured elastomer compared to a
cured elastomer without a filler. Preferably, the amount
of filler is at least 5 parts per 100 parts by weight of ;
(A) and (B) combined. Certain fillers, such as carbon
black, can be present in smaller amounts. Carbon black
is of particular interest, because it is a strong
absorber of ultraviolet radiation, but it still will
cure to elastomer in accordance with this invention,
although the thicknesses curable are not as great with
carbon black as with other fillers, such as 0.30 to
0.40 mm are considered thick section.
The compositions used in this method are
made by mixing (A) and (B) in a weight ratio range
sufficient enough to provide a molar ratio of moles of
-SH group in (B) per mole of C=C bond in (A) of from
0.2:1 to 10:1, preferably 1.5:1 to 5:1. Also, the
compositions must contain at least one of either (A)
or (B) which has at least 100 siloxane units per molecule,
preferably at least 200 siloxane units per molecule.
Although not required, the compositions can
contain other additives such as benzophenone which can
make the curing step even faster although it is very
-13-
~783'~S
fast already, gelation inhibitors can be used such as
p-methoxyphenol, although most compositions are
sufficiently stable without such stabilizers and the
gelation inhibitors can lengthen the cure time, and
also certain free radical sources can be added, but are
not really needed and can significantly hasten gelation
at room temperature and should be avoided.
The method of this invention is useful for
making thick section elastomers such as for films, webs,
sheets and coating. The cure is fast and because the
compositions contain fillers, they have improved strength
and other useful properties such as durometer, modulus
and tear strength.
The following examples are presented for
illustrative purposes and should not be construed as
limiting the invention which is properly delineated
in the claims.
Example 1
A. A composition was prepared by mixing 60.9 g.
of a methylphenylvinylsiloxy endblocked polydimethylsiloxane
having a v~scosity at 25C. between 25 and 35 pascal-seconds
(Pa-s) (hereinafter identified as Polymer D), 6.o g. of a
trimethylsiloxy endblocked polydiorganosiloxane having
5 mol percent methyl(gamma-mercaptopropyl)siloxane units
and 95 mol percent dimethylsiloxane units and having a
viscosity at 25C. of 0.0015 metre2/second (m2/s)~
(hereinafter identified as Polymer A), 22.3 g. of a fume
silica filler having the surface treated with trimethylsiloxy
units and 1.0 g. of benzophenone. The composition was
formed into a film 0.99 mm thick and then exposed to ~V
,
-14-
1C~783ZS
radiation, using a~ Ashdee continuous belt two lamp
curing module having Hanovia medium pressure lamps rated at
7874 watts per linear metre, for 13 seconds under an air ;
atmosphere. The composition cured to an elastomer
having a tensile strength of 1379 kilopascals (kPa)
at break and an elongation at break of 480 percent
and a Die "B " tear strength of 5954 newtons per metre
(N/m). The tensile strength and elongation were determined
by ASTM-D-412 and the tear strength was determined
by ASTM-D-624.
B. Another composition was prepared as
described in A. above except the benzophenone was left
out. This composition was formed into a film 2.4 mm
thick and then exposed to an electron beam from a 2
megavolt electron beam unit with a focused beam and a
0.3048 m sweep. The film was exposed under a nitrogen
atmosphere to provide 5000 joules per kilogram tJ/kg).
The composition cured to an elastomer having a tensile
strength at break of 3861 kPa, an elongation at break
of 1200 percent and a Die "B " tear strength of 1~,213 N/m.
ExamPle 2
Compositions were prepared by mixing the
ingredients as defined below, formed into films and
exposed to W radiation as defined in Example 1. The
film thickness and exposure times were as shown in Table I.
The physical properties were determined by the
procedures described in Example 1 and were as shown in Table I.
A. 106.4 g. of a methylphenylvinylsiloxy
endblocked polydimethylsiloxane
having a viscosity at 25C. between
-15-
i~783ZS
8 and 12 Pa-s (hereinafter identified
as Polymer B),
15.0 g. of Polymer A,
39.4 g. of the fume silica filler as
deflned in Example 1, -
1.8 g. benzophenone.
B. 71.2 g. of a methylphenylvinylsiloxy
endblocked polydimethylsiloxane
havlng a viscosity at 25C. between
1.8 and 2.4 Pa-s (hereinafter ~`
identified as Polymer C),
50.0 g. of Polymer A,
40.0 g. of the fume slllca filler as defined
in Example 1,
1.07 g. of benzophenone.
C. 0.43 g. of polymethylvinylcyclosiloxane
mixture having 3 to 8 siloxane units
per molecule,
37.6 g. of a trimethylsiloxy endblocked
polydlorganosiloxane having 2 mol
percent methyl(gamma-mercaptopropyl)-
slloxane units and 98 mol percent ~ ;
dlmethylslloxane units and having a
viscosity at 25C. of 0.0015 m2/s,
11.4 g. of a fume silica filler having the
surface treated with dimethylvinyl-
siloxy units,
0.38 g. of benzophenone.
3o
-16-
1~783ZS
D. 2.7 g. of polymethylvinylcyclosiloxane
mixture having 3 to 8 siloxane - ~;
units per molecule~
97.3 g. of Polymer A,
30.0 g. of the fume silica filler as
defined in Example 1.
E. 65.9 g. of a dimethoxy(gamma-mercaptopropyl)- :
siloxy endblocked polydimethylsiloxane
having a viscosity of 0.0015 m2/s,
109.57 g. of Polymer E,
25.0 g. o~ fume silica filler as described
ln Example 1, ~ -
1.1 g. of benzophenone.
Example 3
Compositions were prepared by mixing the
ingredients as defined below, formed into films and exposed
to electron beam radiation as defined in Example 1. The
film thickness and the dosages were as shown in Table 2.
The physical properties were determined by the procedures
described in Example 1 and were as shown in Table 2.
A. 53.2 g. of Polymer B,
16.4 g. of Polymer A,
25.0 g. of the fume silica filler as
defined in Example 1.
B. 100.0 g. of Polymer C,
18.5 g. of Polymer A,
41.5 g. of the fume silica filler as
defined in Example 1.
3~.
-17-
. . .~. - ~ , .... .. .
~a783z5
C. lO0.0 g. of Polymer D~
14.0 g. of Polymer A, -~
30.0 g. of the fume silica filler as
defined in Example 2, C.
D. lO0.0 g. of Polymer B,
19.3 g. of Polymer A,
32.7 g. of the fume silica filler as
defined in Example 2, C,
500.0 parts by weight para-methoxyphenol
lOper million parts by weight
composition.
E. 107.0 g. of Polymer B,
14.2 g. of Polymer A,
34.4 g. of the fume silica filler as
defined in Example l,
l.0 g. of benzoyl peroxide,
500.0 parts by weight para-methoxyphenol
per million parts by weight
~ composition.
F. 107.0 g. of Polymer B,
15.2 g. of Polymer A,
34.4 g. of the fume silica filler as
defined in Example l,
l.0 g. of N,N-azobisisobutyronitrile.
G. 106.0 g. of Polymer B,
14.8 g. of Polymer A,
34.8 g. of the fume silica filler as
defined in Example l,
l.0 g. of di-tertiary-butyl peroxide.
-18-
1~783ZS
H. 53.2 g, of a dimethylvinylsiloxy
endblocked polydimethylsiloxane
having a viscosity at 25C. between
8 and 12 Pa-s,
16.4 g. of Polymer A,
25.0 g. o~ the fume silica filler as
de~ined in Example l.
I. 59.0 g. of a methylphenylvinylsiioxy
endblocked polydiorganosiloxane gum
having 99.7 mol percent dimethyl-
siloxane units and 0.3 mol percent
methylvinylsiloxane units and having
a Williams plasticity of about 1.5 mm, -~
41.0 g. of a fume silica filler having the ;-
surface treated with trimethylsiloxy
units, dimethylsiloxane units and
methylvinyl~iloxane units,
16.5 g. of Polymer A.
J. 44.7 g, of Polymer B,
4.9 g. of a dimethylvinylsiloxy endblocked
polydiorganosiloxane having 78 mol
percent dimethylsiloxane units and
22 mol percent methyl~inylsiloxane
unlts (hereinafter identified as
Polymer E),
53.3 g. of Polymer A,
29.9 g. of fume silica filler as defined
in Example 2, C,
500.0 parts by weight para-methoxyphenol
per million parts by weight composition.
--19--
~7E~3Z~ ,
K. 9.57 g. of Polymer E,
65.9 g. of a dimethoxy(gamma-mercaptopropyl)-
siloxy endblocked polydimethylsiloxane
having a viscosity at 25C. of
0.0015 m2/s,
25.0 g. of fume silica filler as described
in Example l.
L. 50.0 g. of a dimethyl(gamma-mercaptopropyl)-
siloxy endblocked polymethylsiloxane
having a viscosity at 25C. of
0.00424 m2/s,
0.48 g. of a trimethylsiloxy endblocked
polymethylvinylsiloxane having a
viscosity at 25C. between 0.000025
and 0.000035 m2s,
12.5 g. of fumé silica filler as described
in Example l. ,
Example 4
Elastomers were obtained by curing the following
compositions in the film thicknesses describes in Table 3
and with the dosage of electron beam radiation as shown
by Table 3.
A. 106.4 g. of Polymer B,
13.0 g. of Polymer A,
59.7 g. of calcium carbonate filler. -
B. 106.4 g, of Polymer B,
13.0 g. of Polymer A,
59.7 g. of crushed 5 micron quartz filler.
-20-
~ 78325
Table 3
Film
Dosage, Thickness,
Composition J/k~ _ mm
A. 7500 5.59
3 35
Example 5 -
A composition was prepared by mixing 3 g. of
a polymethylvinylcyclosiloxane mixture having 3 to 8 siloxane
units per molecule, 97 g. of Polymer A and 2.5 g. of carbon
black. The composition was formed into a film 0.38 mm thick
and exposed to UV radiation as described in Example 1 for
2.7 seconds and an elastomer was obtained.
; ial783ZS
S .
~o
~-- ~ ~ r-- :
a~- ~ ~ I I
-- ~~ ~ I I N
-- Z~ I I N
tD
~d~
a~
E~
rl
O ~ L~ O O
~O N
sO ~ Ir~
~1
~ S
,1 ~ ,1 ~o ~ ~ ~r ,
~ bl) td Lr~ ~) N O N
r-l ~ a~ ~ N
a~ 5
E~
.
~ ~ .
h ^
o ~ a~ . . . ..
b~
~q
~3 ~DN N ~1:-- N
r~l S ~ ~ N ~1 N O
j
S ~ r~
E~ '
o ¢ m
o
C~
--22--
~0783ZS
- o ~X~ ~ ~ ~ ~ ~, ~, ~o
N I ~1 ~I C~ Ir~ Ln oc) ~r) N ~ ~r
S: ~ ~~rl I Lt~ co ~ o~ N (~ ~1 N ~rl o
~ o- Z
E~ h ~-- I 3 ~ N Lt~ l5~ ~1 ) ~--1 r-- ~1
rl N N N ~1 ~1 ~1 ~1
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